One Pipe System, pressure short cycle, no main vents?

extinqt · 12:02AM

Hello everyone, I recently moved into a new house and just got my gas turned on. My steam boiler (peerless 63-04L) is oversized based on my EDR. My current EDR is 279 and the boiler is rated at 383 EDR. My problem right now is it seems that my boiler is short cycling due to pressure. I have the pressurtrol cut-in at 1.5 with a differential of 1. The boiler will turn on and cycle many times before the thermostat is satisfied. I know that it being oversized is a problem, but I have also noticed that there are no main vents and I believe it to be causing pressure to build up very rapidly. I am just trying to improve what I have as best as I can. My question is can someone point me in the right direction with locations for main vents? I will attach photos, I understand the main on the right side (the one that appears to be covered in asbestos insulation) but I am really confused on what is happening on the left side where it T's (one with reducer on top) and splits into 3 different areas. Is each run coming off of that T considered a main? I can take more photos if needed. Thank you!

EBEBRATT-Ed · 1:22AM

I think we are looking at a counterflow system here.

Are the mains pitched up leaving the boiler? (lower on the boiler end)

Need more pics from farther back.

I would guess you have no main vents now and all the venting is done at the radiators.

extinqt · 1:42AM

I tried taking pictures from further back but it is hard to tell in the photos. The pipes are pitched at an upward angle.

You are correct. The venting is done at the radiators, which the vents are also more than likely incorrectly sized. I would like to get main vents on and then work on the radiator vents.

My idea was to tap into the top of the pipes on each supply (I think there are 4 if where it T's on the left counts as 3 separate ones) just before the riser to the radiators.

Jamie Hall · 3:11AM

Yike. Well, yes. Those four pipes could be considered mains I suppose. Certainly for venting purposes. The trick is going to be finding a place close to the ends of them to put vents on. On the other hand, the ones with coloured marking in your drawing are small, so you don't need big vents for them.

109A_5 · 5:14AM

To some degree I would consider it a Steam Main if the pipe serves to bring Steam to multiple radiators.

The purpose of the Main Vents is to vent the air out of the Steam Mains as fast as possible and so the various Mains fill to their ends evenly so the steam gets to the radiators as evenly as possible.

Getting the Steam Mains properly vented may slow down the accumulation of pressure, however once the radiators fill with steam they can't dissipate what the boiler is producing so the pressure will build.

I would not run the system up to 1.5 PSIG. I would add a Vaporstat or another low pressure sensor (a pressure switch) to detect a more reasonable maximum service pressure then use a timer to delay the burner restart, minimizing the short cycling due to pressure.

EBEBRATT-Ed · 6:02AM

@109A_5

Even worse. The op said his cut in is 1.5 psi with a 1lb diff so he is cutting out at 2.5ish

mattmia2 · 7:12AM

how much of the radiators is hot when it cycles off on pressure? if the radiators are mostly cold then it is cycling because the air can't get out. if the radiators are mostly hot all across when the boiler first cycles off on pressure then it is because the boiler is making more steam than the emitters can consume.

One Pipe System, pressure short cycle, no main vents?

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