water boiler heater high pressure worries

Reply

  #1  
Old 02-12-18, 09:15 PM
Member
Thread Starter
Join Date: Feb 2018
Location: usa
Posts: 5
water boiler heater high pressure worries

Hi all.
I have an ACK-O-MATIC gas boiler at my 1800 square feet tri level house,that worked beautifully for the last 10 years(only had to change the pump once 6 years ago).but recently,it stopped heating the house,i noticed the psi in the pipes went down to almost 0. I changed the water pressure regulator,flushed the system(3 zones), it worked but psi fluctuating,40 at times.I then changed the expansion tank,flushed the system,it got stable. at these numbers: 14 psi when boiler is not working, and 26,sometimes 28 psi max when water in being heated. producing enough heat, for the house.I am anxious about the pressure.it never went over 30 though after the last changes.but are these numbers reasonable?
Thank a bunch for any helpful advice.
 
Sponsored Links
  #2  
Old 02-12-18, 09:33 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 45,545
Welcome to the forums.

14psi at idle is pretty normal. I'd say 26psi is at the top edge of where your system should be. That high pressure is caused by your pressure tank. It's possibly not big enough or there is not enough air in it.

You want to avoid having to drain and flush the system as that adds new minerals and air back into the system.
 
  #3  
Old 02-17-18, 10:39 AM
Member
Thread Starter
Join Date: Feb 2018
Location: usa
Posts: 5
Thank you for the reply.
I installed a 4 gallon expansion tank. still the same.shall i add air to it? it's brand new,set for 12psi.do you think i should install an air separator/eliminator? someone told me about them.
Thanks.
 
  #4  
Old 02-17-18, 11:15 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 45,545
I'm not a boiler pro. I can't offer a comment on the size of the expansion tank.

I don't think your issue is air in the system. Air is compressible and water is not. When the system heats up the water expands. The pressure tank is supposed to allow that expansion to occur inside of it. It almost sounds like the system isn't seeing the pressure tank. Is there a valve to it that could be closed ?

A few pictures of your setup there could help here... How-to-insert-pictures
 
  #5  
Old 02-17-18, 03:25 PM
Member
Join Date: Oct 2013
Location: United States
Posts: 1,990
S,
The 14 is fine if it is enough to reach all 3 floors. Personally, I prefer 18-20 PSI but with your expansion situation it doesn't look like that is possible.

If the tank is sized properly for the system there typically should be no more than a couple of lbs. difference between the cold and hot temps.

I would look at an under sized tank or a bladder with low air pressure.

If you replaced the tank with the same size that had been working problem free for 10 years, I would check the air charge in the tank and charge to at least 14 PSI since that is what your cold pressure is.

When your boiler is up to temp, with a screw driver tap your tank. The top should sound solid and the bottom hollow because of the bladder.

If both top and bottom sound the same, (solid) then your bladder has either ruptured or lost its air charge. In either case it must be recharged or replaced.

Hope this helps a little.
 
  #6  
Old 02-17-18, 03:39 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 45,545
He just installed a new tank... charged to 12psi. That's what's puzzling.
Will upping the charge to 14psi make that much difference ?
 
  #7  
Old 02-17-18, 03:47 PM
Member
Join Date: Oct 2013
Location: United States
Posts: 1,990
PJ,
No it won't. From 12-14 is minor. Why I mentioned 14 is because in a perfect world you want your tank charge to be the same as your cold water pressure in the system.

12 should be fine if in fact he has 12. That's why I mentioned checking his tank to see if something happened to the bladder.

That expansion tank or lack there of would be the only cause of excessive pressure between cold and hot temps in the boiler.

Proper expansion room would alleviate the problem.
 
  #8  
Old 02-18-18, 02:27 PM
Member
Thread Starter
Join Date: Feb 2018
Location: usa
Posts: 5
Thanks again for your help.
I tapped the tank while water is hot,top is hollow the bottom is solid( it sits upside down).
I don't see a problem there.i took photos to show you.the pipe between the air vent valve and the water pressure regulator is clean i checked it no blockage,by the way the air vent spits nothing but water when i release it(that's why you see rust on the boiler's top surface.
 
Attached Images    
  #9  
Old 02-18-18, 03:12 PM
Member
Join Date: Oct 2013
Location: United States
Posts: 1,990
S,
So we know you at least have air in the bladder although that tapping test will not let you know how much of a charge.

If you are still getting that much of a swing something isn't right because at those figures you couldn't raise your cold pressure if you wanted without hitting the 30 PSI safety limit.

Do you have any cast iron rads or cast baseboard in your system or is it all just regular copper finned tube baseboard.

Any cast iron emitters requires a larger tank.

Just a thought.
 
  #10  
Old 02-18-18, 07:22 PM
Member
Thread Starter
Join Date: Feb 2018
Location: usa
Posts: 5
copper finned tube baseboard with tons of fins all around the house.
man. i'm thinking of flushing the whole system again zone by zone.i must have caused air bubbles when i changed the parts. as at first i bought a 2 gallon expansion tank,pressure was still going over 30..
While it never exceeded 28 psi since i got the 4 gallon tank(but after the last installation i did not flush nothing).
 
  #11  
Old 02-18-18, 07:35 PM
Member
Join Date: Oct 2013
Location: United States
Posts: 1,990
By flushing are you talking about bleeding the system.

If you drained the system to put the new tank in and didn't bleed it you're probably loaded with air. It wouldn't hurt to bleed your whole system again.
 
  #12  
Old 02-19-18, 12:51 PM
Member
Join Date: Jan 2017
Location: USA
Posts: 304
The new expansion tank has an acceptable volume of only 2.5 gallons of water and is too small for a system with standing cast iron radiators. A better choice would have been the HFT90 with 11.5 gallons of acceptance. The one you have may work but just barely.
 
  #13  
Old 03-10-18, 09:45 AM
Member
Thread Starter
Join Date: Feb 2018
Location: usa
Posts: 5
Problem solved

Hello again,
Just wanted to tell you that the problem is fixed now.Bleeding the system has nothing to do with it.
The issue was the air pressure inside the expansion tank. it never occurred to me if i should check it as it said on the tank "factory filled 12 psi". well it was not. it was 28 psi. once i lowered it to 12 i fixed the problem.
Thank you all especially Spott and Steamboy and everyone.
 
  #14  
Old 03-10-18, 12:33 PM
Member
Join Date: Sep 2009
Location: U.S. Midwest
Posts: 1,340
When you measured 28 psi air in the tank, did you first depressurize the water pressure in the system? If not, then there in no telling what is going on.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes