weil mclain gv pressure drop on ignition

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Old 11-07-17, 08:31 PM
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Smile weil mclain gv pressure drop on ignition

I am working on a GV 4 series 1 natural gas boiler. The boiler starts up verifies flame and then shuts down due to a pressure drop . Using a manometer I verified the pre ignition vacuum to be 1.5 in water. As soon as ignition occurs, the pressure drops to 1 In and stays there
I replaced the vent motor, pressure switch, ignition nozzle, and completely flushed out the power vent and the control module.. No luck
If i bypass the pressure switch , the boiler runs fine.
Does anyone have any ideas what to do next.or have any ideas as to what is wrong. This boiler has run well for the past 20 years.

Thanks
 
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Old 11-07-17, 11:21 PM
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I would replace that boiler... Its seen its day that model. They were problematic. I worked on my share of those, but learned long ago not to throw money at them. I'll walk away. Your lucky it ran well for 20 years...

Those were the edsels of weil mclain IMO...

Probably the combustion chamber is caked up from long time on/off condensation issues or not draining properly..

They have a negative pressure -.20" WC gas valve also and are hard to find anymore.. Pulled teeth to get one christmas eve 2008 for a unit I was servicing. That valve was $600 bucks without shipping... It was the only one I found in all the USA at the time.....
 
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Old 11-08-17, 08:34 AM
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Thanks for the reply..
would you get another Weil Mclain
If not what brand would you recommend

TS
 
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Old 11-08-17, 10:42 AM
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It depends on what you want to spend.. How much radiation and type...

How many sq ft the house?

No I wouldnt go with WM..

Probably burnham for standard boiler.. Mod cons are an option it certain circumstances but they are coastly..

Most likely the boiler is oversized but a heat loss would need to be done.. You can get close IMO with 25 btu per sq ft of home...

The GV4 is a 105k btu boiler.. Pretty big with a DOE of 92 k btu. They were efficiant for the day of 87% so not sure what your looking for..

Gas is cheap IMO...
 
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Old 11-08-17, 10:44 AM
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Also where is your vent for boiler going now? Chimney anywhere? etc etc.

Baseboard?
Cast iron radiators?

How many feet of baseboard in total? Element only...
 
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Old 11-08-17, 11:44 AM
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Troubleshooting — air pressure switch

https://www.weil-mclain.com/sites/de...4-manual_1.pdf


This sight might give you some insight to your problem. Trouble shooting starts at page 67.

Hope this helps a little.
 
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Old 11-08-17, 05:17 PM
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The sq ft is approx 2000 plus 400 sq ft garage
Plus a 40 gallon boiler mate and 40 gallon storage tank...
The unit is vented thru stainless steel pipe approx 30 ft horizontal
inlet air drawn from basement
primary heat ex changer is water to air
separate heat ex changer in garage water to air
The boiler always discharged condensate water
I have been using the wm troubleshooting procedure but it is for the 90+ GV
I not sure the replacement pressure switch is not calibrated for the old GV 4
it seems that the pressure setting should depend on the size of the boiler like it is for the HE series


TS
 
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Old 11-08-17, 05:46 PM
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So 2000 sq ft? And 400 sq ft heater garage?

And you have coils over air? ( Forced hot air with a coil)

It would probably cost too much to install gas furnace and water heater..

So...


I need to know the coil specs in the air handlers. Or how many ton a/c unit you have? I can usually tell by that...


You have about a 62k btu heat loss with garage. If you dont heat garage 24/7 then about 50 k btu boiler.

Your ducts should be 12" round, 16x8, 12x10 etc... or somewhere on that size...

The plate on the heat exchanger should have the coil heat capacity on it...
 
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