Iffy Stat?

[monkey spanners]

Small chill coldroom, +2C, has a few times recently chilled the room down to -6C ish.

It worked fine when i was there.... :confused:

Its an Eliwell id961 or similar model number, basic stat with only a relay for the comp. Set for +2C, switches on at +4C and off as the display changes from 2 to 1.

Theres no solenoid to leak by.

So, I'm wondering if anyone has seen one of these play up then work ok again, i would think if the relay was sticking it would just stay stuck...

Customer then turns it off for it to defrost, then works ok for a while...

I have asked the customer to keep an eye on it and see if the cooling dot is lit up next time it does it or not, if so it must be a software problem, if not a relay problem.

The only other thing i wondered was if they had put cooked food on the shelf next to the temp sensor and given it a false temp reading, but this doesn't explain the unit running if indeed it still was and they hadn't just asumed...

Anyone seen anything similar with these?

Cheers Jon :)

[Grizzly]

I don't know if it is relevant Jon.
Have you had chance to prove the actual probe.
I have known them to go further out of range the lower they go.
Just a thought.
Grizzly

[mikeref]

Hi Jon, had that happen several times with different make and models. Tends to work fine then for some reason out of nowhere it locks in and freezes everything. Now when i come across one i change it.. mike.

[Chunk]

Hi Jon

Had a id974 do the same thing last weekend,another engineer went in and checked it and it was working fine,two days later i get called in because the cabinet is freezing again and found compressor relay stuck on.I punched the controller and it switched it off.

It happens:confused:

[monkey spanners]

Thanks for the replies :)

Turns out it was the compressor relay sticking intermittently, customer kept an eye on it and it did it again this morning, so new stat and probe fitted!

It could do with a bigger relay for the compressor but there wasn't room in the box for a contactor which is all i have on the van, must get some small relays for van stock.

Cheers Jon :)

[james10]

Hi Jon

Had a id974 do the same thing last weekend,another engineer went in and checked it and it was working fine,two days later i get called in because the cabinet is freezing again and found compressor relay stuck on.I punched the controller and it switched it off.

It happens:confused:
That'll do it :D

[lowcool]

fit a dixell,widen the differential,increase the anti cycling time and be sure to have at least three minutes delay at start up,even with a slave relay fitted of which im sure you would have found by now ms.

[Latte]

The Biggest cause of Eliwell failures is the Transformer on the 12v units. The tolerance is 10% either way giving a maximum allowed voltage of 13.2v

Over that the controller still looks like its working but the relays can fail completly or intermittantly. personally ive found they are normally ok up to about 13.8 but anything over thats it. Check the voltage on the output side of the transformer between the two terminals, NOT between the live and an earth

[the chiller]

stick a ranco stat and timeclock on it and that will be that