Typical boiler output temperature ?

[dal5band]

I have a potterton Kingfisher2 which seems to be overheating. The boiler stat is calibrated 1234 Max and at 3 , the radiators are at 70C (using my wife's meat thermometer !) I have had to turn it back as at max, the bolier was boiling (!!!). What is the typical temperature range ? and Max ? for a boiler output ?

 

[PrenticeBoyofDerry]

82 degrees c max.
What type of system is the boiler heating?

 

[dal5band]

It's a traditional radiators and hot water tank but with variations. The Heating and H/W primaries are separated at the boiler with separate pumps which is a bit unusual. The room stat controls the heating pump. The cylider stat controls a 2 port valve and the h/w pump. It was installed back in 1975, but boiler and pumps replaced about 10 years ago, just before the condensing boiler regs came in. Just to confuse it a bit more, the two bathroom radiators are gravity fed with a take off before the pumps which I think is also the expansion pipe. Don't know where the returns go but works fine.

The only thing I can think of is that the boiler stat is failiing as things seem very hot, but it is working at 70C at setting 3 now.