potterton 100e

29 Jan 2006
Reaction score
United Kingdom
Hi all
Hope someone can help
Firstly the problem The CH comes on for a few seconds then goes off and repeats at random intervals some of the rads upstairs get warm/hot but not the furthest away the downstairs cold no rads have been adjusted other than the normal temp adjustment so balancing should not be an issue.
HW fine.
Could it be a temp sensor in the the boiler or something
Please help
Dave :(
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Then I would be looking at a dying pump, or stuck diverter valve.

Just because the pump appears to be working doesn't mean it is.

Sludge is also a possibility.
Sounds to me to be a diverter valve not moving fully.

Do you have a dripping hot tap?

Turn the cold mains off and if you get heating you no its a hot tap or shower letting bye somewhere if you don't you need a new wax diverter assy! ;)
Cheers Gaz
Just how does the wax valve work and do i need to drain to fit
When you open a hot tap, the cold water flowing into the boiler cools the wax stat, causing it to close the valve that normally allows primary heating flow to your rads, giving more available heat to dump into heating your hot water. When you close the tap, the lack of cooling effect combined with the heat transfer to the waxstat from the hot primary water cause it to open the diverter valve, allowing heat to your rads.
The system doesn't need to be drained but the system pressure DOES need to be released & the cold mains to boiler shut off, then when the waxstat is being changed you'll just get some water flowing out of the boiler - nothing a bucket/towel won't handle in the 60s it takes to swap the head.
If replacing just the wax stat then they often do not easily come out.

I would always ensure the boiler is isolated from the CH system or drained down to the boiler level.

Closing the original iso valves usually makes them leak.

Its not really a job I would strongly recommend to a DIYer.

i work on valves for a living but they are medical oxygen with 300 bar behind them not CH with hot water. working on valves is not an issue just dont want to get covered in hot water, just unsure of what is behind what opening and what happens if i open a port
Working with 300 is easy...the components will have quality.

Boilers working at low pressure are abysmal quality. Just dropping the presure down and disturbing a few joints is enough to result in leaks :)
I understand what your saying gasguru but if you forget to wash your hands before starting work you are not really in danger of the boiler blowing up.
Each have there own pitfalls

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