Drop headers

PatNH

Will a drop head add any value to a single outlet boiler? Have low head room and need the drop to add piping above water line.

ethicalpaul

My opinion: yes, just as much value as it will add to a dual-outlet

Tim McElwain

It will also help prevent wet steam and water hammer created because the new steam boilers produce steam much faster and at higher velocity leaving the boiler.

Jamie Hall

Drop headers are useful for two risers, yes, as they alost inevitably give you two swing joints to take the stress off the boiler. They are also handy in low headroom situations. But -- the real reason to use them is the one @Tim McElwain mentioned: much better quality steam.

The Steam Whisperer

Yes, we use them on just about every installation. They produce better steam and allow some wiggle room when hooking up the boiler. Even on a single riser installation they may reduce stress on the boiler since the whole piping system is moving as the system heats up and cools down.

PatNH

Thanks guys,  I will be doing this job this morning,  I will send some pics. 

JohnNY

Just to play devil's advocate here....I'd like someone to show me the difference in the moisture content of a small residential boiler's main distribution pipes piped with a drop header versus a standard header.

nicholas bonham-carter

The devil probably knows a few things about heating, given the purpose of his domain. Population increases, along with a rise of bad behavior must make the expansion of his system a constant activity!
I wonder how that could be measured—maybe with a viewing port of Pyrex glass set into a tee in the drop header, or a conventional header.
The advantage of the drop header is in its capacity to give more mechanical isolation for differences of thermal expansion and contraction between the boiler block, and the header itself, (particularly in the case of welded headers). More wiggle room for fitting the pipes together would be another plus.—NBC

JohnNY

Thermal expansion on a single-riser boiler is a non issue. There’s no way to test for wet steam in the field that I know of and that kind of makes many of the performance benefits of a drop header theoretical.   

The Steam Whisperer

I disagree. Thermal expansion is still an issue on a single rider boiler for 2 reasons.... The header drip can still be fixed to the boiler ( Even Weil shows a minimum piping arrangement with threaded joints on the return) and the system piping also tends to move, causing stress on the boiler.

AMservices

Water hammer is a clear sign of wet steam.
Calculating steam exit velocity is another way we can find if there's carry over.
We can't always see what's happening inside of pipes. So we have to rely on numbers and our senses.
A drop header or a over sized header is doing the same thing a steam/liquid separator would do. It gives a larger area for steam to slow down before entering the mains, and if there's any carry over of water to collect then drain back into the boiler.
Having more swing joints with a drop header makes it easier to work with when connecting big pipe.

Ironman

You can see what's going on in the header. Remember W/M's demo boiler with the glass header?

Someone should be able to post the video of it.

EBEBRATT-Ed

@ethicalpaul
Has glass tubing on his boiler
I think the drop header thing can be over done. I have never had a problem piping to the MFG spec along with boiling out with TSP and skimming.

If I am not mistaken @ethicalpaul piped his boiler with two risers and only 1 was required. With valves on the risers he shut 1 off and had no carryover.

I am sure someone will correct me if I am wrong

The Steam Whisperer

Eberatt. I largely concur....I use the drop header mainly for ease of piping and reduced stress on the castings, though I am sure it helps when boilers start getting fouled. Now If I am piping into a vacuum system, I would definitely go well beyond the manufacturer's piping. Using 2x 3 inch risers on a little 200,000 btu boiler is a bit much. I'd rather put that extra money into better venting and other system improvements ( water meter, etc). If its a side tapped utica/dunkirk I go a little more beyond the minimums.

ethicalpaul

EBEBRATT-Ed said:

@ethicalpaul Has glass tubing on his boiler I think the drop header thing can be over done. I have never had a problem piping to the MFG spec along with boiling out with TSP and skimming. If I am not mistaken @ethicalpaul piped his boiler with two risers and only 1 was required. With valves on the risers he shut 1 off and had no carryover. I am sure someone will correct me if I am wrong

You are right Ed. What I learned for my 63-03L was that the normal recommended piping was fine if the water quality is ok. Neither the drop header nor the second tapping is necessary for my boiler.

