Matt540 Posted January 3, 2023 Share Posted January 3, 2023 Just watching this video and noticed he says he doesn’t fit a circulating pump to the ufh manifold and runs it direct from the heat pump? is this common practice? Just about to start first fix on my build and wondering if I should be doing away with the pump and blending valve and run the pipes directly into the manifold? Link to comment Share on other sites More sharing options...
ProDave Posted January 3, 2023 Share Posted January 3, 2023 Most on here including me would advise keeping the manifold pump and blending valve. I did wire a system with a Grant ASHP earlier this year where they only used the single pump in the ASHP but I don't know how that worked out in practice. 1 Link to comment Share on other sites More sharing options...
JohnMo Posted January 3, 2023 Share Posted January 3, 2023 Things you need to do or be aware of from what I have seen and read in various manufacturers manuals The minimum open volume of water in the "always open" part of system has to exceed the heat pump manufacturers minimum volume requirements. For example Grant state 30L. So preferably one zone? Noticed in the video reference he installed a buffer as a volumiser. Flow rate through the system has to meet or exceed manufacturer min flow rate and not exceed any defined max flow rate. You may need an alternative to a mixer valve to ensure any supply flow temperature exertion doesn't expose the floor to excessive temperature, such as going from DHW cylinder heating to UFH heating duty. Short periods may be ok depending floor makeup etc. I do notice with my mixer the flow temp from the boiler is always a few degrees hotter than the manifold, due mixing. So this would affect CoP. 1 Link to comment Share on other sites More sharing options...
Matt540 Posted January 4, 2023 Author Share Posted January 4, 2023 Thanks guys. Follow up question to this is does the manifold pump generally run off some kind of relay controlled by the ashp to enable at appropriate times or is it on 24/7? Link to comment Share on other sites More sharing options...
PeterW Posted January 4, 2023 Share Posted January 4, 2023 10 hours ago, Matt540 said: is this common practice? Just about to start first fix on my build and wondering if I should be doing away with the pump and blending valve and run the pipes directly into the manifold? No it’s a crap practise that causes more problems than it solves for the sake of £200 for a blender and pump. It gets even worse when the ASHP circulator is a PMW controlled one so the flow rates aren’t constant into the loops so balancing and setup is a complete #€%$£* of a job. The manifold pump and actuators are controlled by the wiring centre / thermostats that then in turn call the heat source. Link to comment Share on other sites More sharing options...
PeterW Posted January 4, 2023 Share Posted January 4, 2023 10 hours ago, Matt540 said: Just watching this video and noticed he says he doesn’t fit a circulating pump BTW I wouldn’t count his videos as a decent source of info.. in one he says you don’t need mag filters in heating systems … which is interesting given it’s a manufacturer requirement to meet the warranty of one of the brands of boiler he fits … Link to comment Share on other sites More sharing options...
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