1996 Weil Mclain having issues

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Edward Quinn

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I have a 1996 Weil-Mclain forced hot water heater with a Beckett oil burner. The system has been great since it was installed. Like all things it now has had issues. First, off the Amtrol 30 tank was replaced, the tankless coil for Domestic Hot water has been replaced. Last week the city was working on the water lines and it is a High pressure they screwed up and charged the line up to high and an air slub hit the heater the backflow preventer was damaged and the pressure reducer was shot both replaced and we found one circulator was gone as well replaced with new. The issue is I also replaced the pressure relief valve and the temp/ pressure gauge and all looks fine pressure remains between 15 and 17 PSI and temp runs between 180 and 200 same as always nothing was changed but the relief valve is leaking and pops off when it is running and hits top temp. It is a Watts 374A good to 30PSI and the system never runs past 17 PSI. Stumped? is it bad even though it is just one week old or am I missing something else? Heat is great in the house and hot water is plentiful no other issues. Any info greatly appreciated.
 

Dana

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I suspect the expansion tank has lost it's charge or was damaged.

Bladder type expansion tanks have a Schraeder valve on one end for pumping up the pressure when the water side is unpressurized up to the anticipated system pressure. That way when the system water volume increases with temperature during a burn it has some volume to move in without rapid or high pressure spikes.

Older type expansion tanks are usually larger and have no bladder- they need to be drained if they fill with water. A tiny leak in one of those results in it filling up with air.

Bladder type:

49296d1428943290-replacing-boiler-parts-where-add-shut-off-valves-boiler-parts.jpg


Old school type:

571r08kbnqft.jpg


(It's the gray horizontal cylinder at the top.)
 

Edward Quinn

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I have the badder type all changed out checked the charge before I put it on right on the money at 15PSI. But relief is still dripping a Watts 374A only 2 weeks old.
 

Dana

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I have the badder type all changed out checked the charge before I put it on right on the money at 15PSI. But relief is still dripping a Watts 374A only 2 weeks old.

How high is the pressure reaching during the burn cycle?

It the opening up at some pressure and dribbling then, or does it drip pretty much all the time? If it's a more or less constant drip there may be some grit lodged in the valve seat, which might be purged by manually opening it up with the lever on the top for a second or so.
 
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