Zone Valve Install Location - Supply or Return?

BigRob

What is the standard location for zone valves? What are the pros and cons for supply and return side installations? A past contractor installed twelve Caleffi Z series valves flowing port B to port A and they slam shut. They will soft close when properly installed with the flow from port A to port B. When I reverse the flow, they will be on the return side. Should I care?

Robert O'Brien

No difference. An ECM pump will solve the banging without the hassle of changing PONPC

hot_rod

Either supply or return. On supply they can help minimize potential ghost flow. On return the operate in a lower temperature. In either case I agree that a delta P circ would be a nice upgrade, for flow modulation and energy savings.

Good that you will correct flow direction☺️

Bob Bona_4

I prefer return. ECM pump should go hand in hand.

BigRob

Unfortunately, the only ECM I believe fits the bill is a Magna3, which is $$. Any suggestions? I need around 30ft head.

SWEI

How big is this house?

BigRob

The building has 12 condos, one ZV, each. Each condo is 1000sf.

SWEI

Gotcha, thanks.

Why such high head -- are all the zones that bad, or are there just a few problematic ones?

Is the head measured or estimated?

BigRob

I've always thought it was pretty high. There is a pressure gauge at the pump outlet, so I have been using that, subtracting my fill pressure. I calculated the pressure drop of the radiant slab in each condo. Eight condos have 3 loops and each is pretty long. Four condos have 2 long loops, and require a decent more head, based on calculations, although I did notice a bit of flow noise in one of the condos closest to the pump, which is why I'm thinking constant pressure or proportional pressure would be perfect. I think the slab pressure drops are pretty close to reality and I have the numbers someplace. The slabs are all 1/2" pex. Each feeder to the slab manifolds are 3/4", I believe. There are 1" trunks. I did calculated pressure drops for the feeder and trunks, but they are estimates. I also talked to the installer and he said he thought he used a Taco 0011. The distribution piping design is unknown. To add even more uncertainty, there was a lot of iron oxide in the system. I am adding garden hose nipples near the pump to flush them out soon.

If there is a way to measure the pressure drop for each individual ZV, I would do it. Is there tricky way?

Side note: I was surprised to see the Magna3 proportional pressure window of operation has such a low max head, especially for a pump with 30ft-ish capability.

SWEI

If you have drain valves on one side of the zones, you can measure the head loss directly. If there are just a few high head zones, you might actually be better of using two different pumps.

As to the Magna3 curves: Properly designed hydronic systems for decent-sized commercial projects rarely require over 30 feet of head IME.

Bob Bona_4

I think the magna's data log it's performance so you can see peak flow and pressure drop, correct me if I'm wrong about the pressure drop part. You're right, they are big $. I was entertaining one to dial in a residential job where the radiant loops were of unknown spec. But I couldn't justify the cost.

BigRob

SWEI said:

If you have drain valves on one side of the zones, you can measure the head loss directly. If there are just a few high head zones, you might actually be better of using two different pumps.

As to the Magna3 curves: Properly designed hydronic systems for decent-sized commercial projects rarely require over 30 feet of head IME.

There are no drains near the slab supply/returns- bummer. The new drains will be on the boiler room supply/returns. I'll recalculate the pressure drops and see if they still make sense, just in case.

Let' me know if I'm missing a way to measure the pressure drop.

SWEI

You could measure them one by one using a single drain and only opening one zone valve at a time. Might put you pretty far up the pump's curve, so I'm not sure how accurately you would get an absolute head per zone (even relative heads would still be useful.)

Zman

Are you measuring the head loss of the existing circulator at whatever flow rate it is operating at? It sounds like you are likely over pumped right now. What is the delta t?

BigRob

I think a couple zones near the boiler room are over pumped when they are individually on. I'm not sure about the delta T in that condo unit.