heating controls

garymul · May 24, 2015

Hi folks looking for a bit of advice, my boiler fires up when there is no call for heating or hot water, the motorised valves for the heating and hot water are both closed but boiler still comes on, i thought that when the motorised valves are shut this cuts off the suply to the boiler and pump. The pump seems to always be running, dont think the motorised valves are faulty due to them only being 2 years old, is there a possible fault in the wiring ? Any advice would be appreciated, thanks

Richard Burns · May 25, 2015

Depending on the type of boiler you may have a small hot water storage tank that is being kept hot to ensure instant hot water, this option is normally able to be switched off in the programming.

Alternatively if you have a frost stat on the circuit and this is set too high then the boiler may come on when the frost stat thinks it is too cold.

Leesparkykent · May 25, 2015

garymul said:
Hi folks looking for a bit of advice, my boiler fires up when there is no call for heating or hot water, the motorised valves for the heating and hot water are both closed but boiler still comes on, i thought that when the motorised valves are shut this cuts off the suply to the boiler and pump. The pump seems to always be running, dont think the motorised valves are faulty due to them only being 2 years old, is there a possible fault in the wiring ? Any advice would be appreciated, thanks

It could be a number of things so without testing it's just guessing. It could be as Richard described or a micro switch could be sticking between the grey and orange on one of the valves or could be an internal fault on the boiler. Get an electrician to check the correct voltage is present at each sequence of switching between programmer, thermostats, valves and boiler.

alanl · May 25, 2015

Faulty valve switch, or faulty programmer relay.
You need to disassemble the wiring at the junction box, and test it live to see where the fault is - dont do this if you are not experienced.

garymul · May 30, 2015

Found the problem, the orange wire from the heating MV is constantly live even tho the valve is switched off and there is no supply from the brown wire, the actuator is only 1 year old which is why i found it strange for it to be faulty, surely they should have a warrenty or something if the valve goes faulty only after a year, cheers for the advice

Leesparkykent · May 30, 2015

garymul said:
Found the problem, the orange wire from the heating MV is constantly live even tho the valve is switched off and there is no supply from the brown wire, the actuator is only 1 year old which is why i found it strange for it to be faulty, surely they should have a warrenty or something if the valve goes faulty only after a year, cheers for the advice

Is the valve spring returning when the supply is turned off? If it is the micro switch is up the swanny, if it isn't returning the body of the valve could be seized and holding the micro switched closed.

Spark1979 · May 31, 2015

Very rare for a valve to fail in this way, more so a new one, I'd check the wiring 1st, normally you do find an error

garymul · May 31, 2015

The valve body is opening and closine fine, the fact that when i turn the htg stat down and it cuts off the supply to the brown wire could only really indicate a internal fault in the actuator since the grey live wire must somehow be connrcted to the orange, cant see it being a wiring fault

Leesparkykent · May 31, 2015

garymul said:
The valve body is opening and closine fine, the fact that when i turn the htg stat down and it cuts off the supply to the brown wire could only really indicate a internal fault in the actuator since the grey live wire must somehow be connrcted to the orange, cant see it being a wiring fault

When 230V is supplied to the brown synchron motor connection the motor begins to turn. The motor is mechanically linked to the valve spindle which opens the valve as the motor turns. Also mechanically linked to the motor is a small arm that acts upon the micro switch when the valve has fully opened. When the valve is in the open position the synchron motor stalls.Since it's not a good idea to simply demand heat while the valve is being supplied 230V to the brown motor connection, the micro switch comes in to play. As the micro switch has now changed state due to the valves internal arm acting on it there is now continuity between the orange and grey wires that are directly connected to the switch. At rest there is no continuity between these wires. It is the micro switch that gives the demand for heat, and letting the boiler know it's ok to fire up.When the 230V supply is interrupted to the brown motor connection, the motor comes out of it's stalled state and the valve is pulled closed by an internal spring. As this happens the internal arm lifts off the micro switch changing its state back to open circuit between orange and grey.

Dave OCD · May 31, 2015

Occasionally I've found that if the 'arm' is very slightly bent [mainly on Danfoss valves] it can slip into the notch at the end of it's travel which is there for manual override/ testing purposes, if it does it will stay there indefinitely until manually released and the boiler/pump will continue getting a switched live supply regardless of control and thermostat settings, this is rare but worth checking anyway.