Three port valve not the answer

[smitje1]

Hi,
Having read several of the posts here concerning radiators warming up when the hot water was heated, I concluded that my three port valve needed replacing. I'm reasonably technical and did the job myself, however, it doesn't seem to have solved the problem. My radiators are still getting hot despite not being activated by the thermostat. I have noticed that when the hot water is being heated the three port valve makes a constant clicking noise as it activates the microswitches and then moves backward and forward past some kind of tipping point. This is what I also got from the old valve, and I'm wondering if there is a fault in the Honeywell control box.

 

[Agile]

It seems that its wired wrongly or there is a wiring error.

All you can do is to check the wiring carefully. Its a little tedious.

Perhaps someone else will have encountered that problem you describe and can say exactly where the error is.

Tony

 

[smitje1]

Thanks for the very speedy reply. Since this problem has only just reared it's head, and before it manifested no changes had been made to the system, I don't suspect a wiring fault. However, I will go check. Why oh why are these things always so damn inaccessible.

 

[jackthom]

If you have a multimeter it would be very useful measuring the voltages on both the white and grey wires to the 3-port valve. Neither should be anywhere near 230V when only the water is supposed be heating.

 

[smitje1]

Hi Jackthom,
Thanks very much for the reply. With the system at rest I measured 240v across the white and grey wires. When I moved the tank thermostat until it engaged the reading across the white and grey wires dropped to +/- 20v (but was not steady). Then the in-out thing started with the microwitches on the three way and the readings went all over the place, as I would expect, since it's basically being switched on and off every second or so.

 

[Agile]

No! You need to measure the voltage on each wire to neutral or to earth!

Look for loose wires in the wiring center.

Measure resistances of contacts on stats etc. When closed should be less than one ohm.

Tony

 

[jackthom]

Hi just to check, when you say across the white and grey are you measuring the voltage between white & neutral, then grey & neutral, ie 2 voltage readings?

(Measuring with the probes connected between grey & white will only hide what's actually happening here).

 

[smitje1]

Hi Jackthom,
Thanks again for your reply. I was measuring across white grey. With the system at rest I measure across white and neutral a small leakage of 13.2 mV and across grey and neutral 240V. With the thermostat on the tank activated I measured 240V across white and neutral and 127V across grey and neutral.

 

[jackthom]

That's a useful result.

Assuming there is no demand for central heating, the white wire should not be at 230V.

So I would be taking a closer look at how this feed (which normally comes from the room thermostat if there is one) has been wired.

 

[smitje1]

Thank you for your reply. I've had to go out for a while. I'll take a further look when I get back. However, as I mentioned earlier in this thread. No work has been done on the wiring so I am not sure how it could now be wrong.

 

[maltaron]

This may help http://www.diyfaq.org.uk/plumbing/controls/midpositionvalve.htm

 

[smitje1]

Thanks for that Maltaron. I'll certainly use that when I check the wiring in the morning. Just for info, what voltage should I expect to read across the white and neutral when the tank thermostat is making contact?

 

[matt1e]

Sounds to me like the second microswitch inside the actuator is permanently closed.
Take the orange out of the wiring centre and make it safe,
now select hotwater ,has the valve stopped motoring? if so the actuator is faulty.

Matt

 

[smitje1]

Thank you all for your helpfull replies. Last night, in order to check the wiring safely I turned off the supply to the control box. Having checked the wiring I turned the supply back on. The hot water required heating, and this time the radiators did not get warm. Since I found no problems with the wiring, I'm leaning towards a fault in the controller. To that end I have ordered a new one, and shall let you all know what the outcome is. Thanks for all your help so far. What a great community.

 

[maltaron]

You may be premature ordering a new control, the fact that it seems OK after powering down appears to show that a software reset has occurred and solved the problem. Also, the memory backup battery can cause problems if dead, although they often cannot be replaced. In saying that though, a new controller will give peace of mind.