Community Forums

speedy43c · 01-02-2020, 08:12 AM

I have a tiny home im just getting ready. I hooked up the propane and tried to light the heater. It lights and then goes out. Ive checked and all the electronics are working right but not enough gas pressure. Its a 40,000 btu Atwood ac unit. Any ideas what pressure regulator I would need. I have a low pressure regulator on it and its not enough. I called my local propane company and they didnt know.

Thx Steve

MSHappyCampers · 01-02-2020, 11:06 AM

Hi Steve! Welcome to IRV2! We're sure glad you joined the gang!

I've read what the pressure should be but don't remember. I'm sure someone will be along to help with that!

Good luck, happy trails, and God bless!

Ndrorder · 01-02-2020, 11:12 AM

The installation instructions for your particular furnace will give the operating settings including the required range of gas pressure.. Explosive gas isn't something to experiment with. Call a plumber.

450Donn · 01-02-2020, 11:15 AM

Have you googled it?
A 10 second google search says 10-11 WC for propane. A standard propane regulator should already be calibrated to that number.

Old-Biscuit · 01-02-2020, 11:16 AM

Tell us more about your propane set up......
Fixed TANK
Portable Cylinders

What Low Pressure Regulator you are using.....
2 single stages or a 2 stage reg?

Propane Systems are 11"WC----that is 0.4 psi----to supply the correct propane to the appliances
Tank/Cylinder pressures can be 100 psi to 250 psi depending on ambient air temps/sun exposure etc.

That HIGH pressure is reduced to 30# using a single stage reg and then reduced to 0.4 psi with the 2nd regulator
OR....that high pressure is reduced to 10# then to 0.4 # using a 2 stage regulator

But the regulator(s) and hose/piping must also be correctly sized for FLOW

So what regulator and model of regulator are you using?

Also........will only 0.4psi in the system it can take SEVERAL igniton attempts to fully establish flow & pressure to the appliance.
So if furnace is attempting to ignite......SPARKING/then lockout----turn Thermostat OFF, then Back on and try it again.
Repeat.....

Pigman1 · 01-02-2020, 11:50 AM

That 40,000 btu heater is probably causing the flow limiters in your system to set and cut off gas flow as if you had a major leak in the system. To idiot proof most common propane systems just about ALL propane spuds have a flow limiter incorporated in them. The spud is a male part with a sloped end (yep, MALE part) that may be connected to a regulator, propane selector valve, line and any of a dozen other parts of the system. To get around these really stupid "protect you from every possible screw up" you can go to a MOBILE HOME supply store and purchase spuds without restrictors, or drill out the steel or plastic balls in the pointy end of the spud. If you're using a colored hand wheel connector to connect to your tank, these also incorporate a restrictor, and the amount of gas they will allow to flow is indicated by the color. A final point, some small 5 gal BBQ type tanks also have a restrictor in their Overflow Protection Valve (OPD). This is actually in the tank valve and cannot be defeated or bypassed. You can, however, buy a BBQ size tank without the OPD restrictor valve. According to Manchester Tank engineers I contacted a few years ago, a valve manufactured with the word ITALY cast into the brass just below the 3 lobe shutoff handle does NOT have a restrictor. I bought 3 such tanks at Lowes about 7 years ago to be able to feed my 2 RV furnaces. They've worked fine, but I'd do a good research check as this was a number of years ago and things may have changed.

LP gauges to measure the 11" WC LP pressure are readily available on Amazon and EBay for not too much $$. I've used mine to diagnose regulator and stove failures for about 8+ years. Well worth the investment.

Old-Biscuit · 01-02-2020, 12:06 PM

Flow limiter (Excess Flow Device ---safety device to limit propane flow if a leak should occur) is NOT OPs issue.

Atwood 40K btu furnaces are common in RVs
Regulators are typically sized to provide sufficient flow for ALL applinaces.

OPD (OverFill Prevention Device) be it one in ASME Tanks or Portable Cylinders do ONE thing and only one thing.
Prevent overfilling past the 80% LIQUID level of vessel.
They STOP Liquid propane from going IN
They do NOT stop VAPOR from coming OUT

speedy43c · 01-02-2020, 12:26 PM

I have a 20 lb bottle on it now. I have used a single stage and and dual stage regulator with the same results. I looked at the info sheet on the furnace and it says that insufficient gas flow would also cause this. This is the only thing on gas in the house. Its like it has enough to light but then goes off immediately the 3 times then goes out on the 3 time lockout.

This is what the book said. Low gas pressure--------------------------------Set pressure to a minimum of 11 ̋ W.C. with all appliances running.Replace regulator if not obtainable.
So it doesn't say what the running pressure is just a minimum. The regulators I looked at say they will supply a maximum of 11" WC

Old-Biscuit · 01-02-2020, 12:35 PM

Quote:

Originally Posted by speedy43c

I have a 20 lb bottle on it now. I have used a single stage and and dual stage regulator with the same results. I looked at the info sheet on the furnace and it says that insufficient gas flow would also cause this. This is the only thing on gas in the house. Its like it has enough to light but then goes off immediately the 3 times then goes out on the 3 time lockout.

This is what the book said. Low gas pressure--------------------------------Set pressure to a minimum of 11 ̋ W.C. with all appliances running.Replace regulator if not obtainable.

So what is the system pressure?

Have you allowed several attempts to insure you have established flow to the furnace?

Typical 2 stage reg used for RV are rated at 160,000 btu flow

20# cylinder will still require 2 regulators....be it a standard 2 stage reg like used on RVs OR a Single stage at cylinder then a Secondary reg at the input to the Tiny Home

Propane pressure entering the dwelling should be 11"WC (0.4 psi)

Ljwt330 · 01-02-2020, 12:44 PM

What is the length of the run from the tank to the furnace? Since it is the only gas appliance in the house, you still may have air in the line that needs to be purged before continuous burning can happen.

speedy43c · 01-02-2020, 01:13 PM

I used a dual regulator off of a gas grill. The steel line runs about 20 feet to a junction and a copper line feeds it from there. There was a cap on one end of the junction and I removed it and purged the line. I have let it cycle several times and same thing lights for maybe 1 second and goes out. Do I need a regulator from a camper/RV place? Im new to this do thats why im asking you guys that are more knowledgeable. I do know a lot about home repairs just not propane.

2Newsomes · 01-02-2020, 02:33 PM

Have the furnace checked, does you stovetop light?. If it quits exactly the same every time it's likely not sensing the flame, then goes into lockout.

clifford j · 01-02-2020, 02:55 PM

The Atwood furnace has a sail switch that monitors air flow, if the flow is restricted it will shut the furnace down after a few seconds after it fired. The OP may not have a fuel supply but a restricted air output.

CLIFFORD

Pigman1 · 01-02-2020, 02:56 PM

It's not necessarily the regulator. It is probably one or more of the multiple flow limiting valves in the system. As a guess I'd say OP probably has at least 3 or more he's not aware of and perhaps one in the OPD valve on his bottle. Easy way to check this is to light a range burner before the heater. If the range and heater both go out or the range goes VERY low, start looking for a flow limiter. If the range, oven, and water heater work OK without heater, definitely a flow limiter. Since the OP says this is the only gas appliance in the house, it makes it harder to troubleshoot without a meter. As I read his post he has tried MULTIPLE regulators.