Pump into or away from Munchkin?

Tom Hughes

I know we have to pump away from the expansion tank. I read Dan's book. But all of Munchkin's literature shows primary pumpson the boiler return with several pumps in series. The secondary pump is downstream of the expansion tank the way it should be. Is that the best way to do it? I would think having multiple boilers in parallel would be better and why not put the pumps on the supply side?

Alan(CaliforniaRadiant)Forbes

They want

the circulators on the return; it pressurizes the pressure switch on the boiler to make sure it doesn't open.

Make sure you read the Vision installation manual. Their piping drawings are very specific.

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Tom Hughes

Multiple boilers

So if you had three Muchkins you would put three primary pumps on the return of each boiler and one seconday pump downstream of the expansion tank?

[Deleted User]

Here's an article about piping this way

http://www.pmengineer.com/pme/cda/articleinformation/features/bnp__features__item/0,2732,2755,00.html




The primary loop also becomes the pressure reference point for the secondary circuit. In effect it acts like an expansion tank for the secondary circuit. Because of this, it's important that each secondary circulator pumps into its circuit, (i.e., away from the expansion tank reference point). This allows the pressure in the secondary circuit to increase when its circulator operates.

Noel

munchkin-man

Primary secondary is suggested simply

so one has the correct circulator to over come the pressure drop in the Muchkin. The manual shows the correct size to be used for each model. It is important that the circulator (s) used for the secondary are sized for each zone.

If one were to install a circulator that is under sized and will not provide desired flow through the Munchkin this could cause flashing in the boiler when the water temp climbed rapidly.

If you were to use one circulator to supply all and had to use a bigger circulator you could get noise in your system piping.

When at all possible use primary secondary. the pumping away is to maintain system pressure so as to keep the water pressure switch closed.

Tom Hughes

My last couple questions and I'll stop bugging you...

Do the piping diagrams indicate P1 (space heating) and P2 (domestic) never operate at the same time? P1 is pumping return water into the boiler. P2 is pumping supply water directly into the indirect tank. So one primary circulator is on the supply and one is on the return. What if I need space heating and domestic HW at the same time?

john wood

I assume you are talking vision 1 here?

If so; Yes the pumps run in an either or situation as the boiler can make low temp or high temp water but not both at the same time. Domestic calls are usually short compared to heat calls and should make little difference in the heating of a structure. On vision, you can set the priority time for the domestic from 0, meaning it will make domestic forever till call is done or up to 30 minutes if you want to set it that way. When domestic times out, boiler goes to heating mode.