Your browser isn't supported
It looks like you're using an old web browser. To get the most out of the site and to ensure guides display correctly, we suggest upgrading your browser now. Download the latest:

Welcome to the MSE Forums

We're home to a fantastic community of MoneySavers but anyone can post. Please exercise caution & report spam, illegal, offensive or libellous posts/messages: click "report" or email forumteam@.

Search
  • FIRST POST
    • zeupater
    • By zeupater 21st Jul 13, 5:35 PM
    • 4,975Posts
    • 6,733Thanks
    zeupater
    Discussion ... ASHP(Air/Air) with Solar pv ....
    • #1
    • 21st Jul 13, 5:35 PM
    Discussion ... ASHP(Air/Air) with Solar pv .... 21st Jul 13 at 5:35 PM
    Hi All

    The combination of a small ASHP(Air/Air) with Solar pv seems to be a valid pairing of complementary technologies which has been raised a number of times on this forum.

    The idea of this thread is to encourage discussion of this combination in order to validate what an appropriate equipment specification would look like in order to maximise performance benefits in a typical domestic environment.

    Obviously, it is well understood that a typical domestic-scale solar pv system will not generate sufficient energy to provide winter heating, but should be considered as being a 'shoulder' months supplementary heat source for well insulated properties ... it is therefore best to concentrate on Spring & Autumn as being the target periods for heat provision, with an additional benefit of provision of cooling in heat-wave conditions such as we've been experiencing recently.

    HTH
    Z
    "We are what we repeatedly do, excellence then is not an act, but a habit. " ...... Aristotle
Page 3
    • Martyn1981
    • By Martyn1981 3rd Jun 16, 3:46 PM
    • 9,805 Posts
    • 14,753 Thanks
    Martyn1981
    This looks like a fairly definite answer:
    2013 study showing real world cop around 2x
    http://www.narecde.co.uk/air-source-heat-pumps-vs-gas-boilers/#.V1FZNyHm270
    Originally posted by michaels
    Hiya Michaels. Remember that this isn't a 'fair fight' between a heat pump and GCH, it's actually 'rigged'.

    What Z and I were pondering wasn't a replacement for GCH all of the year, but a cherry picked solution for part of the year.

    So instead of an ASHP that could provide all heat, all year, it's a much smaller solution (and cheaper) that can supply the smaller amount of heat needed just during the warmer colder months, so to speak.

    This way you get to play with, or distort, the average. So, let's say the COP in Dec is 2, but the COP in Mch is 5 due to the warmer temps outside, you might at first think the average is 3.5 (2+5/2), but you have to take into account the scale of heating needed, let's say 10x more in December, so a real (weighted) COP average (in this example) might be (10x2 +5)/11 = 2.27.

    But if you leave the coldest months to the GCH (Nov to Feb) and use the HP for the 'warmer colder' months Mch/Apr & Sept/Oct, you get to raise the COP average significantly and pick days where the much smaller HP can still supply a significant percentage of the heat requirement ...... effectively 'pick your fight'.

    Also, last winter was quite warm, so I noticed many days where the heating was only on in the morning and evening, but I used my oil rad to keep the chill off one room during the day, so whilst the COP may be lower, it would still be highly beneficial to multiply that electrical input by a factor of 2 or more.

    Mart.
    Last edited by Martyn1981; 03-06-2016 at 3:52 PM.
    Mart. Cardiff. 5.58 kWp PV systems (3.58 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
    • michaels
    • By michaels 3rd Jun 16, 4:55 PM
    • 23,113 Posts
    • 105,242 Thanks
    michaels
    The EST study referenced in your link is for Air to Water heat pumps(and Ground to water). This is for Heat pumps that deliver hot water to radiators/underfloor heating and Domestic Hot water to a tank. There are hundreds of posts on that 12 month trial and its further 12 month extension.


    This discussion is for Air to Air heat pumps, that can double as air conditioning in summer. These are very common abroad - particularly the USA where the warm(or cold) air is ducted to every room.


