Selecting Nano Aquarium Chillers

22 November 2012

Introduction

There is a choice when selecting chillers for nano aquarium tanks of  around 25 gallons or 100 litres or smaller. One can choose between a Peltier chiller or a Freon Chiller. This article will show the differences between the popular brands, using 1/20 hp range as examples.

What’re the Main Difference

Peltier chiller uses an electronic chip whereas Freon chiller uses mechanical compressor to generate the chilled water. The differences are discussed here in detail.

What're the Popular Brands?

In the 1/20 hp range, the popular brands in Singapore are

1. Resun CL150

2. Hailea HC100a

3. Arctica nano DBI-038

Their specifications from the manufacturers are tabulated as follows:-

Brands	Resun	Hailea	Arctica
model	CL150	HC 100a	DBI038
Range (hp)	1/20	1/20	1/20
Type	Electronic	R134a Freon	R134a Freon
Power Input (watts)	200	1101	1651
Power Output (Watts)	150	150 (from a website)	200 (600 BTU/hr)
Ampere (230V)		0.6	0.9 (1.8 @ 115V)
Tank size (litres)	120	50-200
Flow rate (LPH)	1000	200-1000	400 -600
Weight (kg)	8.5	9.2	12
Water Connection (mm)			12 (1/2”)
Dimension (mm)	260 x 310 x 205	338x18x25	195x320x358
Estimated cost (SGD$)	170	300	800

1. Estimated from running current

The Coefficient of Performance (COP)

This figure is never available for the manufacturers. Although COP can tell if one chiller is more efficient than the other,  it will depend on the operating conditions, the cooling as well as ambient temperatures.  Also, most tests in factories are carried out under laboratory conditions where good quality water are often used.

From the manufacturers’ data and some estimation of  input power, one can tabulate the following table:-

Brands	Resun	Hailea	Arctica
model	CL150	HC 100a	DBI-038
Range (hp)	1/20	1/20	1/20
Power Input (watts)	200	110	165
Power Output (Watts)	150	150	200
COP (output/Input)	0.75	1.36	1.21
Performance	100	180	160

Assuming that the chillers are operating under the same conditions and factory tests carried are identical, Hailea 100a appears to be more energy efficient.

Inside the chillers

Stripping out the case, the insides of the chillers are shown as follows:- (click to enlarge)

Comparing the pictures, one can straightaway tell that Resun CL150 has a different configuration. It has no compressor. A refrigerating chip was named to provide the cooling. Also, it uses a plastic heat exchanger for the cool side and an aluminium heat sink with forced air cooling for the hot side of the chip. It is hard to tell from the picture if the  refrigeration chip is actually a peltier chip.

Working out COP for Peltier Chillers

Ultrasonic2 has posted in his webpage a TEC calculator to workout the COP for Peltier chiller.
Enter the various measured data such as hot and cool side temperatures and also the power input etc, the TEC calculator will be able to work out the COP.   As for the freon chillers,  some calculations will be required to work out the cooling power.

Heat Sink for Peltier Chillers

Someone in one of the forums pointed that the size of heat sink does not matter much in Peltier Chiller but this article about heat sink for Peltier will prove him wrong.

Ultrasonics2 and Shine7 have both provided TEC calculation results for their Peltier chips. Their webpages can be found here and here.   It is believed that Ultrasonics2 used the peltier for computer cooling whereas Shine7 used it for aquarium cooling.

As one can see from the following that the COP of peltier chip can vary a lot. In this case, Ultrasonic2’s 0.74 vs Shine7’s 0.54

Also noted that the Shine7’s peltier had a hot side temperature of 52C whereas the Ultrason2 had a temperature of 30C. Also,   the Delta T across the chip was lower in Ultrasonics’s case. The results  suggest that Ultrasonic2 has an extra efficient heat sink. But now, look at Shine7’s heat sink again and compare  to that of Resun CL150 chiller shown earlier (but the real one may be much larger though). 

How to Select the Right Size Chiller

Many aqua and reef enthusiasts pick up some knowledge here and there.  Some uses the one size larger rule and some just blatantly use figures provided by the manufacturers. Some suggested that chiller should be large enough so that it won’t run longer than half an hour on each start. Some preferred shorter operating time citing lesser wear on the compressor.

