Alpha 280E problem

23 Sep 2009
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United Kingdom
I have a Alpha 280E which, when switched on, produces hot water to the rads even when the selector switch is turned to DHW only, the CH stat is turned to the lowest setting and the heating is turned off on the timeclock!
The boiler continually fires up then stops, then fires up again. This means the house is red hot all the time the boiler is switched on.

The CH neon does not illuminate.

Prior to this happening, we had a problem where the rads got warm when the DHW was called for so taking advice, refurbished the diverting valve which was pretty bunged up.
Now we have this problem.

Both flow switches are energised (rods stick out) when the power is on but the primary flow one de-energises when switched off.

Could it be the main pcb?
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Very unlikely be the PCB.
You state that both the flowswitches are made and that the primary one closes when turned off. That is good.
Does the hot water switch come on and off with a demand for hot water?
I think it may be stuck on which will make your rads get hot.
the push road in the pressure differential valve is sticking keeping the dhw micro swith energised or you have a leak on the domestic hot water pipework
The only rod that moves is the primary flow valve which withdraws when the power is turned off. Neither rods move when the DHW is turned on or off.
I have stripped, cleaned and replaced all the rods using a refurb kit.

If I remove the micro switches I can move the rods manually, however the front one DHW is pretty strong pressure.
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Both flow switches are energised (rods stick out) when the power is on but the primary flow one de-energises when switched off.[/quote

so this statement is wrong :?:
Getting me confused now. I'll try and explain.

Neither rods move at all unless I turn the power off to the boiler when the primary flow valve rod withdraws.
Conversely, when I turn the power on the primary flow valve rod moves out again.

Hope thats clearer.

I'll try removing the green wire when my daughter has unlocked the bathroom door and allowed me in!
When you refurbed the valve did you forget to put the spring back in the differancial pressure switch?
Which differential switch?

Just taken green wire off, CH runs and neon comes on! Does this mean the DHW flow valve is jamming? I can push it in though.
Well you are braver than me. I would never attempt to recon a DV. I always replace with new genuine parts for the very reason that you are getting now.
Is there anywhere I can find an exploded view of the diverter valve?

I've just taken the DHW flow valve off to check it. When I push the plastic, pan shaped thing with a needle in it, (sits inside the diaphragm) back into the diverter valve, there is a very strong resistance behind it.

If I then unscrew and remove the diverter, there is a spring, which is about 70mm in length, which goes down the centre of the diverter valve between the two valve seats. When reassembled, that spring is pretty tensioned and exerts a pressure on the diverter valve seat which, as it is in direct contact, exerts the same pressure on the pan shaped thing needle which in turn pushes against the DHW flow valve / pressure switch, rod.

Or have I reassembled it wrongly?, hence the exploded diagram
I have an idea that you put the spring back in the wrong place in the diverter valve thus causing the pin to be constantly out and operating the DHW demand microswitch.

It should ( I think ) go at the front of the boiler compared with the diaphragm so that it pushes the diaphragm backwards to retract the pin.

When I dismantle these I look at the carefully when I open them and reassemble the same way!

ONCE when I was tired at 2345 hrs I put one in the wrong way on a Worcester 240 ! It did not take me long to work out what was wrong.

Thanks for the reply Tony.

When I dismantled the valve (late at night as it turns out) I had a feeling the long spring went at the front, however, when I reassembled it I could not find anywhere it would fit! It seems to fit perfectly between both diverter valve seats though.

Gonna have another go at it.

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