Too Much Air In Hot Water Heating System

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  #1  
Old 11-30-13, 01:30 PM
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Too Much Air In Hot Water Heating System

Have been bleeding air from heat loops, do not seem to be gaining. Have new float type vent on top of American Air Purger. How to test float vent?

Circulating water temp is 180 F, pressure runs 15 psig

When I bleed individual heat/circulation loops ( Close return valve, open drain valve from loop through hose to water filled bucket, I get large air bubbles in water)

Very little system noise as it operates

There are no high point vents on baseboard heaters

Any ideas appreciated
 
  #2  
Old 11-30-13, 04:57 PM
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You're on the right track.

If you have more than 1 zone you will do them individually.

Shut down the boiler and all zones.

Open the supply valve on the zone you're going to bleed.

Leave the the return line valve off and put a hose on the drain valve.

Increase boiler pressure to about 25-28 psi

Open drain valve and bleed until water runs steady

MAKE SURE TO KEEP HIGH PRESSURE WHILE DOING THIS.

If you let pressure go down that's when air gets back into system.

If you have a fastfill valve leave it open while bleeding.

Watch pressure gauge when fast fill is open, if it goes over 30 PSI, relief valve will open.

When zone is bled, shut off fastfill and then close drain valve.

Close the supply valve on that zone and repeat same procedure for all others.

When you're done, drain only enough water from system to bring pressure back down to 15 psi.

Open valves on all zones, put your feet up, open a beer and admire your good work.

Good Luck,
 

Last edited by NJT; 11-30-13 at 05:48 PM. Reason: minor edits for clarity...
  #3  
Old 11-30-13, 05:33 PM
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Is the tire valve cap on the air eliminator loose or off? It should be. Do you have a bladder-type expansion tank (looks like a propane cylinder)? Or a conventional, horizontal, steel tank hanging from the floor joists?

Are you getting heat in all your emitters? If, so, wait for the air eliminators to do their job. How would air have gotten in the system? If it's been continuously pressurized, it couldn't.

The bubbles in the hose-drain bucket may be explained: when you discharge hot water, even if it is air free, the heat will immediately cause air to be released from the water in the bucket, which is saturated with dissolved air.
 
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Old 11-30-13, 05:45 PM
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Circulating water temp is 180 F, pressure runs 15 psig
What is the pressure when the system is COLD?

I suspect that you don't have quite enough pressure in your system, I would expect it to be higher when the boiler is at 180F.
 
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Old 12-01-13, 07:17 AM
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thanks for help and ideas

can it be bled zone by zone with the boiler running?
 
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Old 12-01-13, 07:20 AM
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air eliminator cap is on and very loose have and Extrol snubber in the system

when water runs in to drain bucket small bubbles are normal...these are almost fist sized gurggling type bubbles

all the fineed tubes give off heat the one with the most air is at 2nd lowest level in the house and the least heat
 
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Old 12-01-13, 08:31 AM
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these are almost fist sized gurggling type bubbles
What you need to do is define the root cause of the air in the system and correct the problem, else you will be doing this all over again in a short time.

This is the reason I asked:

What is the pressure when the system is COLD?
Also, you will no doubt need this information at some point along the way:

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

http://www.doityourself.com/forum/bo...sion-tank.html
 
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Old 12-01-13, 11:49 AM
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cold pressure hard get.....

....but it seems to be 15 psig between heating cycles

at end of last heating cycle, was reading between 18 and 20 psig using my best bifocals

water temp drops to 180 F., then appears to go up to about 195 F or so


this is a one pump, 4 vertical zone system; each zone reflects to a living level; very close to a 4 level home


again thanks for your help
 
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Old 12-01-13, 02:07 PM
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very close to a 4 level home
I believe that we are on to that 'root cause' I mentioned earlier...

There is a certain MINIMUM PRESSURE that must be maintained in ANY hot water heating system. That minimum pressure is defined as the HEIGHT of the system from the boiler in the basement to the highest radiator in the system.

The 'formula' for determining this minimum pressure is:

HEIGHT (between lowest and highest points in the system) times 0.432 PSI PLUS 4 PSI.

A four story home is likely to be 35' or more from boiler to highest radiator... let's use that as an example (substitute the actual height of your system to come up with your number):

(35 X 0.432) + 4 = appx 19 PSI ... and that's MINIMUM. This pressure insures that the top of the system will always have positive pressure inside the pipes, never go 'atmospheric' or below, and the system will have less trouble with air collecting.

Once a system goes atmospheric or below, air bubbles will start forming from the water and collect around the system.
 
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Old 12-01-13, 02:10 PM
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Does your boiler system keep itself warm? ( i.e. 'warm start' ) or will it go cold if there is no heat call?

Does this system also provide domestic hot water to the home in the form of a 'tankless coil' inside the boiler?

If so, what aquastat control is on the boiler, and what are the LOW, DIFF, HIGH settings on this control?

Even if it is a 'cold start' boiler, and does not provide domestic hot water to the home, what aquastat control is installed, and what is the HIGH setting on that control?
 
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Old 12-02-13, 08:29 AM
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aquastat

aquastat is a Honeywell L8148A

set at 190F now, seems to cool down and stay at 180F
burner seems to heat water to 190/200F then stops

only readible setting is the 190 temp

highest pressure I have seen is 18 psig at the 190 F temp
 
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Old 12-02-13, 09:45 AM
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Did you understand what I was saying in post #9 ?

If you've got a nearly 4 story home, then you must calculate a higher MINIMUM pressure and adjust your system to operate at this pressure or you will CONSTANTLY have trouble with air in the system.
 
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Old 12-02-13, 10:04 AM
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What you have is a cold start aquastat which means it only runs on a call for heat and does not maintain a minimum temp for domestic hot water.
I assume you've got a separate tank for your hot water.
The control is acting as it should. You can only read one dial because that's all there is.
It is a high limit control with a fixed differential.

As Trooper mentioned,
how high is your house from basement to the highest point in your heating system. As was mentioned, this will determine how much pressure will be needed to reach your top floors. At 19 lbs.(without all the chalkboard wizardry) your good for 40+ ft.
Unless your house is larger than that you seem good. If larger you may need more pressure to reach your high units.
 
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Old 12-02-13, 10:20 AM
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At 19 lbs.(without all the chalkboard wizardry) your good for 40+ ft.
With the wizardy and the laws of physics, and taking into account the extra 4 PSI that must be added to maintain positive pressure at all times, 19 PSI is good for only 35 feet.
 
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Old 12-02-13, 10:58 AM
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adjust pressue?

I thought to raise the pressure via the auto fill valve

1. loosen the nut that holds the adjustment screw

2. turn the adjustment screw downwards (clockwise) to raise the pessure

3. retighten the nut to hold the adjsutment screw in its new place/setting
 
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Old 12-02-13, 11:09 AM
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Yes, that's the basic idea. Go SLOWLY when you adjust the valve as the pressure takes some time to 'line out' after adjustment. I would start with 1/2 turn of the screw and then wait like 15 minutes to see how much difference it made, after than you have an idea of how many turns you need to go.

Remember that raising the minimum also raises the maximum, so you should be sure your expansion tank is correct... the air charge should be adjusted to the same minimum pressure as your feed valve.

Also, if the gauge is inaccurate you are shooting in the dark.
 
 

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