Improperly Converted Expansion Tank?

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Hello. Just bought a new house and working on getting the heating system working properly.

Boiler: Weil-McLain CG-5 Series 12

My main question is:

While looking in the owners manual for my boiler I noticed that the current expansion tank was "not installed properly" and my hunch is that it was improperly modified from the original installation.

The manual's instructions:



There has been some scares with the system over the weekend where the pressure was reading "55 PSI" one time and "70+ PSI" and other time. Once I saw the 55 PSI I called a professional. I'm working with a HVAC company who came out today but it seems like the tech wasn't too knowledgeable on my specific system.

I tinkered with it yesterday (before the pros saw it today) and came to the assumed conclusion that it is the expansion tank that is the issue and possibly the TP gauge as well. The relief valve is definitely bad as it has a slow leak. Today the pros concluded the same thing. The reducing inlet valve was ruled as a suspect contributor to the problem.

The original boiler was properly sized for the house at the time of installation. Since then, there has been two additions to the house and radiators added to the attic/finished 3rd floor.
 

Fitter30

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Boiler should have a 30 lb relief valve should have been relieving way before 55 lbs. Take a few pics of boiler ex tank ,piping around boiler and gauge. That 55 bet it was feet not lbs.
 
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Fitter30

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The drawing of the ex tank i don't like either one especially the one for the bladder tank. Both are not 100% correct because their on the supply side of the pumps. But to make them 100% correct some piping would haveto be redone. It's a older system lets try making bladder tank work.One or two story house? Tools needed to check expansion tank. Tire gauge 50lb and a tire pump. Turn burner to pilot let at pumps run let water temp get 90° or less. Turn pumps off at bottom of ex tank theres a cap that unscrews . Depress valve does water come out? If so tank is bad needs to be replaced. Has its own shut off valve. What is the the gauge water pressure 12lb would be enough for most two stories. Adjust water pressure to the 12 lbs. With tank valve open use tire pump to 12 lbs. Turns pumps on and burner. Look at the boiler tag boiler should be rated at 30 lbs. Then look at relief valve tag it should be set at 30. If boiler is rated at 50 lb and relief matches it ok.
 
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The drawing of the ex tank i don't like either one especially the one for the bladder tank. Both are not 100% correct because their on the supply side of the pumps. But to make them 100% correct some piping would haveto be redone. It's a older system lets try making bladder tank work.One or two story house? Tools needed to check expansion tank. Tire gauge 50lb and a tire pump. Turn burner to pilot let at pumps run let water temp get 90° or less. Turn pumps off at bottom of ex tank theres a cap that unscrews . Depress valve does water come out? If so tank is bad needs to be replaced. Has its own shut off valve. What is the the gauge water pressure 12lb would be enough for most two stories. Adjust water pressure to the 12 lbs. With tank valve open use tire pump to 12 lbs. Turns pumps on and burner. Look at the boiler tag boiler should be rated at 30 lbs. Then look at relief valve tag it should be set at 30. If boiler is rated at 50 lb and relief matches it ok.

I apologize my original post was incomplete.

I am replacing the expansion tank, TP gauge and relief valve. The HVAC company said that the expansion tank was bad, they didn't test it , but I am okay with replacing it with a bigger one since everything is undersized for my house.

So, my original question was if I can just install the new tank where the old tank is, but it seems the general consensus from research says my system should be re-piped to put the circulators after the boiler and the expansion before the boiler, and just leave the air vent where it is. Sounds pretty expensive. Would love not to have to do all that since I just spent all my money on a new house
 

Fitter30

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Repipe would be expensive. The time would be when replacing the boiler. Thats why lets try to make bladder tank work. Did u set up the new ex tank like i described?
 
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Just an update. I contacted Amtrol and they said that it would work as it is configured. Although I modified it a bit to make it easier to work on in the future. Thanks for the help all!
 
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