Thoughts on commissioning a Vaillant Arotherm Plus 12kW

[JamesPa]

4 hours ago, sharpener said:

Have tried to follow the convoluted interaction of the SI, the explanatory memorandum and the original legislation but gave up.

 

Can you say what you think it all means?

Yes

That the defining document (other than the legislation itself) is now mcs-020(a) published April 2024.  This is solely a noise calculation and no longer specifies installation standards or requirement to use MCS.  The title, quoted in article 6, is helpful in confirming this.

Edited May 18 by JamesPa

[Jerry32]

Hi Sharpener,

Many thanks for the reply confirming info on your system.

 

"VWZ AI Appliance Interface module's Live Monitor screens, IIRC the field in question is helpfully called "compressor modulation". Minimum observed value is 27.2%."

 

I'm assuming this is the Vailliant 'normal' customer interface / control panel ?

Therefore as far as I can see, the Vailliant Arotherm Plus 12kWh does modulate well below 100%, it's even better than the assumed 30% most makers would quote, so I'm really not sure what the Vailliant Tech was on about ?

 

This does make me more comfortable about getting the installer to fit one, despite what Vailliant

 have told me.

I just need to reinforce to him that I want it to be a volumiser system, not a buffer tank, or even a volumiser/buffer compromise system.

The Vailliant Tech did tell me that for the 12kWh ASHP I'd need a certain volume within the system to cope with the de-icing cycle, and the size of my system 125 litres, + a volumiser of 50 litres, is well above their suggested requirements.

The installer did suggest a volumiser/buffer style compromise though, as my main headers are 22mm not 28mm pipework, but I'm going to push for the straight volumiser system.

(He's the only installer anywhere near to me, that I'll trust, the rest are to my mind, technically muppets.)

When we come back from France, I'm going to chase him up again, as he's quite busy as an installer, no wonder why, so I'll just have to fit into his schedule.

 

To answer other peoples comments, it's really quite simple to measure LPG bulk tank percentage, as there is a gauge on the top graduated in 5% increments. (Very similar to offshore bulk tank readouts)

Going by my daily readings, and double checking the tank %age values before & after filling, against the delivery lorry figures, it's really accurate.
It also has a makers plate showing total tank volume etc.

So, once you have a daily %age usage, which of course varies dependent on the usage / weather, it is easy to calculate the volume in litres used per day, then convert that using industry standard conversions into BTU or kWh etc.

So I know exactly how much energy is used by the Combi, and then depending on the efficiency used, how much heat energy is put into the house. 

(Even at 100%, a physical impossibility, it comes nowhere near the MCS theoretical calculations, but then we do keep the house somewhere between 18 to 19 degs C during winter, not at the MCS 21 degs C.)

 

I can double check this 'daily usage' against the 'total usage' per year, from which I have to deduct DHW usage during summer etc. This verifies my calculated heating season LPG litre usage, and it's cost.

i.e. over the last 2 years I used a total of 3800 litres of LPG at 78.75p per litre, essentially £1700 per year total, including £128 tank rental, which is about £1500 per year on heating during the 5 'winter months'.

 

Sometimes I wonder why I'm even bothering to chase down an ASHP, I'm not going to live long enough to see parity, let alone financial gain from moving away from LPG to an ASHP !

I guess it really began from having a very large set of bungalow & garage roofs, where I've gone and fitted way too many solar panels 52 / 28000kWp, and in the garage, batteries, 3 / 29.1kW.
(I Thought what's the point of having savings, which are all taxed, so I just stuck the money on the roof instead.)

 

It's just utterly frustrating that I have actual measured data, which is just ignored in preference to theoretical MCS calculations.

They remind me of the ridiculous EPC calculations, which are utter fiction.

What's even worse is after 25 years as an Offshore Oil / Gas Supervisor / Dept Head, I'm being told absolute drivel by most installers, a lot of whom are really not 'competent' at all.

The ASHP industry at the moment just reminds me of the 1980's Double Glazing 'Cowboy' early days, before it got sensible and the 'wide boys' moved onto another method of conning house owners, which was probably cavity wall insulation !

 

[JohnMo]

9 minutes ago, Jerry32 said:

let alone financial gain from moving away from LPG to an ASHP

 

10 minutes ago, Jerry32 said:

solar panels 28000kWp, and in the garage, batteries, 3 / 29.1kW.

Assume you actually mean 28kWp?

Your solar and batteries and time of use tariff will drive the cost per kWh of heat down to almost nothing. If you are paid for export would expect to see you paying almost nothing for electric, which will include all your heat now. Lpg would always be in addition to electric so always a cost adder.

[marshian]

4 minutes ago, Jerry32 said:

I can double check this 'daily usage' against the 'total usage' per year, from which I have to deduct DHW usage during summer etc. This verifies my calculated heating season LPG litre usage, and it's cost.

i.e. over the last 2 years I used a total of 3800 litres of LPG at 78.75p per litre, essentially £1700 per year total, including £128 tank rental, which is about £1500 per year on heating during the 5 'winter months'.

 

It's just utterly frustrating that I have actual measured data, which is just ignored in preference to theoretical MCS calculations.

They remind me of the ridiculous EPC calculations, which are utter fiction.

just for info I have a lot of data on gas usage for my house and one thing that really stands out is summer DHW usage is very very different to winter DHW usage.

 

in summer tank losses are lower due to higher ambient temps in the house

 

water from the mains can be 10 deg higher in temp coming into the house

 

typically my summer DHW usage is 3 to 4 kWh for the heat up - Winter it's closer to 5 kWh - that's a significant % increase that you probably need to factor in

 

MCS I agree is a bit crap - worst case on worst case - might be worth ignoring the grant element and pricing up what you need without

 

EPC pretty much fiction and not really a good guide