Hacking the fridge

Yes, wasn't planning on going into this repair business, until he hands me the bill.

Ordered this Wifi switch and perhaps a 50A relay and upgrading the fridge soon.

On Sunday, October 1, 2017 at 5:28:36 PM UTC-4, snipped-for-privacy@gmail.com wrote:

wrote:

ote:

com wrote:

m wrote:

ail.com wrote:

l.com wrote:

o big to replace.

to defrost it everyday. Right now, we are just flipping the circuit breake r daily. So, i need to wire up a relay driven by the rPi.

mponents to eyeball and test. First check to see that evaporator fan is blo wing when compressor comes on. Refrigerator won't work worth a damn if blow er is broken. Turn the thermostat to off. Remove panel at rear of freezer compartment to get at evaporator. Look for heater element, usually at botto m of coil, unplug connectors and do continuity check, ohmage should be cons istent with 100-300 watts, if that checks okay, look for Klixon type bimeta l clipped to coil in series with heater wiring, check that it is closed, if that checks okay, look for defrost timer ( it will exterior to the refrige rated compartment most of the time but has been known to be connected into icemaker operation), there will be a keyed knob on front, spin it until it clicks into defrost detent, turn thermostat on and eyeball the heater comin g on, getting warm, usually for only 5-10 minutes, then klixon cuts the cir cuit out, watch the water drain into collection pan at bottom of coil, see that it drains, pull veg tray at bottom of fresh food compartment and loca te drain hole, check that water is draining, clear any clogged drains with long stiff wire if necessary (usually clogged with spilled food). Sometimes there is small heater under collection pan in freezer or around its drain tube, if you have a bunch of ice in pan it means heater is open, find this heater and check it, no drainage means no defrost and water just gets reci rculated back to coil quickly, wait out defrost timer for 20-30 minutes to see that it cycles compressor back on, and defrost fan starts blowing. One or more of those stages of defrost operation will fail and indicate the fai led part.

on a separate circuit breaker, with or without compressor running. Water i s dripping out of the evaporator, not blocked inside. I am wondering if th ere is a leak in the refrigerant pipe.

have completely different defrost techniques.

should not be freezing.

rged $450 for a charge. Did they pull vacuum on it and check that it held b efore they recharged? You should have a big defrost timer box located near the compressor. To defrost they usually just cut out the compressor and all ow the evaporator fan to draw the above freezing air through the coil until it melts. They detect melted coil with a pressure switch in the refrigeran t line that switches out when the pressure corresponds to a coil temp of so mething 38-40oF, and then it's followed by a 10-15 minute idle time to allo w the water to drain away, then it switches the cooling cycle back in. Sinc e they keep the coil around 32oF in operation, it is possible for a freeze up if the defrost cycle stops working. You're looking for something that lo oks like this: in the rectanglualr gray boxes to left

, there will be a diagram inside the cover showing you how it is wired in. Or it could be a leak, usually the ev aporator coil, which is usually aluminum, in which case you change out the whole evaporator coil, not worth trying to patch it with epoxy.

ressure sensor next to the compressor, but no timer.

That switch could be defective. You need to hook a refrigerant pressure gau ge into the low side to check. Or the thing is stuck closed permanently and never turns the compressor off. See "Basic Operation of Pressure Controlle d Medium Temperature Walk-in Coolers" at

. I doubt you have a pumpdown unit.

On Sunday, October 1, 2017 at 3:51:47 PM UTC-7, snipped-for-privacy@gmail.com wr ote:

e:

m wrote:

wrote:

l.com wrote:

com wrote:

gmail.com wrote:

ail.com wrote:

too big to replace.

d to defrost it everyday. Right now, we are just flipping the circuit brea ker daily. So, i need to wire up a relay driven by the rPi.

