Piping for New Steam Boiler
Hello All,
I have a new boiler that is 300,000 BTU with an output of 250,000 BTU. I am interested in getting your insight on the header and the takeoffs from the header. Manufacturer recommended 2 inch risers, 3 inch header, and 1.5 equalizer. My 3 mains are one (2 in) and two (2.5 inch). Initially, I was thinking of keeping the recommended 3 inch header and going with all 2.5 inch takeoffs to meet the mains, reducing for that one 2 inch main. Now I am considering a 4 inch header with 3 inch takeoffs that each reduces to its respective main with a 2 inch equalizer. Any benefit to increasing the header and takeoffs and equalizer? Any cons? I have attached a schematic of original plan.
Comments
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I'd like to see that header higher off the water line. Also,.a Gate valve on the pipe in to the Hartford Loop 90. Mad Dog
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I’d like to see the EDR #’s for that boiler.
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@Mad Dog. We are adding a gate valve there just forgot to sketch it in. The water line is much lower than header, just didn’t come out right on the schematic. Thanks!
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@pecmsg. Around 235k btu at full capacity
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The boiler mfg recommendations are the minimum. Your drawing looks ok. If you want to use a drop header and a larger header than the MFG recommends so much the better, but it may be unnecessary.
I don't think anyone that has piped a boiler to the MFG minimum have had issues. Bring the mains down to the header individually as you have shown.
I don't know what boiler you have but 2 2" risers sounds small for a boiler that size. Double check.
I would keep the drop header no lower than the top of the boiler jacket.
Your risers from the boiler should be at least 24" above the normal water line (higher is better)
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@EBEBRATT-Ed the openings on the boiler only allow for 2 inch pipes. I can add two, 2/3 inch elbows to allow for a bigger risers but manufacturer also recommended 2in risers (I have attached chart). Also our risers will be at least 30-32in above the waterline and at least 26inch above the boiler. The header will drop about 8-10 inches from there. Takeoffs will go right off the header separately into the mains.
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Ideally, we like at least the first two main takeoffs (and any counterflow mains) from the header to be at 45-degrees. This prevents the raining of condensate into the supply steam.
We also like 14" on the header between the last supply riser and the first main takeoff.
Brass cap on the mud leg with a drain.
Those fittings ain't cheap! Don't use a drop header without the need for it.
Nice drawing.
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@Long Beach Ed the 45 degrees makes sense but why not on the last takeoff as well? Our first run before takeoffs was closer to 13 inches given the number of takeoffs and space limitation. Thanks for the pointer on the drain.
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Condensate dropping down the last takeoff will run straight to the equalizer, unlike the other takeoffs, where it rains down on the steam supplying later ones, cooling it. A 45-degree takeoff eliminates this.
The 13 inches is perfect.
On many boilers, the mud leg is lower than the boiler drain, so a drain in the mud leg gives some opportunity to clean that out every few years. And it's likely that a drain cock can be unscrewed two decades from now when plug would be hopelessly rusted in place.
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@Long Beach Ed the 45 takeoff makes perfect sense! As for the mud leg, ours is the same level as the drain, so it may be best to utilize an eccentric cap with drain to get better cleaning.
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You could make a case for the 4" header based on the cross sectional area of the risers. A 2" riser plus 2 @ 2.5" equals 12.92 sq in, and a 4" header has 12.73 sq in, a pretty close match. A 3" header only has 7.39 sq in.
The 4" header would slow the steam down more than a 3", but whether or not it is worth the expense is hard to say.
I would keep take-offs from the header at whatever your mains are and not bother to increase them only to reduce them a few feet away, assuming the mains are sized to the edr.
Dennis
Dennis1 -
And the EDR of all the radiators?
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What is the model # of the boiler you have?
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Wait until you see the price of an eccentric cap. Four inch elbow or tee? Hahahahaa!
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No harm with the 4-inch header, except to your pocketbook. Probably overkill, especially if the header's dropped, which would also be overkill if you have room for a nice high header. You have to analyze the benefit in light of local conditions.
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@Long Beach Ed I agree. The only point of dropping the header is to get purer steam…as for the 4inch header, it maybe overkill as you stated. Thank you for the insight!
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If you have sufficient height above the boiler, and the rest of the system is piped properly, you probably don't need to drop the header either. It's needed when low basement ceilings would leave an insufficient distance between the water line and the header.
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I got the cross sectional areas from LAOSH and Engineers Toolbox, so I did not run the calcs from scratch.
I like the looks of using full size tees with reducers, but you can gain some horizontal space on your header by using reducing tees: a 4x4x2 tee is 2" shorter than a regular 4" tee.
Dennis
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Would still be helpful to know exactly what boiler you have.
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@Long Beach Ed
the only reason we are doing the drop header is to get purer steam…in terms of the height above the minimum 24inch water line, we will be well over that with the initial risers (around 30-32 inches above water line) and will keep drop header at least 24 inches above the water line. My concern is with the B dimension because was going to place it on blocking which decreases the height by about 3-4 inches. Has anyone had issues with this difference?0 -
Why the blocks? There's no downside to having more margin on the B dimension and a lot of issues with not having enough.
