Atag 3way valve on return!!

[Paul139]

Hi all
In the install manual for Atag condensing system boilers, it says that the 3way valve must be fitted to the return. At present I have an open vented fully pumped system. And the 3way is fitted to the flow as you would expect. So I rang Atag dealer and asked why fit it to the return and I was told it prevented negative pressure and water hammer. When I mentioned this to some plumbers who fit other types of condensing boilers it was a suprise to them too. Any advice would be appreciated.

 

[Jimbob]

i take it they mean to avoid negative pressure inside the boiler then. Where does the pump go then? If thats what the manufacturer recommends, thats what you should do

 

[Paul139]

Just cleared it all up with Atag engineer.......it's only when using the Atag Valve with weather compensating. If you are not using the outside temp monitor or the Atag 3way valve which apparently rattles when positioned on the flow so they now put on the return.

 

[garygas]

If the MI says must be fit to the return then the 3 port must be fit to the return