sharpener Posted January 27 Share Posted January 27 1 hour ago, Beelbeebub said: Given you have an (oil?) boiler backup - you could use that for the few very cold periods when you estimate it's cheaper to run or the HP struggles. AIUI @M0rtimer had an end-of-life oil boiler which was scrapped, there is provision to add a boiler if req but none in place ATM. 1 hour ago, HughF said: Midea wont be installed with a buffer. Plate or LLH depending on the year of install. LLH also allows mixing leading to increase in entropy and loss of efficiency hence poorer CoP. I thought @HughFyou said the PHX was ?only for warranty reasons when installed with a boiler. The unnecessary extra ?5deg temp drop will especially be a problem when trying to heat the HW given the high demand of 4 ppl going out for the evening. 270 sq m of UFH would I have thought be enough to provide defrost energy with a totally straightforward schematic, 100% of flow to heating or DHW. No buffer, no LLH, no PHX, no secondary pumps. Get rid of all that and you won't need any provision for a backup boiler because the HP will run so much better! 1 Link to comment Share on other sites More sharing options...
Beelbeebub Posted January 27 Share Posted January 27 Is the heat exchanger also being used to isolate a glycol circuit for the HP? Link to comment Share on other sites More sharing options...
HughF Posted January 27 Share Posted January 27 (edited) Midea are supplied by freedom, freedom will have insisted on either PHX or LLH on all installs depending on year of install. They also run with external ‘stat and weather comp set to 55@-2 (if radiators) or 45@-2 (if UFH)…. This is all well documented in numerous YouTube videos by GH, by the tech docs floating around online, and by evidence of installs over on Mars’ ‘renewable heating hub’ forums. Lots of unhappy Midea owners over there. Edited January 27 by HughF Link to comment Share on other sites More sharing options...
HughF Posted January 27 Share Posted January 27 57 minutes ago, Beelbeebub said: Is the heat exchanger also being used to isolate a glycol circuit for the HP? Not as far as I recall, it’s purely on the heating side of the 3 port… Link to comment Share on other sites More sharing options...
sharpener Posted January 27 Share Posted January 27 5 minutes ago, HughF said: Midea are supplied by freedom, freedom will have insisted on either PHX or LLH on all installs depending on year of install. Since Good Energy quoted for fitting a Midea HP I have out of interest read the manual you posted. What is so different about them that makes this necessary? I know Grant are also keen on LLHs but their installation methods are a bit odd in other respects too. What rationale have Freedom provided for their insistence on LLH or PHX, and which way has it gone over time? Yes a PHX will keep gunge from old radiators out of the HP but a LLH won't even do that. And unlike a buffer or volumiser neither will provide any extra stored energy for defrosting. Link to comment Share on other sites More sharing options...
Beelbeebub Posted January 27 Share Posted January 27 1 hour ago, HughF said: Not as far as I recall, it’s purely on the heating side of the 3 port… Is it to protect against any crud in the heating system? Are their units particularly susceptible to dirty water? Most manufacturers seem happy with a good flush and then filters. Link to comment Share on other sites More sharing options...
HughF Posted January 27 Share Posted January 27 1 hour ago, sharpener said: Since Good Energy quoted for fitting a Midea HP I have out of interest read the manual you posted. What is so different about them that makes this necessary? I know Grant are also keen on LLHs but their installation methods are a bit odd in other respects too. What rationale have Freedom provided for their insistence on LLH or PHX, and which way has it gone over time? Yes a PHX will keep gunge from old radiators out of the HP but a LLH won't even do that. And unlike a buffer or volumiser neither will provide any extra stored energy for defrosting. Graham Hendra (he started freedom heatpumps, wrote the toolkit, and has been in the HVAC industry for his whole career) said that the number one issue with the early days of Daikin and Samsung installs (in the mid 2000's) was low flow errors. He decided hydraulic separation was the way to go to avoid all the flow rate issues, especially when everyone had TRVs on their rads. This has stuck.... I believe that now, he (like most of the industry) has come round to the idea of open loop (no hydraulic separation). Link to comment Share on other sites More sharing options...
HughF Posted January 27 Share Posted January 27 1 hour ago, sharpener said: Since Good Energy quoted for fitting a Midea HP I have out of interest read the manual you posted. What is so different about them that makes this necessary? I know Grant are also keen on LLHs but their installation methods are a bit odd in other respects too. What rationale have Freedom provided for their insistence on LLH or PHX, and which way has it gone over time? Yes a PHX will keep gunge from old radiators out of the HP but a LLH won't even do that. And unlike a buffer or volumiser neither will provide any extra stored energy for defrosting. Grant have designed the Aerona3 to be a drop in replacement for an oil boiler running on S-plan. Completely the wrong way to fit a heat pump, but easy for installers. It's a shame as the Chofu unit they rebrand is quite decent. Link to comment Share on other sites More sharing options...
HughF Posted January 27 Share Posted January 27 16 minutes ago, Beelbeebub said: Is it to protect against any crud in the heating system? Are their units particularly susceptible to dirty water? Most manufacturers seem happy with a good flush and then filters. Probably, yes. They are paranoid about low flow errors and subsequent callbacks. Providing separation is an easy way to avoid this. 1 Link to comment Share on other sites More sharing options...
sharpener Posted January 27 Share Posted January 27 48 minutes ago, HughF said: Providing separation is an easy way to avoid this. Yet another instance where avoiding callbacks and so reducing the cost for the installer takes precedence over optimising system efficiency and so reducing running cost for the customer. Link to comment Share on other sites More sharing options...
HughF Posted January 27 Share Posted January 27 17 minutes ago, sharpener said: Yet another instance where avoiding callbacks and so reducing the cost for the installer takes precedence over optimising system efficiency and so reducing running cost for the customer. If electricity wasn't 3.9 times the price of gas, it wouldn't matter. Stupid 'environmental levies'... 1 Link to comment Share on other sites More sharing options...
ReedRichards Posted January 27 Share Posted January 27 (edited) On 26/01/2024 at 11:25, M0rtimer said: Let's compare this with my installation: Annual heating energy (EPC): 15900 kWh Annual hot water energy(EPC): 2987 kWh Heat pump capacity: 12 kW External design temperature: -3.7 C Design Flow temperature: 50 C DHW design temperature: 55 C (max) My annual usage is: 5100 kWh So your heat load is over 25% bigger than mine and your 10 month usage is around 6000 kwH compared to my 5100 kWh in a year; that really doesn't seem too terrible from the economic point of view. And I bet you have room for improvement. The difference is that my system keeps us warm and provides all the hot water we need whereas yours does not. But again I think you will find you have room for improvement. Edited January 27 by ReedRichards 1 Link to comment Share on other sites More sharing options...
JamesPa Posted January 28 Share Posted January 28 (edited) 17 hours ago, sharpener said: Yet another instance where avoiding callbacks and so reducing the cost for the installer takes precedence over optimising system efficiency and so reducing running cost for the customer. It was ever thus. Why do you think most condensing boilers, the advantages of which were much hailed when they first came out, are adjusted when installed so they don't condense most of the time? Edited January 28 by JamesPa Link to comment Share on other sites More sharing options...
JoeBano Posted January 28 Share Posted January 28 Is there a newish study into the effects of short cycling on an inverter driven heat pump short cycling? It’s more a question on my own heat pump. I’ve changed from a 4 port buffer to a 3 port buffer, now I get no temperature loss on the flow, as it stands still getting long run cycles. Link to comment Share on other sites More sharing options...
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