Do you have hot water and no heating, or do you only have heating and no hot water?
If your boiler is working nicely, but you have a problem with either the hot water or the heating not working, it could be your zone valve that is malfunctioning. In this article we're just discussing system or heat only boilers, not Combi boilers. If you have a Combi boiler and you don't have heating, or your heating goes on when run the hot water, your diverter valve could be faulty. This article is for customers who have a separate hot water cylinder.
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In domestic situations, there are two types of Zone Valves - two port and 'mid-position' zone valves.
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To test if your zone valve is working is very easy. Lets say your central heating is not working, but you have plenty of hot water. To test if your zone valve is working, switch off demand for your hot water (you can do this via the timer - set Hot Water to Off).
Now create demand for central heating - turn up the thermostat and make sure the timer is set to 'On' or 'Continious'.
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Identify your Zone Valves - they will typically be in the airing cupboard or close to the pump. A two port Zone valve is on the left and the mid position valve is on the right (below).
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If you have 2 port valves, (you will have two or three of these valves, one for each heating zone and one for the domestic hot water) identify which one is connected to your hot water cylinder. Ignore that one, and feel if the pipe leading into the 'other' zone valve is getting hot (i.e. not the one going to your hot water cylinder). If it is, feel the pipe leading from the zone valve for heat. If there is no heat after the zone valve then it could be either that the motor is faulty, or the valve is stuck. It could also be that the boiler does not switch on.
If you are happy doing some DIY, you can isolate the electricity and remove the head (the silver casing) and take off the motorised part of the zone valve. It's normally just two screws that need to be removed. Once the head is removed, using pliers, move the zone valve manually. Does it move freely? (it only moves a quarter / half a turn). If the valve moves freely, switch the electrics back on, and see if you can open the valve manually. Does the pipe after the zone valve get hot?
Yes? Well, then its probably the zone vale motor that is faulty. It's easy to replace and costs about £40-£60.
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If you have a mid position valve - the one that makes a T junction, one pipe goes to the hot water cylinder (marked B on the zone valve), and the other to the central heating (A). The pipe marked AB comes from your boiler, so it should be hot.
Again, switch off demand for hot water, create demand for central heating, and then feel if the pipe coming off the connection marked A is getting hot. Again, if the pipe is not getting hot or indeed your boiler does not operate, it most likely is the motorised head that is faulty.
Mid position valves are a bit more expensive than two port zone valves but equally easy to replace (the head part).
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When replacing zone valves, don't buy a no name brand. Just by Honeywell or Drayton. A good valve last many years and the hassle of having one go faulty is not worth the £20 savings made from buying a cheap zone valve.
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We hope this article helps a bit.if you need any advice, please do not hesitate to contact us.
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