Radiant Combi: Central Heating but no Hot Water

ChrisUK · 18 Oct 2008

Hi Guys,
We've got Radiant slimline 24 that has been working fine, but suddenly refuses to heat the hot water. Central heating is fine.
Pressure is at 0.5 bar and manual says set at 1.5 initally, but the system seems to be hard plumbed into the water mains. Can't find any input filters, so am guessing it may be the HW flow sensor?
Anyone know how to test it (is it meant to be open or closed when water flows and is it on/off or variable depending on rate?)
Finally, anyone know of a supplier for a replacement flow sensor?
Cheers Chris..

gas4you · 18 Oct 2008

If this is one of those with the 2 pressure neons, then I think you will have to repressurise the boiler/system. See if it works then and if not post back here.

ChrisUK · 18 Oct 2008

Thanks Dave,
Its actually got three pressure lights that double up with a few more as temp indicatiors.
I'm not clear on how to re-pressurise when the system seems to be permenantly linked to the mains (no valves along the mainfold except for the yellow Gas Supply)
Cheers C..

ChrisUK · 23 Oct 2008

My son has now found a valve to top up the pressure and were back on to 1.5 bar, but still no HW.

So any thoughts on the Flow Sensor or, as somebody has mentioned, a HW/CH diverter valve solenoid / motor??

I'm still trying to source spares and loved the coment from one of the other forums that the Radiant Tech Advisor was off site repairing one of their boilers!

gas4you · 23 Oct 2008

ChrisUK said:
I'm still trying to source spares and loved the coment from one of the other forums that the Radiant Tech Advisor was off site repairing one of their boilers!

Thats because the Radiant helpline is run on contract by a heating company/importer down south.

They do not have a set up in this country as other manufacturers do.

Is the ch working?

ChrisUK · 23 Oct 2008

Yep, CH is doing everything it ever did. Turn up the thermostat and the boiler fires up and rads get hot.

HW, turn on and nothing happens. Not a click, a whirrr, zip!

Hence my Question about the flow sensor and diverter valve.

Could all be academic if I cant get any spares though?

gas4you · 23 Oct 2008

Flow sensor seems more likely to me as the boiler is not apparently recognising the hot taps coming on.

As yet, for the very few Radiants I've seen, I have had no trouble with spares availability, apart from a few extra days wait than normal.

Tim69 · 14 Sep 2011

hi chrisuk, just wondered if you can tell me what you found wrong with the boiler back then as mine has the same fault!

ChrisUK · 27 Jan 2012

Have affected solution for last 12 months by replacing the main PCB.
Went for brand new rather than exchange unit from North London outlet, as they didn't have any stock of old boards to repair (so cost me over £300!)

However, now boiler seems to be on the blink again, (no HW whilst CH is still fine). Also found that pressure keeps dropping off, which naturally inhibits CH too. Can't see any leaks, so I am baffled yet again!

Understandably getting fairly hacked off, especially as nobody that's been round to see it wants to work on it - just the "mechanics hiss" and offer to flog us a new one... and Corgi / Safe wonder why they have such a job stopping people DIYing gas.

Good luck!!

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Radiant Combi: Central Heating but no Hot Water

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