Zone heating when it should be off

[gmc600]

Hi,

I have moved into a new build and have a problem that the builder keeps saying is normal, please advise.

The system is a Vokera Mynute boiler with pressurised hot water tank and 2 heating zones. The heating works fine downstairs and upstairs but when it's supposed to be off upstairs and on downstairs the radiators upstairs are still getting hot. I suspect the motorised valve for the upstairs zone isn't closing properly. Isn't the whole point of having 2 zones so that they can be controlled independently? The builder has tested it several times and thinks this is fine. Initially they said it's because the upstairs zone was set to 15 °C between heating periods and the temperature must have been below that, but I've done a test where I set the upstairs zone to off and still had the same problem.

Thanks!

 

[stem]

With the time control set to permanently 'on' turn both room thermostats to their lowest settings and allow all of the radiators to go cold. Then turn only the downstairs thermostat up to its highest setting, the downstairs radiators only should heat up. Check to see if the upstairs radiators heat up. If they do, you have a problem.

If they do get hot I would think it more likely to be a wiring fault. Usually systems with multiple zones use two port valves, and when they fail 99% of the time it's in the closed position.

If in the above test the radiators upstairs don't come on, then try the test again but this time using the time control. Turn both zones off at the programmer, and allow the radiators to go cold. Turn both thermostats up to their highest settings and then turn on at the programmer, only the downstairs zone. Now do the upstairs radiators come on?

 

[gmc600]

Thanks for replying stem.

The downstairs radiators heat up after turning only the downstairs thermostat up.

The valves are two port and there are 3 of them labelled upstairs, downstairs and hot water.

In the second test the upstairs radiators go from cold to warm (but not as hot as when I switch them on at their thermostat, perhaps because I didn't test them for long enough - I'll repeat this to be sure).

 

[stem]

The downstairs radiators heat up after turning only the downstairs thermostat up.

OK, that is as expected, but did the upstairs come on also, or not?

The valves are two port and there are 3 of them labelled upstairs, downstairs and hot water.

That's as I would expect it to be. Unusual (but nice) that someone went to the trouble to label them for you.

In the second test the upstairs radiators go from cold to warm (but not as hot as when I switch them on at their thermostat, perhaps because I didn't test them for long enough - I'll repeat this to be sure).

Hmm. not sure I understand what you are saying here, but I will wait to hear what happens when you repeat the test.

 

[nortonj]

Possible reverse circulation through the return.