air in heating pipes

chap007

Having a problem with air in my heating pipes. I had my heating mech. here 4 times this season for no heat. They said there was air in the system and they purged it each time and they cleaned the top of the spiral vent and also replaced the top of it. They also suggested there might be a leak but I checked and did not find one. I have basic knowlege of how a heating system works and I also purged the system but every 4-6 weeks the same problem occurs. Any advice?

STEVEusaPA

Tell us a little more ....

About your system.  If you can, take some pictures showing all the piping around the boiler.  And especially show your expansion tank.

For starters, 2 different things could be going on.  You have a small leak, and when your feed is opening up, letting in fresh water, the air cant get out, and stays airbound.  Or something is up with your piping, and the air vent is sucking in air, and sending it around the system to get trapped somewhere else.

Paul48

Pressure

Shut the supply water off.....does the system hold pressure?

icesailor

Air

How high is it from the gauge on the boiler to the highest point in your heating system?

How high does thr pressure read on the boiler pressure gauge? What kind of radiation do yu have and how is it vented?



Here's an old tridicator gauge I recently took off a boiler. It shows the relationship between height and pressure.

chap007

air in heating pipes

Burnham boiler approx. 7 yrs. old hot water system with 2 zones. I shut the feed for about 2 hours and lost some pressure on the gauge. I had trouble posting a picture but I'll get them up soon.

chap007

air in heating pipes

I did what you said, shut the feed valve and lost some pressure after about 2 hours, maybe 5-8 psi. .

Paul48

You

have a leak somewhere. It should not lose pressure that quickly.Do you have valves that would isolate the boiler from the system? If so, close those and see if the boiler hold pressure.

billtwocase

7 year old Burnham

be it cast iron,  I would pull the cover off the right side and look for leaks, or look in the chamber for dripping. Any crawl space piping, or heat pipe embedded in concrete?

chap007

Before

I start crawling thru my attic or crawlspace one question. Right before this air problem started I had the heating coil gasket replaced. Is there any chance this might have caused a leak in the heating system? Probably not because that is the domestic water amd not the heat correct? In the mean time my system has 2 zones which I can isolate with ball valves so will shut them individually and watch my pressure gauge.

BobC

Leak at coil - boiler interface

The tankless hot water coil in your boiler is submerged in the water of your hot water boiler. If the problem appeared after that coil gasket was replaced there could well be a problem in that area.



If the mating surface on the boiler and the tankless coil was not cleaned well and torqued down properly there could be a small leak between the boiler and that tankless coil. That gasket needs clean surfaces for a good watertight seal.



Bob

Paul48

If

you find no evidence of standing water from a leak, then suspect a leak on a hot surface that's evaporating quickly.Shutting the boiler off, and letting it cool may produce visible results.

chap007

I shut down my boiler for about 3-4 hours

and after that time I had no evidence of any leaking water around the coil gasket or anywhere else near the boiler. I also checked inside the fire box. I have 2 heating zones first I shut down zone 2 the 2nd floor and lost about 10 psi. this was shut for most of the time. I then opened that one and shut down zone1 1st floor. I began to loose pressure but had to stop and turn everything back on. During the time these zones were shut I left the feed valve open. was I correct leaving the feed valve open and should I have shut both zones together or was I right doing them seperately. While this was happening I double checked all heating pipes thruout the house including the attic and crawl space for leaks with negative results and no evidence of any water. damage.

billtwocase

are you

isolating supply and returns per zone? What type of zoning, circs, zone valves. If this is a 2 story home, I would also see if the feed and return are routed thru an outside wall. Insulation is like a big sponge. You can have a leak for a long time and you'd never know it. I would also like pics of your expansion tank, piping, gauge,zones, etc. What is the lowest, and highest pressure readings?

chap007

I have

a 2 story home with 2 zones cirualtors w/ no zone valves individual thermostats. I shut down each zone seperately and lost pressure however I left the feed valve open. Should I do this again with the feed valve closed?

billtwocase

I see

no way that you can isolate zones. The supply is showing no positive shut off, cant see the returns, but they might have a gate or ball valve. By shutting off only the return, the supply will still feed a leak on an upper floor, etc. You need to have some valves installed to troubleshoot this thing. If the feed is left on, and is set to maintain 12-15 PSI, it should stay at that pressure all the time. I would also look into a faulty boiler gauge.You may have 2 problems

chap007

The returns

have a ball valve for each zone. They are located behind the vertical pipe in the upper right hand side of picture 1. You cannot see them in the picture. My gauge usually reads approximately 22 psi. . If I shut the feed valve and the 2 zone valves, that won't isolate the pipes?

icesailor

Finding Leaks:

You can't isolate your system from the boiler the way it is piped.

If you called ME with your problem, I would take my air compressor and blow/drain the system. "I" can get 99% of the water out of the system with air but don't try it. I know what I am doing. After the system is drained, close all vents and pump the system to 25# PSIG on a gauge. Shut off the air. If the pressure drops, you have a leak somewhere.

It is a lot easier to hear a small air leak than a small water leak. Unless you have high frequency hearing loss, you will hear it. I hear crickets. They hurt my ears so badly that I must kill them immediately before I can continue. I have used a Stethoscope to listen for leaks when trying to find leaks to  fix freeze-ups.

You just need to be careful when using air. And that air eliminator might be a problem unless it is one with the removable can vent. Old Spirovents without the threaded top can be a problem