airbound again

Steve_27

We had an aquastat fail so that our hydronic system could have gone above 200. The system has two air handlers; one on the first floor and one at floor level on the third floor. We have lowered the temp. to 160-180 and have visited the residence at least a half a dozen times to purge air. The boiler pressure is at 20 lbs.

On our last visit, we noticed a small water seepage from the upstairs coil, and it makes up when it calls for heat and expands. However, it slowly seeps once again and drips once each couple of seconds into the drip pan.

In the absence of other causes, we wonder if our airbound again condition is caused by the leak at the coil while air blows across it, or when water flows through it. The coil needs to be changed, but I would like to assure the customer that they will not be airbound again.

Any ideas on my theory, or has anyone else come across this?

Mark Eatherton1

Buy the book...

Pumping Away and other cool tricks" found at Books and More on this web site. Follow the directions and you won't have any more air problems. By the way, a lot of the air you're dealing with is probably coming from the make up water. It carries a butt load of fresh oxygen with it.

Let is know how you make out.

ME

Big Ed

Venturi

You can suck in air through the force of a venturi.....Happens all the time with slab leaks.

Steve_27

venturi

By the force of a venturi, I assume that as the water flows by the failure in the sweat joint or pinhole, it sucks air into it, even though it is under some pressure. If this has been seen before, I would feel alot better in co-oberating my thought already expressed to the homeowner.

Steamhead

That's Correct

and the problem is made worse if you're not Pumping Away. In that case the pressure in your coils will drop when the circulator comes on.

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hr

An air handler on 3rd floor?

An excellent spot for air to trap. I'd make sure you have an auto vent of some sort there. Make sure it is piped to a drain point, should it stick some day.

What pressure are you running? If you have 3 stories above the boiler you may need to increase the fill pressure to facilitate air removal. Adjust the expansion tank pressure accordingly, of course

hot rod

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Steve_27

third floor, yes

The air handler is on the "floor" for the third floor, which makes it about 28 feet or so above the boiler. The pressure that we are running is about 20 lbs. and we have a Taco 010 cartridge unit. We replaced the 007 that worked like a soldier last cold winter (believe it), thinking that more flow would be beneficial.

The cold water seepage from the air handler coil must be the problem. There is a can vent on the inlet supply of the coil.

I understand that pumping away would be preferable, rather than stretching out the air, but the system worked fine for the past 7 years. The coil must be replaced. Thank you for your comments.

Steve_27

third floor, yes, part two

Has anyone heard of a can vent also sucking air in in a venturi situation such as previously discussed in this post. We have turned down the vent's screw cap in order to test this, as well as replacing the can vent entirely. The air still exists every third day or so, in both the third and second zones.

As stated, the coil must be replaced, and then we might be able to concentrate our efforts on other things.

Thanks, in advance.

Mark Eatherton1

How or why did the coil fail?

You stated that the 007 worked like a soldier. It may have dug a trench right through the walls of the tubing (hydrualic Errosion Corrosion). If that's the case, then a 0010 will do it even quicker.

Just something to think about.

ME