The correct chiller sizing should depend on heat loads transmitted into or out of the tank. There are basically the following heat losses/gains that can be found in an aquarium tank; 

1) The heat gain from the light fittings
2) The heat gain from the pump or in-line filter
3) The heat gain transmitted through the exposed glasses
4) The heat gain from the occupants
5) The heat gain through surface and the heat loss from evaporation
6) Others heat gain  such as those from internal circulating pumps, wave makers etc

As the calculation involves complicated thermodynamics and air conditioning engineering, it would not be discussed here. Those interested can read up this article.

Most enthusiasts just use rules of thumb. The thumb rule of using one size larger appear to be more appropriate because the manufacturer’s guideline often did not consider the extra heat load from the other equipment such as lights, pumps etc;  also,  the chiller will age and lost efficiencies. Then one might want to add more equipment such as more pumps in future.  Some manufacturers could also over-rate their chillers.

JBJ has a website that one can use to size various chillers.    Please note the following when using the website:-
a)  For metric to imperial conversion,  use the formula degree F= degree C * 9/5 +32 and 1 US gallon = 3.8 litres;
b)  Remember that actual water temperature refers to maximum water temperature which should be around 30C or 87F for Singapore; 
c)   A 40 watts flourescent fitting will give 50 watts of heat;  40 watts for the lamp and 10 watts for the ballast (25% for magnetic ballast, 20% for electronic ballast and 15% for LED driver);
d)  Assume full tank volume and not actual water volume to be safe. 
e)  It is still good to up one size larger after the calculation.
 
The term horsepower (hp) is often used for sizing a chiller.  One can take that 1 hp=2800 watts of cooling power.  Divide that by COP of the chiller (1.3 for freon and 0.55 for Peltier),  one should get roughly the power inputs in electricity watts.

The manufacturers appear to suggest the chiller should be sized such that the chiller should cycle on 15-20 minutes an hour for chiller to run about 6-8 hours per day. Depending on the setting of the temperature and the water flow rates, it may be normal for chiller to run for 1 hours and stay off for 2-3 hours before the next cycle.

Flow Through Vs Drop-in Coils

There was a misconception that drop-in coils are much more efficient than the normal flow through type of chiller.  However,  this is not quite true as the chiller efficiency depend much on the coil design of the evaporator and the condenser.  The manufacturers can further improve the condenser designs to make chiller more efficient;  such as providing more condenser tubes and fins with improved fan design.  However,  for evaporating coils,  the manufacturers will have to weigh between cost and efficient design as titanium which is often used in aquarium chiller comes with a price.  It is for this reason that the COP of aquarium chillers are never better than window airconditioners.  The following manufacturer's data will show that the amperage drawn for both flow through and drop-in chillers are identical.

Conclusion

Peltier chillers are less efficient but they cost much less. An economic will have to be worked out before choosing the right chiller. On the other hand, Freon chiller may cost more but on the longer term, it will cost less because of higher COP.

Other Reference Sites
tinyurl : https://tinyurl.com/y7p6tev3

Freon Vs Peltier Chillers

21 November 2012

Introduction

There were some interesting exchanges in one local forum about the use of Freon chillers and peltier chillers for aquatic and reef work. Many experienced aquatic enthusiasts in the forum argued that peltier chillers will not work. Those used peltier chillers before was of the view that such chiller is not suitable for reef tanks and cold-stored the chiller. This article will present the differences between the 2 types of chillers and their applications in aquatic and reef work.

What is a Peltier Chiller?

Peltier chiller is often referred to as an electronic chiller because it uses a semiconductor chip that has hot and cold plates.

When there is a current passes through, the chip will transfer heat between the plates for heat to be rejected or produced depending on the polarity of the plates. Peltier chip was discovered by a French Physicist Jean-Charles Peltier in 1834 when he passed a current through to product heat and cold energy from a junction composed of two different materials.   The largest Peltier chip from ebay has a power input around 500 watts.  This has about 300 watts or 1/10 hp cooling power,  good enough just  for a 300 litre tank.  Larger and more efficient ones are being developed.

What is a Freon Chiller?

Freon Chiller uses a compressor to compress gaseous freon into liquid state, then the freon is allowed to be cooled in a condenser for heat to be rejected to the atmosphere. After that, it is allowed to be expanded into an evaporator chamber either by means of an expansion valve or capillary tube. In the process of expanding from liquid to gaseous freon in the evaporator,  it absorbs heat from its surrounding. The cycle repeats when the gaseous freon is returned back to the compressor.

