Commander Posted November 13, 2016 Share Posted November 13, 2016 (edited) I have a pumped, vented, Gas CH / HW system with a room stat, boiler stat, electric programmer and two two-port electric valves that sit in parallel with each other - one does HW and the other does CH. We noticed the pump and boiler have been coming on at funny times, or not going off at the end of the day like they should. Valves seem to open / close fine. I have currently removed the programmer from the wall AND un-wired the electric valves, but the pump is STILL running. Boiler is off. If I turn it all off at the wall the pump goes off, but as soon as I power it on again the pump restarts. The only way to stop the pump is to manually operate the vales open (as they are currently disconnected) which allows the water in to the CH / HW circuits. Presumably this drops the water temperature and the pump eventually goes off. So, I think there must be another thermostat somewhere in either the boiler or the pump (or both?) and this is causing the system to keep running somehow. Any tips on troubleshooting please? Edited November 13, 2016 by Commander Quote Link to comment Share on other sites More sharing options...
Rich260 Posted November 13, 2016 Share Posted November 13, 2016 You have what's known as an S plan system. Without looking at it I can't see if your pump is taking it's power from the end switches on the two port vales or if it's taking it from the boiler (if it has a pumped over run). If you are handy with a multi meter I would take a look inside the wiring center and see if you have 240v on the orange wires of either of the 2 ports when you have both the cylinder and room stats turned down. Here's a wiring diagram if it helps. Quote Link to comment Share on other sites More sharing options...
GMballistic Posted November 13, 2016 Share Posted November 13, 2016 Sorry I can't help Commander but if you're not a Gas Safe registered heating & plumbing engineer then this is not the sort of thing I'd mess with tbh. Personally I'd just get a professional in who knows what their doing. I know they can be expensive but not all of them are that bad, ...my best mate runs his own business doing just this and he's always fair with his pricing. Good luck anyway and hope you get it fixed. Quote Link to comment Share on other sites More sharing options...
Commander Posted November 13, 2016 Author Share Posted November 13, 2016 Cheers. By 'wiring centre' I assume you mean this? My system's wiring doesn't entirely match the diagram. It's a Danfoss system so I'll see if I can find the Danfoss version of your diagram. I'll bust out my multi-meter tomorrow and see. If thermostat is down but I'm still seeing volts, does that mean duff thermostat or duff switch in the valve? Quote Link to comment Share on other sites More sharing options...
Renegade Posted November 13, 2016 Share Posted November 13, 2016 (edited) Its been a while since I was on Gas repairs, but that is a typical fault of one of the valve heads. There is a small syncron motor inside which does not close properly. Main cause is one of the valves them selves getting a bit stiff. If the clock is off and the pump running you can usually trace it to the wire coming from the valve to the pump still being live. That wiring diagram is a typical set up, we mainly used Honeywell so it was the orange wire that would still be live. I'd get someone in if you are not sure. Edited November 13, 2016 by Renegade 1 Quote Link to comment Share on other sites More sharing options...
Commander Posted November 13, 2016 Author Share Posted November 13, 2016 Troubleshooting method then, un-wire one of the valves and test behaviour / volts. Restore to normal then un-wire the other valve and test behaviour / volts. This should allow me to work out which one is / isn't working... job done. Right?! Quote Link to comment Share on other sites More sharing options...
Rich260 Posted November 13, 2016 Share Posted November 13, 2016 Humm your wiring looks a bit hashed up to be honest. If you look in the airing cupboard where your two port valves are, follow the flex that comes from the actuators in to that junction box on the wall below your pump. That would be where I would start to test from. Thermostats are easy to test providing you know which is the common and which is the swich, a diagram should be on the back of the stat that shows you. Just test the continuity across the stat and see if it brakes/ makes as you open and close it. As GM says I wouldn't get too involved unless you know what you are doing as electric shocks are a pita. Quote Link to comment Share on other sites More sharing options...
