3 port valve or 2 x 2 port valves?

Question

i'm designing a new central heating system and i'm confussed as to the difference between a single 3 port valve and 2, 2 port valves do they both do the same job or is one better then the other?

Answer 1

Always use two (2 port) zone valves, much more reliable and simpler than either 2 way or mid position valves.

Answer 2

You use a 3 port valve as a diverter. The water is directed to the central heating, the hot water or part to each. You can do the same job with 2 x 2 port valves and it makes the pipework easier. However,since it is possible for both valves to be closed at once, you need a bypass to protect the boiler and more careful planning with the controls.

Answer 3

old know all is correct although if you have more than 10 rads on your system its better to use the 2 seperate valves which is called an s plan , the other with the 3 port valve is a y plan what ever way you decide the more control you have the more efficient and cheaper to run it will be .

Answer 4

I always fit Sunvic two port motorized valves, these are driven open and driven closed.
They are more reliable than valves that are held open against the spring that is trying to close them.
Spring closed valves are live the whole time they are open, this can mean they burn out - they also use more electricity!
Motor open/motor closed valves only use enough electricity to open or close, no more, no matter how long they are open.