Mitsubishi Ecodan 11.2kW vs Vaillant aroTherm Plus 10kW vs with/without Mixergy tank

[KK_777]

Hello all, we are considering quotes from our installers for the above ASHPs, with or without a 250l Mixergy tank. I am generally of the impression that the Vaillant pump is better, but it is about £1200 more than the Mitsubishi without the cost of building its own little platform and soakaway in the garden (which I have yet to get a quote for). Would be most grateful to hear people's views / experiences on:

 

- The relative merits of Mitsubishi Ecodan vs Vaillant aroTherm - which would you guys choose, taking account of the price differential?  

 

- I assume the mixergy would definitely be a good add on for the Ecodan, but I haven't seen anyone talk about it in combination with the aroTherm - any thoughts on this combo?

 

Thanks in advance. 

[HughF]

Nice to see you over here too. I was going to say ‘post this question on buildhub too’

[ProDave]

Have a careful read of this thread before deciding

 

 

[joth]

9 hours ago, ProDave said:

Have a careful read of this thread before deciding

 

 

 

Agreed. Prior to that thread I had only good things to say about our ecodan, but £100+ per year vampire load might make the premium of the Vaillant seem more reasonable 

 

I considered the Mixergy but eventually decided against it mostly because I didn't want yet another cloud dependency in my life. A standard well insulated tank (Oso geocoil) cost a lot less to buy, has very low heat losses, and Just Works.

 

[PhilT]

In March last year I was faced with a similar choice. After a lot of research and analysis I wanted to go with the Vaillant Arotherm Plus (featuring the R290 Propane refrigerant) but could not find a suitable and safe place to put it anywhere around my house without breaching fire regulations. So in the end I went with the latest Mitsubishi Ecodan R32 single phase model. My electricity usage went up from 3,274kWh pa to 6,542kWh pa vs. an MCS heat loss calc of 16,213kWh implying a SCOP of well over 4. I was using around 21,000kWh of gas in the previous full year! So for me it has been an astonishing success story, but I have no reason to doubt that the Vaillant is capable of at least as good performance. As for the so called "vampire load" although initially I had a concern, after extensive monitoring my Ecodan R32 only consumes around 40-45W when idle so it's just not an issue for me.

[HughF]

1 hour ago, PhilT said:

In March last year I was faced with a similar choice. After a lot of research and analysis I wanted to go with the Vaillant Arotherm Plus (featuring the R290 Propane refrigerant) but could not find a suitable and safe place to put it anywhere around my house without breaching fire regulations. So in the end I went with the latest Mitsubishi Ecodan R32 single phase model. My electricity usage went up from 3,274kWh pa to 6,542kWh pa vs. an MCS heat loss calc of 16,213kWh implying a SCOP of well over 4. I was using around 21,000kWh of gas in the previous full year! So for me it has been an astonishing success story, but I have no reason to doubt that the Vaillant is capable of at least as good performance. As for the so called "vampire load" although initially I had a concern, after extensive monitoring my Ecodan R32 only consumes around 40-45W when idle so it's just not an issue for me.

Bang on the same gas usage as us, near enough...

[Dreadnaught]

1 hour ago, PhilT said:

without breaching fire regulations

 

Which regulations are those? Are those regulations related to the coolant, R290 (propane) only? Is there some form of minimum distance requirement?

 

(Am considering an AroTherm Plus ASHP for my build.)

[PhilT]

2 hours ago, Dreadnaught said:

 

Which regulations are those? Are those regulations related to the coolant, R290 (propane) only? Is there some form of minimum distance requirement?

 

(Am considering an AroTherm Plus ASHP for my build.)

Yes it's in the technical information (R290 clearances). My copy is from early last year - it may have been updated - worth checking for any changes

[m0deller]

Not sure I'd bother with a mixenergy tank with a heat pump as they are optimised for direct electrical heating. I read they need an external heat exchanger with an ASHP?

I had a similar dilemma last summer Mitsu vs Daikin vs Vaillant. Went with the latter in the end, despite it being a little more expensive. Newer refrigerant , higher on-paper CoP and integrates with their smart TRVs. 

Very happy so far. Achieved a CoP of just under 4, despite running it mainly overnight (Octopus Gofaster tariff) when it's colder. 

[HughF]

The more I read about vaillant and their controls, the more I like them. If you’ve got a chance to go with vaillant, choose them. But make sure you get their sensocomfort controls and all their balance of system components too.

[tommyt11]

Ripped out our old vented copper tank in May and replaced with a 210l Mixergy. Solar diverter from a 7.2kWp PV array. Very impressed with how Mixergy drip feeds from excess solar, its low heat loss, and its HW delivery performance generally. We are gunning for a ASHP install in late spring next year (I have already decommissioned the existing WB 30KW heat only boiler - we won't be living in the house during the renovation over winter). I like Vaillant, but interestingly one of their big selling points is high temp operation, ironically I don't need this feature really - we will be charging the Mixergy via heat exchanger, so a flow of say 60, and the heating system is all low temp UFH and large rads, so not expecting to require a heating flow temp of more than 45. House will be well wrapped up in EWI. Will be using weather comp as well. Will be tracking this thread.