What’re the Differences?

As far as the quality of cooling is concerned, there is no difference between the two. This is because water from aqua or reef tank will cycle through heat exchangers of the chillers. For freon chillers, titanium tubes are often used as cooling coil inside the evaporator whereas for peltier chillers,  polypropylene or stainless steel sections are used for heat transfer. No copper or aluminium materials will be used in the water heat exchanger unit.

Apart from this, peltier chillers are often smaller in size except for the electricity consumption.  They are not  as efficient as the freon chillers. Also, there is no difference in the inlet and outlet connection because there is no cooling coil used in peltier chillers.

One aqua enthusiast built this peltier chiller for his 20-litre tank.

What're the Pros and Cons For Peltier Chiller?

Pros

1. Can be easily DIYed. Multiple units can be cascaded to give the desired cooling;

2. Light weight and smaller in size;

3. Can use for both cooling and heating by just reversing the polarity of the peltier chips;

4. Lower capital cost

5. Easier to maintain; no moving parts except the cooling fan; spares are a plenty;

6. Peltier chip claimed to have a life expectancy of 200,000 hrs

Cons

1. Higher running cost ; Freon chiller is 75% more efficient than Peltier chiller;

2. The fans for aluminium heat sinks can be noisy unless a bigger heat sink with less noisy fans or remote cooling can be used;

Design Pitfalls for Peltier Chillers

 

Pitfall No.1

Computer Heat Sink

They are a plenty in the market and often being used wrongly for Peltier chips. A wrong selection of a smaller size not only affects the cooling performance but also results premature failure of peltier chips. Too big a heat sink will cost money although the chiller will run more efficiently.  An economic will have to be worked out for the selection. Water cooling is a better alternative than forced air cooling because more heat can be transferred when properly designed;  and also, cooling devices can be remotely located to minimise fan noises.

The following is a good article to learn more about peltier and the heat sink selection. Read here.

 

Pitfall No 2

Cooling blocks

There are a plenty also from the market but most are designed for computer cpu cooling where clean water are often used. They are either of copper or aluminium type which is not suitable for use in aquatic or reef tanks. They could be corroded or choked up easily after sometime.

It may be more appropriate to use stainless steel channel cut to form a box with both ends sealed for plastic inlet and outlet.  Corrugated stainless steel sheets such as the following can be DIYed to stuff inside the box and stick lightly with non-toxic thermal conductive expoxy glue to help heat transfer.

Polypropylene plastic can also be used as alternative.  The heat transfer characteristic of polypropylene plastic is about as good as stainless steel.

As stainless steel may also corrode over time,  the other alternative is to use titanium tubes either embeded in the holes of solid aluminum block or high thermal heat transfer epoxy which has thermal conductivity comparable to titanium.  Multiple passes can be arranged for better heat transfer.

Confusion about Cooling Efficiency and Coefficient of Performance (COP)

Someone claimed that Peltier has only 8% efficiency as compared to Freon chiller which has 50% when he searched the net and might have tumbled into the following Wiki site. The paragraph in the Wiki site read as follows.  He argued strongly that no chillers will ever have cooling efficiency higher than 100%.

Thermoelectric junctions are generally only around 5–10% as efficient as the ideal refrigerator (Carnot cycle), compared with 40–60% achieved by conventional compression cycle systems (reverse Rankine systems using compression/expansion). Due to the relatively low efficiency, thermoelectric cooling is generally only used in environments where the solid state nature (no moving parts, maintenance-free, compact size) outweighs pure efficiency

For cooling and heating purposes, the efficiency of cooling or heating device is often measured in terms of Coefficient of Performance (COP) and not the Carnot cycle efficient. This is because freon, when allowed to be expanded in the evaporator, absorbs free energy from its surrounding and therefore, the efficiency can be more than 100%. Peltier chiller,  on the hand,  has no such advantage of getting free energy from the surrounding and therefore,  its COP is much lower. 

COP is often expressed as

COP cooling = Qc/W_in

Where Qc is the cooling output and Win is the power input

Normally, freon chiller has a COP around 1.3 whereas Peltier chiller will have a COP around 0.55. Air conditioner has much higher COP around 2 to 2.5 because it has larger and more efficient condenser and evaporator. Commercial chillers would have COP more than 5.0 because they have super large condensers with multiple water passes in the heat exchangers.

