SuperPav Posted January 9 Share Posted January 9 I'm after a small ASHP for the garage/workshop as in a great moment of stupidity I didn't lay any pipes from the main house plant room to the garage for the UFH circuit there. Given the location and layout etc. it's easier/cheaper for me to just get a separate small/cheap ASHP just to run the garage/workshop UFH loops directly. I've been searching ebay etc. and have noticed one of these units for very cheap - Dakin Alitherm 4kW hybrid outdoor unit. It looks like a A2W ASHP, it comes with the controller, but can anyone confirm if it would run without the gas boiler part? From all the documentation it seems like it *should* but there's no installation instructions or details on it being installed in such a way (understandably). Otherwise I'll keep my eyes open for another A2W ASHP for a few hundred £££ this year as there's no real rush. thanks! Link to comment Share on other sites More sharing options...
ProDave Posted January 9 Share Posted January 9 Do you have a link to the ebay item? Link to comment Share on other sites More sharing options...
SuperPav Posted January 9 Author Share Posted January 9 I don't - it's on FB marketplace I think so will need to dig it out on my phone, but it was this unit (with this model code) - EJHA04AAV3, along with some flexi hoses and the controller/thermostat unit, https://www.cityplumbing.co.uk/p/daikin-altherma-hybrid-hydrosplit-4kw-heat-pump-outdoor-unit-ejha04aav3/p/478567 and this is the Daikin manual for the hybrid system: https://www.daikin.eu/content/dam/document-library/catalogues/heat/hybrid-heat-pump/ejha-av3/Daikin Altherma H Hybrid_Product catalogue_ECPEN20-731_English.pdf: Link to comment Share on other sites More sharing options...
JohnMo Posted January 9 Share Posted January 9 They do two versions of the hybrid, refrigerant split and monobloc. The monobloc works with another manufacturer gas boiler. And it just tees in, from what I remember. Would think it would work on its own, a little bit of fudging about. Have a good read of the manual and make sure you are buying the correct model. Link to comment Share on other sites More sharing options...
Beelbeebub Posted January 10 Share Posted January 10 The u it you linked to appears to be a monoblock. It specifically mentions a sealed redridgerant circuit and water as the only connection. It doesn't appear to have a pump and thry mention the boiler does so I assume the boiler pump also pumps the hearpump. So at a minimum you would need an external pump. Link to comment Share on other sites More sharing options...
ProDave Posted January 10 Share Posted January 10 Reading that datasheet in the link above, it shows a graph showing how much heat pump and how much gas it uses vc outdoor temperature. Below 0 it uses all gas. If you fudged it and tried to use it without the gas boiler, I expect your first issue is with an outdoor temperature less than 0, it would refuse to work as a heat pump. I would buy the right thing, a proper monoblock heat pump described as that with no mention of hybrid. Link to comment Share on other sites More sharing options...
HughF Posted January 10 Share Posted January 10 Dream do a 3.5kW unit for under £1k Link to comment Share on other sites More sharing options...
JohnMo Posted January 10 Share Posted January 10 2 hours ago, HughF said: Dream do a 3.5kW unit for under £1k Single flow temp for DHW and heating, fixed duty, so you will need a buffer most likely. Link to comment Share on other sites More sharing options...
HughF Posted January 10 Share Posted January 10 6 hours ago, JohnMo said: Single flow temp for DHW and heating, fixed duty, so you will need a buffer most likely. Not for ufh, just set a fixed temp and pump the water round the slab…. Let it defrost from the slab… 1 Link to comment Share on other sites More sharing options...
JohnMo Posted January 10 Share Posted January 10 32 minutes ago, HughF said: Not for ufh, just set a fixed temp and pump the water round the slab…. Let it defrost from the slab… You could, but not very good for DHW. It only outputs a single flow temp, DHW flow and CH flow temp is done at same flow temp. It really pool pump with a couple of additional features, but not much. Even the inverter one is a single flow temp for DHW and CH, it just modulates it's load not the temperature. Link to comment Share on other sites More sharing options...
