Problems with Thorn Apollo 30/50 ???

Hi,

Have a Thorn Apollo 30/50 conventional boiler piped in a Y plan configuration controlled by a Honeywell ST6400C programmer with a Honeywell V4073A mid position valve. Firstly my high temp stat is dead, i know this because if i let it run on central heating only it will continue to heat till the safety cuts in and extinguihes the pilot. Therefore for the meantime i'm having to use the "low" stat. I have two probelms with the boiler though and was wondering if anyone can help:

1. Boiler noise when running on central heating only - Have bled,bled and better bled it but boiler makes a bubbling hollow sound as if there\\\'s not enough water in it. Btw the pump is relativly new, makes no difference at different pump speeds. I have opened up the bypass fully but it does not quieten down?, when running "hot water" or both it's fine????

2. Pump overrun feature - Does anyone know how to make this feature work with a 6400C programmer?????

Please help me, i really have had enough of this wretched system!!!!

Cheers

Stu

sounds like you have a few problems but your main one sounds like your heat exchanger is scaled/sludged up and as this has a low water content heat exchanger will cause all sorts of problems as the boiler must be 15-20 years old i would cut your losses and invest in a new condensing model

Oh dear,

Gaz,

Thanks for the reply,

It's had a good innings mind for a 25 year old boiler eh?

Could a condensing model be fitted into the existing flow/return pipework?
It's all done in 8mm microbore to the rads as well, is it worth ripping it all out and going for 10/15mm for a better flow rate? Also, if the boilers that old, 7 out of the 9 rads will be as well.

PS, I suppose it would give me great enjoyment to smash the boiler up with a sledgehammer once it's removed!!!!

personally i would be inclined to go for a heat pack boiler and rads combination you could connect onto existing pipework no probs although i would ditch microbore or at least get it powerflushed properly