Thermostat / HW problems


18 Jan 2004
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United Kingdom
Just found this site and thought someone may be able to point me in the right direction before calling out a professional.

Just moved into a flat with a Potterton Netaheat 10-16 boiler system. I am pleased to say that all is working OK, with a couple of minor irritations.

1 - Thermostat: there is a thermostat on the wall in the hallway. However, when the correct temperature is reached, the boiler does not cut out. I have lifted the cover off the thermostat and can confirm there is a live wire and when in the temperature is lowered, the 'switch' is effective in cutting out the return current.

2 - HW: Plenty of Hot Water, but it only heats up when the CH is selected. So currently my only option is to have CH & HW. I worry in the summer when I would only need HW that I will have to have the CH on too. IN addition, the switching seems to be crossed on the system control panel ( a Siemens Landis & Staefa RWB2E): when I select CH, nothing happens. When I select HW I get CH & HW.

I hope it's as simple as needing some re-wiring to the system control panel, could anyone let me have their opinion and how much it is likely to cost?

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does sound like it is wired wrong, havent got the timers' manual have you?
It would be worth checking the operation of the motorised valve or valves.
Thanks to both.

Unfortunaly, no manual.

Not sure about what valves to check, so will get an expert in.

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you want a heating engineer, not a plumber and get several quotes 1st
NP said:
I hope it's as simple as needing some re-wiring to the system control panel

When I think of simple jobs rewiring a wiring centre is not first to spring to mind!
I would go with oilman on checking the valve operation never know!
You might have trouble getting a quote for a problem like " My heating isn't working properly, how much?"!
I would quote you an hourly rate. Quote often the diagnosis is pretty quick, but you have to pay to get it.
It never ceases to amaze me how often all the wires are in the junction box, but not in the right places! Sorting out what comes from where and rewiring is 15 minutes work - all well within the first hour.
OK - but are the valves something that I can check myself? I'm not sure I know what you're refering to. I know of the valves on the radiators, but I think you're refering to some that may be on the boiler?!
Motorised valves - could be by the bopiler or in airing cupd... you may have one or two with 2 pipe valves or one with 3 pipes. Brass things with boxes on top. May be plastic or metal boxes.

From the symptoms though it sound like it's wired incorrectly.
I have located the valve!! It actually has written on it 'Mid Position Valve'!! It's a small unit, in a white plastic casing, that has three pipes connected at a junction - one of the pipes comes from the pump. It is also wired to the timer. It has three letters written down one side - W M H. The question is now how do I check it? I have checked the pump and that works - it vibrates when the Hot Water is turned on, but not when the heating only is selected.
so has this one


w m h

stands for Water, Heating Manual , the 3 positions it can have, does it not have a name (and i dont mean fred)

oh and there's this one

Wow! I am so impressed with your graphics!! :D It's exactly like the top picture - and is made by 'acl lifestyle'. It also says on it 22mm, 240 volts.
but the top one is grey, yours is white. just found out it is a drayton valve £47.00 +vat for a whole one, aparently it has the "industry standard" wiring configureation
You need to check that electrical continuity is maintained to the valve when the programmer and stat are calling for heat. As you don't know if it has ever worked with the wiring as it is you will need a multimeter to check it

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