Baxi 105e pump runs constantly in CH mode

[Dutch85]

I never said that you did, if you read what I said, is that if it was an external control fault, this would ask the boiler to run constantly, so the pump would run and the boiler would keep firing up when the primary water temperature dropped, if it is only the pump that is running constantly and your radiators are not constantly hot then you have a boiler problem and fitting a room thermostat will not make any difference, but feel free to fit one and see who is correct

Wouldn't the boiler keep the pump running when in CH mode as there's no room thermostat to tell it to stop?

 

[D_Hailsham]

I never said that you did, if you read what I said, is that if it was an external control fault, this would ask the boiler to run constantly, so the pump would run and the boiler would keep firing up when the primary water temperature dropped, if it is only the pump that is running constantly and your radiators are not constantly hot then you have a boiler problem and fitting a room thermostat will not make any difference, but feel free to fit one and see who is correct

The OP has said he has no room thermostat, which is confirmed by the pic of the PCB in post #7, which shows the link still in place. So there cannot be any external control fault; the boiler is being turned on and off by its internal thermostat. So the anti-cycling process is being followed.

 

[D_Hailsham]

1 - yes it'll relight for a few minutes, then off, then back on etc

2 - no ideas on the water temperature. It's an analogue dial with no numbers on it.

The row of lights show what the temperature is - from left to right:30; 40; 50; 60; 70; 80 (Deg C)

Does the length of time the boiler is on and off time vary with temperature?

 

[ianmcd]

well if the boiler is also lighting while the pump is running then that is a different , just read your posts again and see you mean with the CH thermostat turned down the pump keeps running , that is normal for your boiler, turn the thermostat up to what you need it at, and turn the boiler CH sector to HW only when you do not want the heating on,and yes fitting a room will switch the pump off but only if the room reaches the temperature selected on the room thermostat, that will never happen with the boiler thermostat turned right down

 

[Dutch85]

The row of lights show what the temperature is - from left to right:30; 40; 50; 60; 70; 80 (Deg C)

Does the length of time the boiler is on and off time vary with temperature?

The temperature depends on how high thr CH dial is set to. It'll raise as the flame is burning then eventually go down until it turns on at a temperature corresponding to the dial position. And yes the time does vary, at first it will be on longer to get the temperature up, then only fire a short amount of time to top up the heat.

 

[ianmcd]

The temperature depends on how high thr CH dial is set to. It'll raise as the flame is burning then eventually go down until it turns on at a temperature corresponding to the dial position. And yes the time does vary, at first it will be on longer to get the temperature up, then only fire a short amount of time to top up the heat.

That is how it works, you are looking for a problem that you do not have

 

[D_Hailsham]

well if the boiler is also lighting while the pump is running then that is a different , just read your posts again and see you mean with the CH thermostat turned down the pump keeps running , that is normal for your boiler, turn the thermostat up to what you need it at, and turn the boiler CH sector to HW only when you do not want the heating on,and yes fitting a room will switch the pump off but only if the room reaches the temperature selected on the room thermostat, that will never happen with the boiler thermostat turned right down

So a room stat will solve the 'problem'!

 

[ianmcd]

So a room stat will solve the 'problem'!

only if he turns the boiler stat up

 

[D_Hailsham]

That is how it works, you are looking for a problem that you do not have

There is a problem but it's not what the OP has been asking about. The problem is that there is no control over the room temperature only over the boiler temperature, which requires a room stat. The boiler will still cycle with the pump running; but evrything will stop when the room reaches temperature.

 

[ianmcd]

There is a problem but it's not what the OP has been asking about. The problem is that there is no control over the room temperature only over the boiler temperature, which requires a room stat. The boiler will still cycle with the pump running; but evrything will stop when the room reaches temperature.

so a boiler can not work without a room thermostat ? total rubbish

 

[Hot&Cold]

I've had a look and it has spade type connectors at the back. I don't want to do anything too complicated!

The integral mechanical timer is a straight out to the BC unit,use the existing 4 wire timer harness. Just swap the 4 spade connectors . That is all you need to do remember the salus is a cheap programmable timer.

 

[Dutch85]

The integral mechanical timer is a straight out to the BC unit,use the existing 4 wire timer harness. Just swap the 4 spade connectors . That is all you need to do remember the salus is a cheap programmable timer.
View attachment 171955

A link wire doesn't have to be removed then? (bottom left)

 

[D_Hailsham]

There is a problem but it's not what the OP has been asking about. The problem is that there is no control over the room temperature only over the boiler temperature, which requires a room stat. The boiler will still cycle with the pump running; but evrything will stop when the room reaches temperature.

so a boiler can not work without a room thermostat ? total rubbish

I agree: I did write rubbish. What I meant to write was:

The problem is that there is control over boiler temperature only, not over room temperature which requires a room thermostat.

 

[Hot&Cold]

A link wire doesn't have to be removed then?

The link needs to remain, The colour of the link wire doesn't matter either.