I don't understand that. "Two contacts" is that the DPST contact in the cylinder stat? What does "the made" mean?Two contacts the made when cold turns boiler on, the made when hot turns the water flow from valve off, so faulty made when hot can cause DHW not to turn off, but has no effect on causing boiler to turn on.
Agreed there's nothing obvious in the pics to keep the stat firm against the cylinder, but the OP said this problem has only started since the weather turned cold and the heating came on, so presumably the stat was working before.As Chris mentioned the cylinder stat is not in contact with the cylinder so either get some net curtain wire (and hooks) or get another stat...
Then go from there.
I suppose to prove this the op could use/drain all the hot water from he cylinder then with hot water set to off and central heating on, if he gets hot water in the tank then the 3 way valve is faultyI don't understand that. "Two contacts" is that the DPST contact in the cylinder stat? What does "the made" mean?
As I said, I don't think it's likely the cylinder stat is faulty and always calling for HW, more likely the 3-port valve is sending water to the cylinder even when the cylinder stat is satisfied.
I think understanding 3 port mid position valve operation is paramount to under how the system works.I don't understand that. "Two contacts" is that the DPST contact in the cylinder stat? What does "the made" mean?
As I said, I don't think it's likely the cylinder stat is faulty and always calling for HW, more likely the 3-port valve is sending water to the cylinder even when the cylinder stat is satisfied.
Agreed there's nothing obvious in the pics to keep the stat firm against the cylinder, but the OP said this problem has only started since the weather turned cold and the heating came on, so presumably the stat was working before.
In normal operation, yes, but isn't it possible for a faulty valve to leave the port to the cylinder open, although the cylinder stat is satisfied?I think understanding 3 port mid position valve operation is paramount to under how the system works.
Three port mid position valve in not powered, HW port is open, boiler runs when HW channel on timer is operated and thermostat on the cylinder is calling for heat
Turning the dial on the cylinder thermostat doesn't seem to do anything, no 'clicks' from the thermostat
That port is always open for sole hot water heating. It is the cylinder thermostat that switches the boiler off not the motorised valveIn normal operation, yes, but isn't it possible for a faulty valve to leave the port to the cylinder open, although the cylinder stat is satisfied?
That port is always open for sole hot water heating. It is the cylinder thermostat that switches the boiler off not the motorised valve
That is, or could be, the problem. Without studying the mid-position valve operation in detail, I would think if something goes wrong it defaults to the HW position, like the either/or W-plan valve. So if CH is calling, the cylinder gets overheated.That port is always open for sole hot water heating. It is the cylinder thermostat that switches the boiler off not the motorised valve
I meant SPDT, not DPST.On the cylinder stat there are two sets of contacts, one set normally open, one set normally closed, don't like that terminology as you need to define normal.
Agreed, I never saw significant advantage in Y-plan. With weather compensation becoming more popular, where mid-position is not an option, perhaps we'll see fewer of them in future. Discussed on here only a couple of weeks ago.I have shown the Y Plan however not easy to test, as the valve is complex. The diodes and resistors in the valve mean need a volt meter to fault find, first time I came across Y plan I also had problems, I felt likely problem was the V3 micro switch, but not sure, Sunday so could not buy a V3 micro switch, so only option was whole valve, and it fixed it.
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local