gas boiler problem

[Exuptoy]

I was gonna suggest Trace Heating tapes.
Fitted loads over the years. Usually on large pipelines which are then lagged but no reason you couldn't.

https://www.traceheatinguk.co.uk/raychem-hwat-m-heat-trace-cable-9-w-m-at-55-c

 

[Exuptoy]

Bit of an explanation here.

https://www.traceheatinguk.co.uk/traceheating-commercial-hot-water-maintenance-cable

 

[Robotstar5]

We had a cavity wax system in the paintshop at work with trace heating on the pipes between the plant room and the application points, trace heating failed one weekend so we spent the next few hours breaking hundreds of metres of pipe at the joints to rod out the solidified wax