I have a Potterton Prima F boiler with an EP3001 controller, a PRT100 thermostat downstairs and in the airing cupboard with the cylinder a Potterton MSV222 valve, a Myson valve (can't see a model number), a Myson Compact CP53 pump and a Potterton PWB1 apparently controlling it all. A diagram can be found at http://www.communitymoneyadvice.com / ch.jpg showing all the bits in the airing cupboard and how they are connected. The labels 1, 2 and 3 I found written on paper tags tied to the relevant pipes (presumably by the builders). The devices P, A and B are the pump and the two valves.
Yesterday I had to switch the heating on for longer, as the house was particularly cold with the snow earlier in the day. Today I find that the heating won't switch off! The only way I can stop the heating is to cut the power to the entire system.
Following earlier posts in this group I have turned off the boiler (by turning the dial on the front to 0) and disconnected the EP3001 programmer. That stops the boiler heating any more water, but the heating still continues to run as I can hear water moving through the radiators. I've confirmed the thermostat downstairs works as I can hear it click when I move it. I don't think I have a frost stat as the boiler is in the kitchen and there's no pipework or suchlike outside the house.
I then visually inspected the valves (as far as you can in a cramped cupboard with little direct light). The Potterton MSV222 has a lever on the side which I can move (with a little resistance) and it then springs back to the original position. The Myson also has a lever, but this only slides between positions marked AUTO and MANUAL without any resistance and doesn't spring to or fro. I also notice a small amount of water appears to have leaked from the bottom of the Myson valve which makes me reluctant to do anything with the power on to the system (I don't want to electrocute myself!)
Can anyone offer advice? It would really help me if someone could explain what each bit of the system does and which valve does what. I think, looking at diagrams the house builders left (the house was built in 1995 but I moved in in November), that I have an S plan system?
I presume the next step would be to examine the valves? If so, which valve does what? Can I open them up without frying myself or flooding the house? I don't even know if the system is open or closed as I cannot find any sign of either a feed tank or a pressure gauge. There's a cold water tank in the loft but not obvious sign of a pipe from that to the airing cupboard.
Any suggestions much appreciated...