Two pipe steam heat banging

2pipesteam

Home built in 1900. I’ve had near boiler piping repiped, but it still bangs tremendously. It is: two pipe, gravity return, no traps, I have found check valves at the returns of the radiators underneath floor boards, one main vent in basement (Hoffman 75H), boiler running .5 psi, each radiator has one Hoffman 1A vent. The boiler is toward the front of the house. Banging is only toward the rear of the house with the longer main. The shorter main has no banging. Shorter main is 15ft, longer is 40ft. There is clicking at the radiators and the banging from the longer main comes up through the pipes. Banging is at the beginning of the cycle. All radiators properly pitched. I have not found any traps or other vents. 15ft main return pipe mostly stays cool except for the pipe closer to the boiler. Long return pipe with Hoffman 75H vent is piping hot and I think that is the issue. What can I do to stop the banging? Water line to wet return is 5”, water line to main vent is 58”, water line to headers is 45”.

SteamSystem.pdf

SystemDiagram .pdf

Captain Who

I think we need a couple more photos from different angles. That's a mess (sorry). So it is counterflow mains? My understanding is that in a counterflow system, the condensate in the main should flow back into the boiler through the equalizer only and the header should be located higher than the equalizer (your parallel header) and elbow into it from above and before where the two mains tee off of it.

Edit to add - sorry. I realized it is a pdf with lots of photos and I just scrolled down and saw them all.

4GenPlumber

Somebody really liked bushings (which cause puddles). Hartford tee looks low from that angle. The boiler has a pressuretrol which means when it's under pressure its running at 1.5 psi (lowest possible cutout). Need more pics, and pics of rads.

Captain Who

Why is this bushed down to such a small diameter from the Tee and then the reducing elbow brings it back up to a larger diameter?

Captain Who

This, the vertical section of equalizer, should be more like min. of one pipe size smaller instead of being bushed down so small. Seems like in a counterflow main situation this might be all the more critical:

ethicalpaul

Just trying to narrow things down for the OP instead of widening things out here—the equalizer size is not causing the banging.

The header sure is weird.

Jamie Hall

How are the mains connected to the dry returns, if at all?

My bet is going to be that that long 40 foot main has sagged. It doesn't take much of a sag to cause a mighty anvil chorus on startup. So… take the insulation off or use a probe, and check the pitch of that main between every single hanger. If there is more than four to six feet or so between hangers, add a hanger and set it to pitch. You don't really need that much pitch — but it has to be consistent and it has to go to a drip.

Captain Who

Above near boiler piping issues were not intended as an all encompassing solution to the problem by any means. We need some more information. Here's a few questions I have. All pipes need to be properly pitched in the system of course, so that there is no pooling of condensate. Wet steam and near boiler piping issues will make things worse but is by no means the main cause of what you are experiencing.

What is happening at the sight glass when the banging occurs? In other words, is it bouncing up and down dramatically? Has it gone down lower than the initial level and how much has it gone down? What is the exact height of the Hartford Loop close nipple relative to the normal water line? What is your water quality like, ie. is it filled with rust particulates when you drain some from the bottom of the boiler?

What boiler manufacturer, model, and size do you have?

mattmia2

header is wrong. i don't think the reducers are a problem but the equalizer should connect after the mains so any carryover returns to the boiler thorugh the equalizer, not gets propelled up in to the main. your equlaizer connects in the opposite direction of the mains.

Captain Who

@2pipesteam You drew your pen and paper sketch as a counterflow main situation. Is that correct, ie. the pitch of the mains goes downhill towards the boiler?

What is the pitch of both the first header and what you referred to as the parallel header? If the other parallel header is not pitched downwards towards the equalizer, and you have counterflow, then you are going to have a problem.

mattmia2

if it is counterflow there should be drips on the mains before they get to the header although you might get away without them on 2 pipe if the header were otherwise correct.