[begosbrian]

Hi, I have a Carrier HVAC 48HJE014 unit for my business. We are based in Westchester County, NY. They are natural gas units. I recently replaced the heat exchanger (actually did it on two units) and it worked out very well. The one unit is acting a little weird, here are the symptoms:
**when heat is called for, the blower motor comes on, the ignitor clicks/sparks but it takes until the third time for it to ignite the furnace. It seems as if the gas does not start flowing right away or until that third try. It is a natural gas system.
**when it's lit, everything then seems to work normal.
**It did have two error codes, one for the flame sensor and one for the limit switch, which were both replaced, then the error codes went away--it did not change the "delayed light" problem however.
**if the unit is up and running all day, at some point there will be a real bad smell of gas inside, which I can only figure is coming from this same unit, because if I shut it down and air the place out, it goes away and we don't have any problems if that particular unit is turned off completely and the other unit is on.
I am guessing that it is either a problem with the gas valve and it not operating and/or opening up properly or whatever control unit tells it to open up.

I'm clearly not an hvac repair guy but have done enough fiddling and watching and repairing on my own to know a lot about the units, but not 100%
If anyone has some useful guidance that would be fantastic!!

 

[beenthere]

Clean the bunrers, and orifices.

 

[begosbrian]

thanks... I can definitely try that but they seem to really work well once everything is lit, so I'm guessing that the problem is not dirt or corrosion

 

[beenthere]

thanks... I can definitely try that but they seem to really work well once everything is lit, so I'm guessing that the problem is not dirt or corrosion

By that logic. The gas valve can't be the problem either, since it works really well when the burners are lite.

Dirt in an orifice, burner or pilot can cause ignition problems, but stll have a good flame one burning.

 

[roughneck]

What's the gas pressure? It would concern me greatly about a natural gas odor getting inside the living space. How is it getting there? Is the heat exchanger cracked? What's causing gas to leak out of the unit? Is the gas valve being powered when the unit is not calling for heat?

 

[begosbrian]

Ok, but it seems like the gas does not begin to flow to the burners until the third round/sequence, not that it's flowing and blocked, you know what I mean...so it really does seem more like a sequence/electrical problem with the gas valve, rather than dirty pipes. I'm clearly not an expert on this but I've been up there with this and the other units a lot

 

[begosbrian]

What's the gas pressure? It would concern me greatly about a natural gas odor getting inside the living space. How is it getting there? Is the heat exchanger cracked? What's causing gas to leak out of the unit? Is the gas valve being powered when the unit is not calling for heat?

Hey roughneck, the heat exchanger is brand new (I just put it in about three weeks ago). It hasn't been very cold here in NY so its been mostly off. It is concerning that the gas smell is getting to the living space, but I can't really figure any solid reason why

 

[begosbrian]

And I have no idea what the gas pressure is, would have no knowledge on how to measure it

 

[roughneck]

Is there voltage getting to the valve during trial? What's incoming and outgoing gas pressure? You'll need to purchase a manometer to measure it.

 

[yuri]

How old is the unit?

Sounds EXTREMELY dangerous if you are getting ANY gas smell in the bldg and you need to figure out why before continuing to use that unit.

If you put the exchanger in and have some kind of a leak in the gasket around it then it is possible gas could get in. However I suspect you have a problem with the gas valve leaking gas. I had a old Carrier with the 3 wire pilot and the valve was sticking open and passing a slight amount of gas during the off cycle.

If you don't have the knowledge or equipment to check the gas pressure etc you should get a Pro and watch him and learn. If it is not lighting properly you can get a gas buildup and delayed ignition and boom. Not something to fool around with.

 

[roughneck]

So, hopefully the OP hasn't responded because he's busy and not because of a gas explosion.......
A gas odor in the living space strong enough to require airing the space out is extremely dangerous.
Been quite a few gas explosions in the semi-local area. Some were actually caused by improper DIY work.

 

[begosbrian]

Ha, still here, just leaving it off and having a professional come help out. Thanks for all the help

 

[roughneck]

Probably a good idea. Best of luck.
Happy new year.