nice problem for all you plumbers to solve for me, thanks

[sknight]

Have problem with boiler noise.
Potterton Kingfisher II RS60 floor standing.
I done significant checks on the system as follows:
Cleaned system with Fernox super concentrate
Flushed
Bled
Added inhibitor
Flushed
Bled
Cleaned with Sentinel X200
Added inhibitor.
Bled
Gravity HW, pumped CH, TRV on all but 2 RADS, Only thermostat is boiler main stat. Pump is on the return leg next to the boiler.
Symptoms:-
Boiler makes hissing noise when getting to temperature, also clanks and bangs.
This is much worse when CH is on.
When only on HW, the thermostat cuts out just after the boiler starts hissing.
When HW and Ch the boiler makes the clanking banging noises before the thermostat cuts out.

There is no air in the system.
The circulation is very good and pump has been tested on all 3 speeds with no effect on the noise.

All TRVs and lock shields have been opened fully to try and increase flow with no effect.

If I turn down the boiler stat the water temperature does reduce but I still get the noises, although the cycle time becomes much longer.

If the stat is on number 4 and CH and HW are on the boiler starts to make the noises, if I then stop the pump by jamming the impeller the thermostat cuts the boiler out almost immediately. This is as if the HW circuit is at temperature but the CH circuit is still below the thermostat setting.
If the CH circuit is at temperature then thermostat still seems to keep the boiler running longer thus make the load noises as the boiler starts to boil the water.

A couple of questions.
The thermostat tail looks like it goes into the middle of the boiler. What temperature is this measuring, water return of CH, HW or both?

Could the problem be with the thermostat not cutting out at the correct temp? I thought when a thermostat went the boiler would either not cut in or would not cut out.

Or is the boiler at the last stages of its life?
This is a cast iron boiler that is 9 years old.
The system when flushed had no sludge and the water was very clean.
No Rads have black crap.

Any help on this would be very helpful as I have not had much sleep due to the noise.

Thanks

 

[Bahco]

Does your bathroom rad have a TRV on it

 

[kevplumb]

Posted: Wed Dec 22, 2004 10:18 am Post Subject: nice problem for all you plumbers to solve for me, thanks

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Gravity HW, pumped CH, TRV on all but 2 RADS, Only thermostat is boiler main stat. Pump is on the return leg next to the boiler


think there is some mention of it

 

[Bahco]

I will read the posts properly one day

 

[ChrisR]

Potterton Kingfisher II RS60 floor standing.

Well of course it make noises. That means it's working.

Need to clean the boiler better. the Superconcentrate stuff is quite gentle, and the X200, though it normally makes a difference, often doesn't solve it.

Use Fernox DS-40 (citric/malic acids) and/or DS-3(Sulphamic acid) or Kamco FX-2 (phosphoric acid) in a powerflushing machine circulated round the boiler and adjacent pipework, hopefully including the points where the feed/vent are connected though these may be onthe cyl loop.
£50 to hire for a day, and a pita to connect to just your boiler I know. You could circulate it round the whole system but if there are any clogged-up weep points, they will leak afterwards.

Then more money on inhibitor, and "Boiler Silencer" can help. You could try that first as the alternative is obviously unappealing.

 

[sknight]

DS-3 and DS-40 are both acidic cleaners.
I was told to keep away from these as it could cause more leaks.
The system is only 9 years ol and I have had only 2 leaks (touch wood!!)
nail and bad solder joint.
Where would these types of cleaners create leaks if any. Th copper pipe work all looks in goog condition, not sure abour the solder joints, but there have been no leaks from them that I know of.

Thanks