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Questions on Caleffi Zone Valve Specs That Will Serve as a Check Valve for a Hot Water Recirc System

Pidge Member Posts: 18
I installed a recirc pump with a pex return line and I'm getting ghost flow which is wasteful and bugs me. Because my piping is mostly vertical, adding swing check valve is undesirable and I understand they are not robust with potable water. Instead I tried piping heat traps with 18 inches of drop.

The heat traps worked great after the water heater was restarted after working on the pipes, and leaving the pump off made the ghost flow insignificant even with 130 degree water the tank. But running the recirc pump for three or four minutes, cause continuous ghost flow unless I close a ball valve between the pump outlet and the water heater inlet.

In December 2016, there was a good thread on hot water recirc (titled: "Aynyone try?") where Mark Eatherton said:

"If a person wanted to make this gravity system as efficient as possible, you could incorporate a zone valve (rated for potable water applications) and set a timer that would open the ZV an hour before the earliest hot water use then close it until the next high use period occurs."

Using a zone valve seems like a great suggestion for my system with a pump that will be indirectly actuated by a momentary switch (24v), when hot water is desired.

Actually, the switch will:
- Start a timer that closes a NO (normally-open) switch in a 24V circuit that directly opens the Caleffi zone valve,
- the end switch of the ZV will turn the pump on when the switch gets to 50% open where the switch closes,
- the timer will cut power to the NO switch, thereby causing the zone valve to close, causing the end switch to open, thereby cutting 120v power to the pump.

The timer recommended by an electrical engineer friend is here:

We're almost to the questions. The zone valve I picked is the Caleffi Z451517 with the following specs:
- Actuator: Z151000 24 V AC
- Body: Z200517
- 2-way
- Normally closed
- 3/4" FNPT ports
- 7.5 CV
- potable water rated

- Low lead <0.25% lead brass body: 1st Question: Is this body really low lead? The Caleffi 2-WAY
ZONE VALVES Z-one Series Z200517 brochure says "Optional lead-free brass body" but I can't find specs that indicate which bodies are and are-not low lead.

- End switch: I'm pretty sure that the 24V actuator only comes with an end switch rated for 24V circuits. This will require a 24V relay that to open and close the 120V pump circuit. But it can't hurt to ask: Is this end switch rated for my Grundfos SS recirc pump which is 120V, 0.22 amps, 25 watts, 1/16 hp?

The zone valve will be installed between the pump outlet and the water heater inlet to stop the ghost flow I'm getting. The pex return line goes to the inlet of the pump.

The timer will be set for 4 minutes because it takes between three and four minutes to get the return T to 112 degrees in the upstairs bathroom. The water heater is on the south side of the basement very close to the 1st floor kitchen sink. The first and second floor bathrooms have faucets inches from the north wall.

To summarize, I have 3 questions:
- Is the valve body I spec'd (Z200517) low lead?
- Is the end switch rated for 120V, 0.22 amps,
- If a relay is required to control the 120V pump circuit, recommendations for a relay will be very helpful.

Thanks for following and any answers/recommendations,


  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    What's wrong with a flow check, either potable rated in the piping or internal to the pump again?

    There was an error rendering this rich post.

  • hot_rod
    hot_rod Member Posts: 22,258
    Z207537 is a3/4 sweat lead free 7.5 Cv
    Z111000 is 24v with switch and wire leads
    Z15100 is terminal block style
    These have a reed type end switch

    If you need a heavy duty end switch 4A then Z111900

    Not really supposed to switch 120V with a zone valve end switch
    We offer a 3 zone switching relay, a bit overkill
    A transformer, 4 square box and RIB relay is an option.

    If you need a electro-mechanical solution?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Pidge
    Pidge Member Posts: 18
    @STEVEusaPA - My pump doesn't have an internal check valve. I'm not a plumber nor in HVAC, so I have no experience with swing check valves. I've heard they are sensitive to calcium/lime deposits in open systems, and they require horizontal placement. Those constraints make them undesireable for my system.

    The ZV is spec'd for open systems, vertical placement, and closes under spring pressure, which should robustly stop ghost flow. Seems like the ZV is a better option for my open system.

  • Pidge
    Pidge Member Posts: 18
    Hot Rod - thanks for the help on spec-ing the correct parts. Also, I never heard of a RIB (relay in box). That's a great solution, the RIBU1C will be perfect for my application - the contacts are rated at 10 amps - my pump only requires 0.22 amps.

    You mentioned "If you need a electro-mechanical solution?," so I'll go thru the steps - you know most of what I'm going to discuss, but maybe you'll find a fault in my logic.

    My objectives are to avoid wasting energy running the recirc pump when it's not needed, and avoid wasting heat/natural gas from ghost flow, and avoid having water go down the drain while waiting for hot water.

    The timer can be actuated from the two bathrooms and the laundry room with momentary button switches located in each of the three locations.

    When a button is actuated, it starts the timer which closes the timer's normally open switch to feed 24vac to the ZV actuator for 4mins (or whatever time I set the timer to). The buttons control the timer, which controls the ZV, and the ZV end-switch controls the RIB, which finally turns the pump on.

    The RIB will be connected to the ZV end-switch and the RIB won't require the heavy duty 4 amp end switch, which means I'll stay within code using 24vac with the end-switch, instead of 120v.

    When the end-switch closes, it permits 24vac to go to the RIB. The energized RIB will close the normally-open RIB contacts which turns on the 120vac pump. The RIB is spec'd for 10 amps at 120v.

    The 24vac signal controls the RIB. There are a number of options. I'll use the one that causes the RIB to close the 120v switch that supplies power to the pump, only when the 24v control signal is connected to the RIB. When the 24v control signal to the RIB is cut, the RIB cuts the 120v power to the pump.

    After four minutes the timer switch opens to cut 24v power to the ZV actuator. The un-powered ZV has a spring that closes the valve, causing the end-switch to open, causing the relay to lose the 24vac supply, which causes the 120vac RIB contacts to open which cuts power to the pump.

    No more ghost flow, and only 25 watts during 4 minutes the pump runs. So I'm anticipating using less natural gas and water, with an insignificant increase in electricity.

    Hot Rod - thanks for the help with the ZV actuator, body, and end-switch and especially the RIB!

  • hot_rod
    hot_rod Member Posts: 22,258
    Basically this will eliminate sending water down the drain. If you start the pump only at a call for DHW, you will still have some wait time

    Recirculating is most often to give you instant hw at the most remote faucet

    Your system will work as a customized solution

    Check some of the new Smart DHW systems from Grundfos and Taco they may get you about the same result

    Also insulate all the hot and returns to minimize heat loss
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream