Primary/Secondary Boiler Plumbing Question

55Trucker

Hi All - I was looking at my in-law's Viessman boiler installation, and something struck me as not right about it. It's plumbed for 4 zones and a DHW tank. It looks like this:



What doesn't look right to me is the left-most circulator. Is it installed backwards? Shouldn't it be pulling from the expansion tank, which is plumbed on the supply side of the primary loop?

hot_rod

The bottom, boiler circ should be pumping into the boiler, the upper circs should be pumping away from the exp tank. Look at the arrows on the pump body to confirm flow direction.

55Trucker

Thank you, that's what I thought. The left one is pumping into the expansion tank, so it was installed wrong. What problems, if any, would be seen with this?

GroundUp

Is the upper pump pumping upward or down? I don't see how the CH and DHW can work simultaneously if the DHW circ is correct and the CH circ is in backwards as the flows would be pushing at each other

55Trucker

The upper pump goes to the DHW tank, and is pumping upward. The left pump is pumping to the right. I don't see how it works either, but they do have heat and hot water.

hot_rod

Both loops should be flowing counterclockwise, are they?

Big Ed_4

The heat and HW circulator direction should be away from the boiler on the secondary . The boiler circulator direction would be toward the boiler .

And to add the zovevalves should be on the return and piped reverse return ..

HVACNUT

No way.

Are you looking at the arrow on the circ body or just motor position?

There would be sooo many problems.

SuperTech

> @HVACNUT said:
> No way.
>
> Are you looking at the arrow on the circ body or just motor position?
>
> There would be sooo many problems.
>

Lol. That was my reaction when I looked at it as well. At least its easily corrected thanks to the presence of the isolation valves.

Alan (California Radiant) Forbes

Nice work!
Yes, the pump should be pumping away from the expansion tank and can't imagine that it isn't already, but it's surprising how forgiving hydronics is.

GroundUp

Hmm, I suppose if the DHW is set up as priority they wouldn't run at the same time so the flow duel may never be present. The flow through the closely spaced tees to the boiler should be left to right, with the left tee being the boiler's return and the right tee being the supply to feed hot water back to the system. If the CH circ is in fact backwards, the flow that the boiler circ sucks out of the primary loop will already be heated because it's flowing backwards, directly from the supply tee so output to the system would be diminished as well as efficiency of the boiler. Also pumping toward the expansion tank plays an ugly role in hydronics with pressure. It could very well be as simple as just flipping the pump 180 degrees and correcting the issue.