Hi everyone, I'm a first time visitor from England and I'm scratching my head. I have a gas combination heater for my central heating and hot water, but I can't produce any hot water unless the central heating is on, and even then if I turn the hot water tap on too much the boiler cuts out resulting in no hot water. Iwould be most grateful for any advice.
Yours Hopefully.
chris.

 

What kind of COMBO unit??
A lennox completeheat or a polaris?

Both are crap, I hope you have neither.

 

Your system has a two way valve that diverts the boiler water either to heat the home or the water for washing. This valve cannot do both at the same time. Your domestic hot water is on the master valve and your heat for your home is on a slave valve. What this means is, if there is a demand for heat the system will come on to heat the home. The moment there is a demand for hot water, like taking a shower, the valve diverts the boiler water to heat the domestic hot water and the heat of the home is stopped until the demand for hot water ceases. Your description of the problem leads me to believe that your system is not recognizing the demand for hot water. It is probably not the two way valve that diverts the boiler water, rather it's probably the relay switch that recognizes the demand and triggers the two way valve. These relays are very easy to replace and not that expensive.