If you're worried about waterline height due to existing wet returns, install a false waterline.
Trying to squeeze the best out of a Weil-McLain JB-5 running a 1912 1 pipe system.2 -
Blocks are probably to keep it out of any water that might get on the floor.
increasing the header and the risers slows down the steam and halps more water drop out, increasing anything else has no benefit. If the tappings for the outlets are 2" i'd probably just use 2" although you could use a tee with a 2.5" or 3" branch and a reducing ell to make the risers bigger but with the drop header even increasing the header is probably overkill.
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@delcrossv precisely why I brought it up…don’t want to compromise the B dimension. Currently return around 70 inches from ground and adjusting for waterline we get b dimension of 46 inches. At operation of 1.5psi we get 45inches b dimension requirement. Hence why I’m concerned if we raise unit by 3-4 inches we will have 2-3 deficit in B dimension. @mattmia2 the drop header consideration in increase in size to 4 inch was an effort to slow the steam and draw out more water (ie purer steam) and risers higher was to ensure again less water gets out and to keep the drop header at least 24 inches above the waterline (but that maybe overkill as others suggested) I am leaning towards just keeping the drop header at 3in with takeoffs same size as mains (as the image shows). As for the blocks…the basement floods with huge storms and it’s an added precaution (nothing in terms of operation of boiler)…other than my concern that this would negatively impact the B dimension as it would be deficit by 2-3 inches…leading to knocking and other issues. But will probably explore false water line as suggested???
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Keep in mind that no one has any evidence to suggest that the MFG minimum piping requirements don't work.
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Do you have any water seals that are high up that would require a false water line?
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Do you have gravity return to the boiler? And you are talking a 2 pipe system, yes?
. Currently return around 70 inches from ground and adjusting for waterline we get b dimension of 46 inches. At operation of 1.5psi we get 45inches b dimension requirement.
1 inch is not enough leeway for comfort. Should be B+ 3 to 4 inches minimum.
Trying to squeeze the best out of a Weil-McLain JB-5 running a 1912 1 pipe system.1 -
@delcrossv yes and yes to your first questions. That’s exactly what I was fearing. But I erred on side of caution and said return starts at height of 70 inches, however the main terminal reduces and connects at slightly higher than that. More like 72, but I figured to give more space for condensate so I measured lower than that point. I maybe barely at exact height to make this work…what are your thoughts? I can also do two things, get 1-2 inch blocks to give 2 inches back to the b dimension height or I can slightly lower the pressure slightly on pressuretrol to account for that difference.
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I'd go the vaporstat route. If you did your math on the EDR right it should never build more than a few ounces of pressure anyhow so maybe the pressuretrol would be fine.
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This, or you'll need a pumping trap. If your pressure will get you within 6" of your available B dimension, a pumping trap on your condensate line would be a necessary fix to make sure you get water into the boiler.
Vaporstat is a lot cheaper if you can get the system to work on ounces.
Trying to squeeze the best out of a Weil-McLain JB-5 running a 1912 1 pipe system.1 -
Alternatively, if you can make a mostly adequate B dimension, you could pipe in a differential loop. If your pressure rises above what the B dimension allows, the loop would trip, pressurizing the dry return thereby turning your B dimension into an A dimension briefly.
The length of the leg on the left between the bottom U bend and the T going to the Hartford Loop will determine the pressure it will trip at. Fourteen inches would be 8 ounces differential pressure. The vent on the differential loop has to be the only vent on the dry return
Trying to squeeze the best out of a Weil-McLain JB-5 running a 1912 1 pipe system.2 -
Is this 1 pipe or 2 pipe? on one pipe the returns are connected to the mains and will stay at the same pressure(minus some trivial pressure drop in the mains).
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@mattmia2 @delcrossv it is a true 2 pipe steam gravity. The steam pipes go to the radiators and at the end there are traps and then return to separate line—dry). One of the main terminals drops and merges with the wet return (perhaps for efficiency…so wet return is warmer thereby reducing the time it takes boiler to produce steam). Where this main drops to merge with the wet return is the highest wet return. The dry return backing up to one main vent (all I see)…before merging back to wet return below the Hartford loop. I was thinking of splitting this dry return so there are two main vents (with one being on left of the boiler and the other the right…currently have only one on right of boiler). Both dry returns would go in separately into the wet return before the Hartford. But if I did that, it seems I could not add the differential loop mentioned by delcrossv. A pumping trap might be an option then because I think I will be very close to the b Dimension. Vaporstats are great and more accurate…but the price is hefty…something that will be considered once the system is up and running.
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@mattmia2 @delcrossv attached is a simplified schematic of system runs. Maybe this will help.
I was going to disconnect return above boiler and add vent and drop it down to vent as mentioned in another post. Then there would be two main vents on either side of the boiler.
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Here are some suggestions and questions. Need heights above WL to dry return. Click to enbiggen.
One BIG vent at the present location should work- lengths and pipe sizes would dial that in.
Note you can't have a separate vent on the short return if you're going to use a differential loop.
Trying to squeeze the best out of a Weil-McLain JB-5 running a 1912 1 pipe system.1
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