Baseboard radiator bleeders corroded

MikeC555

I recently purchased a vintage 1960 house (~ 2,000 sq ft) in north east with oil fired HW boiler, 4 zones (one Taco 007-F5 circulator).. I'd estimate the boiler is 10 - 15 years old (certainly not original). But for whatever reason, the installer kept the old expansion tank rather than using a diaphragm tank. The gurgling I hear when zones are active tells me there is air in the system and a search yielded a few bleeders that look like they haven't been touched in a long time. Should every zone have at least one? Am I looking for trouble trying to use these?

Big Ed_4

You made me feel old with "vintage 1960 " .

Yes , your looking for trouble if you try to use them .... If leaking I would recommend having them removed and pluged .

it sounds like you have a zone valve baseboard system . There should be a way to purge the air out near the boiler ..

mattmia2

is there an airtrol fitting in the line to the compression tank? the system should be set up to collect the air and put it back in the compression tank and keep it there.

Those bleeders look like they may be some sort of ancient automatic air vent which you don't want with a compression tank.

MikeC555

Thank you guys.  They don’t appear to be actively leaking, so I’ll leave them alone.  I don’t see anything resembling an Airtrol fitting, which seems like there should be.  Here is an overall shot of the system.  Would I be better off converting to a bladder tank?

retiredguy

Way back in the 1960's my mom and dad had a similar system installed on the 2nd floor of their home, while I was serving our country. Years later when I became a service tech for an HVAC company, my mom called to tell me a story similar to yours. Here was my fix.

In the summer, I drained the system and replaced vents that look similar to what yours are with a stand pipe and a "coin vent", replaced the expansion tank with a compression tank, and installed purge valves into the piping at the boiler. I refilled the system , purged the system using the purge valves and removed the remainder of the air with the coin vents. All has been great ever since. The home was just sold to the next owner.

kcopp

If you have a conventional expansion tank on the system there should be NO automatic air vents in the system. I see one on the return piping. That top should be closed.
That does not help matters.
The set up w/o the vents air will eventually get back to the expansion tank and quiet the system down.

MikeC555

Thanks,  I was wondering if that air vent was appropriate.  Will close the cap. 

Gilmorrie

I agree - with a conventional expansion tank, that air eliminator, and any other ones like it, must be removed or at least gagged by screwing down the cap.

Please post photos of the expansion tank and nearby piping. There is nothing inherently wrong with a conventional expansion tank. Properly plumbed, they run indefinitely without maintenance - unlike a bladder-type tank that will continuously lose air by diffusion through the bladder and fail entirely when the bladder ruptures within about 10 years or so.

What is the system pressure and temperature?

EBEBRATT-Ed

You should put an air scoop or better yet a Spiro vent or Caleffi microbubble air separator and a bladder tank in next summer

MikeC555

Here is pic of the expansion tank. No sight glass or drain vent, unfortunately. No discharge from PRV, so I least I can assume it isn't water logged. It's a single story house (with basement) so 15 psi pressure seems about right. Temp reads 180 or so.
As (bad) luck would have it, I just learned DHW is kaput. The circ pump on the indirect loop is making vary bad noises and the outlet pipe is not hot (going to indirect coil). Ugh. It's a common Taco 007-F5 and it appears the valving is in place to allow swaping it out without draining everything although I'm not sure what to expect when the bottom flange is loosened. Even with sytem off and zone valves closed, it seems like some boiler water is going to drain out here. The valves in indorect coil circuit will isolate the indirect tank but it doesn't seem the circulator can be isolated. I'm used to the old tankless coil DHW and so am new to this indirect stuff. As such, I'm going to watch the Tech I have coming to replace the pump but am curious if maybe this was not plumbed as well as it could have been.

mattmia2

Are you sure the circulator for the indirect isn't just air bound?

MikeC555

It’s possible, I guess, but there is a vent valve on the downstream side of circulator and no air escaping. 

MikeC555

It’s running quiet at the moment but no apparent HW circulation and motor case is very hot to touch (much hotter than circ for heating zones). Maybe to be expected if it is air bound?

MikeC555

Still waiting for boiler tech to show.  I’m beginning to suspect air may be the problem.  I cracked open the HX outlet line valve for a second or 2 and air did escape.  The pipe then became hot…. I suspect the air vent up top is plugged and the HX inlet line is air bound…

hot_rod

Some manual coin vents would screw into those baseboard ells. So if you do have a system that’s problematic to get air out, you have a second purge option.

If the piping has a lot of ups and downs in it, remote vents can be helpful, mainly at start up.

Gilmorrie

Thanks for the pix of the conventional expansion tank. I see nothing wrong with it, but as far as I can see, it lacks Airtol fittings to help with returning air from the system to the tank or for refilling the tank. The way it appears, you will be annually having to drain and recharge the tank with air. A lot of strangeness here, I think. But, in any case, adding or leaving any air removal devices to the system, as it presently is, is definitely not the thing to do.

If you don't want to change the system to be compatible with a conventional expansion tank, then next spring, rip out the tank, go to a bladder-type tank, and add air removal devices. You will then have to contend with a tank that continually loses a little air over time and that will sooner or later fail with a ruptured bladder.

MikeC555

Thank you Gil.  The main problem was air and the water pressure was not high enough to force it out of the auto bleed.  He adjusted pressure to 25 psi (old gage probably not too accurate), the air bled out of the auto bleed and closing lower ball valve to dead end the loop.  Circulator is now working…. I’ll keep an eye on that pressure as I don’t know how long it took to drop.  The water pressure also helped heating zones.  I am leaning toward installing a diaphragm tank in summer and air scoop. I have an air compressor so keeping the bladder pressure to spec is no biggie.  Will install a new pressure/temp gage too.

mattmia2

If you do change to a diaphragm tank (which isn't at all necessary), put an isolation and drain valve on it so you can isolate it and release the system pressure to check the charge without depressurizing the system.

Use a microbubble air separator like a spirotherm or discal instead of an air scoop.

mattmia2

This fitting doesn't just make it easier to set the tank level but it also reduces the migration of air out of the tank through gravity circulation:

https://www.supplyhouse.com/Bell-Gossett-112010-1-2-ATF-12-Airtrol-Fitting-For-12-14-Compression-Tank-Dia-8624000-p