@iancalderbank - unfortunately there's only a flow rate shown on the bottom right pipe from LLH which is showing the low rate (it's after the Mag one filter).
I can't see an input rate as it were, but could be that's an issue - it seems to ring true with what we're experiencing. The house never seems to get above a plateau of temperature. And I can't think undersizing etc could be an issue as areas of underfloor heating are just not getting it either. I'm almost tempted to have it so upstairs and down close for a while and see if the underfloor area ever goes above 20-20.5C. I suspect not as literally the temperature coming into it is a limiting factor.
In good news the plumber has used those photos to send to Grant to see if that enlightens them somehow.
@crimson when you say "a flow rate shown on the bottom right pipe". that must be the cold return to the HP . so that would imply there IS a flow rate problem on the primary side.
the flow rate on the top right and bottom right will be identical. one goes to the HP (bottom), one comes back from HP (top). same water, no branches or exits.
what "thing on the bottom right pipe" is showing you that "low flow rate" ?
what exact type of filter is installed? as they can themselves restrict flow if underspecced.
@derek-m Hi Derek - it definitely opens, have tried putting into manual and still zone doesn't hit temp.
@iancalderbank - I've set up those temp probes - albeit with no pipe insulation currently. Photos attached. This is when down and up are still demanding heat
I fully agree with Ian's assessment that the primary flowrate from the heat pump is inadequate.
I would suggest that you check all the valves on the flow and return pipework, from and to the heat pump, to see if any are partially closed. Also check if any filters are partially blocked and if possible check that the water pump is functioning correctly.
Also check if there is a bypass valve between the flow and return pipes that may be passing.
@crimson I've just been back through the thread and found your close up photos of the "flow thing" and the mag filter. Good and Bad news I'm afraid. Bad - there's a broken thing. Good - its obvious what it is.
1. Mag filter : I think you have a 28mm pipework. Grants own specifications for the mag one suggests that a single filter can support a maximum of 10kw at DT5. For a greater output, they require two filters in parallel. (or, most people would install a single, better designed filter with lower pressure loss. They exist).
actually I think their numbers of saying it supports 10kw at DT5 are optimistic because looking at the pressure loss chart on page 6 of that doc, pressure losses are in the range of 3 to 5 m of head at the flow rates we'd need for that . That is appalling system design to burn that much head just in the filter. Its taking almost all the available pump head and leaving none left to actually move water. Slow flow rate here we go.
2. "flow thing". thats not a flow measuring devices. Its a flow restrictor. That has no place in a heating system like this, in particular one that is having flow rate problems!!! This should be obvious (maybe not to you, but to your installer). temporarily, you can see if there is any adjustment on the "restriction" that can be wound out as far as possible. But , it need to come out. It itself is slowing the flow down.
summary:
get rid of the flow restrictor - it is not needed and is actually making it worse
get a better mag filter with a lower head loss. the one you have is awful.
On this, a few pages back (apologies I'm doing this when I can around work and losing track now we're in the 7 page mark) - someone mentioned check the flow setting on the ASHP itself. It should be defaulted to 3. Is there a way of checking that? Just thinking process of elimination atm
I've sent this all on - apparently Grant have suggested (not sure if before all this or based just on the temp reading photos earlier) - that the internal pump is turned down - surely that's going to reduce flow even more? Or am I totally misunderstanding that
Thanks ever so much for your help on this. Will see what this other plumber says, who they're sending out. Just totally not understanding the suggestions from Grant. It concerns me they've not reviewed what's on the system, and the fact that as you've pointed out their own documentation refers to using 2 Mag Ones - even if they are not great, surely they should be checking what's in the system before trying things ASHP side. He does refer to "Grant has asked that the units internal pump is turned down", what that means I don't know.
@crimson the internal pump may have been turned down also. but the primary side is badly implemented , has low flow, and will never work properly with that high head loss filter, the temperature numbers you have prove it. If heacol was called in he'd rip those components straight out.
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