Beelbeebub Posted January 10 Share Posted January 10 The dream units are interesting, mainly for their low price. They claim a toshiba scroll compressor (so good brand and good tech). I note they are r410a, which is an obsolete tech, I wonder if they are getting them cheap in some sort of "fire sale". The fixed output temp indicates they have cut costs by having the most basic control electronics for the HP. It's possible they don't even have a reversing valve for defrost. But all we really need is a standard input for setting the temp, and possibly commanding a defrost, say over rs485 or whatever 2 wire bus Opentherm operates as. Then the control system can be a 3rd party unit. But a 10kw unit for £1.5k us pretty much where we need to be. If they could churn out an r290 unit with remote temp SP control that could be a winner. Link to comment Share on other sites More sharing options...
JoeBano Posted January 10 Share Posted January 10 The dream units have been on eBay for the past 4 years. Last time I looked they wasn’t inverter driven so probably cost a fortune to run. Link to comment Share on other sites More sharing options...
JohnMo Posted January 10 Share Posted January 10 18 minutes ago, JoeBano said: The dream units have been on eBay for the past 4 years. Last time I looked they wasn’t inverter driven so probably cost a fortune to run. If you heat a buffer at a fixed temp say 30/35 and have another means of heating DHW and/or use the buffer to preheat water going to the DHW cylinder, shouldn't be be too bad to run. Just how things used to be a decade ago (or more). They are basic heat pump, and they are cheap. The inverter ones are R32 and internet connected (smart) but the functionality is no different to the basic unit, apart from modulation. Link to comment Share on other sites More sharing options...
HughF Posted January 11 Share Posted January 11 14 hours ago, JohnMo said: You could, but not very good for DHW. It only outputs a single flow temp, DHW flow and CH flow temp is done at same flow temp. It really pool pump with a couple of additional features, but not much. Even the inverter one is a single flow temp for DHW and CH, it just modulates it's load not the temperature. I thought the OP was purely looking for a unit to power the ufh loops in his garage/workshop or something, somewhere away from the main house? Link to comment Share on other sites More sharing options...
JohnMo Posted January 11 Share Posted January 11 1 minute ago, HughF said: I thought the OP was purely looking for a unit to power the ufh loops in his garage/workshop or something, somewhere away from the main house? Just reread, yes missed that. The dream unit, can be set to run at a fixed temp, job done. Then leave to look after it's self. 2 Link to comment Share on other sites More sharing options...
HughF Posted January 11 Share Posted January 11 Just now, JohnMo said: Just reread, yes missed that. The dream unit, can be set to run at a fixed temp, job done. Then leave to look after it's self. Yep, it seemed an ideal solution. Buy the smallest one (3.5kW) and just pump it straight to the loops with a fixed flow temp. Link to comment Share on other sites More sharing options...
HughF Posted January 11 Share Posted January 11 R32, inverter driven…. Still not a bargain, but it’s a start. Link to comment Share on other sites More sharing options...
SteamyTea Posted January 11 Share Posted January 11 Any reason for not using an A2AHP as it is just a garage/workshop. 1 Link to comment Share on other sites More sharing options...
SuperPav Posted January 11 Author Share Posted January 11 Thanks everyone for the opinions and suggestions. Following the (fairly obvious) mention of having a look through the technical docs, I've gone through the installation manual for the Altherm hybrid ASP, and it can be configured to block the boiler and exclusively use the ASHP down to -14 with a bottom plate heater (£40 on ebay), or -5 without the bottom plate heater. I think based on that I might try and give it a go if the unit is still available for £500... I've got a circ pump that came with my UFH manifold (which would be ~1m from where the ASHP is going, so should be fine), so that's not a problem. Re: A2A ASHP, yes if I hadn't already put the loops in the slab that's what I'd be doing, but as the UFH is in and a garage will always have fairly rubbish airtightness due to the main door, I figured putting the heat into the concrete slab is better than A2A. but A2A would be a better fallback than a new £2k unit. The dream units look interesting but for the price still a expensive especially given I can't see any proper way to control them using a thermostat to call for heat without starting to rig 3rd party control systems etc. Link to comment Share on other sites More sharing options...
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