Unknown problem with boiler

[cs2kplus]

Hi all,
Last week I turned heat on. Boiler went on. Days went by, seemed like I have to keep cranking up thermostat to get boiler to kick on. Then no matter what, it would not kick on.

Pilot light was lit.

So, I remove old thermostat. Only red and white wires. I joined them. Boiler turned on. when off I imagine due to its own internal thermostat? I put new thermostat on. Easy. Boiler worked.

Next day, house felt cold. No heat in baseboard. turned up thermostat. Nothing. For no good reason, I believe is the pressure release valve on cold water coming in. I opened slightly. Water flowed at a higher rate. In like 30 seconds after doing that the boiler turned on. It's been fine for a day now.

This morning it was off. Just out of curiosity I slightly opened valve again. It turned on. What the? My wife says we have heat and all is well.

When I bled the system in the summer, I usually open that valve all the way. Is it possible the valve is stuck? I assume it is a manual vs. an automatic since it has a handle. I was reading if there was a leak in the system opening that valve would replenish?

My step dad wonders if its the water circulator at the root. I can not hear if its running. I heard some can be very quiet. I feel heat in the pipes. Otherwise seems like I am getting heat. Then again, the farther rooms may be getting less. If the circulator was not functioning, wouldn't the system just shut down? By the way, the pressure is 30 psi, the temp is about 185F.
I could have searched the forums, but my circumstances seem to be my own?

Any thoughts?
Thanks,
Wayne

 

[Jadnashua]

Unless you have a really tall, multi-story building, and have replaced the 'normal' pressure relief valve with a higher pressure one, 30-psi is way too high for static pressure in your boiler...that's the pressure the 'normal' relief valve would open. That's a safety relief valve, and something that normally would never open.

So, most systems operate at a cold pressure of around 12-15psi. There's probably a low-pressure cutout, but often no high pressure one. If the pressure was peaking while the boiler was running, you probably have an issue with the expansion tank. It's either toast, or needs to be properly pressurized.

If the system has air trapped in it, it may not circulate. How to bleed off any air will depend on how your system was installed.

A circulator may be hard to tell if it's actually running without some test tools. There are ways...touch a screwdriver to it, and then put the handle up against your ear...you can probably hear the vibrations of the motor running. The pipe before and after the pump should be hot when it's running. If it's not running when it should, then, you'd check to see if it's getting voltage so it can run. If no voltage, you go back further to check the relay, and so forth. If you don't have the diagnostic skills or tools, you may want to find a friend that does or pay a pro. You need to do some research on your system (the owner's manual probably has a theory of operation section) to get a better feel for what should be happening. That manual usually has some troubleshooting tips and procedures. Those might be in the installation manual versus the operator's manual, though. OFten, if you don't have them, you can find them online. Just make sure you are reading the right one!

Lots of little things, but too great to go into without a specific question.

 

[Sponsor]

 

[Dana]

Jadnashua has it right- 30psi is high enough to open up the pressure relief valves on most residential systems. With a tepid (<< 120F) boiler the system should be pressurized to 3 psi + 0.433 x the vertical height (in feet) between the gauge and the top-most radiation, or 12 psi, whichever is higher.

Whatever your target pressure is after doing that math, a bladder-type expansion tank (with an air valve) needs to be pre-charged to the target pressure plus 1-2 psi. If the tank is undersized or the bladder is shot it can result in very high pressures when the system is hot, high enough to open up the pressure relief valve. Most residential boilers are shipped with 30 psi relief valves which may be why your system is running 30 psi @ 185F. A bladder type expansion tank will ring if you tap the air-valve end with a screwdriver handle, and thud if tapping the water connection side. If the pre-charge was 12 psi and the pressure is 30 psi it may thud even if the bladder isn't shot. If the bladder is leaking, pressing the center pin on the schraeder valve briefly would let water out, not air. (Be extra careful testing that when the boiler is at 185F.)

When filling the system to the proper pressure, turn off the isolating valve between any pressure reducing/auto-fill valve and the potable supply. The PRV/auto-fill valve seats often fail with a tiny seep, slowly over-pressurizing the system over time.

If the circulator isn't running or only delivering low flow you won't get heat to the radiators, even if the thermostat and boiler are working just fine. It won't just shut down. At low flow the boiler just heats up to it's high-limit setting and kicks the burner off until it cools off enough to re-fire, even during a continuous call for heat.

 

[cs2kplus]

Great answers. I am going to create a new post based on my latest situation. I appreciate the valuable info.