Near Boiler Piping Question

Steve Nichols

HI all,

I'm in the process of repiping my Burnham gas fired steam boiler with double risers and drop header.  I am well on the way to making this happen but had a question about the location of the close nipple for the Hartford Loop.  Burnham states a location that is 2 inches below normal water line, which is where it currently is located.  I am guessing that the 2" is from the top of the close nipple since that is when steam can start to back out of the boiler and flow over the Loop,.  Is there any reason I can't increase the distance a bit and use 3" instead?  I hope this doesn't sound like a stupid question but TLAOSH talks about the loop being above the crown sheet of the boiler.  It seems to me that the current location is well above that but I didn't know if that was something I should be looking at.

Several times folks on here have indicated that the piping recommendations by the Mfg. are a mininimum for satisfactory operation.  I wanted to know if this was the case here as well.

I am using two very tall 2" risers to a 2" drop header, separate lines for front and back of house and 2" equalizer.

JStar

Piping

I always go a minimum of 4" below the water line, or 6" above the return tapping on an atmospheric boiler (does not apply for wet-based boilers). I figure that on larger systems, the water level may drop enough to expose the Hartfood Loop connection if it isn't low enough.



In reality, though, I've never witnessed a problem no matter where the Loop is connected. You can even set it up as a Gifford Loop.



http://www.heatinghelp.com/files/posts/276/HPACGiffordLoop.pdf

Steve Nichols

Ok, so lower we go!

Hi Joe,

Thanks much for chiming in.  I wanted to get advice from a professional on this before I get to the repipe of that part of the boiler.  I have been using pictures posted by you, ChrisJ, Steamhead, Hap and others to get a good idea of how the piping can be arranged given existing conditions.  I never would have been able to even tackle this without a good 3' wrench.  They get heavy real fast!

Steve

ChrisJ

Gifford Loop

Glad my pictures could help.

If I was redoing mine again I would most likely do a Gifford loop this time.  Only because I've heard and read they give a more stable water like.

JStar

Loop

The only problem with the Gifford Loop, like all good practices, is that you might have a wily inspector that has never seen it before and fail your install, if they read the instruction manual.



I've never tried a Gifford Loop myself, but The Steam Whisperer has, and maybe some others. They all boast great results.

Steve Nichols

Piping standards/code?

Hi Joe,

You make a very good point.  From my take the inspector was more concerned with chimney liner, gas line size and connection than actual physical piping.  Installation manual was still in the manila envelope with seal unbroken.  Yes, I know that's the first potential sign of a knucklehead, but hey I learned a lot about steam heating in the process.

That being said, I'll probably stick with the Hartford Loop and drop it down about 4" as you indicated.  I would think that with the Loop configuration nearing its 100 year anniversary, maybe it is time to rethink some modifications (such as the Gifford) that would work better with today's low water content boilers?

Is there a standard on the height of the Gifford relative to Normal Water Line?  In the PDF you attached, I just saw  "above the normal waterline".  How far above is best?  This is more of a curiosity question since I love learning about this stuff!  Hell, if I drop my normal water line to be at center of the gauge glass, then I come very close to having a Gifford!

nicholas bonham-carter

Header size

If you can make this change, it will slow down the velocity of the steam in the header before it heads up to the mains--make your header larger than the 2x2 inches of the boiler risers. Probably, 3 inches will be adequate, or 4 inches even better.--NBC

JStar

Header

Good point on the header. We use a 3" drop header for 3 and 4 section boilers. And a 4" drop header for 5 and 6 section boilers. There is a section in TLAOSH that talks about steam velocity. I modified the calculations to make a header sizing chart. Keep the steam exit velocity at 15fps or lower, and you'll do wonders for the system.

Steve Nichols

steam velocity calcs

NBC and JSTAR, I was torn whether to increase the header side to 3" but since this is my very first pipefitting attempt, I'm going to keep it simple.  I'm working slowly, trying to understand how everything should line up, pitch, etc.

 Actually keeping it simple would have been to leave it alone but I am a tinkerer at heart and the near boiler piping was not as good as it could have been.

That being said, I did a steam velocity calc a while ago while I was considering this new project and at the current firing rate, double 2" risers from the boiler give me a steam velocity below the magic 15 fps, so I'm going to keep things as they are and see how the system runs this season. I am using the information from TLAOSH to do the calcs.  The system ran real well so cutting the velocity in half by adding that second riser should make for a nice improvement. 

Thanks again for checking in and sending your ideas/thoughts my way.  If I can ever return the favor I will! 

nicholas bonham-carter

Steam velocity

The 2 risers are an excellent choice, however what happens to the steam when it gets to the 2 inch header? It will once again be forced to increase it's velocity to travel through the header, and that increases the chance of some water being thrown up into the mains.

What size header is shown in the piping diagram? --NBC

Steve Nichols

2" header

I just checked and the Mfg. calls for 2" header in the piping diagram even in the alternate piping diagram showing the drop header arrangement.  This aspect totally escaped me but it makes total sense. 

ChrisJ

Minimum

The mfg calls for a 2" header as an absolute minimum as in if you go smaller all hell breaks loose.



2" header = works, barely.

3" header = much better.

4" header = best.



Expect to pay significantly more to build a 3" header but it will pay for it self. I wanted to do a 4" but could not justify the price for my 4 section boiler.

Steve Nichols

recalculating

I'm looking into what it would take to redo the header if increased to 3".  Stay tuned....