Suprima 70 HE Flow Thermistor Fault

[Mackam]

Hello everyone,

I was wondering if anyone had any clues on what could be wrong on my boiler.

I have a Potterton Suprima 70 HE and it is not working and showing a Flow Thermistor Fault (Red light on, middle flashing and right light on)

It was working fine until I drained down the central heating system to change a leaking rad valve. I forgot to turn the boiler off while I did it but the central heating was turned off (hot water on) so I didn't think this would be an issue. Unfortionately afterwards no hot water and the Boiler was showing a lockout fault, but after a reset the Flow Thermistor Fault.

I haven't reaplced the radiator yet or filled the system back up but the hot water should still work even with the central heating drained down?

Any advice would be greatly appreciated.

 

[tonybhoy]

You have to fill the system up to with water mate regardless of whether you want heating or hot water otherwise the boiler will overheat and conk out as there is no water to go round the system plus you'll probably damage the pump and MVs and the boiler by running them 'dry'.

 

[Mackam]

Ah I thought they were isolated so it would heat water without the central heating being full of water.

Surely the boiler, pump and other parts aren't dry as there is water in the hot tank and pipe work to the boiler, just not the dirty central heating side.

 

[wcavanagh]

Water from the central heating circuit is diverted though the secondary heat exchanger to heat the mains water, so you always needs the heating circuit to be full for running hot water on a combi

 

[Mackam]

Its not a combi does that make any difference. I am guessing since it doesn't work at the moment then the answer is a big NO!

 

[tonybhoy]

Ah I thought they were isolated so it would heat water without the central heating being full of water.

Surely the boiler, pump and other parts aren't dry as there is water in the hot tank and pipe work to the boiler, just not the dirty central heating side.

The only way you can heat your cylinder without your heating system for hot water is by using an immersion heater.

The domestic hot water and central heating systems are completely separate, the MVs and the pump and indeed the boiler are all connected to the "dirty central heating side".

Is this a wind up?

 

[Mackam]

Okay cheers for the info, not sure why you think this would be a wind up I ain't a plumber so came here for advice.

As the water supplys are seperate, the pipe work is seperate and you turn them on individually I thought the boiler would work just heating one side and not the other. Wasn't aware they needed both to be connected for it to work. Seems like bad design having to have both functional but as I said I aint a plumber so I am sure there is a good reason for it.

When I said dirty I was referring to the water that comes out of the central heating, you wouldn't want to bath in that stuff.

Cheers for the advice, looks like I'll sort the rads out quicker than planned!

 

[tonybhoy]

As the water supplys are seperate, the pipe work is seperate and you turn them on individually I thought the boiler would work just heating one side and not the other. Wasn't aware they needed both to be connected for it to work. Seems like bad design having to have both functional but as I said I aint a plumber so I am sure there is a good reason for it.

In order for the system to work like you thought it would work you would need two systems, i.e. boilerX2, pump controls MVs etc etc.

Central heating plumbing and indeed domestic plumbing is really very simple, they've both been around in in their current form for the best part of 2000 years with a couple of minor modifications along the way such as pumps etc.

The word Plumber, derives from the Latin word Plumbo meaning lead and the Latin word Cupro means copper.

 

[Mackam]

Thanks for the help