Return to the Heating & Air Conditioning Forum | Post a Follow-Up

Air locked boiler

Posted by apg4 (My Page) on
Fri, Nov 9, 12 at 15:00

Started having problems a week ago when the gas furnace was working but the radiators weren't. Here's how to fix that - in case anyone needs to know - an wants to save a ton of coin in the process.

At first glance - or rather 'listen' - the furnace itself was making slight hammering noises it never made before. (It's a 15-20 yr old gas boiler.) That should have been the first clue that the water was low. But what I zeroed in on was the fact that the circulator wasn't working.

Purchased a new replacement at Grainger's, then found the same one on-line for half price. (Note to self: never research a price after you've made the purchase.) But a pump in hand is worth twice the price, I guess.... Installation wasn't difficult, but still no heat even with the circulator now running.

Now I had to drain the furnace to install the pump, and both system supply and return valves were turned off for the install. Still the hammering noises when fired up, even with the auto- and manual-fill valves open. Time for Plan B....

I figured that since I drained the furnace, I could refill it at the same place. Made up a short length of hose with double female fittings and connected the furnace drain hose to a another to the closest sill cock. Cautiously, I opened the drain valve - and the furnace audibly began to fill. Previously, I researched this on line and no source mentioned using the drain to fill the furnace; indeed, one HVAC tech said you shouldn't/couldn't do it then tried to sell be some rather expensive - and unnecessary - work.)

Now it's important to get rid of the air that has been blocking the system: open the bleed valve on the expansion tank next to the furnace as well as the one at the piping's highest point. (You may have a galvy expansion tank in the attic.)

Now the auto fill valve is supposed to add water until the system pressure is 10-20#. City water is more than this, so once the air is bled, turn off the water and then bleed off the excess pressure via the same drain until the tri-indicator on the furnace reads 15# or so. Fire it off....

Shazzam! - all is good in the heat department. But that doesn't explain why the auto fill device didn't do it's job or where the water went in the first place. There aren't any leaks....


Follow-Up Postings:

RE: Air locked boiler

your auto fill device has a manual over ride which is for your situation, you got it done anyway. Grainger likes purchase orders and desperate people, they are not cheap as you found out. They used to be reasonable until they figured out institutional sales are much more lucrative and most of the buyers don't know what they are ordering

 o Post a Follow-Up

Please Note: Only registered members are able to post messages to this forum.

    If you are a member, please log in.

    If you aren't yet a member, join now!

Return to the Heating & Air Conditioning Forum

Information about Posting

  • You must be logged in to post a message. Once you are logged in, a posting window will appear at the bottom of the messages. If you are not a member, please register for an account.
  • Please review our Rules of Play before posting.
  • Posting is a two-step process. Once you have composed your message, you will be taken to the preview page. You will then have a chance to review your post, make changes and upload photos.
  • After posting your message, you may need to refresh the forum page in order to see it.
  • Before posting copyrighted material, please read about Copyright and Fair Use.
  • We have a strict no-advertising policy!
  • If you would like to practice posting or uploading photos, please visit our Test forum.
  • If you need assistance, please Contact Us and we will be happy to help.

Learn more about in-text links on this page here