Interesting issue

[Answer-Man]

I had one very similar several years ago, for me it ended up being a dirty connection between the thermocouple end where it screws into the gas valve. Dirty meaning it had some corosion in the gas valve connection. Never had a problem after cleaning the connection. I used a pipe cleaner to get in side, made sure it was good and snug into the gas valve. Tstat area stayed warmer than heater location at night. Heater near an outside wall. T stat was on a pole in the middle of the room. The only thing I could think of why it worked during the day vs going out at night is the ambient area near the heater got cooler at night, Figure the thermocouple contracted a little more at night and it lost a good solid connection.

[theoldscroll]

What is the manifold gas press? What is the MV reading? Percussion problem distinguishing the pilot flame?

Was the gas valve replaced with the exact OEM replacement? Slow open type?

[gonefsihing]

I d be looking the exchanger over very well. When they heat up the cracks open and blow out the pilot. I have seen that before a few times

[Arroz con pollo]

I suggest a Y86 conversion kit if possible and be done with it if you factored out all other draft, or HX issues.

[buford]

Verify correct inlet pressure, on a cold nigh,t when the most heaters are on, at the trouble unit.

[FreeThrowGuy]

Check your manifold gas pressure on both units please

[FreeThrowGuy]

Verify correct inlet pressure, on a cold nigh,t when the most heaters are on, at the trouble unit.

Agreed. While your manometer is hooked up to the inlet, turn on other gas appliances and see if it maintains pressure. Who knows maybe they did a bad load calc on their gas line?

[DavidDeBord]

No input guys? Pilot went out again last night.

It's odd that it's only happening at night, especially " (5 times a week)".

How is this unit Vented? From what you've supplied, I'm assuming that this is a"Standing Pilot", & not Spark, or HSI.

Have you checked the thermocouple, as far as position, being burnt, properly mounted to the Gas Valve etc.?

How is the Flue Terminated? What about the Flue Pipe, ... any Birds nests, or Illegal Immigrants hiding out in it?

[DavidDeBord]

I’ll admit I haven’t worked on a green houses but have found with propane that you will usually find out about regulator issuses or moisture contamination once it drops below freezing at night but will work and test fine when you show up the next day( when it’s warmed up). You may have just enough pressure to run one unit at night or maybe that unit is getting moisture in it at night and freezing, snuffing the pilot. Could be a bunch of things but I like Hvac Marc’s idea best. Eliminates all the problems that go with pilot lights( including possibly your issues) and at whatever your customer pays for propane will pay for itself decently quickly. Payback is even quicker if it’s a business(florist?) and you count lost product, which I would. If nothing else you may have to show up and test the system when it’s in the 20’s and see what’s diifrent at that temp

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I was going to say "Second Stage Regulator", but Makeitcold, kinda beat me to it.

I've seen Second Stage Regulators Lock Up, &/or run out of wack, due to moisture that became lodged in them. I've also seen Second Stage Regulators Fail, because they were Old, & just didn't want to work very well when it got below freezing.

[mikel7829]

What all runs of propane on this property thats shared with the tank?

[Pelican3]

We have had similar problems like this for the last couple of years with Rego brand second stage regs. With no load, they creep up to 20” and higher, then when the equipment fires, they drop down below 5”, and the equipment locks out. I’m not saying this is what is going on here, but just putting it out there. We have changed many Rego regs over the last 18 months.


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