Discussion ... ASHP(Air/Air) with Solar pv ....

zeupater

silverwhistle wrote: »

Me too. Chinooks or Robinsons?

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

silverwhistle

zeupater wrote: »

... from memory it was either a a Vent-Axia or Xpelair,

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!

zeupater

silverwhistle wrote: »

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

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

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

zeupater

zeupater wrote: »

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

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

zeupater

zeupater wrote: »

..... if this glooms clears I'll continue later ....

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

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.

zeupater

Exiled_Tyke wrote: »

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.

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

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.

zeupater

Hi All

Just a quick note to keep everyone in the picture ... I'm pretty sure that I've got the settings & heating directional airflow sussed so that the unit doesn't cycle and just maintains continuous background operation, so the dull & cooler period we've been going through has been pretty useful ...

Not bad, over 1kW.t of heating, a 50" TV, a laptop,
all baseload covered plus the fridge & freezer cutting in & out and there's still change left from less than 400W of pv generation ...

HTH
Z