DHW Getting Cooler

[xdavid]

Excell 80SP, about 12 years old?

Central heating is good but hot water has been getting gradually cooler over past 6 months or so. At first I just ran the water slower but now it's having to run really slow! At first I thought it was just the winter colder water but, thinking back, it has definitely been getting colder and maybe winter has just made it more noticeable.

I'm thinking maybe Domestic Hot Water Heat Exchanger needs replaced? Or can I 'clean' this first to see if it makes a difference? I've got the service manual so don't mind taking this out to have a look.

Only other thing noticeable is that when the hot water tap is turned off, I get a 'whooshing' noise from the boiler. I'm getting to the paranoid stage so that may be normal and always happened 🙂

Oh... and the pressure gauge drops to zero quite quickly when boiler is off, but returns to normal when running. I'm presuming the expansion vessel needs re-pressurised but just mentioning it here for 'completeness'.

Thanks in advance for any comments!

 

[heating-eng]

Excell 80SP, about 12 years old?

Central heating is good but hot water has been getting gradually cooler over past 6 months or so. At first I just ran the water slower but now it's having to run really slow! At first I thought it was just the winter colder water but, thinking back, it has definitely been getting colder and maybe winter has just made it more noticeable.

I'm thinking maybe Domestic Hot Water Heat Exchanger needs replaced? Or can I 'clean' this first to see if it makes a difference? I've got the service manual so don't mind taking this out to have a look.

Only other thing noticeable is that when the hot water tap is turned off, I get a 'whooshing' noise from the boiler. I'm getting to the paranoid stage so that may be normal and always happened 🙂

Oh... and the pressure gauge drops to zero quite quickly when boiler is off, but returns to normal when running. I'm presuming the expansion vessel needs re-pressurised but just mentioning it here for 'completeness'.

Thanks in advance for any comments!

could be the diaphram

 

[wnjswozo]

most likely divertor,quickist,cheapest,try running hot water only with heating off,then feel heating circs,if they start getting warm,then divertor

 

[xdavid]

Thanks for suggestions!

The diaphragm was replaced 2 years ago - that time the hot water just stopped heating completely and I could see that the activator arm thingy was not moving like it should when water was turned on.

Did the diverter test, thanks, and no warming of heating pipes so I took off the heat exchanger to have a look. Soaked it in rad-flush (for car radiators 🙂) and gave it a good flush out - lots of rusty bits came out and noticeable difference in water throughput after a good clean (tapping on side with a wooden mallet seemed to help too).

Good news - hot water back to normal and running well! Even the 'whooshing' noise has gone so I think that might have been pressure in the primary circuit being released when tap was turned off - must have been really gunged up.

This has demonstrated to me that I need to get the whole system flushed out. I'll post separately with a couple of questions on that.

Really useful forum this! I've learnt a lot just by reading other questions - thanks everyone!