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Author:
joeray (OR)
I have a Slant Fin GG150 boiler that drips when it has been runnning. I have replaced the B&G FB38 regulator and the pressure at the tradicator is 10-12 lbs when cool, but climbs to 28-30 when hot. I have also replaced the 30 lbs. relief valve, Watts M335. Currently there is an Extrol Model 30 expansion tank which does not show any water at the valve and feels cool on the bottom and warm on the top when running, the pressure is around 12 lbs to match the incoming pressure. I was going to replace the expansion tank with the same size, but am wondering if I need a bigger expansion tank. The house is all on one zone with about 10 cast iron hot water radiators. What pressure increase should I be seeing when the system is running, it currently rises from 12 to around 28-30 lbs, is that too much of an increase? Would a bigger tank solve my problem?
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Author:
Paul48 (CT)
The pressure in the tank needs to be adjusted while off or isolated from system pressure?
What's changed? Did it work before? Generally, large volume systems like the ones with C.I. radiators can require a larger exp. tank. But, if it worked I'd want to know what changed.
Edited 2 times.
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Author:
packy (MA)
10 big cast iron radiators gives the system alot of volume. an extrol 60 should take care of the problem.
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Author:
joeray (OR)
Thank you for responding. This all started when I tried to bleed my radiators and there wasn't enough pressure. It turned out the pressure regulator was completely plugged with corrosion and debris and the pressure was less than 5 lbs., not enough pressure for the 2nd floor radiators. I can only remember in years past I have been able to bleed the radiators, the system has been unchanged in the 22 years we have lived in the house, I think everything was installed around 1980 and nothing has been updated.
I have taken the current extrol model 30 off the system, ie unscrewed and removed it, and measured the pressure,it was around 10 -12.
I bought an extrol model 30 and the directions recommendeded 150,000 btu units use EX-30 for finned tube baseboard or radient panels, ex-60 for convectors or unit heaters, and ex-90 for cast iron radiators.
I don't think anything has changed in over 20 years, there have been no additions or changes to the plumbing. The system ran for at least several years with low prssure because the intake pressure regulator was plugged up and did not allow the flow of water to regulate the system pressure.
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Author:
Paul48 (CT)
OK....You got all the air out of the radiators,and that was acting like a larger expansion tank. As packy said, the 60 will be plenty. I have an old gravity conversion system, with 2.5" mains in the basement, and C.I. radiators.I had to go with a 60 when we put the new boiler in.
As you now know, those expansion tanks are suprizingly heavy. The 60 will be heavier still. Make sure it's supported well, and hanging vertically. I've seen folks mount the 30's horizontally, and that's not cool.
Edited 1 times.
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Author:
hj (AZ)
quote; the pressure is around 12 lbs to match the incoming pressure.
How are you measuring the pressure. You CANNOT do it with the tank attached to the system unless you have drained ALL the pressure out of the boiler.
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