yet another mysterious bleeding problem

[Deleted User]

year after year, it's the same old problem; no heat to a zone due to air in the fan/coil, floor model heating units  

typical pumping away setup with a taco air scrubber and #67 auto vent that's left capped after bleeding, one circ, and 3 zone valves.  zone 1 is a coil in an air handler, approx 30' away from the boiler and 4' above it, with a #67 auto-vent that's left capped after bleeding.  zone 2 is a coil in an air handler, approx 70' away, also with a #67 auto-vent that's 20' above the boiler, and left capped after bleeding.  zone 3 is approx 45' away but it has three, parallel-piped fan/coil heating units that have manual, screw driver operated vents that are 13' above the boiler.  zones 1 & 2 have never had a problem after initial bleeding.  and even though zone 2's #67 is 7' higher than zone 3's manuals, zone 3 repeatedly air locks all through the heating season.  i'd finally found a small, evaporating leak at the boiler, fixed it, and guessed that that'd be the solution; no luck.  three weeks later, no heat in zone 3

now the details of zone 3 are these; the 'left' fan/coil never locks up.  the 'right' fan/coil, which is on the same level as 'lefty', but 12' over, locks up once in a while.  but when there is a no heat complaint, the 'center' fan/coil, which is 6" above 'lefty' and 'righty' will always be locked up.  so, when i bleed these units in this order, 'lefty' never has air in it.  'righty' sometimes has air in it, and sometimes there's enough air to keep the temp controlled fan from coming on.  and 'center' always has enough air in it to keep it's temp controlled fan from coming on

i'm at a loss, but wondering if i adapt the fan/coils to #67s, might that solve my problem?        

            

Mark Eatherton

Got drawing?

I'm trying to see through your minds eye, but everything looks blurry...:-)



A simple drawing is worth a thousand words.



Wait. maybe if you put on your glasses, I can see it better ;-)



It sounds like the "Ex Brother in law" syndrome, but need to see for sure.



ME

Unknown

Right Marcus,,,,

Sounds like someone was in-love with 67`s eh?  ;-)

kev

Try to

Leaving the caps loose on the main bleeder at boiler. You never get all the air out when purging, when you purge you are only adding more water and that means more dissolved air. 

Mark Eatherton

The use of # 67's...

indicates to me that they system has been suffering from air problems from the get go.



I have seen apartment complexes where there was an AV at the top of every riser, and there was STILL an air problem.



If the pump is not pumping away from the expansion tank, and the distribution piping is not balanced, causing a path of least resistance the lazy flow will cause air to come out of suspension, and in some cases, causes the air vent to become a vacuum breaker, inducing air into the system.



In the apartment scenario, I moved the pump so it was pumping away from te expansion tank, eliminated the AV's through out the system, replace the expansion tank with a bladder type tank, installed an air separator, and have not had an air problem since.



Need to see a drawing :-)



ME

[Deleted User]

naw mark

no b-i-l syndrome.  i did the piping a few years ago, and have repeatedly had this problem with that circuit.  and, i should have added that it's a closed, pumping away from a bladder tank system.  and as a convenience, the 67s have been there from day 1.  and even though i could leave them open bec it's a bladder tank, after the initial pressure filling and bled a few times at operation temp, i close them as a precaution.  bec in other systems, i've seen them corrode closed, and/or leak 

 

and what makes me suspect a leak in the circuit and/or elsewhere, is bec of the large amount of air that bleeds, and the surging at the circ  

 

but as far as a drawing, it'd be so basic as to be near useless, bec i can't pull that much from old memory.  but by tue or wed, i should be able to get a pic of the near boiler piping, and a drawing of the hidden piping   

Mark Eatherton

OK then...

If you suspect a leak, shut off the make up and see what happens to your pressure. If it drops, you've got a leak. If not, you don't.



Try leaving the caps to the AV's open for a week of god cold weather. Once you get all free air out, it should stay out unless you used non barrier tubing...



What did you think I meant by the B.I.L. syndrome?



ME

Big Ed_4

Taco

Is the Taco air scrubber working ??? Just a thought , it would be the only way air can get out.. But also try the leak test , looking for a drop in pressure ...