Why no Large Peltier Chillers?

Peltier chillers are limited to smaller sizes in the market. They usually have cooling power of less than 150 watts or 500 BTU/hr or 1/20 hp. It is not because larger one cannot be constructed or manufactured. It may be because the running cost may become more manageable for smaller sized chillers; moreover, Peltier chiller has a significant cost advantage in this range.

Why Peltier Failed to Work?

Some claimed that Peltier chillers not only failed to work but also tank temperature kept rising.  There are several reasons;  one of which may be there was not enough air cooling for the heat sink when it was placed in the cabinets.  The other could be due to over-rating by the manufacturers.  Some claimed Peltier chillers to have COP of around 0.75 with small heat sinks.

Economics

One can get a 1/20 hp Peltier chiller for about SGD$170/=  and will have to spend around SGD$300 for a similar size freon chiller.  Assuming the cooling power is around 140 watts, Peltier will need about 250 watts of electricity and Freon chiller around 110 watts. At current electricity tariff of 0.2727 per kwh and assuming 48 starts/stops per day with 10 minutes running and 20 minutes resting, the electricity cost will work out to be SGD16 per month for Peltier and SGD$8 for Freon chiller. With that difference in running cost, the straight payback for using Freon chiller will be around 14 months.

Conclusion

Peltier chillers are only good for those who have a smaller budget and not too worried about the higher running cost or for starters who just wanted to try nano reef keeping for a short period.  It is suitable for use as a backup chiller.


Other Reference Sites
tinyurl:  https://tinyurl.com/ybqva9ws

DIY Bed Cooler

19 November 2012

Introduction

To many in the topical countries, air conditioner is an essential thing to have for a good night sleep. A room air conditioner, operating 10 hours per day, will consume roughly about SGD$60 of electricity per month; out of which, 90% is wasted in cooling the room and the walls. This article will share how this much energy can be saved by using a bed cooler.
Note: The same set up can be used for bed heater by using aquarium heaters

What’s a Bed Cooler?

A bed cooler cools only the bed instead of the whole room. It runs chilled water underneath the bed sheet or mattress. To cool an average size room, one will need a cooling capacity of about 10,000 BTU/hr or 2,800 cooling watts; but to cool a person, one will need only 1/20 of this energy; hence, about 90% of the energy could be saved.

What’s Available in the Market?

There are a few brands of bed cooler available in the market. Most sold with a cooling mattress plus a heat pump unit that can generate either hot or cold water. It costs around SGD$800 for a single bed and about SGD$1,300 for a king sized double bed.

What Are the Components?

Each bed cooler consists of a mattress either embedded with silicone tubes or PVC sheets sealed to form tubes for chilled water to be run within.

The cooling or heating water is often generated by an electronic Peltier chip that is powered by a 12 or 24 volts power supply. It has also a pump and a temperature controller where temperature can be controlled or set remotely.   One forumer claimed that he saved about 50% in the September 2012 electricity bill after using the bed cooler.

A Chinese video explaining the workings of a bed cooler can be found here

Where To Buy the Components for DIYs?

For DIY enthusiasts, the bed cooler components including Peltier chips can be purchased all from Ebay. A refrigeration kit consisted of 2 pieces of 60 watts cooling power Peltier chips plus heat sinks, fans etc will cost not more than SGD$50.

Its cooling power is just barely enough for a single bed application after some de-rating.  The other costly items are pump, silicone tubing and a temperature controller (also available from ebay) which may cost another SGD$60 for a single bed. The silicone tubes and pumps can be purchased from local aquarium shops. One enthusiast has constructed an aquarium chiller using Peltier chip and his set up can also be used for the bed cooler project.
One could also buy the water cooling mattress and the temperature controller from China. The set will be cheaper but some said they were not as reliable as buying the complete mattress set from the local stores.

Other Alternatives?

Bar or mini refrigerators will not have the required cooling power for the cooler bed project. A bar refrigerator only have a cooling power of around 70 watts or 250 BTU/hr which is too small for a human load that is around 100 watts or 350 BTU/hr.

One could use an aquarium chiller instead of Peltier chiller except that one may need another circulating pump and a pump sump because the chiller often needs higher flow rate for proper operation.

