I have got a potterton pro max sl linked to a Honeywell thermostat. I want to replace the thermostat with a wireless one but I don't want to put the "heat link" (receiver) on the wall where the current stat is. So my question is where does the wire come from? ideally I want to intercept it at source, but was unsure if it comes from the boiler or the programmer? How can I find out?