Main burner blowing out pilot
Need help working on a Residential climatrol furnace. I forgot the model #. I just installed a universal 24v gas valve and new thermocouple the other day. I got a call back today. Tenant complaint of no heat. I went to check it out again and the pilot went out. I relighted it. I checked the gas pressure and it was reading at 3.5 wc. During the 8 or 9 cycle the main burner would puff back and blow out the pilot. I can't figure out what to do the problem. A little help would be nice.
You need a slow opening valve, or a step opening valve...I do not know what you call them down there.
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Are you reading 3.5" at the inlet to the valve while running? If so, you should probably have 4.5" minimum for the valve to work properly. It needs a pressure differential to operate the diaphram properly.
So I have to get a slow opening valve? I'll look into it.
Yes, I am reading 3.5 at manifold. I haven't check the inlet yet. So you are saying I might not have enough gas pressure?
Check heat exchanger & venting for blockage. But most likely not a slow opening valve.
There is no bad beer, some just taste better than others.
I've seen it before where too low of a line pressure, which can be due to the utility meter, doesn't allow the appliance reg to work properly in the way you are describing.
Originally Posted by xxcels
I've always considered the minimum inlet pressure to be 7"wc.
what's the make/model? should specify if it needs a step valve. If it doesn't you may have a flu blockage.
I also think you may have a flue restriction. You also have a good strong pilot right? just asking. is this propane? if so the pilot has to be clean 1st thing.
If your not getting the results you desire then change. People change from either desperation or inspiration.
Originally Posted by SolarMike
First thing of course is to be sure you have a strong enough pilot flame. Second, is there any flame blowback or rollout when the burners ignite? Third, did this happen before you replaced the gas valve?
If this is a natural draft furnace with an open hood, a blocked flue will have no effect on the burner.
Is the pilot getting blown out, or is the pilot valve closing due to insufficient DC milivoltage?
Make sure the pilot flame is sharp and completely engulfs the thermocouple. Measure the dc milivolts.
If the thermocouple is just barely holding the valve open, the flame only has to flutter away from the t-couple for a couple seconds to drop out the valve.
If it is indeed blowing it out, check for a restricted heat exchanger and if its ok install a slow opening valve.
Worry is a really gross misuse of one's imagination. -- PHM
There seem to but no Data plate on the unit but the cover of the manual
Originally Posted by JPJ13
M# 174-0 Series
Yes, I checked the pilot and there is a strong pilot flame. I putted a new thermocouple there too, measuring at 25mv.
I lowered the manifold pressure to 3.0" wc but still the problem persist
This is a natural draft furnace and I checked the flue vent and it seem to be clear. The heat exchanger look clear to me but I will have to double check when I go back. I didn't bring my tools with me.
I went to double check it today and I have a flame blowback when the main fired up. It will not do this all the time but 1 of 5 tries and it would blow out the pilot.
Burner blowback or rollout upon startup should have nothing to do with the type or style of gas valve. Typically on that style of furnace you are going to have clogged burner ports or dirty heat exchangers. Here is another thought, the times when you have flame rollout, is the blower motor already on during that ignition?