i have a combi boiler the rads work fine really hot. but the hot water only gets warm the boiler fires up fine also when the heating has been on a while the hot water is hot. but if u just use the hot water with out the heating it only gets warm does anyone know what the problem could be its a sime frendly format 80

iain, March 2009

I had the same situation couple of years back. Changed the diaphram and all is ok untill now,so went and got another diaphram.

Rajan Patel, April 2009

Without knowing this boiler very well, it sounds like the diverter valve is not functioning correctly. Most combi boilers have a valve which cuts off the heating circuit and then sends the flow through a heat exchanger that heats the incoming cold water. If the valve is unable to close off the heating circuit when hot water is called for, then the boiler is trying to heat both the incoming cold water and the heating water, when the rads are hot, you will get hot water, when cold, you will get slightly warmed hot water. Need to investigate the diverter valve and its actuator

Jason, March 2009