What is the Set up for the DIY Project?

This article uses an old Resun Aquarium chiller model CL650 for the DIY project that was designed to cool a king size bed of 1.9m x 1.8m. The author got this chiller including the water pump for just SGD$50/= because one reef keeper gave up his hobby while moving his house. The final set up is as shown.

The Pros and Cons of this DIY Vs Commercial Bed Cooler

Pros

1. Aquarium chillers of Freon type are 75% more energy efficient than Peltier chillers. It has a Coefficient of Performance(COP) of 1.3 vs Peltier chiller which has only around 0.55;

2. For DIY, one can suitably place the chiller remote for minimum noise and better ventilation;

3. Can DIY to suit individual requirement

Cons

1. Cannot provide hot water for heating unless a heater is incorporated;

2. Only manual setting although starting and stopping can be controlled remotely by using a remote controlled socket;

3. Not portable and occupy more space.

What Size of Chiller?

The CL650 has a cooling power of 650 watts (1/4 hp) which is over sized for the project. The bigger size chiller will consume slightly more energy but will bring water temperature quicker to the set point temperature. A 300 watts cooling capacity or 1/8 hp chiller should be ideal for the project.

List of Components for DIY Project

The list of components and where to purchase them are as shown.

1) One aquarium chiller preferably 1/10 hp to 1/8 hp modified with external temperature probe;

2) One small aquarium tank insulated with 1/4” thick polyester form to house 2 pumps, a circulating and a chiller pump;

3) One 600 litres per hour(LPH) circulating pump and one 1800 LPH chiller pump as specified by chiller manufacturer;

4) One lots of 10 mm diameter PVC flexible tube from hardware store;

5) One lots of 6 mm diameter silicone tube for the bed cooling from aquarium shops;

6) 2 length of 20 mm diameter PVC plastic pipe as the header plus 2 rubber end caps and 2 pipe connectors for connection to 10 mm PVC tube from hardware stores;

7) 2 small tubes of super glue;

8) One 300 mm long balloon holding stick as stud for the joints between silicone tube and PVC pipes; outer diameter slightly larger the inner diameter of the silicon tube;

9) One lot of 1/4 “ thick sponge sheet from stationary shops, cut to form strips to wrap round the pipes and tubes;

10) One lot of shrinkable plastic tubing from hardware shops;

11) One mattress cover; hereafter referred to the mattress.

What is the most Difficult Part of the DIY Job?

The construction of the bed cooler mattress and the header pipe.

Header Pipe Construction

The header consists of 2 PVC pipe of 20 mm diameter and one 10 mm flexible PVC tube as a return to form a reversed return piping arrangement as shown. This will ensure that water is always first in and last out so that the pressures and water flow are equal in all the tubes.

The author tried 3 different versions to make a joint between the silicone tubes and the PVC pipe; two of which failed with multiple water leaks detected during the tests. The final and working version used a stud embedded in the silicone tube as shown.

First find a plastic tubing slightly larger than the diameter of the silicone tube. A balloon holding stick was chosen and cut into smaller pieces as shown in one of the smaller picture.

Do some experiment first with a short length of silicone tube and a short piece of PVC pipe. Select and drill a hole in the PVC pipe such that the hole should be just large enough to fit the stud loosely. When inserting the stub into the silicone tube, allow the tube to overlap for about 3 mm as shown. This will ensure that the tube can be first inserted into the PVC hole before pressing the stud into position to give the side pressure to seal the joint.

Drilling holes in PVC pipe accurately can be tricky and difficult unless one has a drill bench to hold the pipe in place.  The easier way is to DIY a simple tool using another short length of slightly larger pipe that can be slotted into the PVC pipe.  Drill at least 2 holes accurately on the larger pipe.  One of the holes will be used for alignment and the other for drilling a hole in the PVC pipe.

Elephant brand of super glue was used for the joint between silicone tube and the PVC pipe. With proper selection of the stub and the drill diameter, the stud should provide the required side pressure to make good tight seal for the joint.

This new version had only 2 joint failures out of the 48 joints which is less than 5%. A quick repair fixed the leak.

To facilitate the jointing process, each silicone tube is first rolled and tied up for ease of handling and also for ensuring the tube will be properly segregated for the joints to be made without making any cross over between the tubes.

