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Old 02-17-2011, 12:44 PM   #1
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Need to bleed a hot water baseboard heating system


Hey everyone. I've read through a number of posts on this amazing site in addition to many hours of reading other Internet sites, however, I am still having a bit of a problem with my system. I understand the concept with regards to bleeding the air out of a boiler / hot water heating system however I am a bit perplexed as to the exact steps that I should do on my system.

I have an oil-fired boiler in the basement, an expansion tank (above the boiler suspended in the ceiling), an indirect-hot water tank, and 2 zones (for 1st and 2nd floors). The 2 zone valves are on the supply side with 2 shutoff valves a few feet above/after them. Interestingly though, on the return side, the 2 zones actually join into 1 main return pipe (note - they each have a gate valve) and then on the boiler, there are 2 "spigots" or drain valves: one is located just under/after the circulator and the other drain valve is right at the bottom of the return pipe. In between the 2 drain valves is a shutoff valve as well.

Because of the air in the system (noises, gurgling, etc...), this is what I did: I shut off the boiler, manually opened up my 2 zone valves, closed the valve leading to/from the expansion tank, closed the valve leading to the indirect hot water tank, attached a hose to the 1st drain valve and closed the shutoff valve located between the 2 drain valves (have to do this to isolate the water supply from the return). Then, I started to drain the system and at the same time, opened up the water-supply valve. The water pressure did not go any higher than ~15 PSI, and I ran the system for over 10 minutes. The temp gauge dropped down to the 0 mark at this point, and all of the pipes, etc...were very cold to the touch. At the very end, I opened up all of the shutoff valves and then closed the drain valve, and finally closed off my 2 zone valves.

The issues appear to be better now, however, there's still a bit of "swishing" noise happening. From most of the posts that I've read, it seems like everyone has a seperate drain valve per zone on the return. Given that I don't, I'm not sure how to isolate my zones so I left both open and did it that way. There are the gate valves but they are both connected to the main return pipe so I don't see how closing them one at a time will help...

Any help or advice would be greatly appreciated!
Thanks.

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Old 02-17-2011, 02:03 PM   #2
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Need to bleed a hot water baseboard heating system


Ayuh,... Welcome Brewmaster,...

That's a nice detailed post,...
I see 2 things not mentioned, that are the basis for My questions,...

Don't you have Bleeds out in those zones, or is it buried radiant tubing,..??
Do you have an air-trap/ vent plumbed into the supply side(outbound) of the boiler,..??
Is your expansion tank just pressure, or a bladder tank,..??

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Old 02-17-2011, 02:36 PM   #3
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Need to bleed a hot water baseboard heating system


Hey Bondo! Thanks for the quick reply! I'll try to answer your questions "to the the best of my knowledge": I cannot locate any bleeder valves on any of the baseboards in any of the rooms on the 2nd floor (i.e top zone). I could look around on the 1st floor but that would be for the 1st zone only, and really, the noises are mostly affecting the top/2nd zone. The copper pipes are in the walls and basically it's a series loop from baseboard to baseboard (with fins).

There is not an air trap/vent and the expansion tank is for pressure only (I think...what's a bladder tank?). It has a drain valve at one end and a small, 1/2" pipe coming out the other end which then connects into a larger pipe coming out of the center of the boiler (note- there is another drain valve on this pipe and then there is a shutoff valve). To drain the tank quickly, I connected a hose to the drain valve off of the pipe coming out of the tank, closed the shutoff valve and opened up the drain valve located on the other end of the tank to create a draft/airflow, otherwise, it was taking forever to drain...

The house is ~32 years old and the piping/baseboard setup from what I know is original. The boiler and indirect water tank are new though (2 years), however, the company just took the old furnace out and popped in the new one...no other changes were done.
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Old 02-17-2011, 02:45 PM   #4
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Need to bleed a hot water baseboard heating system


Ayuh,... I'm no expert, but I gotta think there's a bleed Somewhere in the 2nd floor loop...
If not, there otta be,... I'd sweat 1 in myself, at the highest, farthest point...

It sounds like yer tank is a captive air style,...
Bladder tanks are smaller, 'n sealed with an internal bladder...
Google it for a picture..

Have ya got any pictures of the near boiler piping,..??
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Old 02-17-2011, 07:04 PM   #5
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Need to bleed a hot water baseboard heating system


It sounds like you almost did it perfictly but you need to only have one return gate valve open at a time. You need full flow to basicly drag down the air to get it out of the system. If possable raise the water pressure to 20 to 25 psi before you begin blowing it down. Again do only one loop at a time.
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