Adding a room thermostat to old CH system

[GavinW]

Just after a sanity check -- new baby means too little sleep

We've moved into a house with an aging, but perfectly functional, CH & HW system controlled by a Potterton Mini Minder. There's no room thermostat anywhere so we're forever fiddling with the boiler temp.

I've planning to add a room stat. Currently there are two feeds from the Mini Minder -- one to boiler, one to pump. Just checking that a room stat should go in the feed to the pump, not in the feed to the boiler...

 

[gas4you]

Yes, assuming that it is a basic pumped heating, gravity primary set up.

 

[GavinW]

Yes, assuming that it is a basic pumped heating, gravity primary set up.

Yup, it is. Ta!

 

[mogget]

I take it this is a gravity hot water, pumped CH system.

The room thermostat needs to interrupt the signal between the programmer and the pump.

So, for a two wire thermostat, CH ON on programmer -> com on thermostat : call on thermostat -> pump.

For a three wire thermostat, CH ON on programmer -> L on thermostat: switched live on thermostat -> pump. Plus N on thermostat to neutral either at the programmer or the wiring centre.

Sometimes it can be convenient to use a connector block behind the programmer for the new switched live.

While adding a room stat will provide temperature control for comfort, the system will still be rather inefficient (in terms of fuel use) compared to a fully pumped one with independent control.