DHW runs hot then cold

[Caradon]

I have a problem with an Ideal Mini C24 (47-348-18) natural gas combi boiler. Just moved house so not sure how old.
The central heating is fine but when the DHW is used the boiler ignites, heats the water for about 2 mins, flashes the green control light 4 x per second and cuts out. It then re-ignites and repeats this fault.
I have a reciept from the previous owners that state the DHW heat exchanger was cleaned a couple of months ago and a DHW thermistor fitted.The boiler will work constantly if I turn the DHW control switch down but the water is not hot enough.
Any ideas please?

 

[Rob]

Is this all taps?

Unfortunatley cleaning the DHW HE isnt a long term fix and can, as in your case, only last a few months.

You should have it replaced at least and maybe clean the CH system as this is whats caused the fault.

good boiler though!

 

[corgiman]

YAY

finally someone who agress with me about cleaning plated heat exchangers

 

[Caradon]

Thanks for your reply. Yes this is all the taps.
The DHW pressure from the taps is excellent, would this be the case if the heat exchanger was blocked?

 

[corgiman]

Thanks for your reply. Yes this is all the taps.
The DHW pressure from the taps is excellent, would this be the case if the heat exchanger was blocked?

there are two sides to the heat exchanger

1 where the mains water goes through and the other where the central heating water goes through, is the central heating side that is partially blocked

this causes the water to heat up too high and then a thermister tells the boiler to turn off

viola intermittent hot water

 

[nickso]

viola intermittent hot water

i wasnt aware that a viola produced hot water.....intermittant or not

 

[gas4you]

viola intermittent hot water

i wasnt aware that a viola produced hot water.....intermittant or not

Corgi just stringing us all along again

 

[corgiman]

viola intermittent hot water

i wasnt aware that a viola produced hot water.....intermittant or not

Corgi just stringing us all along again

Mange Tout Gas and rob Mange tout

 

[gas4you]

YAY

finally someone who agress with me about cleaning plated heat exchangers

I always have agreed corgi. Never cleaned one out, always replace

 

[Caradon]

I will replace the DHW heat exchanger.
Many thanks for your help.

 

[corgiman]

YAY

finally someone who agress with me about cleaning plated heat exchangers

I always have agreed corgi. Never cleaned one out, always replace

YAY two

a manage et tois rodney

 

[simond]

Me too, we never clean em. You can never be sure you've got it all out.

I am rather concerned that Caradon (as in Caradon Ideal, I guess) is not going to clean his system first. Plenty more muck where the last lot came from.

I thought the Mini was a nasty cheapo boiler made in Italy for Caradon with a wobbly case?? Only thing that was good about them was the dimunitive size

 

[Rob]

I thought the Mini was a nasty cheapo boiler made in Italy for Caradon with a wobbly case?? Only thing that was good about them was the dimunitive size

I thought this was a rebadged biasi m90-24s (with slightly thinnner casing)

 

[ChrisR]

It is - identical I believe, possibly Ideal added iso valves. As to whether it's a good boiler or not, I must say they seem pretty reliable. Would you prefer an Ideal Response?

Cleaning 2ndary HX's: I have a customer with an early Turbomax, on a large system which clogs the HX every year. One year she had a new one, which didn't last any longer. Every year I give her the various other options, but acid cleaning it always restores full hw performance. It only takes 30 mins total, so is cost effective.
For some boilers I have a spare cleaned HX, which I can just swap, and clean offsite in a bucket.

 

[Rob]

There is something quite satisfying about succesfully cleaning a plate HE.

Which reminds me im fitting a new one to an excell 80 next week. Anyone done one of these before looked a little more awkward than just a couple of bolts holding it?