Heating: Gas Boiler to FWA system (think car's heater) air bound?, clogged?, circulator?

[Riickk]

My house has an unusual (to me) Peerless Gas H/W boiler to FWA system similar to an automobile's heating system. The boiler and A/C system were new in 2000. In 2020 the circulator get stuck; wacked it, and it started up, following summer, installed new Taco 007e.
Currently: No heat. Boiler fires up, circulator shows amber LED indicating it's running normally, but there's no hot water getting to the "radiator" in the air handler. I opened the air-release valve at top of radiator, and got 1/2 second of air, then just water.
So... I think the possibilities are (A) the circulator is lying to me, or (B) there's something clogging the 3/4" copper leading to (or away) from the radiator, or, (C) the radiator itself is clogged up, or (D) the system is somehow air-bound {but I can't figure how that could be happening}
Any help in diagnosing what's going on, and, if it's a clog, how to get rid of it, most appreciated! Thanks in Advance.
//

 

[Riickk]

FIXED. Drained system to zero.
Found it was Air-Lock in radiator section.
Turns out the air-release valve spews water everywhere if fully opened, but if just cracked open, you get a hiss of air that eventually -5 minutes- gives you a stream of water. Closed the valve and I got warm water in pipe down to boiler. Oh, and heat.
Now, how the Heck does all that air get in the system?

 

[Geofd]

There should be an air vent on the air scoop try pushing down on that small pin to see if
You get air

 

[Bird Doo Head]

Your heating system is quite rare in residential applications, at least in the states where I've worked hydronics.
It is the most common system for large office buildings, hospital & school campuses and other large installations, but with steam as the medium. How do you like it in general?

If you suddenly found air, these are the most likely culprits:
A) The original fill of water took time to release it's gasses. They finally gathered together and locked your heat exchanger.

B) New water is being introduced. bringing air with it. This means water is escaping. It's important to find the leak before things corrode from the oxygen in the new water.

C) Sometimes a large amount of air in introduced into the system when the expansion tank's diaphragm breaks.
Check the tank's integrity by feeling the side when the boiler is operating. It should be hot at the top half and cool at the bottom half. If it's hot all up and down, it needs it's air pressure adjusted or the diaphragm is broken (releasing air into the system's water).

Therefore if you don't have a leak, this air was from the original water or the air charge from the expansion tank.

A very good idea to have is a deareator (also called microbubble scrubber). Due to the rotating motion of the separator, they scrub out gasses more thoroughly and quickly than a scoop tee. Example: Spiro Vent by SpiroTech.com It wold go in place of your scoop-tee at the boiler. (Usually just on top of the expansion tank)


You can also replace the coin vent (what you had to open to get the air out) on the heat exchanger with an automatic type air vent. It will purge air and other gasses as they arrive at the heat exchanger.
They are available with a float (most common) or wafers. The wafer ones' advantage is that they are silent. The disadvantage is that, after time, they get mineralized and leak. Float Type Example: Maid-O-Mist Series 7 (MaidMist.com)

Paul

 

[Riickk]

Thanks for the info & advice.
There *was* a 7 series "vent" there, but didn't seem to be working unless you unscrewed the valve cap and hit the Schrader valve yourself. I'll install a new one.
Question: Should I arrange the flow from the circulator to fill radiator from the top, or bottom?

 

[Bird Doo Head]

Thanks for the info & advice.

Question: Should I arrange the flow from the circulator to fill radiator from the top, or bottom?

Are you sure it's a radiator & not a finned hydronic heating coil? (When you mentioned Radiator, I pictured a car radiator adapted to the air plenum.) Heating coils look similar, but aren't black and have pipe fittings. They are usually thicker, too.
Or, is this a cast iron radiator in the plenum? (I've seen it, crazy as it sounds. And it works)

First-
Shim so the vent is in the highest corner by even a millimeter or two.

Second-
Ideally, you will have the circulator pumping away from the boiler and just after the expansion tank and air scoop or scrubber. (Not ahead of the air scoop)


Water Flow In Fin Tube Heating Coil:

Many manufacturers of hydronic heating coils pipe internally so the inlet and outlet are on the same end for convenience. (Hi-Velocity's HWC series is an example.)

If yours is as-such, ask the manufacturer or study the coil loops.
If the manufacutrer is unknown or can't help: Low Port Is In High Port Is Out for a hydronic same-end coil. Vent is usually on the piping after the return water exits the coil, just after the coil.

