Heating question

I have a Pro Com blue flame gas heater (propane) in my cattlepanel hoop house. Last year I quickly learned that I had to find a way to vent it and attached a dryer type vent hose to it and out of the GH. This year I have the same setup but I placed the vent opening higher than before. Last year snow covered the opening when it was lower down snuffing out the heater.
I'm having a problem during the day with the heater shutting itself off. I thought it was suppose to power down to the pilot light when the temp it was set at was reached but instead it shuts off completely and the gh cools off. This is happening during the day. At night it isn't happening. Any ideas what's going on? Makes it awkward to leave the gh unattended during the day (and we're getting very cold now).

Thanks!
MollyD

Molly, is there any way you could be getting backdrafts down the vent tubing which is blowing out the pilot light?

Did the heater work properly last year?

Is there a thermocouple on the heater? Are you sure that it drops down to pilot light only?

SB

Hi,

How do I check for backdrafts? Last year it snuffed out quite often till I vented it and after that only when the vent was blocked by snow. That's why I raised it this year to about 40". It now sits higher than the heater which is about 12" off the floor.
I don't know what a thermocouple is so I can't answer that. The info with the heater said it was suppose to turn itself down when it hit the temperature you had set it for and then run again when it cooled off.

Molly

If the thermocouple is clogged, the flame will be burning unevenly and more red. If it is clean, then the flame will be a blue flame. I think if the thermocouple is not working, then the pilot light will not stay lit at all. The thermocouple is where you light the pilot light-where the gas comes out and you light it. Is that right, SB?

You can check for backdrafts by feeling if there is any cold air coming in around the heater that would blow the pilot light out. I had a leak under the wood base of the grhouse in the corner where the heater was once, and the wind was actually coming in and blowing the light out, and it wasn't even that big an opening where the air came in. SB is thinking that the wind is coming down thru your vent and blowing the pilot light out that way. What is the setup where the vent comes out of the grhouse? Does it seem possible that the wind could come thru there, or do you have a hood over the vent opening?

I would call the propane company that you get your propane from and see if they can send someone out there to fix it. I have always wanted to learn how to fix them myself, but they really don't break that often. Whenever they do come out though, I always hang out with them and watch what they do. Unfortunately, I don't think that I will be making my living fixing propane heaters anytime soon.....

tigerlily the flame is blue, not red. The vent has a hood. At night the heater runs fine, no trouble. It's only snuffing out during the day when things warm up. Around 85 degrees it shuts off, not just powers down to pilot the way it should.
We haul our tanks in to fill them up so the propane company won't be of any help to us.

Thanks!
MollyD

Call the manufacturer and order a new thermocoupler. Its the probe thing that sits in the flame of the pilot light. needs to sense a heat differntial before allowing gas flow. easy to replace, and more than likely the cause.

Keith,

Molly,
Are you sure it has a pilot light? Is there a small blue flame that burns all the time? Or is it an electronic ignition type where a small metal plate gets red hot and ignites the big burner?

I don't believe the thermocouple has anything to do with the quality of the flame. (blue, yellowish, sooty, etc.) The thermocouple is the safety device that prevents the main gas valve from opening if there is no flame there to ignite it. (Too much raw gas can make short work of a GH, as in BOOM! )

If you have a pilot light, one that you manually light while depressing the gas valve down, then you do not have electronic ignition.

Many newer heaters/furnaces are using all electronic ignition. This type is a bit more efficient as there is no gas consumed to keep the pilot light lit. When the thermostat is not satisfied it causes a metal plate to glow red hot, and when it is hot enough to ignite the propane, the main gas valve is allowed to open and the main burner is lit.

However, none of this seems to have anything to do with why it will run at night and not in the daytime. We normally have more wind during the day than at night, so if you are having a back draft problem as SB suggested, it would make sense that it would be worse during the windy day vs. the calm night. Typically for a heater to draft properly the top of the stove pipe should be above the highest point of the roof. Ideally you would want to have an outside source of combustion air, although I don't think that is critical in a wide open space like a GH.

Some newer units also have an oxygen sensor that will shut a unit down if it senses that too much oxygen has been depleted from the air. But I don't see why it would change from day to night.

Good luck with the heater, keep us posted when you arrive at the solution.

Nautical

"Some newer units also have an oxygen sensor that will shut a unit down if it senses that too much oxygen has been depleted from the air. But I don't see why it would change from day to night"

From Nautical

I read that these heaters do indeed have an O2 sensor. I would think that there would be more O2 durning the day due to plant photosynthesis. sound like a good mystery!

"If you have a pilot light, one that you manually light while depressing the gas valve down, then you do not have electronic ignition."

This is the kind I have. There is no electronic ignition on this unit. I can clearly see the blue pilot light until it snuffs out.
It does have an O2 sensor but this shouldn't differ during the day. As fourks said it should be fine during the day and have a problem at night instead if oxygen were the problem.

Fourks I'll contact the manufacturer and see what they say.

Thanks!
MollyD

I have a gut feeling that the problem lies in the venting of the unit. I suspect that somehow, by changing the location of the vent, you have reduced the ventilation and the oxygen sensor is shutting it off. Did you lengthen the vent tubing when you raised it? Is is exposed to sunlight now, when it was shaded before? Did you restrict the diameter?

Or try this theory...by raising up the vent opening, you created so much of a daytime updraft of warm GH air going out through the vent tubing that no outside air is coming in.

Just some thoughts. Check the draft with a match or lighter (safely). See if it is any different daytime compared to night. Try moving/shortening/lowering the vent tubing.

Let us know the answer when you figure it out!

SB

I agree with SB-esp if you have the ventless Blue Com model? That was the only model that I saw, was the ventless one. If so-then I am wondering how you attached the vent? The problem may lay there.

I'll check SB. I went looking for Pro Com's web site and what I found wasn't encouraging. Email form but no phone #. Sent a message. I sent them an email but I'm not very hopeful they'll answer.

Tigerlily on GW there were instructions on how to vent a ventless heater. You attach a duct boot at the back of the unit and tape the front off so it draws from the duct boot only. Attached to the boot is a hose (the kind used for venting dryers which goes out of the GH to it's hooded exit. Worked fine last year.

SB I only lifted it a foot or so from where it was before. Sunlight is the same as ever. Didn't make it any longer since I hadn't cut it down when I intalled it last year. No change in diameter or any constrictions.

Sure wish I had bought a vented heater in the first place! Never realized how little oxygen would be in there.

MollyD