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Author Topic: Small ASHP (Split system) Install  (Read 17736 times)
Fionn
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« Reply #45 on: February 11, 2018, 08:23:45 PM »

Sounds great, have you done much analysis on COP during the colder winter months?
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PV - 2.75kW East, 1.5kW South, 2.5kW West. 3 x Flat Plate Solar Thermal with side arm FPHE on 268L cylinder
M
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« Reply #46 on: February 12, 2018, 07:15:56 AM »

Sounds great, have you done much analysis on COP during the colder winter months?

Hi. Simple answer, no.

I haven't noticed any difference, but I suspect that's simply down to whether I have the living room door open a crack (for cats) or wide open. So even if outside temps are 2C or so, the tiny conservatory heats up fast, then maintains temp in the living room fine.

Also, all use is daytime, say from 8.30am to 3.30pm (but starting to widen now with better sunlight), so no fighting with nightime temps.

I'm also using it when generation is too poor, but those days tend to be grey, muggy and a little warmer.

If generation is high, then living room door is wide open, and ASHP temp wacked up to about 24C. Living room sits at about 20C, and loads of heat goes into hallway. Low gen then living room door only cat-cracked and ASHP on 21C, with living room at 20C.

Might sound like a lot of fuss, but it's all been quite natural, and Wifey tick of approval as she says the heat is more natural feeling, and not as stuffy as GCH.
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Just call me Mart.     Cardiff: 5.58kWp PV - (3.58kWp SE3500 + 2kWp SE2200 WNW)
MeatyFool
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« Reply #47 on: February 26, 2018, 01:18:58 PM »

Mart,

This thread has had my thinking for a while.  Our GCH boiler is over 10 years old now, and chances are we will end up getting it replaced with gas again.  But your ASHP reports have left me thinking I should at least be able to reduce gas consumption and possibly eke out our existing boiler a year or two more.

Where my circumstances differ is that we tend to have the house warmer than "average" and to date have had no secondary source of heat.  Our CH programmer has no "+1" button so invariably in the winter it gets set to "once" so is on from 0530 to 2000 (we do have a room stat).  As an aside, if I set the second and third timings better, we might be able to get 2-3 hours a day with the heating off.  A significant saving in itself (3 hours would be 20% - sheesh, doesn't lethargy cost you!)

If I were to try to run with just the ASHP in the shoulder months, I cannot imagine that the heat will travel too far from the inside unit, thereby making other parts of the house feel colder?  Is this your experience?

Someone else has posted how to build your own +1 button on here.  I would suggest that if my wife and I could be trained to refrain from "once"ing the programmer and choosing "+1" when we notice the house starting to feel colder, we could gain a lot of the gas reductions even without the expense of the ASHP.  Of course that is a factor of insulation, and I would say our house is a combination of good, bad and indifferent in that regard!

Meatyfool..

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M
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« Reply #48 on: February 26, 2018, 01:53:01 PM »

Hiya. It will depend on the weather, and obviously today is rather 'extreme', but the blower in the conservatory (more of a small sun room) is running at about 25C, whilst living room is 20.5C with the door half open, and then the hall is colder, but pleasant. Effectively I use the living room door* as the temp control:

if gen is low, I put the HP to about 21c or 22C, the door is just ajar (for the cats),

if gen is high I put the HP to about 25C and leave the living room door wide open to put as much heat into the house (thermal mass battery?).

*That's the living room to hallway door. The living room to sun room is always wide open when the HP is on, as is a small window to the kitchen.

I suspect that in the shoulder months there would be far too much heat without having internal doors wide open, and might, just might mean no evening GCH burn is needed.

So far this winter I haven't put the heating on during the day, which has really surprised me, but it does mean I can go upstairs and find it's 17C or even less.
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MeatyFool
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« Reply #49 on: February 26, 2018, 03:01:01 PM »

Many thanks.

I suspect that we would rarely operate the ASHP on its own.  We do prefer to have the whole house a uniform temperature.  But there should still be massive carbon/cost savings if it reduces gas consumption.

Just need to work on the spousal factor.  Your SF seems to be positive?

Meatyfool..
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Fionn
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« Reply #50 on: February 26, 2018, 03:22:20 PM »

Meatyfool, you could always install more than one mini split or a multisplit.
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PV - 2.75kW East, 1.5kW South, 2.5kW West. 3 x Flat Plate Solar Thermal with side arm FPHE on 268L cylinder
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« Reply #51 on: February 26, 2018, 05:18:59 PM »

Meatyfool, you could always install more than one mini split or a multisplit.