    The COP's quoted for Air to air heat pumps are much higher than air to water. I have not seen any independent trial giving 'real world' COPs but IMO they would be way higher than Air to water.


    As said earlier, my biggest concern would be the potential noise problem to Z's household and neighbours - there is a thread running on this subject.(not all air to Air)


    http://forums.moneysavingexpert.com/showthread.php?t=4357449
    Originally posted by Cardew
    The advantage of air-to-water in a PV context is that it could replace iBoost diversion at hopefully a higher efficiency factor and hot water is in a way a time-shifter / energy storage solution, where as for us at least I suspect air-air is not that useful as we heat 24/7, obviously mostly in the evening/night/early morning in winter when it is dark. Thus the capital expenditure to cover a narrow window of shoulder demand seems unlikely to be cost effective. Perhaps if we also switched to economy 7 during the shoulder months it might make a difference?
    Cool heads and compromise
    • zeupater
    • By zeupater 3rd Jun 16, 10:23 PM
    • 4,975 Posts
    • 6,733 Thanks
    zeupater
    So electricity costs about 4x mains gas per kwh.

    If you were replacing a gas boiler that is used for heating and DHW and say didn't use gas for anything else so could cancel gas and avoid the standing charge would it ever make sense to switch to an ashp given the external temperature profile and heating requirement - for example probably 75% of our gas use is when the external temperature is below 10 degrees c etc
    Originally posted by michaels
    Hi

    That's not what I'm doing ... when the pv is generating a spare ~300W February or November the idea is to use heat-pump technology to multiply this up to a reasonable amount of heat to supplement the log burner - for September, October, March, April and early May the heat-pump/pv combination will provide all of the heat we need, effectively for free.

    It's not an illogical fantasy ... we've had our pv for years and have used the combination of an 800/1600W fan heater and a 400/600/1100W oil-radiator to do what we plan to continue, it's just that we'll be able to extend the period far further into the winter period, from both sides and be far more comfortable too ....

    Anyway, as of this afternoon it's in, it's working and, from tests so far, it's even performing above the manufacturer's engineering data book specifications for today's outside temperature ... this is probably due to the short tube-run, but certainly means that if a COP of over 6.0 is achievable today, the published data is probably not too far out and, in our case, may even be a little conservative .... Early days, but time will tell ....

    On the gas side, we pay a higher unit rate with no standing charge, but normally using around 1000kWh/year the lower tariffs available with standing charges effectively becomes irrelevant .... Gas to us is effectively used as a backup for the DHW when it's been cloudy for a number of consecutive days and for boiling my blood when elderly relatives stay with us over Christmas ... not kidding, I'm usually melting at 27C around 7 metres from the log-burner and a couple of ~90year-olds are hogging my seat by the inglenook ... apart from that, it takes almost a week of temperatures well below freezing to even need the GCH ...

    HTH
    Z
    Last edited by zeupater; 04-06-2016 at 8:32 PM. Reason: spelling correction - brain and fingers not in sync again
    "We are what we repeatedly do, excellence then is not an act, but a habit. " ...... Aristotle
    • zeupater
    • By zeupater 3rd Jun 16, 10:42 PM
    • 4,975 Posts
    • 6,733 Thanks
    zeupater
    This looks like a fairly definite answer:
    2013 study showing real world cop around 2x
    http://www.narecde.co.uk/air-source-heat-pumps-vs-gas-boilers/#.V1FZNyHm270
    Originally posted by michaels
    Hi

    Based on an air pressure of 1016millibars, the measured airflow, the input temperature, the output temperature and the measured power ... the 'real world' COP here today was ~3x the results of the study .... of course, this does not in any way represent the expected SCOP, but as we're not looking to utilise the heat-pump in unfavourable conditions and will only be multiplying the value of our own generation, why would even an abysmal COP of 2.0 be considered a failure? .... for every 1kWh of pv generation used by the heat-pump, you'd be getting 2kWh.t of heat !! ....

