Regulator Pressure Adjustment Not Working

[valkaliban]

I recently installed a new Mr. Heater Big Maxx 80,000 heater model F260560 and I am unable to change the manifold pressure.

When I started it up for the first time, the heat exchange became glowing red hot and filled my garage with a hazy smoke.
I thought maybe it was getting too much natural gas so I measured from the pressure taps and I got the following.

Inlet Pressure (Not Running): 8.4" WC
Inlet Pressure (Running): 4.3" WC
Manifold Pressure (Running): 3.7" WC

The manual states it should be pre-adjusted for natural gas already at 4.0" WC
I tried messing with the pressure adjustment screw but no matter which direction or how much I turn it, the running manifold pressure will not change from 3.7" WC.
I completely unscrewed the pressure adjustment screw to make sure it had a spring.

I'm having a hard time finding time to contact their support line during their available hours.
The heater has not glown red hot since that first run.
Is the regulator broken?
Is 3.7" close enough to 4.0" that I should be fine running it as is?

Thanks

 

[Gizzi]

I assume you are on natural gas. One issue I immediately see is your line/inlet pressure drops below the manufacturer recommended minimum of 5" WC under load. That tells me your gas line is likely undersized or has too much demand on it. That may be affecting the gas valves ability to make adjustments via the manifold pressure adjustment screw. In my opinion, you have a few options. Either upsize the gas line, or put a smaller 40k BTU unit in and see if that will maintain adequate line pressure. Then you'll know if the gas valve is actually defective.

 

[Bert_]

The post above is right.

There's always some drop across the regulator, with only 4.3" inlet pressure you won't get 4" out.

 

[gmcgeo]

I recently installed a new Mr. Heater Big Maxx 80,000 heater model F260560 and I am unable to change the manifold pressure.

When I started it up for the first time, the heat exchange became glowing red hot and filled my garage with a hazy smoke.
I thought maybe it was getting too much natural gas so I measured from the pressure taps and I got the following.

Inlet Pressure (Not Running): 8.4" WC
Inlet Pressure (Running): 4.3" WC
Manifold Pressure (Running): 3.7" WC

The manual states it should be pre-adjusted for natural gas already at 4.0" WC
I tried messing with the pressure adjustment screw but no matter which direction or how much I turn it, the running manifold pressure will not change from 3.7" WC.
I completely unscrewed the pressure adjustment screw to make sure it had a spring.

I'm having a hard time finding time to contact their support line during their available hours.
The heater has not glown red hot since that first run.
Is the regulator broken?
Is 3.7" close enough to 4.0" that I should be fine running it as is?

Thanks

are you using a digital manometer?

 

[TractorJeff]

Mine let out "hazy" smoke the first few times until the "newness" burned off the heat exchanger.
I don't remember if it glowed?
Guys are right in that your supply line is too small and/or too long for its size from the source.