Hot Water Boiler Piping Zone Valves - Boiler piping zone valves are used for zoning hot water systems where multiple zones are needed. Hot water system zoning can also reduce energy cost because hot water heat zones which are not needed can be shut down thereby reducing boiler runtime to provide hot water heat for those specific zones.

Zoning a hot water boiler system can be done by using these zone valves and separate thermostats for each zone. The boiler piping loop is separated using zone valves on a manifold type system with each zone originating at the manifold. The manifold is piped directly to the boiler.

Hot Water Boiler Piping Zone Valves - Thermostats and Zoning

A zone valve is hooked directly to a thermostat. On a call for heat, the thermostat contacts close completing the circuit to the zone valve and energizing a small motor in the zone valve. This motor opens the valve. As the valve opens an end switch in the zone valve closes. This energizes the hot water loop circulator pump via a relay. This causes the water to circulate to the zone where the thermostat is calling for heat. Once the thermostat is satisfied the thermostat contacts open and the motor closes the zone valve. This opens the end switch contacts in the zone valve and de-energizes the hot water loop circulator pump.

Installation & Wiring Diagrams | Hot Water Boiler Piping Zone Valves

Wiring controls can be simple and they can be complex. If you don’t get it right it won’t work and you will blow a transformer. For someone who has wired many, many controls take some advice. First, read the instructions and get a picture of the wiring in your head. Understand the function of the devices you are wiring and the control sequence. Then take it in small steps. Additionally, if the transformer is not wired with a fuse link install one so you don’t blow the transformer.

Of course, you are going to wire all the zone valves with the power off but when you turn the power on, if you didn’t get it right, you could blow the transformer. Systems with old mercury switch thermostats you could also blow the heating anticipator. Simply make sure you understand what you are doing and make sure you get it right. Consequently, double-check everything before you turn the power on.

Installation Location | Hot Water Boiler Piping Zone Valves

Zone valves are typically installed on the return side of the hot water loop no matter the type of loop you have. There advantages for installing on the return side of the loop. One is the return side of the loop has a lower temperature, therefore, the zone valve will be subject to less heat. This likely prolong the life of the valve. If you ask 20 plumbers or boiler technicians you would likely get different reasons for the installation location. Furthermore, installing on the supply side, as long as the valve is rated for the head pressure, will prevent ghost flow into the supply of other zone loops.

Furthermore, there are also other considerations such as before the circulator pump or after the circulator pump. Much of these considerations depend on the type of pump, system operating pressure, the number of zones, and valve type and rating. Lastly, every installation is different with different conditions so make sure you consult a plumber or professional HVAC boiler technician.

VA Rating and Function | Hot Water Boiler Piping Zone Valves

You also need to do the match for the VA rating of the transformer for multiple zones. Find the VA rating for the transformer and then count all the loads you have on that transformer. Then it’s simple math adding those VA rating loads together. Never exceed the VA rating of the transformer. Furthermore, transformers are cheap. Upsize to the next available size or a size that easily accommodates all the VA ratings on the loads.

Additionally, if you are wiring a different zone valve make sure it is compatible. Make sure you understand what’s going on with it and how works. What is the difference between the old zone valve and the new zone valve? Honeywell, Taco, White Rodgers……….doesn’t matter except the function and how you wire it. Always try to get an exact replacement if it’s available. Furthermore, read the instructions and make sure you get it right!!

Zone Valve Wiring Diagrams | Click on the Zone Valve Diagram to Enlarge

These Zone Valve Diagrams represent old thermostats. T87F is the older Honeywell thermostat.

Conclusion | Hot Water Boiler Piping Zone Valves

Finally, to save money by reducing boiler operating costs and energy use installing a good zoning system is the way to go. Initial installation costs will be higher however over time you can recoup that initial cost of installing these zoning systems by reducing boiler operating time and energy use. Instead of having one central thermostat for the whole system and heating the entire structure you can choose to heat only those spaces that are properly zoned thereby saving you money in energy use.

Furthermore, this will only work for heating systems unless you also have a chilled water system which is typically only used in commercial HVAC.

Hot Water Boiler Piping Zone Valves

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