Alpha CB24/28 - CH working fine but minimal hot water

[Leigh-B]

Hi,

I really hope you can help, not sure if i'll be able to fix the problem myself but at least i'll know what to look for when i call out a plumber and hopefully avoid getting ripped off.

Anyway, to the issue itself. The CH seems to be working perfectly, all rads heat up and stay constant. When i turn on the HW tap full flow i get hot water for a few seconds then it starts to run cold. If i slow down the flow of the HW tap it eventually starts to get hot again (this is how ive managed to run myself a bath!) but as soon as you run it faster it goes cold again.

I've read a few posts on here and think it could be a divertor valve or DHW diaphram but if you could confirm that for me it would be appreciated, and any ideas on how much this should cost me to get repaired if possible?

Many thanks in advance

Edit - Just wanted to add that all the lights on the boiler appear to be operating normal. B light flashes once every 5 seconds, and remains on when the boiler is in operation.

 

[Gasguru]

Hi,


Anyway, to the issue itself. The CH seems to be working perfectly, all rads heat up and stay constant. When i turn on the HW tap full flow i get hot water for a few seconds then it starts to run cold. If i slow down the flow of the HW tap it eventually starts to get hot again (this is how ive managed to run myself a bath!) but as soon as you run it faster it goes cold again.

Is the hot water demand with the heating still on - if so sounds like the diaphragm. Some will just change the diaphragm, others will swap the whole diverter. Just the genuine diaphragm kit is around £30 (from memory) and perhaps an hours work + travel.


Do a search, this topic has been covered many times or wait for Dan's response he's the pro on this model.

 

[Agile]

We charge a total fixed price of £106 inclusive including a basic service in the London area if that helps.

I never understand why people always expect they will be ripped off.

A much bigger rip off are the speed cameras which aim to raise money rather than increase road safety.

Tony

 

[DARTHVADER]

I had this problem a few years ago in my girlfriends flat and I replaced the diapragham rubber seal inside the casing of the divertor valve. The rubber was split and hence not pushing the actuator which activates the microswitch, which send a signal to the control panels asking for hot water.

The rubber diapragham memory serving correctly was under a £10.00. the labour was free, the job was easy and the reward was...ahem....great!!!!

 

[Leigh-B]

Is the hot water demand with the heating still on - if so sounds like the diaphragm.

Yes it is, sorry i forgot to mention that. If i turn the boiler to HW only it does exactly the same.

One thing ive noticed that might be worth mentioning is that i can hear a noise coming from the actual Gas Meter. I have one of those pre-pay machines (if that makes a difference) and i can hear a quite a loud hissing noise coming from it when the boiler is drawing gas. It never used to be that loud, its only started happening today which is also when the boiler started playing up.

Is my undertsanding of a boiler correct in that it works at different pressures when using the HW or CH? For example when you put a HW tap fully on a boiler is working full blast but when the CH is going it works at a lower pressure as it doesnt need to supply the hot water as quickly to the rad's as it does to a tap?

If thats correct maybe thats is why my CH appears to be working fine but it could be a problem elsewhere such as a problem with the actual Gas Meter?

 

[Leigh-B]

The rubber diapragham memory serving correctly was under a £10.00. the labour was free, the job was easy and the reward was...ahem....great!!!!

Well done, thanks for the info! Did you have to do anything like drain the boiler or take something else apart to get to it? If its really simple i may just have a go myself

 

[Leigh-B]

I never understand why people always expect they will be ripped off.

Tony

Thanks for the quote. Perhaps i watch a bit too much Watchdog and Rogue Traders

 

[Rob]

If its really simple i may just have a go myself

Its simple if you know what your doing. ever drained and worked on a boiler before?

 

[Leigh-B]

No never, but im pretty good with things like this, can follow instructions very well, take things apart and rebuild etc.

Draining the boiler must be pretty simple no?

 

[Paul Barker]

The rubber diapragham memory serving correctly was under a £10.00. the labour was free, the job was easy and the reward was...ahem....great!!!!

Well done, thanks for the info! Did you have to do anything like drain the boiler or take something else apart to get to it? If its really simple i may just have a go myself

You have a problem because you have jump cut to an amateurs one experience with a different boiler to yours.

Your family will enjoy good hot water performance sooner if you get someone like tony round. The skill of someone experienced in your particular boiler would definately benefit you in this instance.

Or phone alpha and ask for contact details of an independent service agent near you.

Please don't bother following the diy contributors advice.

 

[Gasguru]

Do a search, this topic has been covered many times or wait for Dan's response he's the pro on this model.

Not wishing to decry the expert advice of Dan; of course I meant Paul, but Henry Westons Vintage does that to you

 

[DARTHVADER]

Hi,

The combi was an Alpha 240p and I'm not exactly an amateur as I trained as an electricain from leaving school for five years, although this is not something I do for a living now. I'm a keen diy'r though, but if you haven't the practical experience then I wouldn't have a go yourself. Memory serving correctly I didn't have to drain the boiler just isolate the incoming cold water and mains electricity supply. I also opened a hot water tap to allow the drain off when I opened the body of the valve divertor. It was an easy job but a little fiddly, but like I said it's what you are comfortable with. You are not dissrupting any of the gas parts either (unless you slip with a tool, so be careful!!) as the divertor is water.

The balls in your court, hope I have been of some help and not upset the guys out there doing it for a living.

 

[Leigh-B]

You have a problem because you have jump cut to an amateurs one experience with a different boiler to yours.

Your family will enjoy good hot water performance sooner if you get someone like tony round. The skill of someone experienced in your particular boiler would definately benefit you in this instance.

Or phone alpha and ask for contact details of an independent service agent near you.

Please don't bother following the diy contributors advice.

I dont really want to get into a political argument over who's advice i should take, all i want to know is what you guys think the problem is, how easy it is to rectify and i will then decide on whether i call out a plumber or not.

If 2 or 3 of you guys say its the same thing then when i call a plumber round i will be more inclined to pay for the items you have mentioned to be fitted. If the so called plumber then tells me i need this or that replaced too then i'll tell him to get on his bike......

If its really simple then i will have a go but if you have to drain the boiler etc etc then i dont think i will be.

All i want is advice guys, not to be involved in an argument...please.

 

[Gasguru]

From memory the CB24 diaphragms are not standard hence the higher price.

The Alpha 240 diaprhragm swap can be done blindfold, the CB24 is far more difficult; get some one in.

Lately there appears to have been an increase in "missinformation" by some too eager to post suggestions on boilers/systems they have no knowledge on.

 

[Rob]

Unfortunatley darthvader was referring to a different boiler.

Yours unfortunatley is alot more difficult and like Gasguru said can take up to an hour depending on who you get. Im sure PB has it done in 15 mins.

Worth getting someone in and if you tell them the fault you dont pay for diagnoses time and should cost no more than £120.