Replacement Steam Boiler Piping Advice

Mark_35

Mark_35

Replacement Steam Boiler Piping Advice

I would appreciate comments from the steam experts out there on my piping plan for a replacement boiler. This is a two-pipe Trane vapor system with convectors for terminal units. About 350 sq ft EDR. It operated at about 8 oz pressure with the old boiler. Please see picture and sketch.

The old 4” steam header had two 4” feeds straight up from the old Ideal Model 12 boiler. These header was pretty close to the top of the old boiler – about 12”. Three, 2” steam lines take off at three different locations along the top of the header and pitch down nicely to drip traps at the ends of the mains. The 4” header pitches down to a 2” equalizer line at the right end in the photo. The easiest way to install the new boiler (Peerless 63-4L - 383 sq ft) is to put it right below the header and feed up with two 2-1/2” feeds into the original 4” tees, with offsets for expansion. This does not meet standard “near boiler” piping recommendations, since the three supplies take off at the ends and at the center of the header. It did work fine with the old boiler. The steam velocities will be very low (about 10 fps in the 2-1/2” risers) and even lower in the big header.
Re-piping to put all the system supplies between the boiler feeds and the equalizer would be a lot of work. I would probably have to take out the 4” header and have a very long horizontal run to the equalizer line.

Has anyone run into a situation like this? Am I going to get condensate hanging up in the heater (or in the steam riser offsets)?

Any advice or comments would be much appreciated.

Christian Egli_2

Rules rules rules, everything's got to have rules

Your transgressing header will give you lots of problems. The kinked boiler take offs are just the start.

An old and tall boiler would have taken care of producing dry steam on its own. This is no longer true of modern boilers, so you need a good header now more than ever.

Here are some thoughts.

Leave the existing header as is, call it now a sub-header. Keep it draining into the Hartford loop. Feed this sub-header from the bottom, as is, but not directly from the boiler. Build a new drop header below the level of the current sub-header.

This drop header needs to drain into the Hartford loop and feed it in the correct sequence with the two boiler take offs which you make go straight up first before falling back into the header. No cascading steps.

This drop header, you could place it orthogonally to the sub header. You could also build it in a circling U shape to bring the steam back under the sub-header. This is all depending on where the new boiler goes.

Make sure all your piping slopes (good slopes) with the steam flow and that unboiled steam can stream back to the Hartford loop without puddles.

This way you'll save yourself lots of tears. Hopefully you saved the mating flanges from the old boiler, for reuse.

Best of luck.

Steamhead (in transit)

Don't take the easy way out

it will never work properly. This is what I'd do:

Remove the old riser nipples from the bottom of the 4-inch header and plug them. You may have to cut the nipples out.

Remove (by breaking if need be) the 4x2 reducing ell at the high point of the header. Replace with a 4x4x2 (4-inch run, 2-inch branch) tee, and reconnect the 2-inch steam line to the branch using nipples and a union.

Build a proper drop header for the Peerless boiler. Not sure what minimum size header is called for on this boiler but I'd make it 3-inch. Run the 3-inch output from this header into the new tee (see above) on the old header via a 4x3 reducing ell or coupling. Install your Hartford Loop on the new header and drip the old one into the wet return.

This will not only get the steam moving the right way thru the old header without completely repiping it, but will also slow it down to about where it was with the Ideal boiler.

It is possible for a bit of water to accumulate in the old plugged riser tees, but if you bury the plugs as far as you can this should not cause a problem.

Here's a shot of a "double-header" job we did. In this case the old boiler only had one riser to the five-inch header. We ran the new 3-inch header into the old 5-inch header. The result was nice dry steam, and with proper insulation and main vents this Kriebel Vapor system works great.


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Steamhead (in transit)

Don't take the easy way out

it will never work properly. This is what I'd do:

Remove the old riser nipples from the bottom of the 4-inch header and plug the openings in the tees. You may have to cut the nipples out.

Remove (by breaking if need be) the 4x2 reducing ell at the high point of the header. Replace with a 4x4x2 (4-inch run, 2-inch branch) tee, and reconnect the 2-inch steam line to the branch using nipples and a union.

