Iffy hot water

[garry81]

I've currently got an old Ravenheat 820/20 RSF which came with the house and it has been fine for the past year.

It has now developed this problem with the hot water. Basically if I switch a hot tap on water will come through and then about a minute later the boiler will fire. A few seconds later it will run cold and then fire again a bit later on.

I have checked the fan is running etc and the boiler works fine for the heating. I'm not sure if it is relevant but the other day loads of crystal like pieces keep coming out of the taps and water basically dribbles out most of the time.

I basically need to know what it is likely to be, if it is likely to be an expensive job to get fixed or should I not chuck any more money at it and get it replaced.

Thanks in advance

Garry

 

[LUNAT]

HI

HW /CH sensors faulty
HW heat ex scaled up
HW diaphragm split/damaged

 

[garry81]

HI

HW /CH sensors faulty
HW heat ex scaled up
HW diaphragm split/damaged

Thanks LUNAT. Are any of these possibilities likely to be expensive to fix or relatively straight forward?

 

[Agile]

What is the chemical composition of these crystals?

Or what is their crystaline shape?

Tony

 

[garry81]

What is the chemical composition of these crystals?

Or what is their crystaline shape?

Tony

I'm not sure to be honest but they look very similar to small pieces of rock salt but clearer and rougher.

These are what stumped me because I haven't seen anything like this before.

 

[Agile]

Do they dissove in water?

Do they tinge a flame with any colour?

What is the effect of heat on them?

What is their hardness rating?

Do they dissolve in any acid?

Tony

 

[ChrisR]

Have you got a device on the cold supply, which might be full of water softening crystals?

 

[garry81]

Thanks for everyones help. It turns out the heat exchanger was furred up so was descalled and it now working like new.

Thanks again.

 

[spacethegas]

advice.
start saving for new boiler.