Commercial piping

Jamie_6

I'm trying to explain to a friend why this is wrong and I can not get it across. Any help would be appreciated. We help him install big jobs and I do not want to do it wrong.

With large buildings I understand that as we mix down the line the main @ that point will rise and cause the next boiler to short cycle. Is there any truth to this? Also he wants to use a Tekmar staging control! I tried to explain we will need to rise the intire building on mild days to make hot-water. What would you guys say?

It's in Micro$oft word!
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Mark Eatherton1

Jamie...

Believe it or not, I attempted to post a response to this last night, but for some reason, it wouldn't stick.

Anyway, what you've drawn is essentially a systems that looks like its parallel, but in physical reality, its in series. If all four heat sources are on, each boiler raises that water temperature a little more.

If you had one set of secondary tees, serving all four boilers, each boiler would have the benefit of seeing the lowest returning water temperature. This, in the case of condensing boilers, is a MUST.

I personally think it makes more sense to do it this way regardless of condensing or not, except in avoiding long term condensation potential in boilers that are not designed for it. But that can obviously be handled in your pump logic.

Hope this helps, and I'm sure you'll have more questions.


I'll generate a drawing showing this detail.

ME

Floyd_5

Jamie, I should have gotten back to you...

been way too busy. That is what I was talking about when I said there was some stuff I would change.
Mark is right and here is a pic. that will show what he is going to draw for you.

If you look at the top, the two closely spaced tees come off of the main header to service the boilers. the black pump and the space for another pump are the boiler pumps. The green pump is the DHW pump. If you look closely you can see the the DHW tees come off of the header just on either side of the closely spaced tees. believe it or not when the boilers are making hot water and the space heating is shut down the pipes will go cold just past the tees for the DHW, the water will not migrate to any other place in the system.
Also both boilers will always be getting the same water temp. and the mixed water will be what you are using for heating. The sensors for the Tekmar need to be placed just on either side of the closely spaced tees so that they see the coldest return temp. and the mixed water temp.
The Tekmar will then stage the boiler according to the mixed temp. that it is seeing.

Any more questions feel free to eml me.

I hope I made it clear... I not the best at writing what I'm thinking.

Floyd