Pressure/balance

Jeff_44

I have a one pipe system in good working order - Ocassionally, as the boiler cycles, there will be a random radiator that doesn't get steam. I have plenty of vents on the mains. The boiler is rated at 283 EDR and the load is 286. I have a gauge that reads in ounces and it never reads past zero. How might I track down this issue with the random cold rad AND, might this be related to the very low presssure reading?

ChrisJ

Vents

What vents are on the radiators?

I have this issue with Hoffman 1As getting a tiny drop of water stuck in the orifice and it stops the radiator from heating.



Another cause could be too much venting on the radiators if your boiler is closely matched to the load.  If this is the case you may have to slow up venting on all of the radiators a hair until it comes into balance all of the time.

nicholas bonham-carter

random radiator cold

can you blow into your pigtail, to check that is open? can you check the gauge by blowing into it? it shouls show some sort of flicker of the needle at least.

can you jump the thermostat wires together, and see whether all the other radiators get steam at the same time? is there any short-cycling as the boiler makes steam? is the cold radiator problem truly random, or is it either one of a pair sharing the same riser?--nbc

Jeff_44

Yes

when I blow into the gauge, it responds so I know it's working. The pigtail is clear. I have the pressuretrol and gauge mounted on the pigtail. When the boiler is burning, the needle on the gauge flickers and is in motion, but never moves off zero. In fact, sometimes after the boiler cycles off, the gauge has a negative reading. I'll check and see if the 'random' rads are on the same riser. The boiler does not short cycle.



The vents on the rads seem too fast and on some, I have them at to their lowest setting AND I have some heat tape placed over part of the orifice to slow it down even more. Perhaps this is the place to start.



can you blow into your pigtail, to check that is open? can you check the gauge by blowing into it? it shouls show some sort of flicker of the needle at least.

can you jump the thermostat wires together, and see whether all the other radiators get steam at the same time? is there any short-cycling as the boiler makes steam? is the cold radiator problem truly random, or is it either one of a pair sharing the same riser?--nbc

Rod

Radiator Vents

Hi- What make and model vents are you using on your radiators now?

- Rod

Jeff_44

Rad Vents

Most of the rads have Maid-O-mist. A few have Varivalve Quick Vent and one rad has a Hoffmann #1.

Rod

Try Slower Radiator Vents

I was wondering if you had VariValves.  I would try changing them out for a slower vent especially if they are being used on a large radiators. What happens is they allow a lot of steam to quickly enter the radiator and the resulting condensing creates a large vacuum (big pressure differential) which then "pulls" in more steam.  This demand for steam can starve the other smaller radiators especially those farther down the main from the boiler. Vari Valves can be very useful but just in some particular situations. A lot of us have a few of them collecting dust on our basement shelves as we found we needed to go to slower radiator vents to balance the system.

- Rod

Jeff_44

Thanks

Would the vari-vent also have an effect on the pressure in the boiler. I also tried an experiment and closed all the rad valves and then fired up the boiler. It took about 15 minutes for the gauge began to move. I let it go until it reached 1.5 lbs. and then shut off the boiler. From this it seems that the low pressure is found in the system, not the boiler. Also, the LWC did not shut off but was set at .5 - does this mean it isn't working properly. It's on the same pigtail as the gauge.



Thanks for your help.