Leak , Air lock in heat system ?

RudyA

 New boiler installed , I have baseboard water heat , one zone . There’s about 25’ of the heating pipes in the slab of the house , the rest is all exposed . I have no signs of moisture coming from those areas in the floor . Randomly I come home to no heat and I have to purge the system . When I open the heat pipe loop , it’s a steady stream . When I open the valve to add the boiler to the purge I get pops of air . Then I have heat . I was told I have a leak somewhere but it can run for days with the feeder valve off and I’m maintaining 20lbs of water pressure . Why would it leak sometimes and not all the time ? Is there something else that can cause this since it’s a new installation ?  Note I did install air vents to the system . 

SuperTech

Can you post pictures of the boiler and the piping? Especially where the the pipes go into the slab. 

Have you tried isolating the zone with the pipes going into the slab to see if that zone is the cause of the problem? I've seen a few cases where a leak under the slab caused the problems you described. 

RudyA

 It’s one complete loop . Leaves the boiler to circulator pump to each baseboard heater then jumps from one bedroom to next in the floor , then returns with about 10 feet in the floor . Then enters the basement . I wouldn’t know how to isolate that run besides shutting the boiler feed off and running the heat . And like I said not loosing any pressure .  I’ll try to get some pics , thanks 

RudyA

Mad Dog_2

Boiler piping please. Mad Dog

RudyA

JUGHNE

Those little auto vents have been know to suck air in under certain conditions.

After you have it purged and running, you could screw the top caps down and see it things change.

EBEBRATT-Ed

What pressure is the boiler at? Have you removed the expansion tank and checked the air pressure on the airside of the tank? It should match the boiler fill pressure.

RudyA

I will try that with the air vents .  I haven’t removed the expansion tank for that test as I’m not a plumber . If you’re asking about the boiler pressure it’s set at 20 PSI . 

hot_rod

I don’t see any type of air purger? Those float type vents are high point air vents, really no mechanism to pull air from a flowing stream.

RudyA

So those vents that were added do not solve the problem of air getting into the system ? 

RudyA

And you’re right , I don’t see an air purger , the vents are just teed in 

hot_rod

A vertical version air Sep would press into the piping above the boiler easily.

RudyA

Ok thanks I will definitely look into that 

EdTheHeaterMan

If you are going to the trouble to install that air separator you might as well do it to your best advantage. The proper order for the best air elimination is to place the air separator between the boiler and the circulator pump. Then connect the expansion tank to the bottom of the air separator, and connect the water feed valve at the same location with a tee.

SuperTech

It's probably not helping anything that the piping is undersized. Looks like all 3/4" piping near the boiler?

STEVEusaPA

What do you mean when you say "...I come home and I have no heat..."? The pipes aren't warm/hot, but the boiler is? Could it be circulation?
Are you adding water because it has left the system?
Are you sure it was properly purged in the first place, or are you just taking air trapped in the boiler and pushing it into the zone?
If you can't find a leak with a thermal imaging camera, you may be sucking in air from incorrect piping as others have mentioned.

RudyA

  When I leave the house for work  , I turn down the thermostat . When I come home and turn it back up , radiators stay cold , but I do hear the circulator pump . Then I proceed to purge the system and some air comes out of the hose . After that. , I have heat . And I don’t have to add water manually from the feeder valve . It feeds as I have the valve open to get the air out , When I close the valve the water pressure builds back up , feeder valve stops adding water  Note that this air problem happens randomly as I can go for more than a week and no problem , but then it comes back daily . 

STEVEusaPA

Sounds like it’s sucking in air, maybe from allowing the water temperature and pressure to drop.
Is the boiler coming up to temperature? Is it getting hot anywhere in the piping?

RudyA

 Boiler temp is fine as it serves the domestic hot water as well . Only part of the heat pipe that is hot is before the circulator pump coming out of the boiler  . Pump is hot also . After that the pipe is cold . 

RudyA

I was told to shut this valve off when purging the system . As soon as I open this valve , the steady stream of water from the hose starts skipping with air . Seems like the air is getting trapped between the circulator pump and boiler 

Grallert

Are you purging through that red handled boiler drain upper right of this picture? Looks like you could but you would be purging in the reverse of the normal flow.

RudyA

Yes , that’s where i connect a hose and purge it 

leonz

Hello Rudy, have you turned thermostat all the way up and let it run? That is a good way to push the bubbles out.

RudyA

No I didn’t . Was told to purge it with the heat off 

hot_rod

How much are you setting back the thermostat. Takes some time to get high mass radiator systems heating back up

RudyA

I turn it down to 60 since the weather has been nice . I’ll turn it up to 67 when needed and the radiators get hot immediately. 

fortyyearsin

try closing the air vent at the expansion tank. It looks like you installed it yourself.