Boiler Questions

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Old 11-23-15, 04:16 PM
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Boiler Questions

Hey all,

I have a 1958 single story ranch, no basement, that's using a hot water boiler for heat. The original house has a single zone with a big iron main line running in the crawlspace. Each radiator for that zone comes off and returns to the main line with smaller piping, and each radiator has a bleed valve.

In 1996, an addition was put on the house, along with a new boiler and two new zones. These new zones use dedicated copper piping and the radiators have no bleed valves.

The boiler is in a room off the garage, so it's sitting above the radiators. The lines all go down into the crawlspace.

It has a 1958 solid steel expansion tank, which is mounted to the ceiling in the boiler room.

For the old main zone, things are good. Things get noisy, I bleed the radiators, and everything's fine.

The new zones are noisy with rushing water, which I'm trying to remedy.

Questions for you experts:

1) Should there be an air vent at the junction with the steel tank?

2) One of the original registers also has an air vent, should it?

3) Does it matter that the Zone2 and Zone3 supply lines come off the main line before the line up to the tank? In my head, I see air getting stuck in those two zones because it goes up into them before getting to the tank line.

4) With the boiler on the main level with the registers and the lines going below them both in the crawlspace, what kind of pressure should I have?

5) What's the right way to get rid of the air in zones 2 and 3?

Many many thanks!

 
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Old 11-23-15, 05:47 PM
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No AAV's on the type of system you have.

They should all be removed...

What you need to do is drain that expansion tank... That will probably fix your issue...

There is a procedure and I will find documentation on it...
 
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Old 11-23-15, 06:08 PM
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Other option,
Remove air cushion tank, replace with pre-charged diaphram expansion tank and a good high performance air eliminator.
You should not have to bleed the system repeatedly, your just introducing more fresh water.

No doubt this is going to cost money to do, but if the system is prone to air then this would help eliminate the issues.

Do you need to add water much ? Is there an automatic fill system on it or do you need to manually add water ?
 
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Old 11-23-15, 06:40 PM
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Thanks for the replies! I'll take those air vents out ASAP.

It has an automatic fill that I never hear run (boiler's near my study). When I do bleed it, usually in the fall, the water is nearly black and smells like metal, which I think means the system is pretty tight.

So even though the Zone2 and Zone3 lines split off before the tank, the air will try to go higher? The tank is definitely the highest point in the system, I just have a hard time believing the air will find it...

I'd appreciate any pointers on draining the steel expansion tank.

So...do I just run over to the hardware story and buy copper caps to screw in where the vents are?
 
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Old 11-23-15, 08:20 PM
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So...do I just run over to the hardware story and buy copper caps to screw in where the vents are?
You can leave them in, just screw the cap down tight.
 
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Old 11-23-15, 08:22 PM
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Totally eliminate your air problems with or without replacing the expansion tank. Eliminate all automatic air vents if keeping your current tank. If changing your tank to a bladder type use a good air seperator and no air vents on the return side of the system. Move circulator's to the supply side after the tank connection.
No more air problems or system gurgling noises.
For more info go here comfort-calc.net
 
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Old 11-24-15, 09:14 AM
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The cap on one of the AAVs was busted and the other one doesn't even have a cap, so I'm replacing both with end plugs.

Is the general idea that the air eventually finds its way up to the tank?
 
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Old 11-24-15, 02:53 PM
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Trapped air will always go to the highest point in the heating system, which I think you stated was the boiler. If it's the expansion tank, the air will go there.
 
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Old 11-24-15, 03:47 PM
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Trapped air will always go to the highest point in the heating system
In theory anyway... if there's an air separator, the air would be collected there as it passes by during circulation. See below.

If there are points in the system where the pipes go UP and then DOWN again, air can get trapped there also, even if it's not the highest point in the system.


Is the general idea that the air eventually finds its way up to the tank?
With the type of tank that you have, that's what is SUPPOSED to happen. Fact is though that most were never installed properly such that the air could be collected and passed back to the tank where it belongs.

That type of tank should be connected to an AIR SEPARATOR with a 3/4" tapping ON TOP, and the piping to the tank should all be 3/4" and slope UPWARD all the way to the tank so the air can get where it's going.

Take some pictures...
 