Any of these is what I found can push water past the header into my main riser:

- too high water level, like above the top of sight glass
- too much water treatment / too high ph (this one is very easy to experience)
- Oil, etc

Other boilers with more steam flow may benefit from extra capacity, refer to those excellent PDFs that show the steam rates for every model

here’s one of my videos showing it in action: https://youtu.be/4IymyZB4wlI

here’s carryover from bad water: 

JohnNY

AMservices said:

Water hammer is a clear sign of wet steam.
Calculating steam exit velocity is another way we can find if there's carry over.
We can't always see what's happening inside of pipes. So we have to rely on numbers and our senses.
A drop header or a over sized header is doing the same thing a steam/liquid separator would do. It gives a larger area for steam to slow down before entering the mains, and if there's any carry over of water to collect then drain back into the boiler.
Having more swing joints with a drop header makes it easier to work with when connecting big pipe.

I agree that having more swing joints kind of helps a little, but the rest is, again, theoretical. And by your logic, the absence of water hammer is what? A clear sign of dry steam? @ethicalpaul 's video is pretty clear evidence to me that second boiler take-offs and drop headers are a frivolous expense on many smaller residential boilers.

AMservices

@JohnNY is steam velocity theoretical?
Im not saying a drop header is always necessary but for some boilers im sure it helps.

JohnNY

AMservices said:

@JohnNY is steam velocity theoretical?
Im not saying a drop header is always necessary but for some boilers im sure it helps.

I'm sure you're right too. I'm just saying I'd like some evidence showing that at some point steam velocity is guaranteed to carry water out of a standard header and into the system.

AMservices

Ideally the steam velocity should be under 15 feet per second before entering the mains.
Maximum velocity for 1 pipe riser (the point that condensate can't flow backwards)
2"-23 fps
2.5"-26 fps
3"-29 fps
4"-32 fps

If the velocity through the riser or risers out of the boiler is greater then those values, then using a drop header is necessary.

Page 73. LAOSHR
"The risers out of the boiler should be from 30 to 50% greater in area then the mains, which they feed"

JohnNY

@AMservices Isn't that great info? Thanks for posting.

STEAM DOCTOR

Maybe glass/see through piping should be mandatory. 

JohnNY

STEAM DOCTOR said:

Maybe glass/see through piping should be mandatory. 

Well, it's really an eye opener at least. Again, I'm just not convinced of the necessity of overdoing a header. At some point, the cost to consumer isn't justified by the performance.

ethicalpaul

I don't know about mandatory...I'd rather see the manufacturer's minimum be mandatory per code first

But if I were an installer, I'd definitely sell a premium option of a sight glass on the riser. As I've said before, it's not even much of an extra expense. The ones in my video are $80 and you get a free union thanks to the tri-clamp.

Jamie Hall

I don't think the question should be "are drop headers beneficial". There are two very different considerations here, and for any given application it is going to be a cost/benefit question.

Drop headers can be useful in two ways.

First, they make it much easier to create means -- usually swing joints -- to reduce stress on the boiler -- either from the differential expansion of the boiler itself, or from shifting between the boiler and the rest of the system piping. Are they required for this? No. Is some means of reducing stress required? Yes. Are a lot of systems out there piped without such obvious means? Yes -- but one will find looking around the system that the expansion is being allowed somewhere.

Second, they help in reducing carryover into the system (which is not the only, nor even the most common, cause of water hammer out in the system, by the way). Here again, they aren't really necessary, but they help. In the header, a lot of the effect on water carryover comes from two factors: sheer size, and the way the risers and takeoffs are connected. If the risers and takeoffs are connected on the top, even a small header will work well. Risers on the side, not so well. A single riser at one end on the bottom is fine; two connected on the bottom -- not good, unless the header is very large. Size also matters -- a really big header, approaching the size of the old steam drums, is not likely to be a problem (there's a reason for steam drums on power boilers, especially for turbines!).

