Why my Maxol 12D gravity feed Gas boiler fails to heat water Information, help and advice on many gas related subjects from gas fires to domestic appliances

[Shri]

I have a 15 year old gravity fed Maxol 12D gas water heater boiler that feeds the indirect heating coil in a cylinder situated upstairs. Over the past 3-4 weeks it has stopped heating the water in the cylinder even though the boiler is firing OK and the input pipe to indirect coil is getting hot but the return from indirect coil remains cold.

I suspect that the indirect coil may have become blocked due to severe scaling ! Can you confirm or give me other solutions to look for.

Thanks

[htg engineer]

It could be an airlock scale build up, you have a few options.

Try to clear airlock
Try descaler (probably wont work)
Convert HW, to pump assisted


htg