Mr Heater Big Maxx 3rd burner won't light

[Aseys]

I have a new 50000 BTU Big Maxx installed in my shop. The igniter lights the 1st burner fine and the flame quickly spreads to the 2nd burner but won't spread to the 3rd and the flame sensor shuts it down.
If I just blow on the 2nd burner the flame will jump up and the unit runs fine until it reaches the temp that the stat is sent to.
Sometimes, if I turn the stat down for a minute or two and then back up it will light the 3rd burner but if it sits for more than a couple of minutes it won't light.
Any help would be appreciated. I made a short video - link below.

Thanks!

 

[D45]

Maybe you need the valve adjusted because there's not enough pressure or gas present?

 

[Aseys]

Thanks D45 - I did try adjusting the pressure up and down but with no luck. Also, I should have mentioned that it's been converted to propane. Someone else on here had a similar issue with the 5th burner on a larger unit. His solution was to modify the 4th burner tube somehow...but I'm not sure about that....

 

[Bretny]

Soes this heater have what i call a cross over flame? A flame that connects all burners together? This could be clogged up since you say it runs fine once the 3rd burner is lit.
I had this problem on a older modine. It would build gas and blow the pilot out when finaly lit.

 

[D45]

Thanks D45 - I did try adjusting the pressure up and down but with no luck.

Were you blindly adjusting it or did you use a gas pressure manometer?

Are you sure you have the correct supply line size or required pressure, BEFORE the heater?

 

[naturalgas]

Make sure all the burners are secured properly and flat. the flame from the second burner should run to 3rd to lite it. Also play with air adjustments on burners.


Sent from my iPad using Tapatalk

 

[BJW79]

Hi just curious what the fix was. Mine is doing the same thing, immediately after the Co-op came and filled my tank to 90%, and the timing makes me suspicious. What did you find out?

 

[fitter30]

Size of the lp tank, altitude is it over 2500' 8.5": burner pressure?

 

[gmcgeo]

first thing i would do, is clean the orfice on the burner. Spiders could have webbed over it..

Then test your manifold pressures. should be 10" water column at the manifold