carrier burner lights sometimes

[iceage]

Carrier 48dje064ca package unit with 3 burners. Gas pressures ok, pilot tubbing cleaned but, one burner (first stage) will only ignite when I hold hand over exhaust vent. Other burners run, same type of vendor motor on all 3 burners Anyone have an idea why by holding back exhaust it will allow burner to fire?

[socotech]

Is the wind deflector missing?

[iceage]

Yes. They were all missing ang found replacements

[socotech]

Maybe a wind problem. I have made some wind deflectors out of sheetmetal.

[socotech]

You have the post count. You should apply for pro membership. You will get a lot more answers.

[hands]

It could have a restricted orfice on the burner that doesn't light. You said this unit has a pilot tube, does the ignitor light the pilot at the burner that doesn't fire? The Carrier RTU's I usually work on have an ignitor with cross overs to light all the burners.

[mikeacman]

Looketh for spider webeths in your orfices

[qwerty hvac]

Looketh for spider webeths in your orfices

Check this. Very common on the carrier units.


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[timebuilder]

Wow, that's an old Carrier to have a pilot tube. I haven't had a customer that is still running that era in over two years.

[mikeacman]

Also spider webs in your pilot tube

[iceage]

The pilot tube had been removed and cleaned. You can see pilot flame along bottom of tubing, but peeters out when it hits top tubing(u bend) and doesn't seem to hit sensor to open main gas, until vent is plugged.

[Push It]

check the heat excahnger for a crack in that tube.

[iceage]

Heat exchanger changed in August, baffles included

[hands]

The pilot tube had been removed and cleaned. You can see pilot flame along bottom of tubing, but peeters out when it hits top tubing(u bend) and doesn't seem to hit sensor to open main gas, until vent is plugged.

Have you tried to increase the pilot gas pressure and did you check the orifice on the pilot tube?

[Eadam1985]

might not be getting enought gas pressure coming out of valve

[Dchappa21]

I got a bunch of these I work on, they SUCK!!! What I've found is the newer crossover tubes didn't get drilled out right from the factory... If its an old one that is in decent shape should be good there, don't change it unless you like drilling out the last straight section of crossover tube... It takes about an hour to do.

But the first thing is check the pilot orifice as has been said.. Always use a orifice drill kit with the right size bit.

Couple of other things to check are the baffles in the heat exchanger. Are they in there or rusted out? Air leakage around the draft motor will cause some issues too.

You can also run the pilot pressure in and out to see if it makes a difference.. I still haven't made a tee yet to test the pilot pressure.

I also can't say I've never made the pilot orifice a size bigger.

[Dchappa21]

Oops, missed where you said you cleaned the orifice and the baffles were replaced...

Did the crossover tube get changed with the heat X? Or the gas valve?