Kingfisher II to unvented.

[Nic from Berkshire]

Hi,

First post - can anyone help ?

I've got a relatively old Kingfisher II (R.S.50B) that I want to upgrade to a sealed system. The boiler is rated to 3 bar, so should be suitable. I know that I have to get an overheat thermostat, new control thermostat, interrupter body and lead assembly - these are listed in the installation instructions. However, the interrupter lead assembly is now obsolete ! Everything else is available. So the first question is, any suggestions for someone that might have one in stock ?

Next, I'm not completely sure how the overheat thermostat is supposed to work. Is it that the 20mV or so output from the thermocouple is re-routed through the overheat thermostat, and then back to where the thermocouple used to screw into (now filled by the interrupter). Then under an overheat condition, the connection is broken and hence the pilot light is switched off ?

Perhaps there is a different wiring assembly that would fit into the interrupter body ? Any other suggestions (apart from getting a new boiler !) ?

Cheers,

Nic

 

[heatingman]

Correct, it interupts the thermocouple.
Have a good look at side gaskets before pressurising it.
Try HRPC/ Curzon they often have equivalent part numbers.

 

[twgas]

personally wouldnt recommend prssurising boiler of that sort of age
had a pressurised kingfisher a few years ago for ever leaking finally fitted to f&e tank.

 

[corgiman]

I would also check with one of the Potty boys here or call potterton direct and ensure that the KF can be pressurized

Some boilers just cannot be no matter what safety features they may have

 

[doitall]

Installation
The installation must comply with the requirements of BS
6798: 1987 and BS 5449: Pt 1. The British Gas publication
"British Gas Specification for Domestic Wet Central Heating
Systems" should also be consulted.
Safety Valve
A non-adjustable spring-loaded safety valve, preset to operate
at 3 bar (45lbf/in²) shall be used. It must comply with BS 6759:
Pt 1. and include a manual testing device. It shall be
positioned in the flow pipe either horizontally or vertically
upwards and close to the boiler. No shut-off valves are to be
placed between the boiler and the safety valve. The valve
should be installed into a discharge pipe which permits the
safe discharge of steam and hot water such that no hazard to
persons or damage to electrical components is caused.
Pressure Gauge
A pressure gauge incorporating a fill pressure indicator,
covering the range 0 - 4 bar (60 lbf/in²) shall be fitted to the
system. It should be connected to the system, preferably at
the same point as the expansion vessel. Its location should be
visible from the filling point.
Expansion Vessel
A diaphragm type expansion vessel to BS 4814: Pt 1. shall be
fitted close to the inlet side of the pump. The connecting
pipework should not be less than 15mm. Pipework connecting
the expansion vessel should not incorporate valves of any
sort. Methods of supporting the vessel are supplied by the
vessel manufacturer. The nitrogen or air charge pressure of
the expansion vessel shall not be less than the hydrostatic
head, (height of the top point of the system above the
expansion vessel).

To size the expansion vessel it is first necessary to
calculate the volume of water in the system in litres. The
following volumes may be used as a conservative guide to
calculating the system volume.
Boiler Heat Exchanger: 6.5 litres
Small Bore Pipework: 1 litre per kW of system
output
Micro Bore Pipework: 7 litres
Steel Panel Radiators: 8 litres per kW of system output
Low Water Capacity Radiators: 2 litres per kW of System output
Hot Water Cylinder: 2 litres
If the system is extended, the expansion vessel volume
may have to be increased unless provision has been
made for extension. Where a vessel of the calculated size
is not available, the next available larger size should be
used. The boiler flow temperature is controlled at
approximately 82°C.

The vessel size can now be determined from the
information in Table 4 where V = System volume in litres.
Vessel Charge Pressure (bar) 0.5 1.0
Initial System Pressure (bar) 1.0 1.0.
Expansion Vessel Volume (litres) V x 0.11 V x 0.087

 

[corgiman]

Awight Awight calm darn Flash

 

[Agile]

Thats interesting! The safety valve is usually fitted to the return in most combi boilers.

As the proposed pressurised system is to be retrofitted most people would expect it to be fitted by a competent CORGI as it contains safety devices operating on the gas train.

Tony

 

[petit_pablo]

Im interested to know why the OP wants to convert to sealed.

 

[Agile]

Less corrosion, 2-3% more efficient, no heating pipes in loft, no ballvalve and header tank to fail.

Tony

 

[doitall]

The Op may be interested in re-considering his plans, having read through the distructions.

He will need an overheat thermostat kit 907418
Thermocouple interupt 2 types 640846 & 640845
Overheat thermostat Ranco LM7 P9002 404492
Fitting instructions 559109
Screws and fittings 206764
Pump over-run

And a different Gas control valve, but not sure if its included in the kit.

Several other bits and bobs

 

[giblets]

Surely if the interupter lead is now obsolete then the conversion cannot be carried out as only that part would have been type-approved by Potterton. You would not be able to fit a different wiring assembly without written agreement to do so from Potterton as you would be affecting the safety of the appliance.

 

[doitall]

Surely if the interupter lead is now obsolete then the conversion cannot be carried out as only that part would have been type-approved by Potterton. You would not be able to fit a different wiring assembly without written agreement to do so from Potterton as you would be affecting the safety of the appliance.

The lead can only be a series of wires, and nothing special that I can think off.

Getting the new Boiler thermostat and gas valve would be the hardest part I would have though

 

[Gasguru]

I recently came across a Kingfisher RS50 (not a Kingfisher II).

Was the overheat stat on the flow an approved aftermarket kit? since potterton overheat kits are not listed as ever being a spare. It is just in series with the main stat. The boiler was on a sealed system.

 

[doitall]

No it's different Gasguru.

it has a separate phile which goes into the water way pocket.

See the part numbers I posted.

 

[Gasguru]

Yes those parts numbers are for the Kingfisher II but I wonder if Potterton came up with a simpler solution or whether the flow stat in the image was in fact an "illegal" aftermarket product. Corgi advise no overheat stat on sealed systems is only NCS provided PRV fitted.