blankton Posted Monday at 22:33 Share Posted Monday at 22:33 Hi All. Following a slightly embarrassing issue with a non-return valve, I've got my ASHP up and running. To commission it I've just set it up like a standard S plan heating system on a boiler, with the room stat and DHW stats being effectively on/off switches, controlling the call for heat at the heating and DHW terminals on the heat pump. However, I am aware that I have the potential for some extra goodies on this system. DHW immersion. I think the primary "excuse" for this is legionella, but I'm thinking it might be more useful as a back up in case of breakdown. The heat pump PCB has 2 terminals for "backup DHW immersion", but the installation manual gives no further info on these terminals. I assume I would need to use a relay and not pull 3kw through the PCB. but there is no info on control of the immersion (its a Grant Aerona 6KW BTW). I'm thinking I might take the DHW immersion out of the ASHP equation and just fit a normal timer with "boost" button. This seems a better idea as a backup, as it can be used even if the ASHP PCB is nuked. Buffer tank immersion. I brought a new second hand grant buffer tank (50L) from ebay and it came with an immersion. I'm thinking of at least running wiring for this. Has anyone ever used one as backup to run the UFH? I'm not sure it could keep up, but it would probably be able to run one floor. If anyone has done this, how? If the ASHP was totally kaput (including pump), I'd need to also include an inline pump. I was also wondering if this immersion might be useful to give a "boost" to the heating in very cold weather. Obviously it might not be very economical, but for the handful of very cold days maybe it would be useful. The installation manual seems to allude to this by saying the following "A ‘Volumiser’ tank is simply a vessel used to increase the volume of the system, to meet the system requirements as given below. It will have only two connections, one inlet and one outlet, and it must be fitted in the flow from the heat pump if the volumiser contains an immersion element that is to be used as a supplementary heater. " but other than this paragraph, there is no further information of how to go about this. I could wire it up separately (as I am planning on doing for the DHW immersion), but it would seem better to me if the ASHP knew it was there, so it could call it up if it was going to ice up or otherwise struggling. Any thoughts on this? Final thing is that the ASHP PCB has terminals for DHW and buffer temp probes. At present the DHW stat is just a binary on/off switch, connected to the programmer and general S plan heating controls. I am assuming these terminals on the PCB would take a thermocouple output and therefore allow the ASHP to see the actual temperatures at this point in the system. Have I understood this correctly (again there is not much info in the installation manual). Is there some advantage to the ASHP being able to see the actual cylinder temp, rather than just seeing a "call for heat", but not knowing how far it has to go? Thanks in advance if anyone has any thought on any of the above. I'm currently sealing up any insulation gaps before boarding, so if any more wires want running, now is the time for me to do it. Link to comment Share on other sites More sharing options...
sharpener Posted Monday at 23:00 Share Posted Monday at 23:00 The Grant HPs are re-branded Chofu and IIRC the Chofu manuals online contain rather more detail. Not sure the temp sensors will be thermocouples, IME most seem to be negative coefficient thermistors (Vaillant, Vokera, Viessman). Yours may be different as Grant begins with G not V of course. 1 Link to comment Share on other sites More sharing options...
ReedRichards Posted Tuesday at 14:01 Share Posted Tuesday at 14:01 As originally wired, my heat pump had sole control of the immersion heater. This meant that when my heat pump broke down (a filter blocked very soon after it was installed) then I could not use my immersion heater. I got it rewired to fix that problem; don't fall into the same trap. 1 Link to comment Share on other sites More sharing options...
PhilT Posted Tuesday at 14:11 Share Posted Tuesday at 14:11 15 hours ago, blankton said: I'm thinking I might take the DHW immersion out of the ASHP equation and just fit a normal timer with "boost" button. This is how mine works - completely separate from heat pump and controls. I never use it though😬 2 Link to comment Share on other sites More sharing options...
Marvin Posted Tuesday at 14:17 Share Posted Tuesday at 14:17 We have a buffer tank emersion heater as a back up because we have no gas no oil and no wood burner. Its on a manual switch.... 1 Link to comment Share on other sites More sharing options...
blankton Posted Tuesday at 16:50 Author Share Posted Tuesday at 16:50 17 hours ago, sharpener said: The Grant HPs are re-branded Chofu and IIRC the Chofu manuals online contain rather more detail. Not sure the temp sensors will be thermocouples, IME most seem to be negative coefficient thermistors (Vaillant, Vokera, Viessman). Yours may be different as Grant begins with G not V of course. Thanks. I've found the manual online. Seems similar to the Grant one, except the Grant one has had some sections removed! I'll have to have a better read when back at my pc. Link to comment Share on other sites More sharing options...
blankton Posted Tuesday at 16:52 Author Share Posted Tuesday at 16:52 2 hours ago, Marvin said: We have a buffer tank emersion heater as a back up because we have no gas no oil and no wood burner. Its on a manual switch.... Have you ever used it? How would you circulate the water? A standalone pump, or rely on the ashp to still be pumping? Link to comment Share on other sites More sharing options...
Marvin Posted Tuesday at 17:29 Share Posted Tuesday at 17:29 34 minutes ago, blankton said: Have you ever used it? How would you circulate the water? A standalone pump, or rely on the ashp to still be pumping? I have tested the heater and it works. Never needed to use it. Heating circulation pump runs interdependently. Also immersion heater in hot water tank. Link to comment Share on other sites More sharing options...
Beelbeebub Posted Tuesday at 17:52 Share Posted Tuesday at 17:52 57 minutes ago, blankton said: Thanks. I've found the manual online. Seems similar to the Grant one, except the Grant one has had some sections removed! I'll have to have a better read when back at my pc. The grant/chofu unit is pretty decent and has lots of options. The basic control box is capable but not very installer friendly. Lots of parameters to look up etc. It is perfectly possible to get yourself in a pickle. I believe they have a newer, touch screen, model that has a more user friendly interface. Not tried it though. Link to comment Share on other sites More sharing options...
Dillsue Posted Tuesday at 18:33 Share Posted Tuesday at 18:33 If you're considering space heating backup then a fan heater may well give you alot more resilience than an immersion Link to comment Share on other sites More sharing options...
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