No flow in one circuit of hydronic heating system?

kdegru

There are 4 circuits to this hydronic heating system at the church.  From the top of the boiler there is a manifold feeding hot water to the 4 circuits.  Each passes through a B&G 1" angle Flow control unit.  All the other 3 circuits are delivering heat to their respective areas as normal.  All of the ciirculator pumps are working.  Just recently the largest circuit (serves the most radiation) has failed to deliver heat.  Anywhere in this system I touch there is no warmth at all.  I have checked numerous air purge valves at high points in the system and where I either hear air escape or get squirted with water I now hear nothing see no water squirt.  I am at a loss to explain this.  This heating circuit should be under system pressure and somthing should shoot out of those air purge valves.  When I trace the heat from the boiler output manifold through the B&G flow control valve I feel heat.  Several feet away from this poin the pipe becomes cool as though there is no water in the pipe from that point on.  Could I have alot of air in the system at this point?  I have been watching over this system for over 25 years now and never ran into this problem.  I will call in a contractor if needs be but the funds are very limited here so I will try my best to determine what we are up against.

ed 

Al Letellier_21

no heat in loop

There could be several things at play here. Are you sure the circulator is running. You didn't mention what kind they are, but it is possible that even thought the motor is running, the unit may not be moving water. I would suggest opening the B&G flow control and run the other zones. IF your main zone heats up, then there is no air issue, it is probably a bad circulator. IF the zone does not heat up even with the flow control open, you have an air problem and the zone needs to be purged. It can't be much more than that if nothing has been changed in the system since last year.

Where are you located?

billtwocase

could be a few things

I've seen flowchecks stick closed, B&G impellers rot away, low pressure on boiler, or just a lot of air. Try to manually open the flowcheck to see if it is stuck, make sure the pump is running, check the drive coupling also. The red plastic ones were known for cracking and wouldn't turn the bearing. Check the boiler pressure. It could be a few things. Good luck

kdegru

Follow up on suggestions to troubleshoot hydronic system cold loop problem.

Thanks again for the suggestions.  I found that the compound gauge on the boiler was indicating 0 PSI.  I opened the pressure relief valve and no water shot out of the it's drain pipe.  That seems like there is no pressure being delivered from the B&G (B-38) regulator.  I know that the city water supply is available on the in side of the regulator.  It seems like a failed regulator.  I will need to try a replacement or maybe a rebuild kit.  I will share the results soon. 

kdegru

The problem is resolved.

I opened up the B&G B7 reducing valve and found that the strainer filter was completely encrusted with hard water calcium deposits along with lots of rust residue from the 3/4 inch black nipple used to connect the ball valve that feeds city water to this system. The valve stem assembly was completely frozen in a closed/clogged condition.  I loosened the stem up and flushed and cleaned everything out.  I reassembled and set the pressure and it works fine and we have heat again.  Well almost.  Some radiators on the loop have difficult to get to and rather frozen air purge valves I cannot operate.  They really need replacement.  I will have to craft some kind of tool to get leverage on these very stiff thumb screw type 1/8" MPT valves.  I really hate these valves an have to be careful I do not put too much stress on them.  Worst case I may have to replace them so I can get the air out of this system.  Does anyone use schrader valves (like in tires) as radiator air purge valves?  I do not know if they are up to the temperatures involved.  I now have heat in all radiation except one section that is highest in the system and which I was unable to budge the air purge valves on either end.  I want to thank again those that were kind enough to respond as your responses put me right on the path of the problem.  B&G model B7, (date C-58?) reducing valve.  I have put in a request to the B&G rep in my area to see if the kit can still be available.  The rubber check valve has a hexagonal shape where it seats on the valve stem bushing.