Thank you very much!
What’s actually in that cupboard / what footprint does it occupy out of curiosity?
This is a ‘250’ litre Vaillant cylinder, combo valve, 3 port valve, heat meter, heat pump controls, expansion for heating/hot water, and heating / dhw / dcw manifolds. Footprint is ~700 mm width x 800 mm depth (external to plasterboard); with the cylinder sneaking “into” the stud walls by sitting between the studs on a wall that is only boarded on the one side:
The unitower would also offer a similar footprint; without the efficiency/longevity compromise of running the PCM material.
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Marco,
The internal dims. of the cupboard (a standard tall Howdens unit) is 565w x 575d but you can see from the pics that the Sunamp unit, fitted sideways to allow for existing pipework at the back, needed the right-hand panel removing up to about 650mm to clear the unit. So in effect the cupboard is supported by the ‘deco’ panel on both sides - it wouldn’t fit in just a standard cupboard. Ideally the unit should fit ‘lengthways’ so the little led panel lights are at the front but they don’t tell you anything worth knowing anyway. it was fortunate for me that it could be made to work.
In the cupboard are all the items needed on the ‘internal’ side of the monobloc plus:
25 litre buffer, secondary pump, all the Vaillant controls boxes (VRC720), the openenergy monitor level 3 monitoring items, 2 x heat meters and the Eddi solar diverter. And a ‘Scalewatcher’ box which allegedly minimises scale build-up but I can’t prove its effectiveness. Sunamp recommend something similar, and it was on my old system, so there it is.
When I finally get around to putting the shelf in and doors back on I reckon I’ll still have space for my Dyson vac and charger, broom, etc. 
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Ah!
565 mm is a swine; pretty much nothing will fit those other than 150 litre slimline cylinders. :-/
Having the cupboard sides in place does give lots of room for gubbins mounting. I think I might pinch that idea / take inspiration and use on another project currently under way where the extra space for gubbins would be useful - thanks!
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Hello,
I have ordered the 55/6, no buffer, only heating, 1 circuit, max flow calculated at 40 degrees, “kis” version, so I expect 4+ Scop.
I added also 1x antifreeze valve, but should I consider also a deaerator ?
Reg. The position of the pump, the distance between the pump and the fence is ~1 meter. Based on the test from the Heat geeks, aparently it should be fine, but based on Szymon’s yt videos, it might not….
What is your experience, guys, especially during winter?
They’ve split into two sites, commercial and technical
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With colder weather approaching I’ve updated and extended the charts on my Arotherm Plus Weather Comp Curve Info blog post over on Energy Stats
Tables now show
- indoor target temps of 18C through to 21C
- flow temps for curves 0.3 right up to 1.2
- outside temps of -3C°, 0C°, 5C°, 10C° and 15C°
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We have a storage battery and the inverter is 3kW peak output. Would it be practical to have a set back scheduled on the ASHP for between 18h and 20h, to help minimise grid import while we are cooking?
What sort of power consumption might I expect a 5kW Arotherm Plus to use during set back? Appreciate it will vary based on house size, heat loss, outside temp, etc.
During winter, our gas consumption for heating averages around 45 kWh per day. So, assuming a poor COP of 3, that’s hopefully just 15 kWh of electricity for the ASHP, spread that over 24 hours, am I being overly optimistic that its very approximately 700 W power consumption. Or is there likely to be peaks and troughs?
Looking at your graph the blue line for electricity consumption appears to be under 1kW most of the day. What’s the high consumption around 2am? Water heating during off-peak?
My usual pattern is
- 22:00 to 04:30 setback 19C
- 04:30 to 0730 target 20C
- 07:30 to 15:30 setback 19C weekdays, target 20C weekends (although I might manually bump this to 20C if i’m WFH)
- 15:30 to 22:30 target 20C
So if you look via Emoncms - app view dashboard, you can see the slight variations in electric input and heat output.
My setup (and low heat loss) means i’m running at minimum output of the 5kW model much of the time, especially when warmer than 4C or so, so around 350-500 watts for 2kW heat output.
