As Phil says, its a no-no. Also, you need at least 10o0 litres an hour through the 3KW heater to keep it running so I would guess you will need approx 1300 litres or so for the 4KW. It would be worth checking your flow rates when planning the pipework, taking this minimum flow rate into consideration.
Alan F.
Posted on Jan 5, 2006, 8:53 PM from IP address 213.120.101.21