Cold weather furnace problems

Wrknrvr · February 8, 2020

I am curious if anyone in the Phoenix area has had any furnace problems that go away when it warms up in the am.

So what I am looking for is that your furnace works fine in the evening. But when you get up it is not able to produce heat. You turn the thermostat off and back on and it works when it is warming up outside.

This winter has had some below freezing nights around the Phoenix area this winter. Especially north west of Phoenix.

Just Curious, Vern

Darryl&Rita · February 8, 2020

Dirty contacts in the thermostat?

Kirk W · February 8, 2020

1 hour ago, Wrknrvr said:

So what I am looking for is that your furnace works fine in the evening. But when you get up it is not able to produce heat. You turn the thermostat off and back on and it works when it is warming up outside.

Is this your furnace, ot a customer's? That sounds like the furnace has failed to ignite at some point in the night and it then went into lock-out as more recent furnaces do where the older ones will just blow cold air forever. If the propane bottle being used is getting near empty that could be part of the problem as the vaporization rate slows when the tank is low and temperatures drop. It could also be caused by the 12V system sagging in cold temperatures as can happen when not connected to shore power.

Sehc · February 8, 2020

I have had a related problem. My propane bottle ran to empty. Furnace shut down with no gas. I swapped an exchange bottle but the furnace would not light. I tried a different exchange. Didn't work.

My new knowledge: Must open the full bottle 3/4 turn, start the furnace, then open the bottle to full open. The internal safety valve kept the bottle shut down due to high flow.

Lou Schneider · February 8, 2020

If you're buying propane in the desert, you may be getting a high butane mixture. This happened a few years ago in Quartzsite when one supplier got a deal on "propane" from Mexico that was largely butane. A lot of his customers ran out of gas when the temperatures dipped lower than expected.

You seldom get pure propane, most of what you buy is a mixture of propane and butane designed to vaporize at or below the lowest expected temperature in that area. If there's too much butane in the mix (or in your tank) it can stop vaporizing at low temperatures, leaving you without gas until the tank warms up. The same thing can happen if you fill your tank in the warm low-lands and then move to the colder mountains. Pure propane vaporizes down to -44F while butane stops vaporizing at 31 degrees F.

Edited February 8, 2020 by Lou Schneider

lenp · February 9, 2020

Couple of thoughts......

Could there be some moisture in the tank? Could be freezing when it hits the regulator. Cold nights may be adding to the already COLD propane and freezing any moisture. I have tank and heater I use in my shop (tank is outside) and on very cold nights the pilot on the heater goes out. I suspect moisture because it never goes out during the day when temperature is above freezing.

Second, could the fan be failing and when it is cold it just cannot get up enough speed to close the sail switch?

Is it even trying to run? Fan running? Ignition attempted?

Lenp

Wrknrvr · February 9, 2020

Just a few statements about fuel for lp appliances in RVs.

With purchasing lp in Arizona it should have Propane which evaporates at about -44 degrees. Then it most likely has some butane mixed in also. Butane evaporates at about 32 degrees.

Then they may just happen to put in isobutane also. Isobutane evaporates at Boiling point: 10.94°F (-11.7°C).

Now this gas was never really figured in my thoughts of lp gas.

Yesterday I had a small propane bottle in my residential fridge for a few hours. I did not check the temperature of the bottle. Now that bottle was filled from a 20 lb lp bottle filled at the local supplier. A small warm bottle of propane was put on a regular propane torch. It had a flame as you would expect it to have. Then the freezer bottle was installed on the same torch. The flame was considerately smaller. I am thinking that the butane was not evaporating. And the isobutane was not evaporating since the flame was smaller on the chilled bottle. Also the pressure of propane at or near 0 degrees may play a factor in this subject.

More test today with temperature control hopefully. I do not have time today to do a scientific test. Nor do I have the ability as a lab would.

Just thinking, Vern

This winter I had a few new AFMD Atwood furnaces that when the weather was cold did not produce as much heat during until the temperature warmed up outside.

Edited February 9, 2020 by Wrknrvr

rpsinc · February 9, 2020

I dont have experience with the appliances that you mentioned above but I do with a Wisconsin 4 cylinder in a concrete saw that is converted to run on LP. If the ambient temps get to only low 50s, the cylinder will freeze up and prevent the liquid from feeding the saw and shuts off. I then have to replace the cylinder with another, while the 1st one thaws. Seems to be pretty high ambient temp for this to happen.

rickeieio · February 9, 2020

Perhaps on your saw, the fact that it's consuming the gas at a higher rate causes it to drop the pressure faster, making the liquid much cooler than the ambient air temp. Test the temp of the tank when it shuts down.

Ray,IN · February 10, 2020

On 2/8/2020 at 10:34 AM, Sehc said:

I have had a related problem. My propane bottle ran to empty. Furnace shut down with no gas. I swapped an exchange bottle but the furnace would not light. I tried a different exchange. Didn't work.

My new knowledge: Must open the full bottle 3/4 turn, start the furnace, then open the bottle to full open. The internal safety valve kept the bottle shut down due to high flow.

Actually that happens when the valve is opened rapidly, it's not how many turn open. What happens is, the safety flow restriction valve senses the pressure imbalance/excessive flow rate and closes. Closing the valve for a few seconds then slowly reopening restores gas flow.

Wrknrvr, The control voltage at the thermostat is measured in millivolts, a tiny bit of corrosion can break the continuity,

Edited February 10, 2020 by Ray,IN

KodiakJack · February 17, 2020

During my Arctic Engineering course the professor had video from the Alaska pipeline construction where ice was being melted with a propane weed-burner and each time the flame started getting low the burner would be directed at the bottle to get it going again. No kidding.

Later,

J