Big Maxx 50k, converted to LP, but not enough flow

[tristanlee85]

I got my Mr Heater Big Maxx 50k heater installed and had an HVAC installer come out and verify my NG to LP conversion and make sure it was getting the proper flow through the valve. I believe he said for LP, we were looking for ~10.5" WC. However, with the adjustment screw maxed out, he was only able to get 9" WC.

He mentioned that I probably need a regulator coming off my LP tank, which didn't make much sense to me. My setup is (2) 100lb tanks, with this regulator: [can't post links apparently, regulator is MEGR-253H]

According to the specs (model is MEGR-253H), it is already set for 11" WC.

Plumbing out of the regulator is 3/8" immediately converted to 1/2" all the way to the heater. Could the 1/2" pipe be causing that much of a drop? My gas lines have been tested to 120psi air with a very soapy solution and no bubbles are present.

 

[SuperD]

What is the pressure ( WC) set at on your MEGR-253H regulator? Should be around 11-14" WC there first. There is a regulator in the Big Max as well. When you say 10.5"WC is that at the furnace or at the tank supply regulator? How long is the distance from the tank to the heater?

 

[Unhdsm]

When I converted mine I thought the screw was bottomed out because there was a little ridge that made it stick a little but it turned out there was quite a bit more to go.

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[ceddington88]

You might need to ditch the regulator you have at the tanks and go with an adjustable multistage regulator. Length of run and number of fittings are required to size gas pipe correctly but you should be good with 1/2” for almost 200’ run for 50k Btus. Also min and max manifold pressure requirements should be on a label somewhere near the burner door.


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[The Cobbler]

was there a spring in the kit to install in the gas valve? was it installed?

 

[Partsguy57]

I got my Mr Heater Big Maxx 50k heater installed and had an HVAC installer come out and verify my NG to LP conversion and make sure it was getting the proper flow through the valve. I believe he said for LP, we were looking for ~10.5" WC. However, with the adjustment screw maxed out, he was only able to get 9" WC.



He mentioned that I probably need a regulator coming off my LP tank, which didn't make much sense to me. My setup is (2) 100lb tanks, with this regulator: [can't post links apparently, regulator is MEGR-253H]



According to the specs (model is MEGR-253H), it is already set for 11" WC.



Plumbing out of the regulator is 3/8" immediately converted to 1/2" all the way to the heater. Could the 1/2" pipe be causing that much of a drop? My gas lines have been tested to 120psi air with a very soapy solution and no bubbles are present.

I'm far from a expert. I put up a big max 80000 btu converted to lp . I did it all myself with reg at propane tank and 3/4 line to heater(ten feet) and the best I got pressure wise is 9 ( same as you) works fine heats shop very fast. Is not having perfect pressure a problem? I don't know. Am I worried about it? Nope. Works fine moving on.... ( I doubt line size is a problem as my is bigger with same issue)

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[tristanlee85]

What is the pressure ( WC) set at on your MEGR-253H regulator? Should be around 11-14" WC there first. There is a regulator in the Big Max as well. When you say 10.5"WC is that at the furnace or at the tank supply regulator? How long is the distance from the tank to the heater?

I haven't tested it myself at the regulator, though specs on the manufacturer's site says it is set to 11" WC. There does appear to be an adjustment screw on it which I just noticed yesterday after posting this. I ordered a manometer that should be here tomorrow so I will know for sure.

was there a spring in the kit to install in the gas valve? was it installed?

There was a different spring and nozzles that were switched over to LP.

My run length is not long, probably 20ft. There's no downside about only getting 9" WC right now, other than I think being closer to 11" the manifold of the heater will result in quicker heat up.

 

[Partsguy57]

I haven't tested it myself at the regulator, though specs on the manufacturer's site says it is set to 11" WC. There does appear to be an adjustment screw on it which I just noticed yesterday after posting this. I ordered a manometer that should be here tomorrow so I will know for sure.







There was a different spring and nozzles that were switched over to LP.



My run length is not long, probably 20ft. There's no downside about only getting 9" WC right now, other than I think being closer to 11" the manifold of the heater will result in quicker heat up.

That's what I came up with... no downside running mine at 9 that I can tell so I moved on.

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[Muc]

I installed a 45,000 BTU beacon morris that I converted to LP. It’s hooked up to a 120 GALLON tank with 30 ft of 1/2” pipe.
When I first fired it up the flame had too much yellow. When I checked the pressure it was 9.5”. So I adjusted the tank regulator to 11.5” and heater regulator to 10.5”. Much better looking flame. Surprised that you have a good flame at 9.0”.

