Purging advice needed - 1st time


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Old 10-24-09, 09:45 AM
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Question Purging advice needed - 1st time

I'm need to purge my hotwater baseboard system myself, and just want to run what I'm planning past the group to see whether there's any problems with what I'm planning. It's my first time doing this.

It's a two-zone system, one on the main level and one on the lower level. The upstairs zone is 2 parallel loops. Boiler fires just fine and the family room/bedrooms loop heats well. Family room loop is on the same level as the boiler; the other loop is one level up. I run the system at 220 degrees and about 20 lbs.

You can see a diagram of my system at http://acornbay.textdriven.com/tmp/h...ing_system.pdf, and a photo of the output side of the system at http://acornbay.textdriven.com/tmp/heating/IMG_0869.jpg.

I had the system worked on this summer, adding a short fin tube segment in the dining room segment to heat the floor in front of the kitchen sink, so some air probably got into the system.

The problem I'm wanting to fix is that part of the upstairs parallel zone is heating fine (the dining room loop), but the other part is not (the living room loop). The radiator at the input end of the living room loop feels slightly warm, but is cold through the loop. I have purged both ends of that loop and get water at both ends.

My working theory is that there is air in the living room loop that is somehow preventing parallel flow through that loop.

1. Can I safely close the valve that controls the dining room side of the loop, to drive all of the flow through the living room side?
2. There's a venting procedure in the Bell and Gossett Airtrol manual that I've never done -- any reason I should not do that?
3. Any suggestions on purging a long run? The living room run is probably 40' of Crane cast iron baseboard. Are there situations where on a long run like that you have to purge a bunch of water to get to the air?

Other suggestions also welcome.
 
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Old 10-24-09, 10:55 AM
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You are probably correct that there is air trapped in the parallel zone.

1. No reason at all not to try that.

2. Don't do anything with the airtrol or expansion tank until you are done purging the air from the zones. After you are done purging, it would not be a bad idea to completely drain the expansion tank. This won't necessarily help with the air in the zones, but if it hasn't been done in ages, it may help control the pressure in the system.

3. It could possibly take a bit of time... but in some cases you may need to take further steps to get those air bubbles to move through the system. Try #1 first.

Why do you run the system at 220 ? that's kinda crazy hot actually!

What is the system pressure when the system is COLD vs. when the system is HOT?
 
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Old 10-24-09, 12:09 PM
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Thank you for pointing out where the fill & purge instructions are. I've been looking for that as I recall seeing it, but now where I saw it.

NJ, the 220 F is called out in the B&G fill/purge instructions. I agree though, it is on the hot side.

Steve, for the living room loop, check if there are more bleeders on it. Sometimes they are on each end under the covers and/or in the middle. If not then I'd close the valve to the other parallel loop to force the air through the system.

I looked at your diagram and picture and did not see an air separator device. There should be one there as once the system is up and running the air needs to be purged back to the compression tank.

Al.
 
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Old 10-24-09, 12:32 PM
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Is the gas line to the boiler COPPER? If I'm not mistaken, I think that's a big no-no...
 
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Old 10-24-09, 02:08 PM
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More info

Thanks for the feedback everyone.

220 degrees -- that's what the boiler was set at when I had it installed ~3 years ago. Cold pressure is about 12 at 80 degrees. I was thinking that was kind of hot, but haven't had a reason to change it. Seems like there is a lot of discussion about 190 as the preferred number around the 'net.

Copper must be code here -- the boiler installer and water heater installer (2 different companies) both used copper for the gas line, and both passed inspection. I see discussion on it being OK for certain types of gas.

Air separator -- the Airtrol just before the tank is an air separator -- see http://www.bellgossett.com/literature/files/599.pdf for details.
 
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Old 10-24-09, 04:12 PM
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Seems like there is a lot of discussion about 190 as the preferred number around the 'net.
reason to change it
I'd set it down to 180... that's the de facto 'standard'. Unless you don't have enough radiators/baseboards in the home, 180 will be fine. Lower high limit is going to save you fuel. 220 is actually sorta dangerous... it's above boiling, if you open a bleeder on a system with 220 water in it, it will immediately flash to steam... sorta like opening a car radiator cap when it's overheated... BLAM! superheated steam, peeling your skin off.

I see discussion on it being OK for certain types of gas.
Certain kinds of gas... LP ... but in general NOT natural gas because of the sulphur content. The sulphur eats away at the pipe from the inside out. No sign that something is going wrong until you have a gas leak. If your gas supplier can guarantee that your gas is low enough in sulphur content, your inspectors are OK with it, and you, forewarned with this knowledge, can sleep at night, then so be it... or, maybe you do have LP and not NG ?

the Airtrol just before the tank is an air separator
Actually not... that is a fitting that makes it easier to service the expansion tank by allowing air into the tank when you drain it. B&G makes other fanciful claims, but it is definitely not an air separator of they type that OB was speaking.

He was asking about an INLINE type of separator, or an air SCOOP... but the fact is that depending on the the boiler, and where the tank is tapped into the system, you may not need one. If you haven't had problems with air gurgling around the system, or circuits not heating because of trapped air, don't worry about it.
 
