How to connect underfloor heating to a Y plan system

13 Aug 2010
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United Kingdom
Hi, I need some advice/information relating to adding underfloor heating to an existing heating system.
My current system is an open vented, Y plan, with the boiler in the garage and the 3 port valve and pump upstairs in the airing cupboard (the 3 port valve is plumbed on top of the pump). The new underfloor heating manifold has been installed in the garage next to boiler, with 22mm flow and return taken from near top of boiler.

I plan to get the boiler replaced and was thinking of going to an S plan system, with 3 zone valves (DHW, CH and underfloor). My question relates to the positioning of the existing pump. If I simply replace the 3 port valve with two 2ports, then with only the underfloor heating calling for heat, the existing pump will be trying to pump into 2 closed valves - i.e. it's not going to work? So, do I need to move my pump to be next to the boiler, so it can provide flow to any of the 3 zones?
Or alternatively should I go for a system boiler with an integral pump?
Or have I misunderstood how the pump shifts water round the system?
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You've misunderstood, the existing will pump though the UFH zone valve and blending valve when required and you should also be fitting a bypass if req when converting to s-plan anyway

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