Testing for leaks

After having completed the joints for the silicon tubes, it is important to test the joints for leakage if any. Pressure test the joints to at least twice the height difference between the pump and the bed plus any increase in pressure due to the pumping. If one does not have a pressure testing set, one could raise the testing pump to the required height as shown. Put old newspaper underneath the pipe for detection of any leak and do the repairs as necessary.

The Bed Cooler Mattress

Finally, lay the mattress flat on a cleaned floor surface and put the silicone tube etc in place with the PVC pipe header laid about 50 mm to 80 mm from the top edge of the mattress so that one can hide the header in-between the bed and the headboard. When the silicone tubes are laid in proper place, hold the tube in place by thread and needle, ensuring that no needle will ever punch a hole in the silicone tubes.

The details of the bed cooler mattress construction and the set up are as shown here.

Insulation and Vapour Sealing

The header and the 10 mm flexible PVC tubing that connects the header and the pump sump are then wrapped around with ¼” sponge strips, edge to edge to prevent condensation.

In addition, the header has a piece of cloth wrapping around and stitched to the end of the mattress to prevent any stress that may be put onto the joints due to pulling or shifting of the mattress during operation.

The connecting 10mm PVC tubing together with sponge strips is then sealed inside shrinkable plastic tubing often used for covering bamboo sticks.

Hiding the PVC header in between the headboard and the bed not only for aesthetic reason but also for extension of cooling to underneath the pillow where, at times, hands and arms putting underneath the pillow can be cooled for a good night sleep. Also, the joints are the weakest part. If there is a water leak, it won’t wet the bed.

To prevent the mattress from “running away”, there is a need to strap the mattress to the edges of the bed.

The Pump Sump

The author uses a 25 litres aquarium tank as a pump sump. It is then insulated with 2 layers of 1/4" thick  polyester foam to prevent condensation. Silicone glue was used on the edge of the foam to stick to the tank.  There will be a need to treat the water as bacteria will flourish also when there is air in the water.  Chlorinating the water is one best solution if one is using aquarium chiller and plastic pumps with porcelain shaft like Eheim.

Cost

The author uses most components from his store including an old 25 litres aquarium tank and the 600 LPH pump. The estimated additional cost was not more than SGD200/=. If new chiller and pumps are required, another SGD300/= may have to be added.

Testing and Performance

The consumption was measured by a data acquisition machine which recorded the energy consumption in minutes for 3 types of cooling for 3 different nights:

a) A Panasonic inverter air conditioning cooling the room @ 25^oC;

b) The bed cooler of this project, cutting in @ 23^oC and cutting out @ 25^oC;

c) The bed cooler plus Panasonic inverter air conditioning operating as an air dehumidifier with temperature set to 27^oC.


The result is as shown.

For the same bed and about the same weather condition, the cooler bed project saved about 90% of the energy bill. A variation is to use the cooler bed with existing air conditioner as a humidifier by turning up the air conditioner cooling from 25^oC to 27^oC. This variation will allow those who still want dehumidified air for good night sleep. The energy saving measured was around 50%.

Post Mortem

1. Equal Length of Silicone Tube

The author only estimated the length when cutting the silicone tube into pieces. This resulted tubes having different length causing unequal pressure and flow. During start up, more than 2 sets of tube have no water flow and hence,  no cooling on parts of the bed.  Fortunately, by lifting the PVC pipe header up and down several times solved the problem.

2. Stitching the tubes

When tubes were laid onto mattress, author started stitching from the header end, assuming the tube would have no crossovers. When he found the crossovers at the end, the tubes were all stitched in place. Therefore, it is important to start stitching from the ends first.

Other Observations

The Feeling of Silicone Tubes

One can feel the silicone tubes on the bed by finger touching but not the body. This is because only fingers and toes have sensory nerves.

Bed Heater

The bed cooler can be used also for bed heating purpose.   Some Aquarium chiller for example the Resun 650 has outlets for connection to external heaters such as aquarium heaters that can be immersed in the water tank. Resun's controller will regulate the temperature. Alternatively,  one could use the heater's thermostat to achieve similar result but the temperature control may not be so accurate.

Conclusion

The project has been successfully completed. It is a good project not only to save money but also to share the knowledge to others who can also benefit from it.

