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I have a propane patio heater similar to this one...

enter image description here

I have an issue where the flame will slowly die down over a period of time. Let's say within 30 minutes it goes from full flame to something that barely stays lit. When the flame gets tiny, you can hear the propane hissing through the lines like it's being restricted.

If I wait an hour, I can re-light it and it's full strength again for a while and within 30 minutes, the problem will repeat.

I've disassembled and cleaned it out a couple times but this problem continues. The unit is never stored outside, however, I got it used and it's always had an issue staying lit. I have not yet replaced the thermocouple because the previous owner claimed this was already done.

I'm looking for troubleshooting suggestions that will conclusively narrow down the source of the problem and/or cleaning tips. The gas orifice at the pilot is too small for a pipe cleaner, but I've already tried solvents such as carb cleaner and it makes no difference.

The pilot is blue with an orange tip. When first lit, the burner flames are blue, but as it dies down, the tips turn orange.

What I don't understand is why it performs great when it's first lit. I'd think if this whole problem was caused by dirt, the flame would be restricted all the time.

Can anyone shed some light on this?

EDIT: There seems to be some confusion here. This unit is 8 feet tall, only runs on a 20-lb PROPANE tank, and this problem is occurring in 58 degree F and warmer weather.

  • Are you getting frost buildup at the tank valve? Rapidly expanding gas requires quite a bit of heat, which it takes from any nearby object or medium. Are you in a somewhat humid climate? – isherwood Dec 18 '15 at 17:57
  • @isherwood, there is no frost build-up at the tank. Temps in the high 50's a few days ago near Chicago. – Sparky Dec 18 '15 at 18:11
  • @isherwood, yes, I understand what you said about heat extraction. Of course outdoor temps are relevant as propane expansion within the tank is proportional to ambient temperature. Now what good is a patio heater in 58 degree weather if the tank gets too cold to function? – Sparky Dec 18 '15 at 18:17
  • Only possible: If LPG (not Propane) partial use and refilling will differentially tend to use Propane and not Butane so that over time the mix moves to mainly Butane. So at 1st you burn the Propanbe but as this runs down you get an almost pure Butane feed. Check this by trying a tank which has been refilled from empty. If it too does this the above is not the issue. If this IS the issue, emptying the tank (sob) and refilling cures it. Always emptying tank and not part refilling prevents the above. – Russell McMahon Dec 19 '15 at 0:27
  • @RussellMcMahon, it's definitely propane; refills purchased from national retailers. I have several 20 lb. tanks and this issue has been ongoing over many months. – Sparky Dec 19 '15 at 1:22
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It sounds to me like a restriction at the regulator, not the control valve. You mentioned that the previous owner had done some work on it, make sure that he/she did not replace the regulator with one that does not deliver the design flow/pressure. In this case, adequate flow/pressure depends on proper regulator back pressure setting (they are rated in "inches of water" back pressure). If the regulator setting is too low, it will not deliver an adequate flow/pressure of gas.

If this is the case, the initial proper operation followed by diminishing performance is explained by the volume of gas in the 8' tall hose assembly, with a slow reduction in adequate volume being delivered by the undersized regulator. I had your exact problem when I attempted to swap out a leaky patio heater regulator with a BBQ regulator that had a different pressure setting.

Like this:

  • Regulator is initially open because of low (zero) downstream pressure.
  • 8' tall hose fills with gas until rated back pressure downstream of regulator is reached, regulator closes.
  • You open control valve and light heater, regulator opens as downstream pressure drops.
  • Damaged, defective, clogged, or undersized regulator cannot supply enough gas to maintain proper flame height as pressure drops, but does stay open and deliver gas according to it's pressure setting, which is not enough for adequate flame propagation.

It's worth checking, anyway.

  • I am now suspicious of the regulator. There is nothing on it indicating it's rating, however, there is a tag and it mentions "BBQ grill" in several places. Not sure if this is just a generic tag or if somebody actually replaced it with one from a BBQ grill. – Sparky Dec 19 '15 at 1:16
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One of two things is happening... either your propane tank is getting cold enough to reduce its internal pressure, or your tank valve, regulator, or some other orifice is frosting shut.

Propane tanks contain liquid fuel which vaporizes to fill the available space in the tank. As it's used, heat is required to vaporize and expand the fuel. This heat comes from the tank itself, hardware attached to the tank, and the surrounding air. Eventually, when the system gets cold enough, pressure drops in the tank.

As a result of this cooling, frost may build up at critical points along the fuel flow path. Restriction could result in lower flame as well.

Learn about regulator frost

A possible solution is to have several tanks on hand, keep the spares indoors, and swap them out on occasion. If the heater runs on small 1 lb. tanks you may also be able to fit a larger 20 lb. tank for better service.

  • As I stated in the comments, there is no frost anywhere on this tank, valve, hoses, etc. – Sparky Dec 18 '15 at 18:18
  • The frost causing the problem would be inside the hardware. Ask any pilot about carburetor icing. My answer proposes another possible explanation and solution as well. – isherwood Dec 18 '15 at 18:21
  • Quote: "You may also be able to fit a larger 20 lb. tank for better service." ~ That IS already a 20 lb tank. That's a picture of an 8-foot tall heater. Nobody swaps tanks every 30 minutes to keep a patio heater working in near 60 degree weather. – Sparky Dec 18 '15 at 18:22
  • You can argue with me all you want, but up here in MN where it's really cold at times we deal with these issues regularly. One tactic in the ice house is to put the tank partially in front of the heater. Obviously that's not an option in your case. Best of luck. – isherwood Dec 18 '15 at 18:25
  • If the regulator was frosting up, then this patio heater is useless junk. I am not using it outside of normal operating parameters. – Sparky Dec 18 '15 at 18:25

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