Not been about for a while - it's been a bit of a year - but getting back into my project now and the next step is to connect up the water underfloor heating in the extension into my existing heating system.

 

I believe the existing system is S-plan fully pumped open vented, with a couple of anomalies / issues:

• The pump is on the return, rather than flow - I understand this was common in the past.
• The system was extended when previous owners extended into the loft. The upstairs radiators are teed directly into the rising vent pipe, with no motorised valve - so even if running hot water only, the flow also goes upstairs. We've worked around this by turning the TRVs fully off upstairs in the summer, but it's not ideal...
• The heating 2-port valve has now failed (stuck part-open). The pump and both 2-port valves are buried behind / below the tank and almost impossible to access for maintenance. I'd basically have to remove the water tank to be able to work on / replace the failed valve.

 

So as part of connecting in the UFH, I want to take the opportunity to fix / reconfigure the existing pipework in the airing cupboard. I'd like to fit a magnetic filter, and relocate the pump & valves so that they're accessible in future. 

 

I've attached a rough drawing of the current setup and what I'm thinking of doing. For clarity, the boiler itself isn't in the airing cupboard - it's a Baxi Bermuda gas back boiler, mounted in the wall the cupboard backs onto. In future, we plan to get the boiler replaced / potentially move to an ASHP - but that is a whole other project that I can't start thinking about (it has a lot of knock-ons) until the extension is finished. So I'm looking to do enough now to be able to connect in the UFH and keep the system running in the short-to-medium term, I can cope with it not being a perfect solution.

 

Any advice / comments would be very much appreciated!

 

 

 

Moving the pump and valves somewhere accessible is the right call. That will pay for itself the first time anything fails. Fit the magnetic filter on the return just before the boiler. Give the UFH its own zone valve with a blending valve so it can run at its lower temperature without dragging the radiator circuit down with it.

Must admit I hate S and Y plan as all it does is add inefficiency as you have to run one flow temperature. Not a fan of zones either, and you are creating 3. But you boiler is pretty old I take it being a back boiler.

Circulation pump and heating system doesn't care if pump is on flow or return so either is fine, making it accessable is best.

Why I don't like zones, you are generating areas of no flow for the boiler, it then has nowhere to dump it's heat, so if one zone is only open you drive the boiler into an inefficient zone, where it switches on and off a lot, rather than settling into a slow steady run mode.

You have said you have TRV on radiators so they will look after room temps, so why not a single thermostat in the hall to demand heat or switch it off, then have one 2 port for all CH and one for DHW heating. Less to go wrong less to buy, less to install and happier boiler