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Zone Valve AKA 2 Port Valve

May 26, 2021

What is a zone valve and what does it do?

A zone valve is a valve that controls the flow of water to the heating system, not to be confused with a three-port mid position valve that will also control the hot water cylinder.

A zone valve can also be used to separate different heating zones with in a heating system, maybe underfloor heating from radiant heating or possibly each floor or even each room could be ‘zoned off’ and controlled independently from one another.

The heating zone valve simply completes an electrical circuit between the external heating controls and the boiler. When the external controls are ‘calling’ for heat a motor with in the zone valve becomes energised and motors across, opening the valve to allow water to flow and simultaneously completing the electrical circuit to energise the heating appliance.

What can go wrong with a zone valve?

There are two main faults that commonly occur with zone valves, either they fail to close fully allowing the heating to come on when it should be off or, the motor burns out and they do not bring on the heating when they should.

At the back or along the side of your zone valve you should find a little lever, this lever controls the motor. With everything off the zone valve should be fully closed and the lever should have a slight bit of resistance when you try to move it.

When the external controls are calling for heat the lever should move freely from side to side indicating the zone valve is energised and in the open position.

Quick tests

If the external controls are calling for heat and the lever on the zone valve moves freely but the boiler doesn’t come on, it’s likely the motor has failed, or you have another electrical problem.

If the external controls are off but the lever on the zone valve still moves freely and the boiler stays on it’s a good indicator that the motor is sticking, causing the circuit to remain energised when it should be off.

If the external controls are calling for heat but the zone valve lever has resistance and the boiler doesn’t fire, it’s probably a fault with the external controls or another electrical issue.

If the external controls are off and the zone valve lever has resistance, but the heating still comes on when it should be off, maybe when the hot water is set to be on, it will mean the valve hasn’t closed fully and you’ll probably need the heating system cleaned and the zone valve replaced.

Temporary Fix

If the heating is staying on there’s very little you can do other than turn the radiators down or turn the hot water off and wait for a gas safe engineer to come and repair the fault.

If the boiler is staying on when there is no demand for central heating or hot water you should turn the power off and get a gas safe engineer quickly, depending on the system you have and other factors it could be quite dangerous if the water reaches boiling point.

If, however, you notice the heating isn’t coming on at all you could try moving the heating zone valve lever across to the fully open position and setting your hot water to be on. This will allow some heat to flow around the heating circuit while you wait for your Gas Safe registered heating engineer to come and repair the fault.

How long should a heating zone valve take to repair?

The time it takes to repair or replace your zone valve will depend on what type of fault you have, how big your home is, and where your zone is installed.

If the valve is easily accessible and you only need a new motor a competent, professional engineer should be able to diagnose and repair the fault with in an hour.

If you have a big house and the zone valve is installed in the basement and the heating system needs to be drained and the whole zone valve needs replacing it, could take up to half a day or longer.

How long does a zone valve last?

How long the zone valve lasts will depend on the condition of your system and how often it’s used, we’ve replaced zone valves that were only a few years old and some zone valves that were 20 years old.

On a clean heating system with average use, there’s no reason your new zone valve shouldn’t last 20 years.

On a dirty heating system with the heating and hot water coming on and off frequently throughout the day the life expectancy will decrease.

How much should a zone valve cost to repair or replace?

Again, the cost to replace or repair the heating zone valve depends on the specifics of your fault. If just the motor needs replacing expect to pay around £135+VAT. If the head of the zone valve needs replacing expect the price to be around £160+VAT. If the system needs to be drained and the whole zone valve needs to be replaced expect the quotes to start at about £292+VAT increasing with the size of your house and how dirty the system is, also be prepared for a separate quote to powerflush the heating system.

All the above prices assume the engineer has the required parts on their van and the faulty items are easily accessible.

At Heatsy we carry a wide range of genuine van stock, heating zone valves and synchronous motors to give us the best chance of repairing your heating system in the shortest possible time for the best possible prices.

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Please remember, we’re heating experts so if you need your boiler repaired, a new heating installation or if you’re struggling with anything we’ve discussed here feel free to get in touch with us now so we can see how our solutions might help you.

Thank you for reading.

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