Solid fuel backboiler - drilling?

[maintain2let]

We have a customer with a solid fuel (coal) fire and old fashioned back-boiler behind it. We are fitting a new combi system but the customer wants to keep the fire. Obviously the BBU needs to be safe and I have heard of them being 'drilled' to make sure there is no pressure build up inside when the fire is lit.
I am thinking if the flow and return are left uncapped this can't happen anyway?

Has anyone had any experience of this?

 

[Gray0689]

If you leave F&R uncapped that's ok but will put out a lot of steam better to drill then no water in system

 

[maintain2let]

Thanks for that, where abouts would you drill through to hit the heat exchanger?

 

[Gray0689]

Just drill a few holes in front of boiler

 

[Danny100uk]

Yeah I would drill it as well but i would suggest leaving it a little while before lighting fire to allow water to dry up so no water in them also lag or remove pipework near boiler that can be touched as it may get really hot.