    HTH
    Z
    Last edited by zeupater; 03-06-2016 at 10:45 PM.
    "We are what we repeatedly do, excellence then is not an act, but a habit. " ...... Aristotle
    • zeupater
    • By zeupater 3rd Jun 16, 11:02 PM
    • 4,975 Posts
    • 6,733 Thanks
    zeupater
    The EST study referenced in your link is for Air to Water heat pumps(and Ground to water). This is for Heat pumps that deliver hot water to radiators/underfloor heating and Domestic Hot water to a tank. There are hundreds of posts on that 12 month trial and its further 12 month extension.


    This discussion is for Air to Air heat pumps, that can double as air conditioning in summer. These are very common abroad - particularly the USA where the warm(or cold) air is ducted to every room.


    The COP's quoted for Air to air heat pumps are much higher than air to water. I have not seen any independent trial giving 'real world' COPs but IMO they would be way higher than Air to water.


    As said earlier, my biggest concern would be the potential noise problem to Z's household and neighbours - there is a thread running on this subject.(not all air to Air)


    http://forums.moneysavingexpert.com/showthread.php?t=4357449
    Originally posted by Cardew
    Hi Cardew

    Running ours today and forcing it to 'High Power' on heating with an external/internal temperature difference of >10C the outdoor unit certainly was pretty noisy for a few minutes before settling down, nearly as noisy as the birds in the garden, or a car at 30mph about 50 metres away (well that's what I compared it to) .... but this is a setting to force the system to perform at the absolute maximum .... so far under normal conditions the unit seems to be more akin to a desk fan crossed with a pretty quiet fridge than a helicopter ... and we get plenty of helicopters around here so no-one would probably notice even if it was ! ...

    Anyway, we don't intend to use the 'High Power' setting much, so it shouldn't be an issue ...

    HTH
    Z
    Last edited by zeupater; 05-06-2016 at 1:17 PM. Reason: -er + re
    "We are what we repeatedly do, excellence then is not an act, but a habit. " ...... Aristotle
    • zeupater
    • By zeupater 3rd Jun 16, 11:30 PM
    • 4,975 Posts
    • 6,733 Thanks
    zeupater
    The advantage of air-to-water in a PV context is that it could replace iBoost diversion at hopefully a higher efficiency factor and hot water is in a way a time-shifter / energy storage solution, where as for us at least I suspect air-air is not that useful as we heat 24/7, obviously mostly in the evening/night/early morning in winter when it is dark. Thus the capital expenditure to cover a narrow window of shoulder demand seems unlikely to be cost effective. Perhaps if we also switched to economy 7 during the shoulder months it might make a difference?
    Originally posted by michaels
    Hi

    The issue with Air to Water heat-pumps is the the COP reduces as the water temperature increases, There are some pretty reasonable high temperature units available which have a potential to achieve a decent COP, but the overall performance is very much aligned to the particular installation, the user settings and how the householder wants to use what they've got. With DHW you're normally targeting 50C+ even in <7C average winter conditions, which usually means a relatively poor overall performance.

    As Cardew raised earlier, split unit air to air technology is pretty mature ... what's changing now is the high-pressure related performance and, importantly, both the range of operation available through high-performance inverters and the 'power saving' settings which are being built into the control systems ....

    I find it interesting, but then again, I've always questioned the relevance of 'crowd think' and find many obscure ideas interesting ....

    HTH
    Z
    "We are what we repeatedly do, excellence then is not an act, but a habit. " ...... Aristotle
    • Martyn1981
    • By Martyn1981 4th Jun 16, 7:33 AM
    • 9,805 Posts
    • 14,753 Thanks
    Martyn1981
    it's even performing above the manufacturer's engineering data book specifications for today's outside temperature ... this is probably due to the short tube-run,

    HTH
    Z
    Originally posted by zeupater
    Hiya Z, loads of questions, so thanks for all the data so far, but I'll limit my start to - what is a short tube-run?

    My preferred location for the two units would be approx 3m apart, plus a ceiling to floor drop of about 2m more?

