2nd zone air in pipes issues.

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Old 01-10-13, 01:25 PM
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2nd zone air in pipes issues.

Hello, I've had an issue with my upstairs (2nd) zone for a couple of years now. We have a hot water furnace/boiler with baseboard forced hot water.

Over the past few months I've deduced through reading online that the upstairs thermostat or zone control valve is not working and is the cause of no heat. I just replaced the zone control valve motor, it was an easy fix for me and cheap. I could never move the auto-manual arm on it and now I can. That was the reason i believed the zone valve was somewhat at fault. I'm not 100% sure this was the root cause but the control arm now moves easier. Anyway before neither the thermostat nor simply crossing the two wires together at thermostat area would call for heat. Now after the replacement the furnace turns right on. Ok, so one problem may be fixed now I have another problem.

A minute or so after the heat was called and furnace started up I got a lot of loud bangs from furnace area, mainly the expansion tank, but the pipes as well. Not the normal bangs and pings when a heating system like this starts but sort of violent bangs. I checked the psi and they were normal, though the gauge reads entire system pressure so it's not showing what zone 2 is at alone. I think it's due to low water pressure/air. I disconnected the two wires at thermostat and within a minute the bangs stopped as the furnace went to stand by. Zone 1 has since come on as normal heat operation and no loud bangs.

My question is is this air in pipes and is it so much air that I could hurt the system having it refill itself? Having the system not working well in a year or so I could see that there is a lot of air in this zone. What is the best way to flush out an abundance of air?
 
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Old 01-10-13, 01:41 PM
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Hi Billium!

The first thing is to make sure you have a pressure gauge that is accurate so that you have a 'baseline'. You must have at least 12-15 PSI when the boiler is cold. Read this:

http://www.doityourself.com/forum/bo...ure-gauge.html

Next, you need to know that the air charge in the expansion tank is correct, so read this and follow the 'step-by-step' in order to properly recharge the expansion tank.

http://www.doityourself.com/forum/bo...sion-tank.html

You won't hurt the boiler by adding water if you turn it off and allow it to cool to 100F or so before you add alot of water.

Are there air bleeders on the baseboards upstairs?
 
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Old 01-10-13, 01:45 PM
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Yes, a large amount of air moving through the piping can cause some pretty horrendous sounds, especially when it goes through a valve, elbow, pump, etc...

Does your system have an 'air scoop' and a functioning automatic air vent?

Your expansion tank is the 'newer' type that looks like gas grill propane tank, yes?
 
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Old 01-10-13, 01:51 PM
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The current pressure gauge is built in body and has a ridiculous range of like 0-500 but its pretty spot on around 12-15psi. I can try the add on arir gauge too though. Yes it has an air release valve and yes the ex tank looks like a small propane tank.

If I were to bleed the air myself do I open the thrush valve or purge valve at furnace area? I won't do any purging until I know more however. And finally yes the upstairs end point has a air valve looking thing I guess I would turn.
 
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Old 01-10-13, 02:22 PM
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a ridiculous range of like 0-500 but its pretty spot on around 12-15psi
C'mon Bill, yer X-ajeratin a bit ain't ya? 500 PSI gauge on a boiler? Heck you would almost not be able to see the difference between 12-15 and sittin' on the 'pin'!

What I'm saying is that OK, maybe you are reading that 12-15, but is it ACCURATE?

After you check/charge the expansion tank;

First thing I would do, with the boiler OFF and cool-ish, is raise the pressure in the boiler manually as far as I dared without lifting the relief valve.

Then, ONLY IF THE VALVE IS NOT ALL CORRODED and stuff... you don't want it to break when you open it... open the upstairs bleeder and get as much air out as you can before running the pump again.

Then, before refiring the boiler, reset the pressure to 12-15 and give it a try...
 
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Old 01-10-13, 08:47 PM
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Double checked it once more and it's 0-500 in Kpa, sorry for confusion there. In psi it's 0-75. The air bleeder is covered in what looks like hard water stains, though the tip does rotate freely. Could I open the upstairs bleeder without adding pressure? And would I open the upstairs bleeder after the heat has been called and pump starts pumping, and loud bangs begin, or without calling for heat.
 
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Old 01-10-13, 08:54 PM
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Could I open the upstairs bleeder without adding pressure?
No, there's no point in that at all. If there is no pressure in the boiler in the basement, there will be even LESS pressure two floors up. In fact, NEGATIVE pressure, or a VACUUM could exist and all you will do is suck more air INTO the system.

To raise water to the second floor, you need at LEAST 12-15 PSI in the system, and if you are bleeding you will be letting pressure OUT as you do so, so always start by manually raising the pressure to like 25 PSI before you start.

And would I open the upstairs bleeder after the heat has been called and pump starts pumping, and loud bangs begin, or without calling for heat.
To START with, get as much air out of the system BEFORE you fire it up.
 
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Old 01-10-13, 09:13 PM
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Makes perfect sense. Do I introduce the added water pressure through the water pressure valve until it reaches the 20#s? I noticed you mentioned adding water without lifting the relief valve.

This isnt my picture but I have a very similar valve.
http://i257.photobucket.com/albums/h...Picture040.jpg

I know if I raise this lever it will raise water pressure.
 
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Old 01-11-13, 06:34 AM
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Do I introduce the added water pressure through the water pressure valve until it reaches the 20#s? I noticed you mentioned adding water without lifting the relief valve.
Yes, lift the 'fast fill' lever until you are in the 20's... then, as you bleed, keep an eye on the pressure because it will drop back down as you bleed. You will be up and down the stairs quite a bit. If you have a helper with a cell phone...

Of course you don't want to add so much pressure as to open (lift) the pressure relief valve, so if you are unsure of your gauge accuracy, go slowly...
 
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