You beat me to it.

The last couple of weeks I've had way more watts than I need, and could easily have run another HP too. I don't need to, but I would certainly suggest anyone thinking about to just consider maybe a more 'meaty' unit, perhaps 5kW and a dual split with two units, the second one used for additional property heating when gen is high.

My system is quite big, but I'd expect a 4kWp south facing system to be doing even better at this time of year.

@ Meaty, BTW, if it helps, the lounge was 16.8C when I popped in there today at 2pm, so that's what would have happened in the living room. Upstairs at 5pm (nowish) when the GCH kicked back on, the temp was 16.1C, but to be fair, it's bleeding cold today. But that gives you an idea of what heating I've hopefully avoided and gotten for 'free' (give or take the ,000's I've spent).

Other thoughts, which I may have posted previously, if your boiler does fail, then at least you have a secondary source of heat, and the AC was absolutely priceless last May when we had that crazy heatwave, which would have made me quite ill otherwise.
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Just call me Mart.     Cardiff: 5.58kWp PV - (3.58kWp SE3500 + 2kWp SE2200 WNW)
MeatyFool
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« Reply #52 on: February 26, 2018, 06:17:07 PM »

Thanks again.

I'm going to have to research this some more.  What I need to get straight is placement.  A split unit in the living/dining room would be great as it backs onto an outer wall that has very little footfall and would be ideal for the outside unit.  if I place another inside unit in rooms further away, that is a lot of pipe work for a multi split.

I can be very easily sold on this!

Meatyfool..
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M
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« Reply #53 on: February 28, 2018, 10:53:03 AM »

I lost!

Have had to put the GCH back on today, first time I think during the day in 2018, the morning burn (5.30am to 7.10am) couldn't compete with the steady loss of thermal mass heat over this last week, and it's blumming cold outside. Also, partly my fault as I reduced the morning and evening burns as temps rose in Feb.

The ASHP is on, and the dial set to '11', with sun-room and living room warm, and door partly open (dog is here at the moment and he's considerably bigger than the cats), but upstairs is just too cold.

Hopefully normality will be restored on Sunday when temps bounce back up.
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Just call me Mart.     Cardiff: 5.58kWp PV - (3.58kWp SE3500 + 2kWp SE2200 WNW)
stannn
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« Reply #54 on: February 28, 2018, 11:21:09 AM »

You need more dogs Mart, big ones with no fur.
Stan
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2.45 kWp PV (Navitron supply), 40 evacuated tubes (Navitron supply), Clearview 650 log burner with back-boiler heating cottage and water, 2 off 50W border collies, 1 off 35W cat, 1 off 25W cat.
gnarly
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« Reply #55 on: February 28, 2018, 01:19:00 PM »

Yes that's my experience with a mini-split in freezing weather too.  Remember these things only put out 2.5 kW or so (and that goes down once you get into frequent defrost cycles) so no way can it heat an entire house.  Also they tend to ice up as the drain gets frozen.  Mine also gets very noisy.
They are great 90% of the time and really save money and co2 but you do need an alternative heat source whether GCH or multiple big dogs!!
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M
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« Reply #56 on: February 28, 2018, 04:00:06 PM »

You need more dogs Mart, big ones with no fur.
Stan

Actually I owe poor Richard an apology, despite being a large fella, he is more than capable of 'slithering' around a mostly closed door, whereas the cats take the view that if the door gap is marginal, then they should shove it full open. Gits!
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Just call me Mart.     Cardiff: 5.58kWp PV - (3.58kWp SE3500 + 2kWp SE2200 WNW)
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« Reply #57 on: February 28, 2018, 05:55:39 PM »

Quick update, leccy import this Feb was 10kWh's more than last year, and 20kWh more than 2016, 10kWh more than 2015. So my hope of importing no more than 200kWh more than before still looks good, as monthly import appears to be less than the +30kWh I guessed at (x 6 months pa).

I don't have monthly gas figures for previous years, only quarterly, but Jan and Feb are a slightly higher than 2/3rds of an average 1st qtr, which seems OK, assuming Mch's are normally warmer, and also my Mch gen is more than Jan + Feb combined, so I'd hope to be able to use the HP more, and from earlier to later, plus a better COP as outside temps rise.

