Can a Caleffi Z-one Relay control both domestic hot water heating and space heating using one boiler?
March 03, 2016

Can a Caleffi Z-one Relay control both domestic hot water heating and space heating using one boiler?

Yes, the relay controls have the ability to prioritize DHW demand and they also have the ability to operate a specific pump for DHW demand. This can be done with the Caleffi ZSR Z-one switching relay or the ZVR Z-one valve relay.

"Priority" logic is DIP switch configurable on the board. During "priority", when the DHW aquastat energizes to call for heat, the relay control disables the space heating outputs and all the boiler energy is used to heat the DHW tank. When the DHW tank is satisfied, the space heating is re-enabled.

The Caleffi Z-one Wiring Guide shows wiring schematics and piping schemes for many common applications, including priority control. And, our archived Zone Relay Controls for Hydronic Heating Coffee with Caleffi webinar from February 2016 covers all the features and functionality of the relays, including the new 2016 enhancements. Take a look at these great resources, at your convenience.

Contact your local Caleffi supplier if you have any questions about applying the Z-one Relays; we appreciate your business!

Categories in which appears
Blog post comments
October 28, 2020

I need helping deciding how to connect all my pumps to a ZRS104 4 zone relay controller.
We have a main boiler loop pump,1- 3 zone radiation pump loop and 1 DHW heat exchanger boiler side pump and 1 DHW tank side pump. How should we wire in to have the best control for all pumping needs?

October 29, 2020

Glenn, I see in your photo you have both zone valves and pumps. The pump control would be the ZSR model so a ZSR104 would provide you the four zone control. Zone 1 i would recommend using for the DHW because you can select the "priority" setting to make that the priority zone. Zones 2-4 would be for space heating. Please follow this link to the wiring guide for our zone relays and if you have any quesitons or want to discuss contact our tech support line at (414)238-2360

Ron Vickers
November 21, 2022

Hi I installed HTP 45n indirect hot water heater to my 78 series Weil McClain boiler. Water temperature from water heater is to hot in faucets.
I would like to install mixing valve and relay. Could you send a recommendation for install one of your mixing valve and install instruction and diagram if available. Has supply and return from boiler and cold water feed and hot water feed from hot water heater to faucets. Any help is appreciated. I can send pictures if needed.


In reply to by Ron Vickers

November 29, 2022

Ron, We have a few options for mixing valves. If this a residential home the 521 MixCal or 520 AngleMix could be good solutions. Sizing the mixing valve is important because every mixing valve has both minimum and maximum flow rates. Piping is also important, especially if you have a domestic hot water recirc. line in the home. The piping diagrams are in all of the installation instructions. I would recommend contacting Caleffi Tech Support at 414-238-2360 for help in selecting the correct option. We can provide the piping and installation instructions for you.