[MrNewton]

I had a call for a server room unit, building manager said the display was showing a trip on a pressure switch, and that they had done power shut done the night before.

So I was thinking the obvious one that the power shut down naturally shut down the pumps, wasn't able to transfer the heat to the water, and tripped out on high pressure.

Open up the unit, and it was actually tripping on L.P. Reset everything, started her up, and tripped again withing 30 seconds. Used my electronic detector, no leaks. Then put some solution on anyways just for piece of mind, no bubbles the rest of the time I was there. Coil was spotless, filters were fine, but I removed them temporarily for testing. Evap fan amp draw was bang on, belt was fine, etc.

So when my gauges were on, it would run fine, normal temps/s.h./s.c./ and delta t. Then it would trip out on low pressure regardless. So I just bypassed the l.p. control and it ran as per manufactures specs without issue.

This lp control is mechanical, it's not a digital one, or using thermistors or anything. SAGINOMIYA is the make of it. Just a standard looking control, with no electrical aspect to it aside from the contacts.

I also tried to adjust the cut in and differential just in case it was out of calibration a bit, but nothing I tried would make a difference.

I have a new lp control on order, so basically what my question is,
Has anyone ever seen an issue like this after a power shut down? I don't really get how a shut down could affect a mechanical control like that. So is there something obvious I might be missing? I'm thinking it's just a coincidence with the shut down, but I would rather have a second opinion.

It's an ecoslaire (by dectron)
Model: smfa030gz456fifsciklot



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[Red Man]

Sounds like a coincidence to me

 

[lytning]

What is the temperature where the condenser is? BTW there is no coincidence.

 

[MrNewton]

It was 72-73F.
It's just a little coaxial condenser in the bottom compressor cabinet of the unit that runs on a water loop

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[pecmsg]

SH , SC fine but tripping on LP. I don't think so.
FWIW never bypass a safety and leave it.

 

[MrNewton]

I didn't leave it bypassed. Sh and SC were fine like I said. Those controls can take a flop. All I was asking was if anyone has seen a power shut down cause one to go bad

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[mixsit]

Cold weather/data units - often = a time delay function of a few minutes across the LPCO to let a system pressures get up to speed.
A thought to toss in.

 

[MrNewton]

Ya there's a delay with those guys. That's why it would run for about 30 secs before shutting down. Contacts wouldn't close no matter what the pressure was.

Since it probably was shut down mid cycle, it wouldn't have been able to pump down, and the switch would've been closed on start up. I don't really think that would have damaged the control, but you never know I guess.

This is assuming the switch actually conked out after the power shut down. 2 other units in the room, there's always the possibility that nobody saw it until the shut down since the other 2 units were still maintaining space setpoint.

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[MrNewton]

Sorry probably closer to a minute actually, I didn't time it to the second, but I would say a minute (ish)

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[MrNewton]

I also set the cut in as low is I could get it, and they still wouldn't close. 100% confident in calling the controller. I would just like to be able to attribute it to a cause if possible.

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