DHW not kicking boiler into life

[nopy99]

Hi,

I have a Potterton 24i and lately it has developed an annoying habbit.
My kitchen tap, when fully open, does not seem to kick the DHW into action. the boiler takes no action and just sits there. Every now and again it kicks in. I do not have this problem in the bathroom however have to open the tap fully to get the boiler to kick in. It seems as if the boiler is not registering a call for heat when taps are partially opened. It may be worth noting that the kitchen tap has a poor flow rate.

Do I have a faulty DHW detection valve? the boiler has been in for a year and we have never had this problem before.

Any suggestions/advice will be most welcome

 

[chrishutt]

Do I have a faulty DHW detection valve?

Yes. It may be a flow switch or a diaphragm and is usually (don't know this boiler) fairly straighforward to replace.

 

[gas4you]

May be an inlet filter blocked.

If its a Gold combi you should have a 3 year warranty on it, as long as you had it serviced after 12 months

 

[baxpoti]

Part No. 248734 req'd if it's an instant (preheat)

 

[nopy99]

Yes its the preheat version but i dont think it is a "gold". I will check the receipts and the benchmark book as I think it may still be under its warranty. To be honest im a bit peeved that its conking out so soon.

Thanks for all the advice.

How much should i be paying for labour to replace this part. I am within the confines of the M25.

 

[Agile]

I am assuming that part number is for the electrical switch. It would be unusual for the diaphragm to fail after such a short time.

We have to charge a fixed repair charge of £84 which includes a service and fully checking the boiler performance.

Replacing that switch is not quite so simple because it included half the wiring loom. It could have been made easier with a plug and socket.

Some people make it quicker by cutting the wires and using a choc block.

Tony

 

[weareleeds]

Have you considered that the kitchen tap may be faulty does it only dribble out (you will need approx 9 litres pre min which is a litre jug in about 6 secs)

 

[baxpoti]

Min Working
DHW Flow Rate 2.5 l/min

248734 is the dhw differential on the front of the pressure differential assembly

248838 is just the Diaphram - DHW/DIFF - Instant

 

[Agile]

248734 is the dhw differential

I think thats baxi speak for the microswitch and half the wiring loom!

 

[baxpoti]

It's the hydraulic part! (the wet bit)

 

[nopy99]

Yeap,

Had a look in the manual and saw that the minimum operating DHW flow rate is 2.5 litres per minute. Done a test already and the kitcken tap (hot side only no other taps in the house open) managed to fill a 2 litre bottle in about 40 seconds. This satisfies the minimum flow rate listed in the book although its abit close to the tolorence.

Checked the Benchmark logbook and the warranty is still valid, however BAXI want a proof of purchase as the instaler did not register the boiler (or tell me to regsiter it...GRRRRR). Need to have a dig around for the invoice now. I would have though that the Benchmark logbook would have been sufficient for Baxi.

I dont think it would be the microswitch as th eboiler does register a call for heat from the bathroom taps. I rekon its the diagphram not actuating at low flow rates far enough to "click" the microswitch.



Thanks to all the replies, im convinced its the DHW flow detector/diagphram. Anyway, Will let the forum know when/if heateam come around to fix it and what the diagnosis is.

 

[nopy99]

PROBLEM SOLVED FOR FREE!!!

thought the tap filter may be blocked so I took out the little gauze that sits in the mouth of the tap and it was furred up with limescale really badly. Tried the tap without the gauze (stream straigtner) and boiler kicked in straight away even on a very low tap open setting.

Anyway, I have defurred the gauze and its a-ok now. I will be doing the same on the bathroom tap as im guessing that may be furring up as well.

As mentioned earlier, we live i a hard water area. Is all this limescale going to destroy the heat exchanger? should i look to putting a water softner in place?