Build a proper drop header for the Peerless boiler. Not sure what minimum size header is called for on this boiler but I'd make it 3-inch. Run the 3-inch output from this header into the new tee (see above) on the old header via a 4x3 reducing ell or coupling. Install your Hartford Loop on the new header and drip the old one into the wet return.

This will not only get the steam moving the right way thru the old header without completely repiping it, but will also slow it down to about where it was with the Ideal boiler.

It is possible for a bit of water to accumulate in the old plugged riser tees, but if you bury the plugs as far as you can this should not cause a problem.

Here's a shot of a "double-header" job we did. In this case the old boiler only had one riser to the five-inch header. We ran the new 3-inch drop header into the old 5-inch header. The result was nice dry steam, and with proper insulation and main vents this Kriebel Vapor system works great.


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Mark_35

My original plan was similar

Many thanks. I had originally come up with a scheme using a new header below to original one, but when the contractor suggested this design, I thought I would give it a fly on the Wall. I am glad I did.

My original plan had the steam running from the new header up into the first (on left) 4x4x4 tee and the other tee would be plugged. That is not quite as nice as Steamheads suggestion, but keeps me from using up as much space in the basement. Think this would work?

Christians idea to use both tees is nice, but this may be more than I need. Peerless only recommends a 2-1/2" header for this boiler. I would go with 3" header and a 3" feed up to the old header.

Mark_35

Question on Photo

Steamhead;

Did you loop the risers down into the steam header for a reason or was it because of lack of space. Most diagrams show risers entering header from side.

MarkB

Steamhead (in transit)

That's what a \"drop header\" is

If the boiler needs two or more risers to the header, a drop header is the way to go. The extra swing joint in the elbow to the drop makes the piping a lot easier to assemble, and it allows easier expansion and contraction of boiler sections.

Go to the Library section of this site, click on "Steam Piping" and you'll see a lot of drop header pics.

Your plan might work OK but it does involve a "bullheaded tee" in which steam is coming into the branch and you expect it to go both ways. This can cause some pulsation and a bouncy water line. My suggestion takes up a bit more space but doesn't have any bullheads.

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Mark_35

How is this plan?

Steamhead and Christian:

Here is a plan that has most of the features you two suggest - (except the drop header, which I can add). There is one area of the 4" header (on the left) with counter flowing steam and condensate, but the steam should be pretty dry by the time it gets here. What do you think?

Is it worth it to go the extra mile and replace the 4x2 elbow at the end and pipe up at that location?

Steamhead (in transit)

The bullheaded tee I mentioned

is shown on your diagram, where the 3-inch riser comes up from the new header into the branch of the tee on the old one. This is not a good idea as explained before. Go the extra mile by replacing that 4x2 elbow with a tee and piping into the tee the right way. You'll love how well it works.

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Mark_35

Drop Header Question

Anyway, you have me convinced. We will go for the end feed and drop header.

I checked out those photos of drop headers. Look nice. Do I measure the 24" rise from the water line to the high point of the piping (that is the inside of the inverted U) or to the bottom of the drop header itself?

How come the none of the installation guides (Peerless, Dunkirk, W-M) show drop headers? I don't think that Dan's "Lost Art.." even mentions it.


MarkB

Steamhead (in transit)

And please

post pics when it's done!

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Steamhead (in transit)

Ahhh

you edited the post. My reply was to the original version.

The 24-inch height is generally measured from the center of the sight glass to the top of the riser. I like to take it a bit further and measure from the top of the glass to the top of the riser. The height of the riser determines how high any carryover water must go to reach the header. 24 inches of riser height will generally keep the water in place. More height is better if available.

Piping diagrams generally show a minimum required configuration. There's nothing wrong, for example, with making the header piping 2-1/2- or 3-inch instead of a specified 2-inch minimum. But if the diagram calls for a 3-inch minimum and you use 2-inch, you'll have problems.

The same applies to drop headers. They might not be required in the minimum configuration, but their benefits are obvious. I do know that Burnham provides drop header diagrams for at least some of their steamers.

Also remember that "Lost Art" came out in 1992. Since then we've uncovered a lot more good stuff about steam heating. I really wish he would do a "second edition". Ya listenin', Dan?

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Mark_35

That's what happened

I did edit it while you were responding to the original post. I have noticed that ASHRAE Systems Chapter 10 on steam does show drop headers on all their hookup diagrams.