No idea if any of this means much yet, or will ever, but it's an interesting little exercise, and hopefully the info will grow more useful as the years go on.

Edit - just used my Solaredge monitoring to check export, and from that I get a consumption figure (import + generation - export), and that came to 304kWh's with an import of 168kWh (Jan 212kWh). That's my highest consumption figure since I was able to start tracking it last Aug. My consumption in Jan was 288kWh, which makes sense as the HP has been really going great guns this month. So the HP has allowed me to turn the house into a heat battery for some excess generation.
« Last Edit: February 28, 2018, 06:01:47 PM by M » Logged

Just call me Mart.     Cardiff: 5.58kWp PV - (3.58kWp SE3500 + 2kWp SE2200 WNW)
MeatyFool
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« Reply #58 on: March 05, 2018, 12:40:58 PM »

Mart (and others!),

I would be happy to go with an alternative heating technology just if it had a CO2 benefit but spousal factor has to cover financial outlay as well.

I can't help thinking I'm being a complete lemon here, hopefully somebody can put me straight.

I am buying electric at 12.18p, gas at 2.825p, and let us assume (say) a COP of 3.  So electric consumed 12.18p, gas saved 8.475p.  Negative return. Yes, the boiler isn't 100% efficient, but even at 90% (10 year old condensing gas boiler), the numbers aren't close.

Wikipedia does state "A high COP of a heat pump may not entirely overcome a relatively high cost for electricity compared with the same heating value from natural gas".  So maybe no cause for confusion at all.

I recognise that Mart refers several times to using the PV output, but my PV is in and operational, so I am "already" using that free leccy.  I can't use it several times over!

Yours confused.

Meatyfool..
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M
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« Reply #59 on: March 05, 2018, 01:09:24 PM »

Mart (and others!),

I would be happy to go with an alternative heating technology just if it had a CO2 benefit but spousal factor has to cover financial outlay as well.

I can't help thinking I'm being a complete lemon here, hopefully somebody can put me straight.

I am buying electric at 12.18p, gas at 2.825p, and let us assume (say) a COP of 3.  So electric consumed 12.18p, gas saved 8.475p.  Negative return. Yes, the boiler isn't 100% efficient, but even at 90% (10 year old condensing gas boiler), the numbers aren't close.

Wikipedia does state "A high COP of a heat pump may not entirely overcome a relatively high cost for electricity compared with the same heating value from natural gas".  So maybe no cause for confusion at all.

I recognise that Mart refers several times to using the PV output, but my PV is in and operational, so I am "already" using that free leccy.  I can't use it several times over!

Yours confused.

Meatyfool..

Hiya. I'm not sure it'll ever pay back just on gas savings, so you are probably right there. But it's important to place some value on having a secondary heat source, and some cooling, though that will be very rare.

At a COP of 3, expect to replace 4 units of gas (75% efficient), so 12.18p leccy v's 11.3p.

But, and here's when the numbers become more a leap of faith. Some of that leccy should be PV, I already had the PV, but I was exporting most of this. Today the ASHP went on at 8am and I've been importing little to nothing so far even though it's quite grey as total gen is around 900W.

Next, it's a dishonest comparison. I'm heating the living room (and sun room) with the ASHP, but saving on GCH for the whole house. The more the rest of the house cools, the less heat I lose as the differential between indoor and outdoor temps reduces.

I appreciate that the GCH will have to work harder when it comes back on, but I still save by having less 'all house' heat.

Also, whilst I'm happy to use a COP of 3, since the UK average is apparently 2.9 for an ASHP, do remember that in this case you will be avoiding night time use, and the worst of the winter use, so the average COP is probably better as you pick and choose the best times to use it.


Just to be clear, I'm not sure this is a great idea, it just seems like a good one to try, and a bit of fun, and as you mention, I'm pretty sure CO2 wise I'm doing the right thing as the PV I consume, or leccy I import, will cost the grid 2kWh's of gas (for every 1kWh of leccy), so taking the COP into account, should deliver 3-4kWh's of heat, giving a 2 to 1 benefit .... I think?
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Just call me Mart.     Cardiff: 5.58kWp PV - (3.58kWp SE3500 + 2kWp SE2200 WNW)
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