Motorised zone valve mounted the wrong way round

15 Nov 2016
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United Kingdom
I have Drayton ZA5 zone valves for hot water and central heating in the house that we have just moved to. Things are not right because the boiler is cycling every minute. Measuring flow and return temperatures indicates that the problem is insufficent flow through the system. The plumber who came out changed the pump which did not fix it. However, he did notice that the zone valves were mounted the wrong way round with flow B to A. He was not very concerned and said it might be something to be addressed the next time the system is drained.
Now since the problem is not fixed I started thinking about the zone valves being the wrong way round. If I examine a Drayton valve body (I have a spare), I can see that the valve is a gate valve. Surely mounted the wrong way the water flow will be pushing the valve closed and restricting the flow. This can't be good for the motor either. Does anyone have any experience what happens if these zone valves are mounted the wrong way round? Could this be the reason for my poor flow? Thanks for any feedback
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They have a direction of flow for a reason. I suspect he may not have been 'too concerned' as he'd just fitted a new pump that you may not have needed.... Is the situation any better with the new pump?

Regardless the valves need turning to be in the correct direction, if indeed they are wrong.
Why did you apparently pay for a pump which was not needed?
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Why did you apparently pay for a pump which was not needed?

Because I suspect the OP engaged a 'Heating engineer' to fix his system, so trusted the guy to do this. Having perhaps wrongly diagnosed the pump, the guy then felt he had to mention the valves as changing the pump probably hasn't achieved anything other than lightening the OP's wallet.
How does anyone with any brains put a valve on the wrong way round unbelievable I suspect the
plumber left it cos he knew he'd get called back.The trick is don't have him back get a proper plumber in to swop the valve round,this will proberly sort out the problem.Bob.
Fitting incorrectly then they usually 'thud' when closing , dependant on circulator head then longevity will be short lived.
As Steel says the only problem I have seen when fitted in reverse is noise when closing
Thanks for all the comments, and the answers as to what happens when the valves are the wrong way round. To be honest I am losing confidence in my plumber. When he tells me the zone valves are the wrong way round then I have no reason to doubt him. However, in taking a closer look myself I find that the zone valves are mounted the correct way round!! So how can he get this wrong? A layman might wonder why, if the flow is from right to left, is it marked A - B on the grey plastic actuator housing. But a real plumber knows the A to B direction of flow is marked on the bottom of the brass valve.
Anyway that doesn't solve the problem of why my boiler is short cycling.
What boiler do you have and is the motorised valve the only one fitted? Do you have a cylinder? Is there a motorised valve on the cylinder circuit? What happens if you only run CH ( HW is off)? Check the pipes to the cylinder with CH zone running. Check the flow and return pipes under the boiler
Hi DP, thanks for your interest. Since my problem turns out not to be the zone valves I have made another post entitled "short cycling rayburn boiler" and put the details answering your questions there.

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