Honeywell Zone Valve Problem

Honeywell Zone Valve 8043 Model

Honeywell Zone Valve Problem - I have a Honeywell zone valve (8043E). I have spent time trying to understand exactly how this valve works, and I am pretty close, except for one thing: the motor. When the thermostat makes, that causes the slow-motion motor to turn, which opens the valve.

Eventually, when fully open, a tang presses the end switch to turn on the circulator pump and ignite the boiler (via red wire circuit). Though the thermostat is still closed (because we’re heating), something causes the motor to stop. What is this mechanism?

Honeywell Zone Valve Problem

I can’t imagine it is controlled in any way by the end switch as the only electrical connections to the motor are the two yellow leads that connect to the thermostat circuit. When the Honeywell motor on the zone valve is isolated, and 24VAC is applied, it will run until the cows come home. I have tested this. While running, I have grabbed the brass gear and applied resistance. It does not stop; it continues to run. So “resistance” is not the mechanism to make it stop. I don’t believe in magic. What causes the Honeywell motor to stop at the top of the zone valve open arc? Please help! Thanks!

Honeywell Zone Valve Problem - Reply

Thanks for the question and for visiting High Performance HVAC!! Honeywell zone valves are pretty straightforward on how they work. I can’t say about the valve you have right now, but all the valves I have worked, along with valves powered by actuators, come either Normally Open, Normally Closed, or Modulating. The power to the motors for these valves typically remains constant until the circuit is open, whatever method is used to control the valve. The Honeywell 8043 is Normally Closed. When it is powered up, it opens. When the power goes off a spring return closes this valve.

Specifications Sheet

Honeywell Zone Valve

hot water boiler zone valves 2 positionI have read the specifications sheet for this valve along with other specification sheets. Quite frankly, this is not something I have ever thought of. Any zone valve I have worked on or installed, either worked or didn’t work. I can only surmise that there is a mechanism that will allow the valve to open. A mechanical stop built into the valve. The Honeywell motor energizes and the zone valve rotates to the mechanical stop (in the open position). The motor remains energized until the thermostat (call for heat) opens and de-energizes the Honeywell motor.

The spring return moves the valve to the closed position. I can also only surmise this question is out of pure curiosity on how the valve works. Since the valve is simple and straightforward on the operation, troubleshooting is similarly straightforward. Installation is simple with both the hot water boiler piping loop and the wiring. It is important that the valve is installed according to the flow arrow. The head should be removed for sweat connections to prevent damage. Once the soldering is completed the head replaced on the valve. Wiring involves three separate connections: The transformer for 24-volt power, the thermostat to provide control, and the end switch to control the circulator pump.


Honeywell Zone Valve Problem - The bottom line answer to your question is the thermostat controls the opening of the valve. When the thermostat satisfies the motor is de-energized and the valve closes by a spring return.

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Honeywell Zone Valve Problem

Zone Valve Questions from our Readers

What is a zone valve end switch?

A zone valve end switch is a switch that closes when the valve opens. On a call for heat from one of the zones in the boiler loop, the zone valve opens. Once the valve fully modulates open, that action closes a switch on the end of the valve, called an end switch. That completes a circuit and tells the boiler aquastat control (or other control) to turn on the circulator pump. When the thermostat is satisfied, the zone valve closes. That action breaks the circuit and turns off the circulator pump.

How does a Honeywell zone valve work?

See the answer to my previous question above.

How a Honeywell Zone Valve Works - Video