When it gets really cold (sub zero), this can rise to 1.3kW input for 4kW output.
Have a poke about on my link above to see the difference when the temps dropped last winter.
I’m running lowish flow temps (mainly in the 30s), hence the unit runs low electric.
If you’re having to run 50 flow for example, it will talk more juice for this.
And yes, DHW runs overnight and sometime in the afternoon (currently 00:30 and 14:00)
Hope that helps.
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Using the ebusd interface i’m trying to better understand the relationship between compressor rps and flow rate/pump speeds on DHW with a view get better COP.
If you look at the COP charts here for the 5kW model you can see that COP falls off a little once you take the compressor past 97 rps.
COP on the left, heat output on the right. Match the same box on each chart.
Top charts are 35 flow, 30 return and the second 45 flow, 40 return.
it’s similar story for 55 flow for those that go higher too. 
Granted it’s only about 0.2 to 0.3 better COP, but you know… Top of the SCOPS and all that. 
So on my own system with my Mixergy, I started playing about with DHW pump speed to see if I could get close to 97 rps.
50% pump speed on DHW gets me to 95 rps. So I ‘should’ get slightly better COP now, albeit at the expense of heat output, looks to be around 0.5kW less.
Obviously, you could just run in DHW Mode: Eco and always runs at 50 rps. But I tried this and couldn’t handle 90+ minute hot water runs on my 250L cylinder.
Anyone else with a normal cylinder willing to see if their COP improves dropping their pump speed?
You can also use quiet more which reduces the compressor by 30%, which would take you from 120rps->90rps.
So is Vaillant reducing the compressor RPS in line with the reduced pump speed configured? Does it do the same for heating? It would be weird if it did for heating given “auto” doesn’t adjust the flow rate down when the ASHP modulates down.
Set-back is one option. But a better option IMO is to set the quiet mode to be active from 18-20hr. This will limit the compressor which in turn limits the current. I think I already answered this question, and gave current values for noise reduction %'s numbers on FB, right?
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I’ve finally gotten around to starting to monitor our Arotherm+ 7kW this weekend (it was installed back in March/April).
Overnight (when colder) the runs look fine - at least an hour runtime per cycle, very smooth and with good COP.
Today as things have warmed up to 10C-12C outside I get a strange dip in the flow temp and heat output on each (short) cycle - but during the dip the electricity input does not also reduce.
Has anyone seen this before?
The unit is mostly running at minimum heat output (~3kW) even overnight wheh the temp was 6.5/7C.
Common Arotherm behaviour, nothing to worry about. Take a look at most of the Arotherm on the heatpumpmon list. 
5.5 COP at 10C outside on a 7kW is just about on spec, so system looks to be working well. 
Thanks Mick - well I won’t worry about it then but I do wonder what it’s doing!
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John Cantor was observing this same phenomenon on his Mitsubishi…
It’s something to do with the “compressor discharge temperature” and where the evaporation happens.
Here’s a chart i’ve pulled together from the Vaillant Czech sheet.
This simple graph shows the COP you should expect to achieve at various outside temps.
As you can see, my 5kW model can’t reach the same COP heights as the larger models.
I’ve finally made peace with this fact now.
Using the Heat Pump app I think it makes it easy to see if your installation is hitting expected outputs?
Just pull out a heat run at one of the outside temps from the graph and match up the outputs?
COP 5.27 on heatpump app versus 5.1 from the Czech spec. So that’s good.
Same here, 4.6 from both.
Mick,
Something caught my eye on this graph. The graph is based on 35/30; at 0C outside it claims 3.8kW max output for 5kW unit. This seemed low to me from what I remember so I went back to the table on your blog from the Vaillant brochure which has the various outputs and COPs crossed referenced with outside temp and flow temps, and there it says 6.9kW for same outside and flow temps. Which one is correct?!
Cheers,
Tom
Ah wait the graph from the Czech sheet is for COP, even thought the title says its for KW output?
Yeah, I ballsed up on the titles, sorry. good spot, i’ve updated.