Boiler and Pump never stop

[shiggyshag]

HI

I have just got a new house and am having some problems with the Heating Etc.

It has an Ideal Classic boiler, two valves (honeywell), Pump, room stat and tank stat.

Now the problem is this when the timer is off the boiler and pump are still running and the radiators stay hot the only way i can save money on gas at night etc is to switch the boiler off at the on off switch. but the pump still runs.

I have had a good look at the wiring etc and believe this is where the problem is. I have compared this to the wiring on the boiler instructions and timer instructions and it looks a bit messed up as there is a continuos live feed to boiler and pump.

The boiler has the normal Neg, Live and Earth as does the Pump.

Now I can wire up all the parts as it shows in the instructions but my concern is this. When wired correctly there will be no live feed to pump and boiler unless the timer is on and so is one or both stats.

Is this normal for the boiler to be completely without any power when the timer etc are off?

I hope i have made some sense to what im trying to explain here.
Any help,advise or direction will be gratefully received.

Thank you

 

[stem]

This is tricky as there are different methods of wiring these systems. Here's a basic guide. Once you understand how it works it should help you fault find.

The programmer has 2 channels one for hot water and one for central heating. Each when "on" provides a live output which I will call the switched live. This live goes off when the heating (or Hot water as appropriate) is turned off by the programmer.

When you say you have 2 valves, I'm assuming that they are 2 port valves, one controlling the hot water and one the central heating. This is known as an "S" plan and is the easiest in terms of wiring to understand. Both valves are identical with regards to wiring so I'll just describe the central heating.

The switched live from the programmer is wired to the live of the thermostat, when the thermostat is asking for heat, the live is switched through to the live on the motorised valve (brown wire). The valve opens at the same time an internal microswitch is operated turning on the boiler using the grey & orange wires. One of these wires will be permanently live and the other will be the switch to the boiler. On some installations (usually with older boilers) not requiring a pump overrun, this contact also controls the pump.

Boilers with a pump overrun facility have a special set of terminals for the pump built into the boiler. This keeps the pump running for a while after the boiler has switched off. In order to do this the boiler requires a permanent live which it uses to control the pump and also for any frost protection facility. Your boiler manual will tell you if it has an overrun.

Unfortunately as you are new to the house, it's difficult to know if the system has ever worked properly, it could be wired incorrectly, however here are some pointers.

1. Check the live wire at the room thermostat, does it go on and off as the programmer switches the central heating on and off? If not the programmer may be faulty, or the wire from the programmer to the room thermostat is connected to the wrong terminal at the programmer, there is usually a circuit diagram on the programmer so you could check.

2. Is there a wiring centre (junction box) with all of the wires for the motorised valves inside has the motorised valve brown wire shorted across, or have a "whisker" touching a permanent live terminal.

3. Is the central heating valve jammed open, or been manually wedged open . Sometimes people do this when a valve fails to allow the heating to work. Try turning the thermostat fully up, wait a few seconds and then turn it down to the lowest setting. You should hear the valve working. (or take the lid off and watch the mechanism) If not, and the live supply measured at the brown wire to the valve is going on and off as the thermostat is turned up and down, the valve is faulty.

Hope this helps.

 

[nickso]

.

I have compared this to the wiring on the boiler instructions and timer instructions and it looks a bit messed up as there is a continuos live feed to boiler and pump.

before you start taking all the wiring apart check the microswitches in the valves are not jammed on for whatever reason. each has a grey and an orange wire in the wiring centre. grey is permanent live, orange is demand. with the programmer off test the orange wires....if its 240v the test each individually to find out which valve is faulty.

 

[shiggyshag]

Hi There

Thank you for your help

Yes i understand everything you have said. The Boiler doesnt have a pump overrun and the stats are turning on and off i have tested this with an electric screwdriver.

It is deffenatly wired that the boiler and pump have a live feed on always.

My real question is, is it correct for a boiler to be switched off completly when no heating is required ie the live feed switched off and then when it is required again to be switched on.

Thank you very much for your reply

 

[nickso]

some boilers will need a permanent live and others dont. if it has no pump overrun then its unlikely yours does. what does the instructions say...they are the final word on that.

if you are confident then rewire it to the instructions. s-plan wiring isnt hard.

 

[shiggyshag]

OK

so its the S plan then.

It all looks good to me to do it this way as i have no pump overrun and just Live, Netural and Earth on the boiler.

Cheers

 

[nickso]

you should only have to rewire the parts that come from the valves to the boiler/pump the get it working properly but check the rest is correct anyway.....wonder why its been done the way it is?.