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Old 11-25-15, 04:10 PM
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Well, draining the tank helped quite a bit. There's no more rushing in either Zone2 or Zone3. There were some pretty big gurgles from the crawlspace on up when the tank drained, so a lot of that air popped. I don't think the tank was water logged.

Also took out both AAVs.

So both the return and out piping from Zone2/3 goes up then down, plus each radiator in Zone2 and Zone3 does the same (crawlspace up to baseboard then down again).

Here's the front on the boiler system.



Here's a better pic of the back piping, which goes down/out to the crawlspace. It seems to my non-professional brain that any air coming out of the boiler would hit that first junction and go up to Zone2/3 if they were open and get stuck.





Does anyone think that moving the junction up to the tank before the first split to Zone2/3 would make a difference?

Also, the pressure cold is about 15ish, hot about 20ish. The house is a kind of T shape, with the boiler being on the bottom of the T with piping running all the way out to both ends. Since it has to cover a fair amount of ground at the same grade or below, I'm thinking that 20psi hot makes sense. How's that sound to y'all?

Thanks again!
 
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Old 11-25-15, 05:38 PM
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really an air seperator that can be directed up to the air cushion tank should be installed after the boiler and before the pump on the hot supply side of the boiler.

What they made was some pretty good air traps with those up - downs. Taking out the AAV's might be a bad idea, or at least getting a coin vent to purge the air id it air locks the zone.
 
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Old 11-25-15, 06:05 PM
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Hmmmm... Yeah see how it works first...


I would maybe follow TO,s suggestion somewhat... But for less work I would install a regular bladder type exp tank in place of old one and add AAV;s at both those high point loops you show...

Put the one back too that you show as gone.. Put the bladder tank on the ell to the left of aav in your pic...

Minimal work..

I myself are not a fan of the air seperators as TO says should be installed..

But thats me...
 
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Old 11-25-15, 08:12 PM
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well, if we are talking about a modern expansion tank....
I would not use a standard air seperator, I would use a honeywell powervent or Caleffi, or any of the other high performance types.

AAV's scare me, they will always leak.
Pump should be from the boiler into the system, so do that while putting in the air scrubber.

Just my 2 cents anyways.

I am in no way a fan of the old school air seperator, the space they require to be installed correctly is never done, and that makes them mostly useless.
 
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Old 11-25-15, 10:06 PM
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Hm - so there are actually four up/down sections, two coming and two going away from the boiler. Would all four need AAVs or coin vents?

How about the radiators in the house with no bleed valves? Wouldn't air get trapped there too?
 
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Old 11-25-15, 10:19 PM
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You need to tell us more if we are to help. Is this a monoflo tee set up for the loops? You need to post more pics of piping......
 
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Old 11-25-15, 11:02 PM
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Sure thing - what else do you want to see?

That first pic of 'From House/Gone' shows:
  • The big original main line with a three wire rotary valve and manual shutoff valve coming up from the crawlspace
  • The other two lines coming up from the crawlspace, one flush against the wall, each with honeywell zone valves, coming together and then going into a single point in the main line.
At first glance at the pic, the return lines in the front and the outgoing lines in the back are hard to differentiate, but they just happen to line up a little too well in the pic itself

After that, the line goes across the top of the boiler behind the heat exhaust tube, down the side of the boiler, in into the pump, and then into the boiler.

The "From City/To House" pic shows
  • A pressure relief valve with a big yellow tag on it
  • The main line coming out of the top of the boiler
  • A junction with a split going up into zones 2/3 (each with manual valves)
  • A second junction with the city water line and the expansion tank
  • The main line then dives down to the crawlspace.
You can kind of see the return piping in the right hand side of that pic, which is shown better in the first pic.

Thanks!
 
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Old 11-26-15, 07:11 AM
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What I mean is if the loop is set up like this..

[ATTACH=CONFIG]59319[/ATTACH]

Or like this

[ATTACH=CONFIG]59320[/ATTACH]
 
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Old 11-26-15, 01:03 PM
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Gotcha!

The original 1958 main line is like the second diagram: The main line is a big pipe that runs under the house and then each radiator has smaller lines that branch off up to the radiator and the back down into the main line. Each radiator in this zone has a bleed valve.

The newer 1996 zones are like the first diagram: They run under the crawlspace and up into each radiator, no branching for each radiator. These radiators have no bleed valves.

Happy Turkey Day!
 
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