glowworm swiftflow combi turning off and on?

It sounds as thought the domestic secondary heat exchanger is choked up, not allow sufficient flow from the main heat exchanger and therefore causing the primary water to oveheat. This shut down the burner and when it cools, it fires agaiThe only solution is to fit a new plate to plate domestic heat exchanger. They are available at keeptheheaton.com. Usually around £100. From: chris@higginsheating.co.uk.

Chris Higgins
March 2009

I had the same problem. Almost certainly related to the flow switch. In my case it seemed the water pressure was not quite enough to keep the flow switch open. I could prove this by partially opening a hot tap while I had a shower - it would solve the problem but obviously waste heat and water.

Solution in my case was simply to open the input tap a tiny tiny amount, to speed up the water flow slightly. It's easy enough to locate with the boiler manual and easily adjusted with a screwdriver. I had to open it really the tiniest amount I could. If you open it too far, water will flow too fast and won't really be hot when it comes out.

Good luck!
-Mark

Mark Smith
November 2005

have a look at the flow switch this is located at the cold water point of entry. it is a brass fitting with a ball bearing inside, as you open your hot tap this causes the bearingto carry to the top of the valve with water flow. when it does it causes the magnetic reed switch located on the outside of the valve to make a circuit. you can put a multi meter on both wires and you should get a complete circuit when you open the hot tap.
They can get worn and they have a circlip inside to retain the ball, ihave often found the clip broken and jamming the ball.
Angus

angus
September 2005

we have the same problem - in winter in Canberra, Australia
Sorry I don't have an answer!

aw
July 2005