 

[Adk Mike]

100 pound tanks or 100 gallon tanks ? Big difference. Line size combined with the distance from the heater. Tell me how far they are away and I’ll size it for you. Regulators should be a quality twin stage at the tanks. Tanks hooked and going down together. Or if a long ways from the heater it requires a requlator at the tank and maybe one on the building. At any rate easy to make work right. I’ve done this for years.

 

[LS6 Tommy]

I installed a 45,000 BTU beacon morris that I converted to LP. It’s hooked up to a 120 GALLON tank with 30 ft of 1/2” pipe.
When I first fired it up the flame had too much yellow. When I checked the pressure it was 9.5”. So I adjusted the tank regulator to 11.5” and heater regulator to 10.5”. Much better looking flame. Surprised that you have a good flame at 9.0”.

My thoughts exactly. You should be underfiring at 9".

Tommy

 

[tristanlee85]

Well I decided to buy a cheap manometer so I wouldn't have to bring the HVAC guy back out. I took the adjusting cap off my regulator on the tank, rotated the spring clockwise until it bottomed out. That didn't increase anything, so I backed it back out to its factory setting. I am reading ~8.45". The end of the flame is a bit more yellow than I would desire. I'm not sure why I am still maintaining such a low flow.

 

[tristanlee85]

100 pound tanks or 100 gallon tanks ? Big difference. Line size combined with the distance from the heater. Tell me how far they are away and I’ll size it for you. Regulators should be a quality twin stage at the tanks. Tanks hooked and going down together. Or if a long ways from the heater it requires a requlator at the tank and maybe one on the building. At any rate easy to make work right. I’ve done this for years.

I have (2) 100lb tanks. I just measures the lines and it is ~20ft of 1/2". I can't link to the regulator since my post count is low, but it is the Marshall Excelsior MEGR-253H Excela-Flo Auto Change Regulator, 2 stage auto-switching.

 

[tristanlee85]

Ok, cancel all of this. What it boils down to is my HVAC guy is a turd. He said he had to basically bottom out the screw on the valve to get 9", which according to my meter is actually ~8.655". I measured the regulator at the tanks and it was flowing ~10". Minimum tank inlet pressure is 13", so I increased that bad boy. I went back to the valve on the heater and adjusted it more. It wasn't bottomed out as he suggested. So now I have a tank inlet flow of 13" and a manifold outlet flow of 10.5".

So much for paying the pro to do it.

 

[Adk Mike]

Your line size is fine. 20 feet of 1/2 copper will run 76,000 BTU’s. A 100 pound tank will vaporize 50,000 BTU’s when it’s full at 0 degrees. So the first thing to do is get a regular twin stage regulator. Rego or Fisher are the two main brands. Get a tee block and pig tail so both of those tanks go down together. That will allow it to vaporize better. With your current setup drawing on only one tank at a time. Your starving for gas when it’s bitter cold. With warmer spring weather it will work better. You need at least 10.5 w/c. 11 in a perfect world.
If you had a gas company in the area that you like and could trust have them set a 420 tank they hold 100 gallons or the same as 4 of what you have now. With the correct regulator it will work just fine. Keep me posted on how you make out.



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[gmcgeo]

adk mike is dead on, i only set 420s dot or 120 asme tanks on a garage unit like this a 100# 23 gallon tank is not big enough to run this, it can but i don't recommend it. rego has a good lv404b34 twin stage that is 1/2" outlet and 1/4 inlet for a pol pigtail
or you can go with a b4 rego but a b34 is all that is needed. you can adjust pressure from the b34 and then at your manifold.

 

[tristanlee85]

A tank that large was beyond my budget for this heater to be honest. As mentioned above, I was able to adjust the regulator and valve to now get the desired flow. I will take the advice of switching to a different regulator so that they can both be ran together vs the switchover like I have now. I was not sure how long a single tank would last me in the garage. I use my 125k space heater to get it up to temp when I plan on being out there for a while, and wanted this overhead unit to be a quiet source for maintaining that temperature. The reason for single tank at a time was so if one was empty when I really needed it, a simple switch over while the other was off getting filled.

If I end up going the route of having the heater run at all times, it will probably be more cost effective just to tie in to the NG line. Again, I don't think I will be using it that heavily at this point to need NG or a larger LP tank.

I do appreciate everyones' input!

 

[TractorJeff]

Another thought would be to manifold two primary tanks together as suggested for one source, then set a single tank for the switchover. That way you could maintain heat without getting air in your line when getting the 2 primary tanks refilled. This would solve the rate of vaporization during cold weather issue!