Propane line

[fitch]

Hi All,
I have a MHU75 Big Maxx in my 24x40x10 pole barn. My ceiling is insulated with 15" and closed up with partical board. I am curious what size copper tubing should be used from the low pressure regulator to the 1" OD black pipe outside my barn wall tha is hard plumbed to the heater. I have been using 1/2" OD (3/8" ID) for the past couple of years and it never really put out the heat that I thought it should. I still run another source of heat (convection) from time to time. I consulted with Mr heater, and they suggested moving to .625 OD (1/2" ID). Curious what others have done.

 

[CNGsaves]

If your propane feed is on low pressure side, then your only option is GO BIG with the pipe to your heater. With only 1/2" line, you surely having been starving the 75K Btu heater.

What is distance from 1" black pipe LPG supply line??

Any chance you could go high pressure back to main tank (ie buried yellow plastic pipe), and then add regulator outside garage, then copper or black pipe steel for last leg to heater??

 

[A_Pmech]

The LP-Gas Serviceman's Manual from Rego is available online and will answer all your questions:

http://www.regoproducts.com/pdfs/L-545_Servicemans_Manual.pdf

 

[Kingcreek]

Propane is low pressure. My whole house is only 1/2" copper line to the reg on the house and I never had any problems with LP boiler, water heater, and range. Even if all is in use at same time.

 

[Jackfre]

…and all the conjecture will stop once a manometer placed on the appliance tells you what is happening. Call your lp company if you cannot get your hands on one.

 

[fitch]

what does a manometer do?

 

[fitch]

I changed out the 1/2" od line (3 ft) and replaced with 5/8" and a new regulator. Furnace fired up. Still does not heat the 960 sq foot like I thought it would. Mr Heater is telling me to get a ceiling fan. Probably not a bad idea. Also am checking into side wall foam board insulation 1 - 1 1/2" thick. $$$$. Anyway, thanks for the responses.

 

[Jackfre]

what does a manometer do?

A manometer measure pressure. You connect it to a 1/4" tap on the gas valve or at a tee before the unit and it will show pressure at the unit. Usually prior to firing you will see decent static pressure and then when the unit fires, if the line is undersized the pressure will drop. If it stays up your line is adequately sized. Most manuf say that your pressure should not drop more than 10% of the recommended pressure.

 

[dave67fd]

Your 960 sq ft isin't being properly heated because it isin't insulated. 15" in the ceiling maybe ok but if it's only closed up with particle board and no insulation thats your problem. My 75k big maxx heats my 1000+ sq/ft just fine.

Spend your money on insulating the walls and get a ceiling fan and you'll be suprised. Of course if your heater isin't running at it's highest efficiency thats a big contributor as well.
Have a proffesional check your gas "line" and "manifold" pressure. Confirm your vent is cleaned and free of any obstructions.

Regulator should exceed the BTU requirements and should never be mounted inside at the heater.

 

[fitch]

Thanks for the input. On the ceiling fan, I have found one a Home Depot (60"). With a 24x40x10, how many will it take? I was thinking 2. Any recommendations?

 

[fitch]

I had a service tech place a manometer on the furnace and it read 1.51 wc and it should be 11-13 wc. He said its either the regulator or the 100 lb cylinder may have a bad valve. I talked my propane company and they said the 100 lb cylinder is too small to run it 75000 btu furnace. Does anyone run a 100 lb cylinder? Also, my heat tubes are like brand new. The tech said the furnace is starving for LP thats why the tubes look so clean. When the furnace was installed, they did the conversion kit.

 

[mrobins297aaa]

I don't have all the facts and figures but i can't believe a 100# cylinder won't run that heater, you got something wrong there.

i run my 75K instant water in my barn off of a barbque tank and it runs fine.

try hooking up a barbque tank thats full to that black pipe and see if it runs that heater, make sure the tank has the regulator on it,............those regulators on those barbque tanks put out 11"-13" so it should work, it may not work for very long because those small tanks cannot produce enough vapor for very long without losing pressure but it'll let you know if you have a problem with the valve or regulator on your present system.

don't forget make sure you have the regulator on the barbque tank.
as far as the conversion kit if they didn't do it you would have the opposite problem because the ng orfices are larger.........so it be over heating

 

[mrobins297aaa]

if you don't have a extra regulator you can pick one up with the hose for a few bucks at homedepot

 

[mrobins297aaa]

as a matter of fact I remember years ago when we were doing new houses trying to get some heat in the houses for the drywallers and before the basemnet was poured.
we hung the furnace by straps, converted it to propane and hook it up to 100# propane tank.............and when the basement was poured and the ng was hooked up we came back and reconverted back to ng

 

[432bullet]

My shop is 40ft by 60ft with 14ft high ceiling and I run 6 small ceiling fans as needed. It helps a lot.

 

[Travo131]

Depending on what kind of regulator you have they can be adjusted. I am assuming you just have a 2 stage regulator. Don't buy one of those cheap ones from menards spend the 75 bucks and buy a fisher or rego.

 

[toyotadriver]

I run an 80k btu Big Maxx from a 100 lb tank and it works fine. I ran 1/2 inch black iron for about 20 feet or so and it works perfectly. Single stage regulator on the tank.

I heat 1200 sq feet but mine is well insulated.

 

[toyotadriver]

I had a service tech place a manometer on the furnace and it read 1.51 wc and it should be 11-13 wc. He said its either the regulator or the 100 lb cylinder may have a bad valve. I talked my propane company and they said the 100 lb cylinder is too small to run it 75000 btu furnace. Does anyone run a 100 lb cylinder? Also, my heat tubes are like brand new. The tech said the furnace is starving for LP thats why the tubes look so clean. When the furnace was installed, they did the conversion kit.

There's your problem. You aren't getting enough pressure. Probably a bad regulator. Doubt that the 100 lb tank has a bad valve.