components to eyeball and test. First check to see that evaporator fan is b lowing when compressor comes on. Refrigerator won't work worth a damn if bl ower is broken. Turn the thermostat to off. Remove panel at rear of freezer compartment to get at evaporator. Look for heater element, usually at bot tom of coil, unplug connectors and do continuity check, ohmage should be co nsistent with 100-300 watts, if that checks okay, look for Klixon type bime tal clipped to coil in series with heater wiring, check that it is closed, if that checks okay, look for defrost timer ( it will exterior to the refri gerated compartment most of the time but has been known to be connected int o icemaker operation), there will be a keyed knob on front, spin it until i t clicks into defrost detent, turn thermostat on and eyeball the heater com ing on, getting warm, usually for only 5-10 minutes, then klixon cuts the c ircuit out, watch the water drain into collection pan at bottom of coil, s ee that it drains, pull veg tray at bottom of fresh food compartment and lo cate drain hole, check that water is draining, clear any clogged drains wit h long stiff wire if necessary (usually clogged with spilled food). Sometim es there is small heater under collection pan in freezer or around its drai n tube, if you have a bunch of ice in pan it means heater is open, find th is heater and check it, no drainage means no defrost and water just gets re circulated back to coil quickly, wait out defrost timer for 20-30 minutes t o see that it cycles compressor back on, and defrost fan starts blowing. On e or more of those stages of defrost operation will fail and indicate the f ailed part.

, on a separate circuit breaker, with or without compressor running. Water is dripping out of the evaporator, not blocked inside. I am wondering if there is a leak in the refrigerant pipe.

y have completely different defrost techniques.

it should not be freezing.

harged $450 for a charge. Did they pull vacuum on it and check that it held before they recharged? You should have a big defrost timer box located nea r the compressor. To defrost they usually just cut out the compressor and a llow the evaporator fan to draw the above freezing air through the coil unt il it melts. They detect melted coil with a pressure switch in the refriger ant line that switches out when the pressure corresponds to a coil temp of something 38-40oF, and then it's followed by a 10-15 minute idle time to al low the water to drain away, then it switches the cooling cycle back in. Si nce they keep the coil around 32oF in operation, it is possible for a freez e up if the defrost cycle stops working. You're looking for something that looks like this: in the rectanglualr gray boxes to left

, there will be a diagram inside th e cover showing you how it is wired in. Or it could be a leak, usually the evaporator coil, which is usually aluminum, in which case you change out th e whole evaporator coil, not worth trying to patch it with epoxy.

pressure sensor next to the compressor, but no timer.

auge into the low side to check. Or the thing is stuck closed permanently a nd never turns the compressor off. See "Basic Operation of Pressure Control led Medium Temperature Walk-in Coolers" at

. I doubt you have a pumpdown unit.

Yes, sound very much like what we have. Will check the switch. Thanks aga in.

Did you ask? They usually charge by the hour. Freon is not cheap. If you have a leak and don't have it fixed it will be another $450 before long.

--

Rick C 

Viewed the eclipse at Wintercrest Farms, 
on the centerline of totality since 1998

to replace.

rost it everyday. Right now, we are just flipping the circuit breaker dail y. So, i need to wire up a relay driven by the rPi.

eryday solve it for now.

ow much he would charge to fix the problem.

ou

It actually seem more like a control problem. If we don't defrost, ice bui ld-up in evaporator and temperature gets too high. After defrosting, tempe rature gets too low and close to freezing. According to the link Fred gave, it could be pressure controlled switching. However, we can also add in te mperature sensor and compressor switch.

This SSR can be switched from the rPi, along with the USB thermometer.

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g to replace.

efrost it everyday. Right now, we are just flipping the circuit breaker da ily. So, i need to wire up a relay driven by the rPi.

everyday solve it for now.

how much he would charge to fix the problem.

you

.

uild-up in evaporator and temperature gets too high. After defrosting, tem perature gets too low and close to freezing. According to the link Fred gav e, it could be pressure controlled switching. However, we can also add in temperature sensor and compressor switch.

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I am about to submit my repair estimate to the owners (relatives). I think they will have a sticker shock; so, give them enough time to think about i t.

A defective pressure regulator is causing the compressor to run all the tim e, icing up the pipe and evaporator coil, raising temperature to over 10 de grees. The cheapest hack is a Raspberry Pi, with temperature probe and sol id state relay, without breaking the refrigant seal. Otherwise, $500 just to recharge the refrigant.

