Honeywell V4043H 2-Port Zone Valve (22mm)

In-Depth Look

The motorised zone valve is the component that directs hot water to the correct circuit in a central heating system: either heating or hot water. The Honeywell V4043H is a widely used valve for this role.

Replaceable Actuator

The key advantage of the V4043H design is the separable actuator head. When the motor or microswitch fails (which it will eventually), the actuator head unclips from the valve body. The new head clips on without touching the pipework, without draining the system, and without soldering. For a heating engineer on a callout, this makes the repair quicker and simpler.

S-Plan and Y-Plan

In an S-plan system, two V4043H valves control the heating and hot water circuits independently. In a Y-plan system, a single 3-port valve (the Honeywell V4073A) handles both circuits with a mid-position.

Verdict

The Honeywell V4043H is a widely used 2-port zone valve, and the replaceable actuator design makes the eventual repair straightforward. This page covers the 22mm compression version (V4043H1056); other sizes are made, so check the model suffix.

How It Compares

The Honeywell V4043H1056 is a 22mm 2-port zone valve. It is normally closed and spring return, with a manual lever and a mains-powered actuator, also called a powerhead, that can be replaced without draining the system. Replacement heads are sold for V4043H bodies in 22mm, 28mm and 1 inch. A 28mm version of the valve also exists, with the code V4043H1106.

A zone valve opens and closes the flow of hot water to one part of a heating system, such as the upstairs radiators or the hot water cylinder, so each zone only heats when it needs to.

The main thing to understand is how this valve fits into the two common layouts.

A 2-port valve like the V4043H is for S-plan style arrangements. It is not a swap for a 3-port mid-position valve, because the pipework and wiring are different. Other makers, such as Danfoss and Sundial, also make 2-port valves, so check the pipe size, the body type and the actuator wiring before choosing a replacement.

Thermostatic radiator valves are a different thing. They control a single radiator, while a zone valve controls a whole circuit. Our page on the Drayton TRV4 thermostatic radiator valve covers that type.

Heating and electrical work should follow the manufacturer’s instructions, and a qualified person should carry it out where required.

Common Questions

What does a zone valve do, and how do I know it has failed? It opens when a room thermostat or programmer calls for heat in its zone, and closes when the call stops. Common symptoms of a fault are a zone that stays cold, a zone that stays hot when it should be off, or a motor that hums or clicks without the valve moving. The cause can be the actuator, the valve body or the wiring, so diagnose before replacing.

Can I replace only the actuator head, and do I need to drain the system? The manufacturer states that the powerhead can be replaced without draining down the system. Isolate the electrics first and use a qualified person if you are unsure.

What is the manual lever for? It lets you open the valve by hand, which is useful when you are filling or bleeding the system, or checking whether the valve body is stuck. Return it to the automatic position afterwards, otherwise the zone may stay open.

What is the difference between S-plan and Y-plan? S-plan uses a separate 2-port valve for each zone. Y-plan uses a single 3-port mid-position valve that can send flow to heating, hot water or both. Which one your home has depends on how the system was installed, so look at the valves before ordering.