Update 1:  Leak Repair  1 April 2014

1.  The bed cooler finally leaked at the silicone joints to the PVC header.   Fortunately,  most leaks were  just minor triggering leaks that wet the bed liner and the header hiding the header pipes.  Repairs was done immediately within 30 minutes by disconnecting the outgoing pipe at the pump to prevent water back flow,  then cut the silicone tube and inserted a new stud.  The new joints had extended length of silicon rubber over the stud and a longer stud were used as shown.

To prevent leak from other joints,  all the joints were built up and covered by epoxy glue,   applied several coats, using a small brush over and around the exterior part of the joints.

2.  Sewing the silicone tubes to a bed cover was a bad idea as the bed cover could not be washed regularly.   The tubes were  now re-attached to 3 pieces of cloth;  2 of which were 10" wide with the header piece about 20",  allowing 10" to wrap the header pipes.   The clothes were then tied round to the bed using strings to fix the position.

3.  To support the header pipe, 2 pieces of  20 mm PVC pipe were cut and shaped to form pipe support stands as follows and placed at both ends of the header pipe to support the header pipe.  The flat part of the pipe support stand went under the bed cushion.

Update 2:   Air Lock in system

When there is air trapped inside the tube or pipe,  the pump will not work and no water will circulate.  To purge the air out,  reverse the input and output of the hose from the bed cooler.  If the pump is correctly sized,  one should see air bubbles purging out.  Repeat the process if necessary

References
How to Service Resun CL650 Aquarium Chillers
Freon vs Peltier Chiller for Reef Keeping
Cut Cooling Bills by 90%
Spot Cooling Cuts Aircond Bills by 50%
Bed Cooler A worthwhile investment

Servicing Resun CL650 Aquarium Chillers

18 November 2012

Introduction

Many reef keepers will have an aquarium chiller to keep the reef tank at temperature around 25C to 27C. Many complained about noisy chiller and insufficient cooling after sometime in operation. Some have problems maintaining proper temperature with chiller turning on and off frequently although it was working properly before. This article aim to introduce some basic about chiller operation and how to service them, taking Resun CL650 as an example.

What is in a Chiller?

Chiller has 3 components; the compressor, the evaporator and the condenser.

It works like a refrigerator. The chiller uses a compressor to compress gaseous freon into liquid state, then the freon is allowed to be cooled in a condenser for heat to be rejected to the atmosphere. After that, it is allowed to be expanded into an evaporator chamber either by means of an expansion valve or capillary tube. In the process of expanding from liquid to gaseous freon in the evaporator,  it absorbs heat from its surrounding. The cycle repeats when the gaseous freon is returned back to the compressor.

What can be wrong with the Chiller?

Like refrigerator, the chiller’s compressor is hermetically sealed.  Freon should never leak unless there is a piping leak which topping up of gas will not help. Most compressors can last more than 5 years. The evaporator has no moving part if they are the capillary type of expansion system as shown in the picture. The electronic controller is usually quite reliable and no servicing is usually required. Therefore, the condenser is often the cause of most chillers’ cooling problem.

What can be wrong with the Condenser?

The condenser has 2 components: the radiator and the cooling fan.
The radiator often gets air clogged with dust and dirt and the cooling fan will need oiling from time to time for efficient operation. Dirty condenser will cause high compressor ratio, thereby increases the amperage of the compressor, causing the motor protection thermal overload to come on and off and hence,  the complaint. This CL650 chiller has almost 40% of the condenser coil area clogged up with dust as shown.

 

How to Service the Resun CL650 ?

CL650 is a ¼ HP chiller capable of cooling 650 litres or 140 gallon reef tank. It has a cooling power of about 650 watts. To service, first make sure the electrical supply is off by unplugging the power supply plug. It is best to service in the toilet area as water flushing may be required.  

1. Removing the cover

Remove the 8 small screws at the bottom of the case,  4 on each side. Also remove the 2 big plastic nuts attached to the water inlet and outlet on the top of the case.

The case will not come off until one has also removed the right side recess handle bar because it is tucked underneath the evaporator box. To remove the recess handle, one must release it by pressing the 2 plastic catch on its sides. It can be difficult to access this catch as it is hiding inside the box.  Some patient will be required.

As the case is removed, make sure the cable connector to the case and the wiring connecting the control box are also removed.

