Added radiator stays cold

British Bloke

I hope somebody can help me with this please. I have just installed a new radiator to my downstairs bathroom. I have a pumped boiler and have drained and bled the system and rads twice but still the rad stays cold. The pipe to the thermostatic valve gets hot but nothing else. To install the rad i teed off the radiator above using 10mm microbore equal tees as all my rads are in microbore. All the other rads including 2 downstairs work fine but not this one. However if i turn the other rads off the new one heats up fine, but if i turn them back on and fire the boiler up it stays cold again. Please help!!

John@Reliable_4

Check this link http://www.heatinghelp.com/newsletter.cfm?Id=28

Aidan (UK)

As I understand it.....

.....you’ve connected a new radiator downstairs using 10mm equal tees on the flow and return pipes serving an existing radiator on the floor above. Have I got this right?

I assume you’ve done the obvious, i.e., bled all the air out of both radiators; the lockshield radiator valve is fully open, isn’t it?. I’d then think the problem is probably that there’s too little differential pressure at the tees to generate the flow rate that you need.

If you shut the valves on the upstairs radiator, you may find you get some flow through the downstairs radiator. If so, then it’s a matter of adjusting the lockshield valves until both radiators give some heat. I’d leave those on the downstairs rad fully open & gradually shut the LS valve on the upstairs radiator.

If this doesn’t get it working, you need to get a competent technician to look at it. Sorry, but there’s just too many possibilities to do a long-range re-design. You can only get so much heat down a 10mm pipe for a given pump, probably around 1500W; you may be trying to get a quart out of a pint pot.

Don't try to get Monoflo tees from your friendly local plumbers' merchants. They won't know what you're talking about.

Which abbey?