    I'd hope to position the outside unit under my PV canopy on the ESE wall. That way it should get some shading during the summer (cooling), but some direct sunlight in the shoulder months (heating).

    May I ask what unit you went for so I can start revising some specs, and get back into this.

    Thanks.

    Mart.
    Mart. Cardiff. 5.58 kWp PV systems (3.58 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
    • zeupater
    • By zeupater 4th Jun 16, 12:48 PM
    • 4,975 Posts
    • 6,733 Thanks
    zeupater
    Hiya Z, loads of questions, so thanks for all the data so far, but I'll limit my start to - what is a short tube-run?

    My preferred location for the two units would be approx 3m apart, plus a ceiling to floor drop of about 2m more?

    I'd hope to position the outside unit under my PV canopy on the ESE wall. That way it should get some shading during the summer (cooling), but some direct sunlight in the shoulder months (heating).

    May I ask what unit you went for so I can start revising some specs, and get back into this.

    Thanks.

    Mart.
    Originally posted by Martyn1981
    Hi

    Like an excited kid with a new toy, I was up and ready to play quite early this morning, well as soon as I'd had a coffee and breakfast ... ... in reality that means that the unit has been running on pure pv for about 3.5 Hrs so far today ...

    Our indoor unit is mounted a couple of inches from the ceiling on the inside and the outdoor unit is on wall brackets about 12" off the ground so that we can sweep and weed the patio below it (with a block paved patio fighting weeds is a full time job!) ... the tube runs (feed&return) go through the wall and drop to the outdoor unit in plastic trunking, have a couple of alignment bends and that's about it ... probably somewhere in the region of 2.5 metres of separation. Of course the tubes are individually insulated with Armaflex (same as our solar thermal runs), but with opportunity for heat loss over distance, my preference was to keep the run short.

    Regarding two units ... I looked at that too, still might consider a second unit but decided that one may actually deliver the majority of what I wanted to achieve so I'd try a single unit first and keep my options open. If we went for a second unit at the same time I'd already decided that two outdoor units would provide some form of redundancy if there was an issue. Other considerations on a multi-split revolved around the indoor units being around 10m apart, there being little cost advantage, a loss of power restriction flexibility and no readily available data on multi-split performance when only one indoor unit is required ....

    As you know, we've considered this for a while and I've really done the research. The main consideration is matching the heat-pump to low pv generation conditions, so the main requirement is to concentrate on maximum efficiency, performance range (High/Low) and linking this to controllability ... and of course, as Cardew mentions, noise levels (both indoor & out). Looking at what's out there and comparing one make/unit against another I kept coming back to using the Toshiba Daiseikai 8 range as a benchmark, so, as I could find nothing to beat it on specification and as it's what I became most familiar with for available performance data comparison, that's what's on the wall now .... the range is by no means the cheapest option out there, but that's not the issue, my criteria is performance based value for money .....

    We're currently heating, watching a 50" TV, using a laptop, charging two mobile phones, covering all background power usage and ... wait for it ..... using a grand total of 300W - so somewhere in the region of 170-200W is heating the house with a COP multiplier in current conditions of somewhere around 6.0 (according to engineering data and our own tests yesterday) ... this is exactly the kind of performance we need for the shoulder months - all I need to learn now is how to optimise the unit to suit conditions, which means airflow patterns, setting daily temperature programs, using internal doors as heat-flow baffles etc, then look forward to Autumn (did I really say that! - ) ...

    HTH
    Z
    Last edited by zeupater; 04-06-2016 at 10:32 PM. Reason: grammar
    "We are what we repeatedly do, excellence then is not an act, but a habit. " ...... Aristotle
    • silverwhistle
    • By silverwhistle 4th Jun 16, 7:24 PM
    • 2,761 Posts
    • 4,176 Thanks
    silverwhistle
    On the gas side, we pay a higher unit rate with no standing charge, but normally using around 1000kWh/year the lower tariffs available with standing charges effectively becomes irrelevant .... Gas to us is effectively used as a backup for the DHW /SNIP/
    Originally posted by zeupater
    Effectively the same as I operate, although with a smaller terrace house and only me to keep happy, apart from visitors (as described above!). I'd like to get my gas usage under a thousand as it's just over at the moment. Repairs to my rear wall and replacing a draughty back door are all part of my incremental improvements.