2.  General

Check the compressor and its piping for visible oil leaks.  If there is,  most likely there is a freon leak somewhere.  Servicing the chiller by cleaning up will not help.  The leak must be found and repaired with the freon recharged.

 

3. Check the condenser fan

Check the fan for free rotation using fingers or else remove the fan which is held down by 2 bolts.

To remove the fan blade, first remove the circular spring clip coiled around the fan shaft leaves. If the rust prevents the easy  removal of the fan blade, use a small hammer to carefully knock the centre of the fan blade after having released the “leave” using a small screw driver.

Once the blade is removed, check for free rotation of the motor shaft and oil the bearings first with WD40. If the fan have been making noises during operation, it may be necessary to remove the shaft and oil the bearings and the shaft together with good quality grease such as lithium grease. Removing the shaft will require some patient and care so as not to break the bearing housing which can be quite brittle. Reassembling the motor rotor will require knocking the shaft of the rotor with a screw driver from side to side to centre the rotor for the screws to be tightened down.

When remounting the fan after cleaning the condenser coil, make sure the blade is free to rotate without touching any metal work.

4. Check  and  Clean the Condenser cooling fins

Make sure the fins are cleaned using a tooth brush, carefully brushing the fins in the direction of fins. If the dust is so built-up like it was shown in one of the pictures above for CL650, then spray cleaning chemical to loosen the dirt first. After that,  wait for about 10 minutes and then water flush out the dirt stuck in between the fins. Apply flushing water carefully ensuring that no water will wet the cooling fan motor or compressor motor or any electrical components especially the control board which should have been removed by now for safe keeping. Wrapping the electrical parts with plastic bags or even clothes will help.

If the cooling fan has not been removed and is still in position,  make sure the coil of the fan is properly covered with plastic bag to prevent water from shorting the coil.

5. Reassembling

Reverse the procedure just described above. It may be difficult to put back the control board when the case is in place as one can only access and place the box properly from inside the case using the feeling of hand and fingers.

Relocating the Internal Probe

One can relocate the internal probe by removing the plastic nut that holds down the sensor to the evaporator box on the top. To seal the hole, one can cut a small piece of rubber and use it as a seal before screwing back the plastic nut. Sometimes, the sensor may be stuck underneath the evaporator coil. A screw driver to shift the coil a little to the side will help to free the sensor.

Remember that once the sensor has been removed, the chiller will have no internal sensor to stop the chiller and it can work itself to freeze point if the external pumping system stops working.

Testing

Important Note:  The following test should be done only when you know what you are doing

Plug the chiller to the mains supply.  Connect the water tap to the inlet and the outlet to the drain.  Turn on the tap for moderate water running,  then start the chiller.   If the compressor motor is running, check for its proper working by hand feeling the temperature of the compressor's discharge (tube leaving the compressor and entering the condenser) and the suction tubes (tube entering into the compressor from the evaporator box). One should notice the discharge tube is always much warmer than the suction tube. If there is not much temperature difference, most likely the compressor is not working properly and it is time to repair or retire the chiller compressor.  

If the temperature sensor has been relocated,  make sure the chiller will not run for longer than necessary period to perform the test which should not be more than 15 minutes.    .

Start/Stop Problem

Chillers are usually sized such that they will cycle on 15-20 minutes an hour so that they will run about 6-8 hours a day.  When they start/stop too often,  it may be due to a water flow problem or there may be a faulty temperature sensor.   Improve the water flow by first cleaning the canisters that is used to filter the water.  Some chillers may have cooling fins at the coil to improve heat transfer.  They may trap debris.  In that case,  back flush the chiller (connecting water pump to the outlet of the chiller) may loosen up and flush away the trapped debris and improve the water flow.   Changing existing pump to a  bigger one may help.  Relocating the temperature probe or installing another temperature controller with probe in the  sump or the tank would definitely help. 

Conclusion

The servicing has cleaned out all the dirt stuck onto the condenser coil.  The fan also worked without any knocking or bearing grinding noise. Wattage measurement found that the chiller has worked within the specification of about 490 watts.

References
Selecting Nano Chillers for AquariumHow to Service Resun CL650 Aquarium Chillers
Freon vs Peltier Chiller for Reef Keeping
Cut Cooling Bills by 90%
Spot Cooling Cuts Aircond Bills by 50%

Other Relevant Sites
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