Heil Furnace - Honeywell Smartvalve

WNYHVAC

Hello Everyone,

Used the forum for tips and tricks first time posting.

Got a bid a head scratcher here from a emergency customer call no heat. Furnace is a heil that uses the Honeywell smart valve (SV9501M2528 ) Valve was replaced three months ago by another company, as was the HSI. Furnace gets a call for heat, inducer kicks on you can hear the valve click, ignitor glows...no gas coming from pilot. I have gas coming into the valve and nothing coming out to burners. Customer stated he was able to manually light the burners but I could not replicate. Tested voltage on the valve I got 24volts, ignitor works. I am stumped other then to say the valve is bad and needs to be replaced...again. This is a first for me that wasn’t a faulty ignitor, valve due to the bad boards which had a recall. 

mattmia2

clogged pilot burner? position of the ignter/pilot burner/main burner so the ignitor isn't igniting the pilot? general draft issue?

WNYHVAC

mattmia2 said:

clogged pilot burner? position of the ignter/pilot burner/main burner so the ignitor isn't igniting the pilot? general draft issue?

I can check the pilot burner but I’m not getting any reading for gas coming out of the valve. Ignitor and pilot valve are positioned properly I tried to manually light no gas is present. There should be a gas reading on the opposite side of the valve even if the pilot tube was clogged. 

mattmia2

Does it need to prove the pilot burner before it opens the main valve?

WNYHVAC

mattmia2 said:

Does it need to prove the pilot burner before it opens the main valve?

So I assumed that could be the case as well and found the supporting documentation from a troubleshooting on specifically these valves. However wouldn’t manually applying a flame with a lighter to the flame sensor trick the system? 

. As the circuit is completed, the igniter is powered and the pilot gas valve is opened with the igniter lighting the pilot gas. In those systems using an EFT the Smart Valve sends a 16 VAC signal to the EFT to start the time delay which dictates the amount of time that must pass prior to energizing the air handling blower.

The flame rectification / proving system proves the pilot flame is lit (in less than 2 seconds) and allows the main fuel valve to open and to simultaneously shut down the igniter. The flame proving system continues, monitoring only the pilot gas flame. The main fuel valve remains open until the call for heat ends

mattmia2

If the circuit is from the pilot burner tube to the igniter, maybe not if the flame doesn't encompass the pilot burner

HVACNUT

Is it a negative pressure gas valve? That could be why your not showing manifold pressure but the burners can be lit manually. Which should never be done btw. Check pressure drop during ignition on the inlet side of the gas valve. Is it an OEM igniter in the correct location?

ratio

Is there a pressure test teat on the pilot line? The main valve won't open until it proves the pilot, so if the main valve is where you are checking gas pressure, zero is expected at this point.

Pull the pilot line off & make an adapter to check the pilot pressure directly. If that shows zero during an ignition attempt, there's something going on with the valve. If it was just replaced, I suspect excessive pipe dope or tape, but it could still be a defective valve.

HVACNUT

I'm pretty sure there is no pilot. HSI ignition. 

WNYHVAC

ratio said:

Is there a pressure test teat on the pilot line? The main valve won't open until it proves the pilot, so if the main valve is where you are checking gas pressure, zero is expected at this point.

Pull the pilot line off & make an adapter to check the pilot pressure directly. If that shows zero during an ignition attempt, there's something going on with the valve. If it was just replaced, I suspect excessive pipe dope or tape, but it could still be a defective valve.

I have checked only the gas on the outlet shown in the diagram, there is no pressure drop on the inlet when the system is turned on. I cant here or smell gas coming from the pilot tube, could rig up something to test pressure.

ratio said:

Is there a pressure test teat on the pilot line? The main valve won't open until it proves the pilot, so if the main valve is where you are checking gas pressure, zero is expected at this point.

Pull the pilot line off & make an adapter to check the pilot pressure directly. If that shows zero during an ignition attempt, there's something going on with the valve. If it was just replaced, I suspect excessive pipe dope or tape, but it could still be a defective valve.

The excessive pipe tape intrigues me however the customer said back in May when the valve was replaced it fired up every attempt when testing...Obviously being May they didnt have a need for heat until now.

HVACNUT

I guess there is a pilot. Can you post the wiring diagram?

WNYHVAC

HVACNUT said:

I guess there is a pilot. Can you post the wiring diagram?

Jamie Hall

I sometimes ask dumb questions (well, perhaps more than sometimes...) but... have you double checked all the wiring and the integrity of any connectors? And you have voltage where you need it, when you need it?

ratio

Sure sounds like the valve is bad. Might just be mechanically stuck, did you try some percussive maintenance?

I just had two DOAS units both with second stage gas valves stuck. One freed up by flipping the switch on it back & forth while it was trying to open but the other one wouldn't. I'll be replacing it in the next few weeks. I believe the reason they stuck was because they sat there for 2-3 years. (we were the 3^rd or 4^th contractor on the job, <sigh>)