    I can't afford or justify heat pumps, but I am thinking of getting a single room MHRV unit for the bathroom. I did a very bad job of retro-fitting a burnt out normal extractor but as my girlfriend is a qualified electrician she knows she's provisionally booked to fit one.

    Any recommendations from the experts? :-)
    • silverwhistle
    • By silverwhistle 4th Jun 16, 7:30 PM
    • 2,761 Posts
    • 4,176 Thanks
    silverwhistle
    the unit seems to be more akin to a desk fan crossed with a pretty quiet fridge than a helicopter ... and we get plenty of helicopters around here so no-one would probably notice even if it was ! ...
    Originally posted by zeupater

    Me too. Chinooks or Robinsons?
    • zeupater
    • By zeupater 4th Jun 16, 8:51 PM
    • 4,975 Posts
    • 6,733 Thanks
    zeupater
    Effectively the same as I operate, although with a smaller terrace house and only me to keep happy, apart from visitors (as described above!). I'd like to get my gas usage under a thousand as it's just over at the moment. Repairs to my rear wall and replacing a draughty back door are all part of my incremental improvements.

    I can't afford or justify heat pumps, but I am thinking of getting a single room MHRV unit for the bathroom. I did a very bad job of retro-fitting a burnt out normal extractor but as my girlfriend is a qualified electrician she knows she's provisionally booked to fit one.

    Any recommendations from the experts? :-)
    Originally posted by silverwhistle
    Hi

    I know someone who fitted a 'cheap' bathroom 'trickle' heat recovery unit ... think it was about 300 from 5crewfix (so not that cheap!), but they don't seem to be in the catalogue any more ... anyway, it fixed the condensation problems they were having much better than the powerful extractor which it replaced ... from memory it was either a a Vent-Axia or Xpelair, I can't remember which so wouldn't have a clue as to the model .... have a look on the web to see what the current line-up is ....

    HTH
    Z
    "We are what we repeatedly do, excellence then is not an act, but a habit. " ...... Aristotle
    • zeupater
    • By zeupater 4th Jun 16, 9:23 PM
    • 4,975 Posts
    • 6,733 Thanks
    zeupater
    Me too. Chinooks or Robinsons?
    Originally posted by silverwhistle
    Hi

    Effectively anything ranging from Chinooks through Merlins, Apaches, Pumas & Lynx right the way through to Squirrels etc ... if it flies below a rotor it'll be heard from our back garden at some time or other so if the heat-pump was really noisy the letters of complaint would likely end up being addressed to the MOD ...

    Z
    "We are what we repeatedly do, excellence then is not an act, but a habit. " ...... Aristotle
    • silverwhistle
    • By silverwhistle 5th Jun 16, 7:22 PM
    • 2,761 Posts
    • 4,176 Thanks
    silverwhistle
    ... from memory it was either a a Vent-Axia or Xpelair,
    Originally posted by zeupater
    Thanks. These are the ones I've seen and for me don't think the humidistat model would be worth it:
    http://http://www.vent-axia.com/range/lo-carbon-tempra.html


    Round me we also get the distinctive sounds of Spitfires and Harvards going over, sometimes in wing pair formation, plus the kids have just gone past on their mobile sewing machines, so think I'd be ok!
    Last edited by silverwhistle; 05-06-2016 at 7:23 PM. Reason: spolling
    • zeupater
    • By zeupater 6th Jun 16, 12:42 PM
    • 4,975 Posts
    • 6,733 Thanks
    zeupater
    Thanks. These are the ones I've seen and for me don't think the humidistat model would be worth it:
    http://www.vent-axia.com/range/lo-carbon-tempra.html
    Originally posted by silverwhistle
    Hi

    Looking at the link above the model which used to be in the 5crefix catalogue looked more like the HR25 range, but not sure ...

