Frozen evaporator coil with no feed to it?

[chilliwilly]

Went to look at a walkin freezer yesterday, found evaporator frozen up and e2 alarm (elliwel), but didn't have a probe on the van.

Went back today to fit a probe only to find that the temperature wasn't pulling down. After eventually getting a roof permit from the site, I found that the sol valve coil was burnt out.

Removed it and shoved a magnet over it and it started up straight awsy. Had to reconfigure wiring inside control panel so controller drove compressor contactor, to prevent compressor over running after temp was reached and during defrost.

Although there was 25 foot of line set, I was worried about the XV balancing and allowing the evaporator to flood and slug the compressor, I took an educated guess and ran it anyway. And the high side held against it and now running sweet again.

Hopefully back next week to fit sol valve, the only thing I didn't understand is the evaporator was iced up giving the e2 alarm, but the sol valve coil was burnt out. So how it was fed is a puzzle?

[chemi-cool]

The coil might have burnt just before you came.
I like your risky solusion,

[passandscore]

The burnt solenoid coil may have nothing to do with the iced up evaporator and have something to do with the solenoid valve itself. If the solenoid was leaking by it would cause the evaporator to not defrost properly and ice the coil up. You may have arrived after the coil failed and simply observed a frozen coil thinking that the 2 were related.

Just a thought.

I guess you will know next week when you arrive to replace the solenoid valve. Iced up coil may equal a leaking liquid line solenoid valve.

[chemi-cool]

The burnt solenoid coil may have nothing to do with the iced up evaporator and have something to do with the solenoid valve itself. If the solenoid was leaking by it would cause the evaporator to not defrost properly and ice the coil up. You may have arrived after the coil failed and simply observed a frozen coil thinking that the 2 were related.

Just a thought.

I guess you will know next week when you arrive to replace the solenoid valve. Iced up coil may equal a leaking liquid line solenoid valve.

Leaking SV will be frozen and the liquid line up to the TXV.

[monkey spanners]

Yeah i'd change the whole valve just in case, have had water solenoids where the plunger sticks half way and it will burn the coil out.

Customers think they are paying for you to save them money but really they are paying for it not to break down again.

[install monkey]

e2 will only be displayed if evap sensor goes out of range- or broken / open connection- maybe excessive ice build up caused a terminal block to short??
if eleccy defrost u need to check all elements work,defrost duration,termination temp, fan delay setting, all fans operate, door sealing correctly.
as for the solonoid valve- replace the coil only if u prove its seating correctly and not passing.

[chilliwilly]

That's what I thought at first, but when the sol valve shuts off the pressure switch would open on the low side due to the suction of the compressor that in turn would shut the compressor down.

When I found the coil was burnt out, there wasn't so much as a trickle through the site glass, and the compressor was off. As soon as the magnet was on the sol valve that's when it opened and showed through the site glass. And when removed the high side starved and the compressor shut down, again with no sign of a trickle.

But like you say I will find out next week when I fit the new coil. Maybe the relay contact on the controller is starting to weld up?

[install monkey]

typically after 5yrs replace em- as usually rated for 30,000 switches, as ur controller is only normally powering a sol coil theres no load on the relay.

[monkey spanners]

Had one the other day on a fosters that was programmed for hot gas when it was electric defrost, worth checking as it would keep the coil energised during defrost.

[flyinkiwi]

Although there was 25 foot of line set, I was worried about the XV balancing and allowing the evaporator to flood and slug the compressor, I took an educated guess and ran it anyway. And the high side held against it and now running sweet again.

Oops! I read that as "took an educated guess and ran away"!

What brand of valve was the original? I have seen certain brands do silly thing when they fail.

Is your second probe failure interfering with correct defrost operation, causing evap to retain ice?

[nike123]

PTC and NTC probes are not some resistors as we may think. They are semiconductors. When probe is faulty, in some range it can show good values (voltage, resistance, temperature on display) and in some range can have way off values. Therefore, if it is showed E2 on display, than I would change it in any case, or I would check R/T or V/T ratio trough the entire operating range of that probe.
I strongly doubt that actual temperatures in that place where anywhere near the operating limits of that probe to cause it to show E2 (out of range) error on display. That would be below -50°C or above 110°C (or simmilar extremes).

[chilliwilly]

Yes I agree with install monkey on that one, although they're my first choice of controller, the system is only around 16 months old.

And also I have found similar with what monkey spanners says. Its a 974 controller but has electric defrost for some reason. Maybe to do with the length of the line set? Infact that's why I had to reconfigure the wiring so the controller drove the compressor contactor directly, as the compressor was still running when manual defrost was activated.

I tested the probe with a blow lamp and my meter against my hand held probe, and there was a substantial difference,

I wouldn't have run the system if there would a have been more than a strong probabillity of liquid slugging the compressor. I was more concerned that the XV might have had a bleed equaliser, but never the less the line set length would have offered some accumulation, even if the XV had been fully open. No more risky than topping off an initial charge on the low side in the liquid phase. Hence my educated guess regards trusting the XV to hold back the high side. After all how many air con systems have a sol valve on the high side, or some of the cheaper build fridge systems?

[chilliwilly]

Well finally went back to it today, the system had been keeping temp with the sleeve magnet over the sol valve plunger, but suction line was thick with ice even over the armaflex.

Replaced sol valve coil, reinstated control wiring and monitored system for a couple of hours, ice finally cleared off armaflex as you'd expect. Unable to tell if evap coil had iced up any more than normal, but judging from the suction side, it probably did.

[passandscore]

I'd recommend replacing the armaflex. Saturated armaflex serves no purpose.

[chilliwilly]

It was just over the armaflex, probably due to the evaporator being partially flooded causing the low side to be lower pressure, and the time of year. If I go back to service it I'll change the section that goes into the condenser unit if it seems perished.