If you put a microbubble scrubber, like Spirovent, you can skip the vent on the finned coil and any other heat exchangers. Also, if you can pipe for a forced purge, you can skip the vent on the unit, but keep one on the air scoop.

Hope this Helps!
Paul

 

[Riickk]

Are you sure it's a radiator & not a finned hydronic heating coil? (When you mentioned Radiator, I pictured a car radiator adapted to the air plenum.) Heating coils look similar, but aren't black and have pipe fittings. They are usually thicker, too.
Or, is this a cast iron radiator in the plenum? (I've seen it, crazy as it sounds. And it works)

Just to follow up - I replaced the float-type air valve with a new one, refilled the system, and all appears well. Here's a photo of the "radiator" / heat exchanger - it's connected with 3/4" copper, and is around 3" thick (??)

 

[Bird Doo Head]

Can't see the coil, but from the enclosure, I'd say- Yup, that's a hydronic coil made for the purpose. The AAV you installed is in a good place. I think you'll be all set!
Paul
PS: When next it's empty-
Fill from the supply pipe (top) if you have valves to allow this. Close the valve that is on the discharge pipe to isolate the return side. It's probably close to the photo. Open the coin vent that is on the bottom of the return pipe & fill very slowly. Much of the air that is in the coil will be purged out of the coin vent as you fill. (The presence of the coin vent hints that you have the valves needed to fill from the supply pipe.)

 

[Riickk]

Fill from the supply pipe (top) if you have valves to allow this.

Quick question...
Since you call it the supply side, should the circulator be setup so that it supplies the heat exchanger from the top? Or does that make any real difference, given the loop is so small.

 

[Bird Doo Head]

Quick question...
Since you call it the supply side, should the circulator be setup so that it supplies the heat exchanger from the top? Or does that make any real difference, given the loop is so small.


Supply is the pipe leading away from the boiler. (Return is the term for the one coming back from the radiation units.)

Your heat exchanger needs the supply (hot) water to enter the top and the return (cooler) water leaving the bottom to work properly and not get air bound as easily. Whether the pump is pushing the water into the coil (supply side) or pulling it out (return side) does not make too much difference in a small house system. "Pushing In" and "Pulling Out" aren't ideal terms because the system is a closed loop, but those are the best words my aging brain can conjure up. Performance wise, other factors are more important, as kinda-sorta explained below. (Caution! It might be pretty boring.)


Boring Stuff Ahead...
Ideally, use the "Pumping Away" schematic for perfect performance and easiest purging.

Briefly How-
The pump(s) is (are) on the supply side. The air separator and expansion tank will be on the supply pipe after the boiler (18" minimum straight pipe into the scoop if a scoop-tee type separator). The circulating pump(s) will pump away from the expansion tank. The automatic fill valve will be piped into a tee between the expansion tank and the air separator. This location is the point where there is no pressure change. The pump can't affect the fill pressure.

With this set up, the pressure from the circulator is added to (rather than subtracted from) the static pressure in the system. Your pump(s) will have far less cavitation, thus last longer and pump more efficiently. The entire system will also be quieter up in the building. (I've found that the noise difference is more noticeable on large systems with dozens or hundreds of radiation units).

Automatic air vents certainly work better and forced purging will be much quicker and easier. (Actually, when pumping away and with purge and isolation valves in the correct places, you can ignore your vents on radiation forever.)

I wouldn't worry too much about this. In my house, the heating person decades before I bought the house put the circulator on the return, about as far from the point of no pressure change as possible. The only place I hear noise is a little from a flat panel radiator and in the piping in the basement. The cast iron radiators & baseboards are nearly silent. Purging was tedious, so I installed a micro bubble separator to solve that.

I zoned the house and the zone valves are on the supply side. (Not great for the valve seats, but little re-piping was needed.) When I replace the boiler, I'll re-work the whole "early 20th century" piping to pump away and replace the zone valves with circulators.

You seem to have a keen interest in hydronics and a good understanding, so attached are a couple of articles I found today that you might find interesting.

There is also a very good book available titled Pumping Away & Other Really Cool Piping Options by Dan Holohan. Since Gil Carlson passed away, Dan is the pinnacle of hydronic engineering knowledge (steam, too). You can learn more on his forum HeatingHelp.com

I hope this helps and if I confused you, please don't hesitate to post again.

Enjoy Today!
Paul