    HTH
    Z
    "We are what we repeatedly do, excellence then is not an act, but a habit. " ...... Aristotle
    • zeupater
    • By zeupater 7th Jun 16, 4:00 PM
    • 4,975 Posts
    • 6,733 Thanks
    zeupater
    Hi

    In response to a query on another thread, I'll run a quick trial so that a heating power profile over at least a couple of hours can be seen ...

    Starting at a position where we're generating 1.70kW and consuming 200W and the temperature is showing as 22.5C on a digital thermostat about 18" above the floor, leaving all internal doors open I'll look to raise the raise the temperature in the room with the heat-pump to 24C and let the heat drift through the house ... settings will be as I expect to use the system, including software limiting the maximum power consumption .... the unit hasn't been used today, so it'll be representing a true start-up

    13:10 - 0W
    13:11 - 400W
    13:12 - 800W
    13:13 - 1200W
    13:14 - 1200W
    13:15 - 1200W
    13:16 - 1050W
    13:17 - 800W (22.6C)
    13:18 - 700W
    13:19 - 150W (22.7C)
    13:20 - 0W - Sleep
    "
    13:25 - 0W (22.8C)
    13:26 - 0W
    "
    13:31 - 430W (22.7C)
    13:32 - 500W
    13:33 - 550W (22.8C)
    13:34 - 530W
    13:35 - 530W
    13:36 - 580W
    13:37 - 580W
    13:38 - 550W
    13:39 - 550W
    13:40 - 550W
    13:41 - 0W - sleep (22.9C)
    "
    13:58 - 400W
    13:59 - 430W
    14:00 - 450W
    14:01 - 550W
    14:02 - 550W
    14:03 - 550W
    14:04 - 580W (23C)
    14:05 - 600W
    14:06 - 580W
    14:07 - 0W - sleep
    "
    14:28 - 80W
    14:29 - 550W
    14:30 - 550W (23.1C)
    14:31 - 550W
    14:32 - 600W
    14:33 - 500W
    "
    14:37 - 500W
    14:38 - 0W - sleep (23.2C)
    "
    14:46 - 0W (23.3C)
    15:03 - 350W
    15:04 - 430W
    15:05 - 580W
    15:06 - 550W
    "
    15:10 - 550W (23.4C)
    "
    15:12 - 550W
    15:13 - 0W - sleep
    "
    15:29 - 530W
    15:30 - 580W
    15:31 - 550W
    "
    15:38 - 0W - sleep (23.5C)
    15:54 - 480W
    15:55 - 530W


    ... Okay, there's around 3 hours of heating which has raised the internal air temperature of the equivalent of somewhere around 2-3 average properties by 1C. It's noticeable that the initial start sequence draws more power than standard running - this is most likely down to reaching operating pressures and temperatures ... after this initial ~1200W (max was probably ~1500W for a few seconds) the system has been pretty consistent at ~500W-550W. To place this into context, at today's outdoor temperatures the manufacturer claims that ~500W equates to ~3000W.t of heating and at 550W it's ~3400W.t, so in both cases a COP in excess of 6.0.
    Airflow within the house doesn't seem laminar at the moment, you can feel subtle changes between still air and a very slight draught .. this, combined by producing in excess of ~3kW of heat is probably the reason behind the system cutting in and out, however, I'd expect this to change as the air temperature and heat-pump setting converge and the inverter ramps the power down. If heating one or two rooms we would have reached temperature some time ago, but it must also be remembered that with today's outdoor temperatures there is very little heat loss, all that's happening at the moment is we're raising the temperature of the building's thermal mass ....

    I'm going to close a pair of double doors now in order to change the airflow and reduce the volume being heated ...

