How to purge system?


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Old 11-05-05, 02:26 PM
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How to purge system?

I have a 3 zone forced hot water baseboard heat. The cold pressure on our boiler is almost 25psi which from research I know is way too high. So I was releasing some water from the boiler and the pressure was slowly lowering...soon the boiler was empty, so now I'm assuming I put tons of air into the system.

I've looked a bunch of places and can't find good directions on how to purge the lines. We don't have bleed valves on the baseboard. We have 1 supply line valve and 3 return line valves, one for each zone. From what I've read on this site, I turn off the boiler, turn off the supply line, but what do I do with the return valves, close all but the zone I'm purging?
 
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Old 11-05-05, 04:55 PM
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Nicole12

You do not want to turn off the supply but you do want to close the zones you are not purging. Don't purge until you know there is air in the system. Adding fresh water to a system is one of the worst things you can do to it.
 
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Old 11-05-05, 07:42 PM
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Since I emptied the boiler, I would assume that air would have gone into all 3 zones. So can I just hook up a hose, leave the supply on and leave all 3 return valves open, bump the pressure to around 25psi and purge, and repeat this a few times to make sure all the air is out, or do I want to just leave 1 return valve open at a time? Another website said to leave the supply open and have the returns closed at all times. Very confusing. Again our system only has 1 fill valve, purge drain for all 3 zones but each zone does have it's own return valve shutoff.

I do have the gas co. comingo out next week to service the boiler, hopefully they can at least show me how to purge the system.
 
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Old 11-06-05, 05:32 PM
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Nicole12

The gas company's service tech should be able to show you how to purge the system. Most service people don't mind at all showing a homeowner how to do something like this.
 
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Old 12-17-05, 08:22 PM
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Originally Posted by Grady
Adding fresh water to a system is one of the worst things you can do to it.
Why is that??

Charlie
 
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Old 12-18-05, 07:18 AM
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Grady can probably answer better, but from my research, it's because fresh water contains air so basically you purge you system but then add more air back into it with the fresh water.
 
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Old 12-18-05, 09:54 AM
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Originally Posted by nicole12
Grady can probably answer better, but from my research, it's because fresh water contains air so basically you purge you system but then add more air back into it with the fresh water.
You are correct. In addition to the air there are chemicals which are either corrosive or deposit forming. Obviously you want to keep the addition of those sorts of things to a minimum.
 
 

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