Chaffoteax Celtic FF. Still going strong apart from hot wate

[tryitandsee]

Chaffoteax Celtic FF Combi.
Problem - Hot water flow rate has to be 'choked' all the time to get a hot flow.

As this boiler seems to just keep on going, I'm reluctant to replace it at the moment.

I have replaced the main heat exchanger with replacement spare. Fired up the boiler and no discernable difference with hot water flow rate. Still disappointed with result.

Took all pipe work apart around the flexible hose connecting pump and got rid of quite allot of black sludge etc. Started to think I was getting somewhere. Put it all back together again, same disappointing flow rate.

In desperation I have taken the secondary heat exchanger out from the boiler and brought it home with me tonight to try and descale it.

Can this be done successfully?

On first flush under the kitchen tap, clean and seems ok.
Then tried caustic soda (that's all I had in the house) more black crud, then I tried lime scale remover, all now running clear.

When I put it all back together tomorrow is there any other part that needs cleaning that I have missed.

Rads get really hot, but this hot water flow rate is so slow.

These boilers are so basic, I quite enjoy taking the bits apart to see if I can repair it, sad I know............

Any comments much appreciated.

 

[kevplumb]

brave man

make sure you clean BOTH sides of the h/ex whilst it's off

might be worth giving the diverter valve a dose of looking at if you have it drained anyway
worth changing the diaphram and the water governor as well

 

[pannierstan]

Dont forget they have a water throttle on the front of the D/V

When you say crap flow rate. What IS the flowrate

A. From the cold tap
B. From the hot tap

Chaffs will only do about 8 l/min even when top notch if you want 60 deg at the tap.

Have you checked gas pressures and gas rate??

Stan

 

[tryitandsee]

kevplumb, good idea, will overhaul diverter valve whilst drained down.

Stan, fantastic flow rate from cold taps and good flow rate from hot tap when water throttle fully open. When throttle fully open, no better that warm at most. I just seem to remember it getting hotter, flowing at mid throttle position.

You are probably right in that the chaff is doing what it can, which is 8L/min, which seems so painfully slow when running a bath full.
It's probably past it's prime.
Cheers for the reply.

 

[kevplumb]

if it's still working now fella yev got a good un look after it

 

[pannierstan]

If the gas pressure is dropping high/low and not high/off then its getting as hot as it can.
The DHW stat is in the outlet pipe and this controls the low rate solenoid.

Best thing to do is check temperature of boiler flow on right as opposed to tap water temperature.
You could do with a proper sensor but the temp guage on the boiler(if its still working) will give you some idea and a thermometer under the tap will do that bit.
If you have more than 15-20deg difference between the 2 then the calorifier is not transfering heat due to sludge scale or both.
You might be lucky to push 9 l/min at 55-60 deg if its brand new especially at this time of year when in coming main is only 5 deg.

Stan

 

[tryitandsee]

Just to let you know, fitted the secondary heat exchanger after descaling with caustic soda and fernox lime remover in kitchen sink. (boss not to happy with that) and bingo, hot water flowing a treat, no noisy kettling and no burner cutting out when throttle shut for minimum flow.

Lost all my finger prints in the process, hands now resemble dried walnuts....but what the hell, it was worth it.

I really thought it wouldn't have made such a difference. There really wasn't that much lime build up, but what little there was is now gone, making it as good as new.

By leaving it soaking in a strong concentrate over night appears to have worked. I wonder if flushing insitu would have had the same results. I suspect you would not get the same strength solution flowing round.

The point at which scale forms would be really only the heat exchangers (excessive heat etc.) and I think that the pipe work is a bit of a red herring.

I will soak all heat exchangers next time!