    HTH
    Z

    #edit - backlink to original thread ... http://forums.moneysavingexpert.com/showthread.php?p=70789865&posted=1#post70789865
    Last edited by zeupater; 08-06-2016 at 1:41 PM. Reason: +"
    "We are what we repeatedly do, excellence then is not an act, but a habit. " ...... Aristotle
    • zeupater
    • By zeupater 7th Jun 16, 5:13 PM
    • 4,975 Posts
    • 6,733 Thanks
    zeupater
    .. I'm going to close a pair of double doors now in order to change the airflow and reduce the volume being heated ...
    Originally posted by zeupater
    Hi

    Right, I've done that and used the fan only setting to stir the warm air around the ceiling around for a while, so here's a go at just 2 rooms with double doors (open) between ....

    It's gone pretty dull outside ... now generating 514W

    16:31 - 250W (23.8C)
    16:32 - 600W
    16:33 - 1000W
    16:34 - 1400W (23.7C)
    16:35 - 0W - sleep (23.8C)
    16:46 - 400W (23.7C)
    16:47 - 450W
    16:48 - 450W
    16:49 - 500W (23.9C)
    16:50 - 500W
    16:51 - 530W
    16:52 - 530W
    16:53 - 530W
    16:54 - 550W
    16:55 - 550W
    16:56 - 0W - sleep
    "
    17:09 .... calling time there for a while .... the clouds are really bubbling up and we're now only generating 143W and using 150W, but this represents what will happen anyway ..... if this gloom clears I'll continue later ....

    HTH
    Z
    Last edited by zeupater; 07-06-2016 at 11:32 PM. Reason: -e, -s
    "We are what we repeatedly do, excellence then is not an act, but a habit. " ...... Aristotle
    • zeupater
    • By zeupater 7th Jun 16, 8:23 PM
    • 4,975 Posts
    • 6,733 Thanks
    zeupater
    ..... if this glooms clears I'll continue later ....
    Originally posted by zeupater

    Back up to generating 413W, temperature 23.8C at 18:52 when switched back on .... start-up was pretty quick, briefly touching around 1400W again, and it's now settled down to 400W after about 5 minutes ...

    18:57 - 400W (24.0C)
    18:58 - 270W (24.1C)
    18.59 - 270W
    19:00 - 270W
    19:01 - 270W
    19:02 - 270W (24.3C)
    19:03 - 270W
    19:04 - 270W
    19:05 - 270W
    19:06 - 280W (24.4C)
    19:07 - 300W (24.5C)
    19:08 - 0W - sleep
    "
    19:14 - 470W (24.3C)
    19:15 - 350W
    19:16 - 300W
    19:17 - 200W (24.5C)
    "
    19:23 - 200W (24.6C)
    19:24 - 0W - sleep
    "
    19:32 - 200W (24.3C)
    19:33 - 270W
    19:34 - 200W (24.4C)
    19:35 - 200W
    19:36 - 200W (24.5C)
    19:37 - 200W (24.6C)
    "
    19:41 - 200W (24.7C)
    19:42 - 0W - sleep
    "
    19:50 - 480W (24.4C)
    19:51 - 350W
    19:52 - 270W
    19:53 - 270W
    19:54 - 270W (24.5C)
    19:55 - 200W (24.6C)


    Okay, we've got a settled pattern now with around 200W to 270W (today's conditions that's ~1250W.t to ~1700W.t) being needed to continue to feed the thermal mass of two rooms totalling somewhere around 50sqm of floorspace ..... when we were running tests over the weekend, once the temperature was fully settled the unit was operating at around 100W to 150W (~600W.t to 900W.t) and I would expect that to be the case if this test was continued for a while longer ....

    It's 8pm, the sky is cloudy and we're generating 147W ... the heat-pump has just cut-out again and the house is currently using 130W, that's a 50" TV and everything else which is plugged in combined, therefore it's likely that any pv generation above 400W could be made use of thus saving the log pile for when it's really needed ... in reality, generating between 800W & 1000W should make allowance for the fridge & freezer cycling and provide a little leeway, but I'll let everyone know when heat is actually needed .... it's a little warm in here at the moment, so I'm off to open the patio door and put the kettle on !! ...

