Good pressure reading on gauge but low pressure light on

20 Aug 2010
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United Kingdom
Ive just removed a towel radiator form the upstairs bathroom and capped off the pipes as I will shortly be fitting a new suite.

I turned the system back on topped up the water so the pressure was back to normal and bled the radiators. Theres was no air in any of the radiators. The other thing Ive noticed is that 2 of the other upstairs radiators are cold not even the pipes that connect to the radiators are warm this also includes the pipes thats are capped off. Ive also doubled checked and there are no leaks.

Ive no idea what the problem could be with regards to the light coming on.

The boiler I have is a Saunier Duval SD30e Fanned Flue Combi

Any there something Ive missed?


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Faulty sensor is a possibility, I'm not 100% familiar with that model though.
Generally, if the pressure is up and the LP light is on it may well be your sensor. Is your pressure gauge accurate? There is a low water pressure switch on that model and thats where I'd start.
The connection into the pressure switch is probably blocked by some black gunge.
As far as I'm aware there is no issues with the accuracy of the pressure gauge.

[There is a low water pressure switch on that model and thats where I'd start

yes its the low water pressure switch that the light is on red

The Pressure gauge (dial) reads 1.8 which is back to how it was before I removed the the radiator
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OK is it a straight forward procedure to remove the blockage or do i need to get a plumber in?
It is a fairly easy procedure. If you have the MI's you could DIY it, if you have the confidence. If not get a boiler repair man and not a plumber.
I would not expect 98% of the UK population could DIY it.

For a start 50% are female!
Go to the gassafe web sit to get a qualefied heating engineer to remove the low water pressure switch and clean/replace it. may as well have serviced at the same time.

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