Rich260 Posted November 13, 2016 Share Posted November 13, 2016 First thing I would try is put it all back to how it was. Turn on just the heating via the programmer, turn the room stat up/ down and see if the CH 2 port opens/ closes accordingly. Turn on just the hot water via the programmer, turn the cylinder stat up/ down see if the HW 2 port opens/ closes accordingly. That will at least give you a starting point to work from. 1 Quote Link to comment Share on other sites More sharing options...
Jonny B Posted November 14, 2016 Share Posted November 14, 2016 As mentioned above, it's going to be one of two things causing your fault. Most likely is a sticking end switch (microswitch) in one of the zone valves. What boiler (make and model) do you have, because the other option is the pump overrun is staying on (if it has a pump overrun) if the pump is wired from the boiler rather than straight from the zone valves. If you have a multimeter the safest way to test the zone valves is to turn the power off to the system and check for resistance across the grey and orange wires of each valve. If you test one valve at a time, if they are working correctly, with the valve shut you should get OL (no continuity/ open circuit) measuring orange to grey. If you find you are getting continuity across either of the valves then there is your problem (orange to grey is reading through the switch) ie stuck microswitch/ switch is still made which will keep the pump and boiler on. As I mentioned this is the safest way if you're unsure of the wiring because you're not live testing. There are a few other ways of testing/ double checking but I would start with the above. If you want to clarify anything I've said feel free to drop me a PM. Quote Link to comment Share on other sites More sharing options...
EcoFriendlyAL Posted November 14, 2016 Share Posted November 14, 2016 I had a new system installed and it kept coming on at random times. It turned out it was simply the frost protection had been set to 15C instead of near freezing. Quote Link to comment Share on other sites More sharing options...
Commander Posted November 14, 2016 Author Share Posted November 14, 2016 Looks like it's a sticky switch in the CH valve... Messing around with the HW and it all goes on/off ok. Do the same with HW and it comes on ok, but won't go off unless I turn it off for ages at the wall. Will do some more testing tonight before I go buying new valves... at least it's only a two-port one, shouldn't take long to swap over... PITA position though! Quote Link to comment Share on other sites More sharing options...
Renegade Posted November 14, 2016 Share Posted November 14, 2016 You can usually just change the head, check the model. A couple of screws hold it on. When that is removed there will be a shaft stuck out, a bit of turning with pliers may loosen it off. But a seized valve is what knackers the motor. There is a rubber ball that sticks to the inside when not used for a while. Generally it is the heating valve as it is left off all summer. Good idea to turn it on now and again during summer. Quote Link to comment Share on other sites More sharing options...
Jonny B Posted November 15, 2016 Share Posted November 15, 2016 If you've narrowed it down to just being a sticking microswitch you can change just the valve head. On those Drayton valves the head just unclips, not even any screws to undo (unless it's a really old valve that was built all in one). If they are the ones that just unclip, there will be a little black button on the side of the valve head, it's directly opposite the indicator that is labelled A and B. Just push the little black button in and pull the valve head towards you and it will release from the brass valve body. As mentioned, check the spindle of the valve body is free to move. Then it's just a case of clip the new valve head back on and wire in the 5 wires. There is no need to drain any water from the system to replace just the valve head/ actuator. Quote Link to comment Share on other sites More sharing options...
Commander Posted November 19, 2016 Author Share Posted November 19, 2016 Thanks for all the help - after some time spent checking wiring diagrams and checking functionality with my multi-meter, I established it was the actuator on the CH that was at fault. I had a British Gas BGMVSP-2 actuator and it turns out that it's nigh identical to a Drayton ZA5/679-2, so I bought the Drayton unit (as I couldn't find another BG one) and just fitted the new actuator to the old valve, it just clips on, wired up the 4 wires and job done. Direct fit, dead easy, problem solved. Thanks again, Richard Quote Link to comment Share on other sites More sharing options...
Jonny B Posted November 19, 2016 Share Posted November 19, 2016 The British Gas valves are just a Drayton valve, made by Drayton but branded for BG. You won't get another BG valve for it apart from out the back of a BG engineers van. Glad you've got it sorted 👠Quote Link to comment Share on other sites More sharing options...
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