Baxi Solo 2 heat exchanger

IanL · Feb 27, 2011

I have a Baxi Solo2 60 PF running pumped HW and microbore central heating. The system has got bunged up over the years and I seem to have poor circulation causing short cycling of the boiler and frequent overheating trips. The radiators do not get very warm because the boiler only runs for short periods.

I have replaced the pump which is running on speed 3. The motorised valves have also been replaced as the HW one was failing to close at times.

I have also flushed through all the downstairs radiators and pipes back to the manifold. TRVs have been removed and all new rad valves fitted. I think that this should provide enough of a heat sink to keep the boiler running.

I now think that the heat exchanger may be partially blocked. Would it be feasible to remove the flow and return connections and attempt to backflush the heat exchanger? Even if unsuccessful, at least I would then be fairly sure that it was worth replacing.

Any ideas welcome.

aggis · Feb 27, 2011

The boiler & system will require power flushing, use of strong chemicals. Then prob' a filter fitted after to protect.

IanL · Mar 6, 2011

I was reluctant to use strong chemicals and high pressures in my 30 year old system so attacked it myself.

I ruled out the heat exchanger as a problem as the HW was actually working OK.

I eventually found a complete blockage on the downstairs CH flow 22mm flow pipe. The installer had created a low point and compounded the problem by fitting an elbow here. I cut out this section of pipework and flushed the whole lot through with a hose pipe and managed to clear the upstairs system as well. Spirotech Magnabooster2 fitted.

I now have hot radiators throughout the house and just need to balance the system.

I understand that the design temperature drop across the boiler is 11 degC. I obviously need the by-pass open to allow for boiler shut down without overheating. How do I set up the required flow rate?