Fridge behaving weirdly

[duncan99210]

Or at least not like it used to do...

First off, it's a pretty standard Danfoss compressor hooked up to a plate in the fridge compartment. When switched on, it used to happily hum away to itself for a few minutes, then shut down for a period before starting up again. Now, it still works fine for a time then gets into a pattern of starting up for a few seconds and then shutting down. Keeps doing that for a period (which can vary from five minutes to an hour or more) before suddenly deciding to start working again as it should.

The set up is 18 years old and I spent money on it three years back having a man refurbish it and fit a new plate, since when it has run fine until now. I'm reluctant to spend more money on a man coming out to fettle it and then have it die on me. So, before I have it put down and replace it, anyone any ideas on what might have gone wrong with it and is there a do it yourself fix? Oh, and I've cleaned the contacts where the electrical supply arrives at the compressor and the voltage reading as the compressor starts (or tries to) is well in excess of 12.7v.

 

[Caladh]

The hunting you describe is normally down to either lack of volts - down to 11.8v I think, poor wiring (connect straight to the house battery via breaker/fuse, or - low gas. This US web site is especially helpful for troubleshooting boat fridges and how they actually work ! No relation.
http://www.kollmann-marine.com/

 

[NormanS]

We have a similar fridge arrangement. In the winter we have shore power, and if the battery charger is on, the fridge doesn't like it, and cycles on and off continually. However, we also have a domestic 240v fridge, which we cannot use in the summer. Our solution is to use the domestic one in the winter, and the 12v compressor one in the summer. The domestic one makes a handy galley locker in the summer.

 

[macd]

Caladh's post (#2) is correct in summarizing the common causes of your"weird" fridge behaviour. If practicable, the easiest test is to disconnect the existing wiring and jury-rig a suitable feed direct from battery bank to fridge. If the weirdness goes, you've nailed it.

Vyv Cox gives a useful guide to diagnose gassing issues, here: http://coxeng.co.uk/heating-and-refrigeration/recharging-marine-refrigeration-systems/

(You might want to bookmark that site: it replaces Vyv's old Sharepoint site which no longer works.)

 

[superheat6k]

Caladh's post (#2) is correct in summarizing the common causes of your"weird" fridge behaviour. If practicable, the easiest test is to disconnect the existing wiring and jury-rig a suitable feed direct from battery bank to fridge. If the weirdness goes, you've nailed it.

Vyv Cox gives a useful guide to diagnose gassing issues, here: http://coxeng.co.uk/heating-and-refrigeration/recharging-marine-refrigeration-systems/

(You might want to bookmark that site: it replaces Vyv's old Sharepoint site which no longer works.)

This does sound like a voltage issue, but could be an old compressor about to give up the ghost.

Whereas Vyv's instructions are perfectly viable, the advice to adjust overcharge by venting off any excess is illegal anywhere in the EU and certainly in the UK. Removal or charging of refrigerant requires an F Gas registered engineer, properly equipped with the correct tools, none of which are either cheap or likely to be found in an average DIY workshop.

R134a is also itself now being phased down and a crisis is supply has already started in the UK following the current phase down now reaching a 46% reduction from the quantity of HFC refrigerants in use in 2015. This has pushed the price to unbelievable levels, with a 6 fold cost price increase in one year.

 

[Heckler]

This does sound like a voltage issue, but could be an old compressor about to give up the ghost.

Whereas Vyv's instructions are perfectly viable, the advice to adjust overcharge by venting off any excess is illegal anywhere in the EU and certainly in the UK. Removal or charging of refrigerant requires an F Gas registered engineer, properly equipped with the correct tools, none of which are either cheap or likely to be found in an average DIY workshop.

R134a is also itself now being phased down and a crisis is supply has already started in the UK following the current phase down now reaching a 46% reduction from the quantity of HFC refrigerants in use in 2015. This has pushed the price to unbelievable levels, with a 6 fold cost price increase in one year.

As with most of the regs, pretty stupid. What happens to the dozy housewife who "defrosts" the fridge with a sharp knife and punctures the evaporator? Does she get fined? In practice, venting a slight overcharge is neither here nor there in the grand scheme of things! By the way, nobody has ever given me a good explanation as to how heavier than air freon gets to the ozone layer to destroy it!

 

[macd]

By the way, nobody has ever given me a good explanation as to how heavier than air freon gets to the ozone layer to destroy it!

Presumably you don't believe in gliders, either? Or even the water that signposts their courses?

 

[superheat6k]

As with most of the regs, pretty stupid. What happens to the dozy housewife who "defrosts" the fridge with a sharp knife and punctures the evaporator? Does she get fined? In practice, venting a slight overcharge is neither here nor there in the grand scheme of things! By the way, nobody has ever given me a good explanation as to how heavier than air freon gets to the ozone layer to destroy it!

An accidental release is not an offence, a deliberate release is. I didn't invent these rules, but I do by the nature of my business have to both be fully acquainted with and follow them.

Personally I also wonder about how heavier than air freon achieves this, plus only at the South Pole region. Interestingly the cynic in me observes the fact the the discovery of the ozone hole, followed by the phase out of CFCs has more recently been followed by the Governments of the World claiming the first Global environmental win, as the hole has apparently become smaller. Or it could just be a natural phenomenon after all the hole has only been observed for a minute period in Earth development timescales.

BTW HFCs such as R134a do not destroy ozone, but do have a very high global warming (greenhouse gas) potential, which is why the Politicians have decided they must go - shame they haven't given us anything else sensible (as in non flammable) to replace them. Expect more refrigeration system related fires in the future. The domestic fridge that started the Grenfell fire was charged with a HC hydro carbon refrigerant, e.g iso-butane or propane. This means when said housewife punctures the evaporator plate and then closes the door the spark from the light switching off could result in the fridge exploding.