Pri/ Sec piping

Bob Sweet

Have existing PS system with micro AS , exp. tank and fill valve on secondary heating circuit.

Would like to pipe in another sec off primary loop for indirect WH. To try and keep cost down I'd rather not move exp tank, air seperator and fill valve to primary loop.

Would install series of relays to cycle system pump and boiler pump together, and priority to cycle indirect pump and boiler pump together.

Would it work?

Thanks

hr

Consider pulling the indirect

off the boiler like this. Really no sense in warming, or circulating the primary loop, and two or three pumps for priority DHW loads.

You will need check protection on the circs, but you end up with short piping runs and loads of flow to the indirect.

I'm not sure if any of these drawings are what you have? The end two drawings show how it could be done.

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Bob Sweet

Bob Sweet

hr this might help

Bob Sweet

hr this might help, I'm sorry it's so large a jpg, I'm a rookie.

hr

You could do it

that way. It looks to be the indirect is a secondary, if I read your drawing correctly?

I suggest you pipe the indirect as a parallel loop to the boiler. This way you avoid flowing the entire primary loop for a DHW call, you only need to run one circ, and you can generally shorten the piping if the tank is located next to the boiler.

Some boilers, like the Crown Cabo actually come equipped with a circuit board to prioritize this DHW and drop off the primary pump.

Also most of the small condensing boilers both prioritize the DHW and allow the boiler to run up to a higher temperature. The Weil Ultra runs to 190 on a DHW priority call. All built into the circuit board.

I pipe mine a bit different from Siggys drawing. I pull the supply from the indirect before the purger. It still "sees" the expansion tank, and air removeal is generally handled by a small air vent on top of many indirects. It just further shortens the piping.

The Grundfos Super Brute is an excellent pump for this. In addition to the intergral check, you can choose speed 3 for the indirect tank and really make HW happen fast

This article got me to change my ways, from secondarily piping indirects


http://www.pmmag.com/CDA/ArticleInformation/features/BNP__Features__Item/0,2379,66806,00.html


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Bob Sweet

hr I REALLY appreciate

your knowledge and your time Thank you!

sebast

p/s

Bob
I have seen this style p/s why the stand off piping. It does not make sense to me? The only reason I can see that this would be used if you are not using flow checks on the system pumps and you are using closely spaced tees for p/s without checks?

Rich

Bob Sweet

Rich

Your drawing is putting two seperate circiuts in parralell zoning, the closely spaced tees allow the seperate secondary circuits to run independant of each other decoupling any pressure differential, when different size pumps are running at the same time. The longer the loop lengths the more apparent the problem will be.

I'm not sure if I answered your question, check out Dan's book "Primary Secondary Made Easy", in the book store.

sebast

Bob
I still do not follow, my secondary circs would run independently or together. And if my circs are sized properly, I do not understand your meaning of decoupling the psi diff. You would still have the same psi diff with the stand off piping? I will read more into that section of the book.
Thanks

Rich

Bob Sweet

Rich

Read pages 1-10, Dan explains much better than I. These guy's are good!

sebast

Thanks Bob
I understand now, I would be loosing gpm between my supply zones. With the stand off piping I can carry all of the btus to those zones.

Rich