Trane voyager spark no ignition

[Wiseguy91]

Hey folks, I'm new to the forum. Told a buddy i had a problem and he said to come here. I'm working on a Lp Trane GRAA 350000 btu rooftop. Got a call after the propane tank was refilled because the unit failed to light. Purged the gas train and still got nothing. Checked for spark and had a bright one. The gas valve manometer port was striped so I changed it out (Honeywell single stage standard opening). Changed pilot assembly while I was at it just in case. Gas pressure was 10.8 in. Only thing I can think of is bad mix but I've tried a range of pressures. Does anyone have any ideas?

[jmsmars1]

checked for 24v to valve? was the 10.8 in WC the inlet or outlet?

[alcomech]

Are you sure that is a spark ignition and not a hot surface ignition.
What is the Model No. and Serial no.
Is that a two stage gas valve.
Did you say that you replaced the gas valve and if so was that an O.E.M. parts replacement.
You have to be careful because sometimes those valves are rated for negative manifold pressure.
Are the controls Microtech

[jayguy]

he mentioned that the unit is a GRAA which is a make up air unit originally designed by Sterling. it is a spark pilot ignition. as mentioned before, you measured the gas pressure where? the inlet gas pressure is important, but with no fire, the outlet is important too...got gas coming out of the pilot?

[Wiseguy91]

Thanks for the responses. I have 24v to gas valve and pressure was measured going in. Adjusted pressure but haven't measured the pressures out yet. Pilot valve has gas coming out but won't light from the spark. I replaced the valve that with the same single stage Honeywell that was on it. On my way to the job site now so ill keep you posted.

[Wiseguy91]

Pilot assembly*

[Wiseguy91]

Also the pilot assembly was not a LP so I changed the orafice. I assumed they where all the same but this could very well be the problem.

[hands]

Is this a Direct or Indirect fired MAU?

[Wiseguy91]

Indirect. But I managed to figure it out. The pilot assembly was not putting out the proper amount of gas becouse I used the wrong nozzle when I converted it to propane. Whould have been nice to just get the right assembly the first time but it was 2 weeks out. Switched out the nozzle abd cleaned out a ton of soot from the burners and she fired up. Original pilot assembly was clogged up bad too. Thought it was wierd for a 4 year old unit but it sits unused most of the time.

[valdelocc]

Great! glad you didnt have to call a HVAC contractor, they are expensive you know.

[Wiseguy91]

Contractor=My boss I'm in training in a family business.

[Betabass]

Good job........

Beta