    Lots of data for anyone to ponder over - hope it's useful, but do note that the unit I have used in these posts is at the very top end of current heat-pump performance, both in terms of COP and operating range and therefore should in no way be considered typical ... Power readings as taken exclude power factor correction, but should typically be within +10% overstated ....

    HTH
    Z
    Last edited by zeupater; 08-06-2016 at 1:48 PM. Reason: added approx W.t conversion at today's outdoor temperatures
    "We are what we repeatedly do, excellence then is not an act, but a habit. " ...... Aristotle
    • Exiled Tyke
    • By Exiled Tyke 8th Jun 16, 10:14 AM
    • 371 Posts
    • 994 Thanks
    Exiled Tyke
    A very interesting and useful discussion. Thanks everyone. Does anyone have views or experience of portable units? We have a big house so am interested in being able to move it into different rooms. As most have said here, it doesn't have to pay for itself but needs to be good value for money and offer a reasonable level of comfort in Summer and shoulder months. I'm hoping to get away with spending as little as 300.
    Install 28th Nov 15, 3.3kW, (11x300LG), SolarEdge, SW. W Yorks.
    Install 2 Sept, 600W SSE
    Solax 6.3kW battery
    • zeupater
    • By zeupater 8th Jun 16, 12:07 PM
    • 4,975 Posts
    • 6,733 Thanks
    zeupater
    A very interesting and useful discussion. Thanks everyone. Does anyone have views or experience of portable units? We have a big house so am interested in being able to move it into different rooms. As most have said here, it doesn't have to pay for itself but needs to be good value for money and offer a reasonable level of comfort in Summer and shoulder months. I'm hoping to get away with spending as little as 300.
    Originally posted by Exiled Tyke
    Hi

    We've had a portable aircon unit (cooling only) for years, the type which you vent the hose through the window.

    Our unit has rarely been used, but on the odd occasion where it's been exceptionally hot for a number of days it's pretty good at it's job, but not very efficient. The way they work is to effectively remove heat from internal air by drawing loads in, splitting the airflow, transferring heat from one half to the other, then blowing the cold part around the room and pumping the hot half out of the window .... of course, the volume of really hot air pumped out must be replaced by more warm air being drawn into the house somewhere else, so this drives the overall efficiency down.

    As mentioned, our unit is cooling only, however, the instruction manual states that a reversible unit is available, but I don't know whether they're readily available in the UK, you'd need to check .. as for efficiency, well yes it will do the job but don't expect a decent efficiency, but more importantly, they're not inverter units, they simply cycle between full power on and off, so probably would be useless to match with pv in low light cool shoulder month conditions where there's an indoor/outdoor temperature differential of 10C-15C and the window's open, which is likely double the typical difference when summer cooling is required and pv generation is high ....

    You could look to drill through the wall and permanently install the unit in a similar way to a tumble dryer, but that takes away much of the flexibility you may need .... ours came with a basic through wall pack, but it's still somewhere in the garage in it's unopened bag.

    HTH
    Z
    Last edited by zeupater; 08-06-2016 at 1:51 PM.
    "We are what we repeatedly do, excellence then is not an act, but a habit. " ...... Aristotle
    • rodee13
    • By rodee13 9th Jun 16, 11:14 AM
    • 56 Posts
    • 310 Thanks
    rodee13
    yes we have a portable unit as well (10 years old now), its got both heating and cooling although I use it mainly for cooling only and only at night when it gets too hot so not much use with PV. The big plastic hose pipe is the main aesthetic problem with these units but its very useful for a good night sleep. Actually it depends on what bothers you more - heat and humidity or the sound of the portable aircon.
    3.99KW SunEdison (14 * 285W) all black, SolarEdge inverter, iBoost+, 27 Oct 2015, London
    (40 tilt, 25 East from South, some tree shading from mid Oct to mid March)
Welcome to our new Forum!

Our aim is to save you money quickly and easily. We hope you like it!

Forum Team Contact us

Live Stats

1,215Posts Today

6,452Users online

Martin's Twitter