1. Rpi
2. 0 Rpi + PR
3. 00 Rpi + PR + CR
4. 00 Rpi + PR + CR + CC
5. 00 Rpi + PR + CR + CC + EC
6. 000 New fridge

Rpi: Raspberry Pi controller PR: Pressure Regulator CR: Compressor CC: Condensor Coil EC: Evapulator Coil

Pick a number.

e:

big to replace.

defrost it everyday. Right now, we are just flipping the circuit breaker daily. So, i need to wire up a relay driven by the rPi.

r everyday solve it for now.

er how much he would charge to fix the problem.

If you

ng.

build-up in evaporator and temperature gets too high. After defrosting, t emperature gets too low and close to freezing. According to the link Fred g ave, it could be pressure controlled switching. However, we can also add i n temperature sensor and compressor switch.

id=p2057872.m2749.l2649

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nk they will have a sticker shock; so, give them enough time to think about it.

ime, icing up the pipe and evaporator coil, raising temperature to over 10 degrees. The cheapest hack is a Raspberry Pi, with temperature probe and s olid state relay, without breaking the refrigant seal. Otherwise, $500 jus t to recharge the refrigant.

Replace the pressure switch.

Could someone explain how does low refrigerant cause evaporator icing?

--
Boris

Den mandag den 2. oktober 2017 kl. 13.43.22 UTC+2 skrev Boris Mohar:

if it makes the system run at a lower pressure the refrigerant evaporates at a lower temperature

Have you checked the defrost heater. That was the problem when mine, started icing up. Ordered a new defrost heater from Ebay. Easy install. That was 2013 or 2014. Mikek

No defrost timer or heater. Regulated by mechanical pressure switch, which is stuck on ALL THE TIME. Will add in digital control and solid state relay, running 30 min on and 30 min off duty cycle. Defrost during off cycle.

What brand and model is this? Mikek

if there is less refrigerant, it all evaporates before getting to the end of the evaporator.

Therefore there is less TOTAL cooling , but the part that does still contain refrigerant will get to to a lower temperature.

So fewer total BTUs are being moved, but over a smaller area lower temperature are obtained.

So PART of the evaporator can freeze when the refrigerant is low.

m

Do you know WHY it is icing? Could the defrost heater be open? How about a failed defrost timer? Or, a siezed-up fan motor?

These are pretty common failures, and hopefully the parts are still available.

Jon

Probably custom build. Russell evaporator. Tecumseh 2.5KW 1HP compressor. Likely bigger than your kitchen.

it

So,

t a

Defective pressure regulator. Running 2.5KW compressor 24/7. But fixing i t would empty out the refrigerant and another $450 to recharge. The repair guy should have replaced the pressure regulator before recharging refriger ant. Failed to do so, i don't trust him to come again.

BTW, anyone got info on DIY refrigerant recharge kit?

OK, that is different! It likely uses hot gas defrost. there will be a timer, relay and a valve that runs high-side gas direct from the compressor through the evaporator coil for a couple minutes each cycle. It may have to defrost every couple hours. You will likely hear it doing the defrost cycle if it is working. It will make a big click and a whoosh noise when the cycle starts.

If the tech has had to add refrigerant twice already (prior message), then there probably IS a leak. But, he may not have checked that the defrost system is working.

The reason low refrigerant will cause freezing is the evaporator coil is a long tube, and the system is designed to fill most of the tube with boiling liquid. When the refrigerant charge is low, the evaporator is only partly filled with liquid, concentrating the cooling effect on one part of the coil, which freezes. As that area ices up, the iced area moves down the tube. When the charge is low, all the pressures drop, the refrigerant boils at a lower temperature, and the thermostat keeps the compressor running all the time to maintain temperature. All this promotes freezing.

Jon

You might have a bad (or misadjusted) thermostat. If the box DOESN'T have a thermostat, it should be trivial to add one.

Jon

The problem with replacing the pressure switch is it requires opening the refrigerant system! Then, you will have to recharge the system.

A simple thermostat mounted inside the box will do the same job, but without having to open the refrigerant system.

Jon