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Old 10-24-09, 07:45 PM
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Scoop

Ahh, I see what you mean. While it's mentioned in their air control tech note, it's really more about managing the level in the tank.

I've adjusted the high limit and am running a test now to verify it.
 
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Old 10-24-09, 08:24 PM
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Is this a valve?

So when I put the diagram together, I was assuming that http://acornbay.textdriven.com/tmp/heating/img_0874.jpg is a valve. But now that I'm about to turn it -- is it in fact a valve? I've already had my shower for today
 
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Old 10-25-09, 09:24 AM
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Originally Posted by stevep001 View Post
So when I put the diagram together, I was assuming that http://acornbay.textdriven.com/tmp/heating/img_0874.jpg is a valve. But now that I'm about to turn it -- is it in fact a valve? I've already had my shower for today
Looks to be a balancing valve. Used to adjust the flow of water through a zone, or around a bypass loop or something similar.

Al.
 
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Old 10-25-09, 09:50 AM
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OK to use for shutting off loop

So that is the valve that I'm planning to use to shut off one of my parallel loops. I'm going to mark the position of the valve so that I can move it back. Any reason I shouldn't use that to force the flow down the loop with the (presumed) air lock?
 
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Old 10-25-09, 10:55 AM
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Looks like a 'plug valve', and if that hasn't been turned in ages, it can be difficult to move...

Is there a nut on the side opposite the square head?

The 'plug' part of that valve is tapered, and fits precisely into the bore in the valve. If it is really tight, you can slightly loosen the nut on the backside of the valve... and lightly tap on the bottom of the stem... you may get some water leakage, but once you tighten the nut again it will stop.

You may be able to turn it just fine, try it first, but Justin Case you can't...
 
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Old 10-26-09, 06:38 PM
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Next steps

Ok, here's where I'm at. Thank you everyone for your help so far.

Limit switch is set to 180 degrees. Pressure is 20lb at 180.

Good news is I was able to get both plug valves working with a minimum of effort.

Bad news is that I discovered that there are actually three parallel loops on the main level. One of the loops that is working is connected to one that is not.

http://acornbay.textdriven.com/tmp/h...ing_system.pdf is updated to show what I know about the system. The problem loop is the living room loop. It is fed from the same pipe as the dining room loop.

http://acornbay.textdriven.com/tmp/heating/img_0878.jpg is a photo of the start of the dining room run.

A couple questions at this point.

1. Can I use that valve to shut off the dining room run?

2. You'll see at the top the sort of bleeder valve that is installed. When the screw is loosened, water sort of comes spraying out. Is there a way to attach some sort of hose to this to permit bleeding for longer periods?

I also found out that the people who installed my new loop to heat the kitchen floor knew about this condition, tried for a couple hours to fix it, and gave up. Of course they didn't let me know for a month. Grrr....
 
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Old 10-27-09, 08:17 AM
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Problem resolved -- with a couple follow up questions

After all of that fiddling, I ended up figuring out what the problem was. There was a valve (like http://acornbay.textdriven.com/tmp/heating/img_0878.jpg) at one of the baseboard heaters that was closed. Once that was opened, I could hear water start to flow through the living room system and it heated right up. The valve was probably closed at some point during the installation of the loop in the kitchen.

So the questions:

1. I'm guessing that I can use those valves (see link above) to balance the flow through the parallel loops, correct?

2. There was some discussion by NJ Trooper early on about draining the expansion tank to the correct level. The instructions for the AirTrol valve (http://www.bellgossett.com/literature/files/599.pdf) indicate that I can use it to set the level in the tank.

3. I've gotten by for 6 years without an air separator -- any thoughts on how I would benefit from adding one? Note that the boiler's main outlet is a side outlet, and the expansion tank is fed through the top relief valve outlet. I'm assuming it is plumbed this way to increase the chance that air ends up in the expansion tank.

Thank you once again for the help on this forum -- it's really been useful. I'm surprised at how hard it is to find information on how to run these systems.
 
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Old 10-27-09, 10:01 AM
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Yes, those pesky valves can be an issue , good to hear that it is working.

As for the air separator, if pulling from the top of the boiler is working then I wouldn't worry about it. IOW, if the system doesn't become air bound and/or the expansion tank quickly water logs, then you are good to go.

Note that it isn't unusual to pull the air from the top of the boiler. B&G used to have fittings to do this. Where there was a separator in the fitting along with the hot water supply to the emitters being pulled from the same fitting.

This fitting (discontinued form what I can tell) is shown in the AirTrol pdf that you linked.

Al.
 
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Old 10-27-09, 03:16 PM
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Yeah we talked about draining the tank... but I'm sorta with Al, if it works, leave it alone!

You had stated the pressure when hot was 20 PSI at 180, and that's fine.

As long as the pressure when cold is not less than 12 PSI, leave it all alone.

So, let the system cool off.

If when the boiler is cold, the pressure is much less than 12, you may need to drain the tank, and get it full of air. Don't let that Airtrol hype carry ya away. Those things aren't the cat's meow. Most times they don't do what they say they do...
 
 

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