So is a drop header required for all installations? No. The installer needs to weigh the advantages and disadvantages and select the best solution -- on a cost/benefit scale -- for the job.

hvacfreak2

For modern boilers a drop header is probably essential ( but the only sight glass that would matter is the riser (s) to the system imo ). Insulation of the header ( straight or drop ) is a better bang for the buck in my travels.

Neild5

STEAM DOCTOR said:

Maybe glass/see through piping should be mandatory. 

I am not sure I would want to know what glass pipe would cost on the 5" riser on my system.

STEAM DOCTOR

5" pipe and related work is quite expensive. Probably would not notice the difference. But I could be wrong. 

EBEBRATT-Ed

It boils down to riser velocity but that isn't all. Two different boilers with the same capacity will act differently.

But generally keeping the velocity down keeps water in the boiler

ethicalpaul

Neild5 said:

STEAM DOCTOR said:

Maybe glass/see through piping should be mandatory. 

I am not sure I would want to know what glass pipe would cost on the 5" riser on my system.

The largest I could find was 4”, suitable for a 3-1/2” npt pipe.

How many sq ft of steam is your system?!

Neild5

ethicalpaul said:

Neild5 said:

STEAM DOCTOR said:

Maybe glass/see through piping should be mandatory. 

I am not sure I would want to know what glass pipe would cost on the 5" riser on my system.

The largest I could find was 4”, suitable for a 3-1/2” npt pipe.

How many sq ft of steam is your system?!

There is 2565 sqft of EDR. It's a 20 unit apartment building from 1927 that went condo in the 90's.   

JohnNY

Neild5 said:

ethicalpaul said:

Neild5 said:

STEAM DOCTOR said:

Maybe glass/see through piping should be mandatory. 

I am not sure I would want to know what glass pipe would cost on the 5" riser on my system.

The largest I could find was 4”, suitable for a 3-1/2” npt pipe.

How many sq ft of steam is your system?!

There is 2565 sqft of EDR. It's a 20 unit apartment building from 1927 that went condo in the 90's.   

A single 5" outlet supplying 2,565 sq. ft. EDR? Is this a Scotch-Marine-type boiler or maybe an atmospheric boiler like a Weil-McLain LGB-9 or similar?

Neild5

It is a Peerless TC-II 4 section boiler.  It was just installed by Dave @The Steam Whisperer.

JohnNY

Beautiful job. Wow.

JUGHNE

Great looking job....some serious piping there.
Is that a pressure transducer installed? Hi/low fire?

The Steam Whisperer

It's a full mod burner. We installed it in anticipation that
TRV's may be installed on the one pipe system.

Neild5

Once it gets up to pressure, the pressure gauge needle looks like it is stuck, it does not move but the burner controller will drop to 40 to 60% fire and varies every second until the thermostat is satisfied. 

Onepipe

Quick question for drop header design. I have installed a few but I have always had headroom on this particular boiler that I am working on I have low headroom for the main tie in. Is it OK to drop the header below the 24" above the water line? I always like to say at min 24" above the top of the boiler but I would need to drop down to about 12-16" above the boiler before I tie into the supply line. Is that OK to do or am I asking for hammer? Its a two pipe header and im a huge fan of swing joints. Also I always try to have some pitch on my headers towards the equalizer leg but I am seeing a lot of drop headers that have no pitch. Is it OK to run the header level?

Jamie Hall

Yes it is Ok. You still need to go up the 24 inches or so for the initial rise, but then you can ben over and drop as low as you like so long as you stay above the top of the boiler. I'd still run the header with pitch, though.

EBEBRATT-Ed

@Onepipe as @Jamie Hall said yes you can drop the header. The bottom of the header must be above the water line under any condition the boiler runs at. I would keep the bottom of the header at least at the height of the top of the boiler. Higher is better.