New Boiler Short-cycling on Pressure Cut-out

mattmia2 · October 29

https://forum.heatinghelp.com/discussion/comment/1816906#Comment_1816906

The drip that is connected in the middle of the header probably isn't hurting anything but it is there because the header isn't plumed properly.

This reducing ell that I circled isn't correct, it should be where the arrow is pointed down in to the header or as a reducer in the vertical section. The reducing ell in the horizontal section prevents the water from draining from the header in to the equalizer. The installer incorrectly tried to fix that by adding a drip to the header instead of putting the reduction in a vertical section.

KC_Jones · October 29

I just realized something. It appears both ends of that header have a reducer, so there is definitely water laying in the header all the time with no way out. The drip is literally on the high side of the dam doing effectively nothing.

So odd.

mattmia2 · October 29

https://forum.heatinghelp.com/discussion/comment/1816923#Comment_1816923

yeah, i just saw the second reducing ell as i was marking up that picture and thinking flow in the direction of the equalizer, but with both reducing ells it is trapping water in that header they reused from the previous boiler (or 2)

KarlW · October 30

Here's an alternate (and admittedly less likely) explanation I didn't see posed:

Do you have radiator valves off or TRVs? If you aren't actively heating the full EDR, then your boiler is effectively even more oversized - so you would be hitting the pressure cutoff much sooner.

My system which is fully TRV'd (and smart) regularly short cycles regularly this time of year as it is only heating as few as 4 of 14 radiators at a time.

dgn · November 8

In spite of the recognized flaws in the near boiler piping (pipe size reduction coming off the header, 3 mains coming off of a single takeoff from the header, etc.), the extensive skimming that was done completely stopped the short cycling and there's no water hammering. Though we're not yet into the fully cold heating season the full system is heating well, no pressure buildup whatsoever (I have monitored it regularly especially when fully hot), and quiet as anything — overall better than the previous boiler. All that said, I think I'm good for now. Thanks everyone for your input. Lots of good minds and experience here.

neilc · November 8

don't be surprised, or discouraged, if in a week or 2 you have to skim again, lots could be thrown up in the system to return later

let it run and keep an eye, and ear, on it

New Boiler Short-cycling on Pressure Cut-out

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