Boiler piping

Greg Maxwell

I'm involved in a job where we are going to take 2- 7 section Biasi SG boilers and pipe them together to a common main. The boilers will be 1-1/2, piped into a 2" main. I would like to know if anyone out there has a piping diagram for injection from each boiler into the main, so I dont have to flow through both boilers at the same time. The boilers are going to be staged - lead/lag.

NYplumber

P/S

Using primary/secondary you can join them in parallel into the main. I usually set the controls to alternate which boiler leads every X amount of hours.

lchmb

taco

Has a nice control package for just this type of setup. Simple but effective...

Greg Maxwell

Boiler piping

We are going to be using an AQ251 H/W control on this, I am just wondering about piping the boilers into the main. I'd like to use injection. Each boiler will have its own pump.

Larry (from OSHA)

you might try this

The Knight install manual has great diagrams.   Page 40 might be what you are looking for.



http://www.lochinvar.com/_linefiles/KBII-I-O%20Rev%20D.pdf





Hope this helps.



Larry

Jason_13

Piping

http://www.comfort-calc.net/Multiple_boiler.html

Check this drawing one. It is very simple but the point is made.

CMadatMe

Low Loss Header

Gets piped the same way as multiple condensing boilers.



http://www.caleffi.us/en_US/caleffi/Details/Magazines/pdf/idronics_1_us.pdf

meplumber

2" sounds small

For 2- 7 section boilers.  My gut reaction would have been 3" or at least 2 1/2".

CMadatMe

Pipe sizing

ME is spot on. Each of those boilers has a heating capacity of 279. Boiler supply and returns need to be 2" and the header 3" to move the 558 if your designing around a 20 degree delta-t.

Greg Maxwell

Main Size

Looking at a velocity of 5ft per sec for 50gpm, and a head of 4.6ft, my chart says 2".

hot_rod

parallel pipe

them. It can be done with or without a hydro-separator, depending on your pumping requirements on the boiler and load side.



Be sure the piping is sized for the flow rate you are desiging around.



hr

Greg Maxwell

Parallel

Rod, I like that piping diagram. I'll forward that onto the contractor. I however wont use a hydroseperator, I'll figure closely spaced tees. Seperators are an aweful lot of money for whet they are.

Thanks

Jean-David Beyer

Seperators are an aweful lot of money for whet they are.

Since I am not a pro, I do not know the answer to this question. I know what the manufacturers of hydraulic separators say.



If you include the cost of an air extractor and a dirt separator, and the labor of plumbing them in, is the cost of an separator still unreasonably high?

CMadatMe

Exactly

And we haven't even talked about no temp drops across the zones.

Jean-David Beyer

no temp drops across the zones

Can you explain that? If you have closely-spaced Ts instead of hydraulic separator, and the common pipe on the load side is sufficiently large (which would be required with hydraulic separator as well), you would not get temperature drops with the Ts either, it seems to me. Drops with Ts would be a problem if you used separate pairs of Ts in series, one for each load (which would make sense sometimes).

Greg Maxwell

Hydraulic seperators

Yes, by hundreds

CMadatMe

Not On a 20

Degree delta-t you won't. Need 2-1/2 at 5ft per second. Ran it thru Siggy's software just to check myself.

CMadatMe

No Temp Drops

Because I would be piping antler style as shown in HR's pic above on the secondary side. You might be interested in these JD



http://www.caleffi.us/caleffi/en_US/Site/Technical_library/Idraulica_magazine/index.sdo

NYplumber

Buffer

Buffer tanks offer a lot in one package. I have been incorporating them into all my installations and have been more than pleased with the outcome. Results are as follows: air separation, dirt separation, hydraulic separation, parking space for btus, and if there is an internal coil, hot water or snow melt can be used too.

meplumber

2" Pipe.

The last time I looked, 2" pipe would only carry about 450 MBTU at a 20* delta T.  You need to up size to 2 1/2" to carry that load.  You calculations didn't take into account the delta T.

Jean-David Beyer

I have looked at Caleffi's hydraulic separators...

... and they seem to be fine devices. If you do not get labor for free, it seems to me that it makes a lot of sense to use one of these instead of closely spaced Ts, an air extractor, and a dirt separator.



However, the losses to which you allude would be the same whether you used closely spaced Ts near the boiler supply and return, or whether you used an hydraulic separator. On the load side, if plumbed as in the illustration, above, the parallel piping would be the same whether one used an hydraulic separator or the closely spaced Ts. The thing called "field constructed headers (typical)" would determine the temperature loss between the various load circuits, and provided those are of sufficient diameter, the loss should be negligeable.

CMadatMe

Pri/Sec

Your correct in that blending inside the LLH produces as drop in water temp but I am referring to a drop across the zones as multiple zones open. In a true primary secondary piping arrangement you do. I'm using my i-pad so don't have a diagram to show you but did find this nice articlen written by our host.





http://t4engr.com/understanding_primarysecondary.htm

CMadatMe

Wrong thread

Hey ME that was his other thread on the piping. I think you mean 35gpm on a 20.

Jean-David Beyer

I am referring to a drop across the zones as multiple zones open.

I do not know what you mean by a "true" primary-secondary piping arrangement. There are several primary-secondary arrangements I have seen. One is shown in the diagram that appears earlier in this thread. I would consider that "true". Another would have a series loop on the load side of the closely spaced Ts, with a set of closely spaced Ts for each load drop; there would be a circulator to drive flow through this secondary loop. I would consider this as "true" as the first.  In this arrangement, the first load loop, would get the hottest water, and each following loop would get colder water (assuming all loops were running). But this would be the same whether the primary loop (the one containing the boiler(s)) were separated from the secondary loop by closely spaced Ts or an hydraulic separator.