Baxi bermuda 50/5 inset issue

[chriz297]

Basically when i have hot water/heating on there own it fires up for a couple of minuets then goes to a red light, will restart it a few times then nothing.

but when i put them both on together it works fine without a problem. Any ideas on what it could be?

 

[Chalked]

Hi.
As this is a gas appliance. It will need the services of a gas safe engineer. It could be something as simple as a pump, air lock or a boiler problem. Without seeing this one it's not easy.
Look on gas safe website and put in your postcode.