repeatedly getting air into baseboard hot water - need to find root cause

DCContrarian

https://forum.heatinghelp.com/discussion/comment/1893963#Comment_1893963

A properly-functioning hot water system should never be refilling.

mattmia2

https://forum.heatinghelp.com/discussion/comment/1894069#Comment_1894069

and a modern one doesn't have shaft seals…

but they turned off the makeup water and it is holding pressure so it is most likely air that didn't get out from the initial filling.

Geosman

This boiler design likely includes a pressure sensor that will fault off the boiler if the pressure drops below 10 psi. If air is entering the system it is likely coming from the fill water source. If on well water there could be dissolved gasses (CO2) that are released from the water as it sets there in the home. If the fill line comes off the top of a domestic line it is likely collecting this air slowly over time until the system calls for additional make up fluid. The zone with the black pump seems to be the one that collects the air? I question if the spiro vent is working as it should. Ultimately you may have a system leak somewhere. If not a leak from the home side of the system, try capturing any condensate from the boiler to see if it might continue when the boiler is not in use. I've had to replace a boiler section on this style due to a sand hole in the casting that showed up several years post installation and was not discovered until it was noticed that the condensate water had an antifreeze color to it.

DCContrarian

https://forum.heatinghelp.com/discussion/comment/1894169#Comment_1894169

Again: there is nothing normal about using makeup water.

Turn off the makeup water, take the handle off the valve and hide it.

mattmia2

pretty sure they said it is off a couple posts ago…

losing tiny amount of water isn't abnormal, even good packings can lose a little bit of water.

hot_rod

It seems every time we poll, it is an even split between people that leave the fill valve on vs off. Probably a little of fill valves sieze close from no use conditions.

We see systems without fill valve or water connections occasionally also, glycoled systems.

Within a week or so or running, a leak free system with a good working microbubble device and any O2 oxidizing the ferrous metal, the system should not have any air, bubbles. It should stay that way.

It is a pretty rare condition to see a pressurized hydronic system go sub atmospheric if the system is piped with the pumping away method.

It would appear that the air is not being purged 100%, as opposed to air entering

pedmec

What type of system are we talking about? baseboard? radiators?

What is the highest heating emitter piped above the boiler?

My thoughts on this is that you are forming a vacuum in the system at a high point which is allowing air into the system. As pointed out by @mattmia2 the first takeoff after the spirovent is the black circulator which is the offending circulator. Putting cold water back into the system from a leak you can't identify does not put that much air into the system if its just replacing what you are losing. There would be a constant deaerating of the system providing the spirovent works.

Now if you have the highest radiator sitting at just the fill pressure in the system then there is a chance every time it cools it will pull air back into the system. I used to see this a lot earlier in my career. Direct return radiator system would heat up and be fine but then the summer would come, the system would cool down, pressure drop, and then all the air vents or packing on the valves would allow air to slowly creep back into the radiators on the top floor. And of course all the circ's are on the return so you don't have the luxury of having the circulators help you bleed the system.

i would bleed these big brownstones all the time until i realize what was happening. Year 1, boss never goes to the job so he's no help. It's something you figure out on your own because you know somethings not right and systems constantly air bound should not be happening.

DCContrarian

@hot_rod : "Within a week or so or running, a leak free system with a good working microbubble device and any O2 oxidizing the ferrous metal, the system should not have any air, bubbles. It should stay that way."

And I get why people leave the makeup water on: during that week, while the air is working its way out, water needs to be added every time air is released. And it's generally not worth making a trip back just to turn the makeup water off after that week. But it's not doing the owner any favors having it on.

hot_rod

https://forum.heatinghelp.com/discussion/comment/1894248#Comment_1894248

my method was to leave the fill on for a month or so when first started, return for a checkup and consider closing the valve then

Most mod cons have pressure or flow protection, typical cast, maybe not

Solar thermal systems do not have fill systems and they see wide temperature swings to boot.