PSC or pump ?

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PSC or pump ?

Post  bobtv on Mon Dec 14, 2009 9:20 am

Hi, I've fitted new gledhill original heater elements. and the overheat retro kit. all worked well........then pump became intermittant. replaced with STANDARD Grundfos 15/50 pump. It worked for a few days then became intermittant again
Checked PSC board pump output, and its around 130v
1. is the board faulty outputting 130V, although its the only way it can control pump speed i assume?
2. is a normal grundfos 15/50 pump unable to start turning at 130v, or do i need a "special" pump (although SEGEL, advertise their pulsacoil pumps as grundfos 15/50 s)
3. Should the board output 240v to start pump then reduce to 130v to modulate ?

sorry for all the questions, but i've spent £200 on overheat kit, 2 new heater elements, (only one was open circuit, but may as well change both while at it,) and now this.

Thanks in advance
Bob

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Re: PSC or pump ?

Post  Mike the Boilerman on Tue Dec 15, 2009 2:09 am

Hi Bob,

Sadly your old pump was probably fine. They rarely fail. I suggest you put it back in and sell your new one on eBay! Yes they are a bog standard Grundfos 15/50.

The problem is an intermittently failing DHW sensor. The upper one. Get a new one from SEGEL. I suggest getting two actually, they are rather prone to failure.

Cheers, Mike

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already replaced both sensors

Post  bobtv on Tue Dec 15, 2009 2:23 am

morning Mike, thanks for fast response.

Sorry i forgot to say also fitted both new sensors PHE and DHW, when i fitted elements and retro kit. The old DHW one, when moved cable it showed faulty LEDs on panel, so i changed them both.

It must be the PSC then, ? although LEDs seem to be pulsing correctly.

Is 130v enough to start pump moving ?

Cheers for info Mike,

PS, the next flat i buy with a pulsacoil, i wont touch it, you will have the job to service and commission it....definately,
regards

Bob

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Re: PSC or pump ?

Post  Mike the Boilerman on Tue Dec 15, 2009 2:36 am

Hmmmm it 'could' be the board then. The board usually starts the pump at about 50Vac and slowly ramps up to 220Vac or so after 30 seconsd or so if the water is still not hot enough. If you've got a steady 130Vac all the time a tap is running then yes, board failure.

You can't rely on the LED correctly flagging a faulty sensor though.

Cheers, Mike

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