Low Gas Flame

[MHS]

I have a Heat-N-Glo 6000XLS-NF that has worked very well for the past 16 years. When I started it up this year the pilot was good but the flame was very low, even when I adjust the variable valve to Max. Cleaned and vacuumed the unit but no improvement. The thermopile is 536mv with no flame and 220mv when the flame is on. What type of test can I do on the valve to see if it is bad?

Valve: Robertshaw – Grayson, 7000 MVRB-5-LC, 770-826-467, LC 1.7” – HI 3.5”

Thanks,
Mike

 

[DAKSY]

What parts did clean & vacuum? Did you pull the burner? Did you remove the burner orifice?

 

[MHS]

I removed the burner and vacuumed it and the surrounding area. I placed the vacuum with the brush attachment on the orifice but did not remove it.

 

[DAKSY]

I removed the burner and vacuumed it and the surrounding area. I placed the vacuum with the brush attachment on the orifice but did not remove it.

That's where I'd look for an obstruction in the gas flow. Remove the orifice using a 1/2" wrench & make sure the gas line behind it is clear. Use a pipe cleaner or a Q-tip to clean that area...

 

[MHS]

Bob, I removed the orifice per your recommendation, cleaned and replaced it. No change to the flame.
Mike

 

[DAKSY]

Bob, I removed the orifice per your recommendation, cleaned and replaced it. No change to the flame.
Mike

Ok, Mike. Have you checked the gas pressure at the OUT port?

 

[altmartion]

as daksy said, the next step should be gas pressure. in and out.

 

[DAKSY]

Sounds like in is OK, based on the mV readings, but, yeah, I'd check both. If IN is OK, & OUT is hinky, you may have a bad regulator head. Since 2000, I have seen exactly TWO bad valves. They don't fail very often...

 

[altmartion]

Sounds like in is OK, based on the mV readings, but, yeah, I'd check both. If IN is OK, & OUT is hinky, you may have a bad regulator head. Since 2000, I have seen exactly TWO bad valves. They don't fail very often...

are you saying inlet gas pressure test by mv? very cool, but how and how accurate? I have never heard of or even thought this could work.

 

[DAKSY]

are you saying inlet gas pressure test by mv? very cool, but how and how accurate? I have never heard of or even thought this could work.

No. What I'm saying is that your thermopile readings are excellent & if the INCOMING gas pressure is too low, you probably won't get mV readings in the ranges you're seeing. The way to test the pressure is with a manometer on the IN/OUT ports...

 

[xtrordinair]

If anything else on gas is acting up then you got a regulator problem ,if you have a gas key type shut off make sure its turned all the way on ,sounds silly but ive seen it happen,as daksy said you need a manometer if the F.P. is the only thing acting up

 

[MHS]

Ok, Mike. Have you checked the gas pressure at the OUT port?

Have not checked the In/Out ports yet, will need to find a manometer. Will get back to you with the pressures. Thank you.

 

[MHS]

Ok, had to make a manometer. This is what I got for readings. For the OUT, I recorded the min and max setting for the variable flame valve.
IN = 0.25 in.
OUT low = 2.5 in.
OUT hi = 4.5 in.

 

[altmartion]

something is wrong. you can't put out more than you get in. and if those out number are real than they are wrong.

 

[altmartion]

I just realized I don't know what fuel you are using. lp or ng?. either way, that reading is not right. if ng your MIN inlet pressue should be 5" wc
the lp MIN inlet pressure is 11" wc. are you sure you are using the right port?

 

[MHS]

It’s a NG system. I did not believe it either so I did it twice to check and got the same readings. I’m sure I’m using the correct ports, with the tube on the OUT port I turn the flame height knob from Lo to High and got the 2.5 to 4.5 water in the tube. Is there a continuity or other test I can do on the valve?

 

[altmartion]

It’s a NG system. I did not believe it either so I did it twice to check and got the same readings. I’m sure I’m using the correct ports, with the tube on the OUT port I turn the flame height knob from Lo to High and got the 2.5 to 4.5 water in the tube. Is there a continuity or other test I can do on the valve?

no, you need to get a good reading on the input. if your incoming gas pressure is low you can't get the manifold pressure right. I don't think that valve has an inlet test port. you may need to find another one or use the port on the regulator.

 

[MHS]

Attached is a photo of the valve. Has both IN/OUT ports for testing.

 

[altmartion]

does everything else work that is ng? it seems like you should call the gas company and have them check the regulator. weather it is the problem with your heater or not. it could cause serious problems that actually could be a safety hazard. low gas pressure is dangerous.

 

[MHS]

I have an all gas house, range/stove, hot water, clothes dryer, central heat, barbeque and fireplace. Built new 16 years ago, no issues with any other gas appliance. The fireplace worked fine until I shut it off last spring.

 

[altmartion]

did you clean or inspect the vent and intake?

 

[DAKSY]

Bob, I removed the orifice per your recommendation, cleaned and replaced it. No change to the flame.
Mike

Just rereading this again, Mike. Did you clean the gas line BEHIND where the burner orifice mounts? That's where these nasty little spiders like to buiold their nests...

 

[MHS]

Last time I just removed the orifice and cleaned it. This time I disconnected the burner tube at the gas valve exit. Used a pipe cleaner and then blew out the tube with a can of compressed air. Also blew some air in the exit port of the gas valve. The flame now is at normal height. Decided to retest the IN/OUT pressure with the Manometer following the same YouTube video from FireplaceNow as I did before. Got the same results as before:
IN = 0.25 in. (pilot off)
OUT low = 2.5 in.
OUT hi = 4.5 in

I retested the IN with the pilot on this time and had the correct pressure: IN = 8 in.
So is the video wrong? Should the pilot be on when testing the IN pressure or off?

 

[altmartion]

you should not ned the pilot running to test incoming gas pressure. something there doesn't seem right, but not sure if it is the cause. leave the monometer on and let it run though it's stages until it fails. whatch for any variation in pressure.