help with heating

[rob5]

Hi all,
I hope that you kind people can help or offer advice with this problem.
I have a gravity fed water/heating system with a glow warm boiler, room thermostat and a sunvic three port(?) motorised valve, danfoss CP715 programmer, danfoss type AT tank thermostat and a wilo gold 60 pump. I have a total of 13 rads over two floors with 11 of them fitted with thermostat valves. ( I hope I got all of that right!)
My problem is that the rads get hot whenever the water is on even though the rads are turned off at the programmer.
I thought that it might be the motorised valve stuck open so I took it off and watched it when turning on the programmer to the three positions of , both, water and then only heating. It appeared to work ok so I also checked the actual valve on the pipework and that seemed ok as I was able to turn it by hand. I also notice that the loft central heating tank is occasionally dripping from the overflow and it seems that water is being pushed up into the header tank. I'mstuck so any advice appreciated. thanks, Rob

 

[Softus]

You said that you turned off the CH valve by hand - when you did this, did heat still reach the rads?

FYI, it's possible for the valve to be operable (seemingly) but for deposits on the valve ball to prevent it from fully closing. If that's the cause then it's time for a new valve, AND a good system clean out AND the use of a chemical inhibitor when refilling.

 

[rob5]

Softus,
thanks for your reply and advice which was helpful. I am just in the process of changing the motorised valve because when I tried to turn the spindle of the old one it hardly turned at all so I assumed that it was jamming or faulty.
unfortunately I have had to change some of the pipework because the old valve was 28mm with reducers to 22mm and I could only get a 22mm valve and actuater. I am struggling with draining down because I know the hot water storage tank needs to be drained (using the bottom drain valve)but still lots of water coming out of the motor valve when loosened, where is this coming from and do I need to drain something else as well?
Rob.

 

[Softus]

Hi rob5

Yup - jamming spindle is a sure indicator that a new valve is needed.

I know that many 28mm valves are readily available, e.g. from Honeywell, so are you trying to match a slightly obscure make/model?

In any case there's no advantage in using a 28mm valve if the pipework is 22mm.

If you're just changing the MZV and nothing else then you don't need to drain the cylinder (aka hot storage tank). All you need to do is drain the CH (central heating) system - these two systems are physically separate, which is why you have water coming out where you don't want it to.

I can give you much more advice if you tell me whether you have (a) an open vented system or (b) a pressurised system.

(a) is characterised by a 4 gallon F&E (feed and expansion) cistern, usually in the loft.

(b) is fed from cold mains and somewhere there will be a pressure guage that you're supposed to monitor.

S.

 

[rob5]

Hi Softus,
thanks for taking the time,
my system does have a F&E tank in the loft and I was coming round to thinking that might be the one causing the problem. I had drained down some of the CH by connecting to the drain valve at the rad on the ground floor but possibly not enough perhaps?? Going to try again in the morning
Rob

 

[Softus]

Hi rob5

Did you prevent water flowing into the F&E cistern before draining? I don't mean to be patronising but you didn't mention that you isolated it so I'm just checking.

Another point - turn off the programmer and all system components in order to stop the pump running (if you have one).

Anyway, you could reduce the time taken to drain (and re-fill) by closing all radiator valves, but keep going until no more water flows. Leave the DOC (draw-off cock) open until you're ready to re-fill. Before closing the DOC again I always replace the washer so that it's in prime condition for next time (which is sometimes sooner than you expect).

And when you re-fill, go into the loft and observe that a decent amount of water exits the F&E cistern to make sure you don't have a blockage.

After refilling and before turning the pump back on, open the rad valves again and vent air from all rads.

S.

 

[rob5]

Softus
lots of good tips so thanks, its much appreciated, I did isolate the F&E but not sure that I left it long enought to drain sufficiently. I will let you know how I get on.
Rob