[Chanmenie]

On 09/07/2022 at 20:37, m0deller said:

Not sure I'd bother with a mixenergy tank with a heat pump as they are optimised for direct electrical heating. I read they need an external heat exchanger with an ASHP?

I had a similar dilemma last summer Mitsu vs Daikin vs Vaillant. Went with the latter in the end, despite it being a little more expensive. Newer refrigerant , higher on-paper CoP and integrates with their smart TRVs. 

Very happy so far. Achieved a CoP of just under 4, despite running it mainly overnight (Octopus Gofaster tariff) when it's colder. 

Having checked on their website it appears  Mixergy make a specific heat pump tank which is optimised to work with heat pumps, I was considering a Mixergy tank with a Vailant heat pump.

[JohnMo]

 

8 minutes ago, Chanmenie said:

Having checked on their website it appears  Mixergy make a specific heat pump tank which is optimised to work with heat pumps

It's just an external plate exchanger kit that's added, that makes them suitable for anything.

[Chanmenie]

39 minutes ago, JohnMo said:

 

It's just an external plate exchanger kit that's added, that makes them suitable for anything.

So is the Mixergy tank worth considering in your opinion John ?

if not whats the best alternative 

[joth]

19 hours ago, Chanmenie said:

So is the Mixergy tank worth considering in your opinion John ?

if not whats the best alternative 

 

FWIW my biggest issue with Mixergy is having a hot water tank that's dependent on a Cloud hosted web service.  Honestly I just don't want that sort of complexity in my life, and I'm as early-adopter techie nerd as anyone. If they had a good story for local-only supported mode of working (software package or firmware controller, and local-only API to control it) I might have a very different opinion. [They have some tacit support for enabling this, maybe]

 

I'm a fan of KISS for a UVC. Personally my OSO Geocoil 300L is working great, but even simpler is a UVC to spec from Telford or Newark cylinders or similar.

 

 

On 10/07/2022 at 17:58, HughF said:

The more I read about vaillant and their controls, the more I like them. If you’ve got a chance to go with vaillant, choose them. But make sure you get their sensocomfort controls and all their balance of system components too.

 

So FWIW the drawbacks I hear since this comment (mentioned elsewhere on this forum) with Valiant, and their controls specifically, are

- the need for an overpriced coding resistor to enable cooling mode. (Workaround posted elsewhere)

- lack of ability to enable cooling / call for cooling via API or Modbus, so manual intervention needed in otherwise fully automated M&E system. (Workaround not yet identified) 

@Dan F is the expert.

 

If you want heating only, the Valiant seems an excellent option.

 

[Dan F]

7 hours ago, joth said:

FWIW my biggest issue with Mixergy is having a hot water tank that's dependent on a Cloud hosted web service.  Honestly I just don't want that sort of complexity in my life, and I'm as early-adopter techie nerd as anyone. If they had a good story for local-only supported mode of working (software package or firmware controller, and local-only API to control it) I might have a very different opinion. [They have some tacit support for enabling this, maybe]

I actually bought the Mixergy Modbus interface to enable me to do all control locally without a cloud dependency, so it is very doable.  The installer commissioned it with the standard controller though and I haven't got round to fitting the Modbus controller yet.  That said I haven't found using the control or app to be complex at all (simpler than stting up and interfacing with modbus anyway) and if connectivity is lost everything (apart from the app of course) continues to work locally without an issue.  What the controller app allow you to do is:

- Set temperature  (which you could easily do in your ASHP controller too)

- Set target charge level (this assumes partial charging via top coil or immersion heating)
- View graph of top/bottom temperatures and % charge.

- Setup schedules (which you could easily do in your ASHP controller too)

The smarts (which I haven't tested yet because I turned it off fairly early on for some reason) is allowing it to automatically decide when to heat the tank and to what charge level and temperatue based on, supposedly, the your usage patterns and tarrifis.

 

Aside from the PHE (which uses a pump) and enables, according to them, a more effective us of the tank capacity it is still a UVC under the covers, so while not the simplest of UVC's it's still simpler than something like a Sunamp IMO.

 

A good part of the value IMO of the Mixergy approach is the partial charging story which I bought into and plumbed for.  While this works great, what I've realised is that heating a UVC in this way, while possible, is not efficent and I really need to switch to the PHE and heat the whole tank at once.  This is because you are constantly needing to provide a 60C flow temp, ramp than ramping up from 10->60C as the UVC heats up.  There are other avantages of Mixergy aside from this though.

 

7 hours ago, joth said:

So FWIW the drawbacks I hear since this comment (mentioned elsewhere on this forum) with Valiant, and their controls specifically, are

- the need for an overpriced coding resistor to enable cooling mode. (Workaround posted elsewhere)

- lack of ability to enable cooling / call for cooling via API or Modbus, so manual intervention needed in otherwise fully automated M&E system. (Workaround not yet identified) 

@Dan F is the expert.

This is spot on.  Excellent summary of my various posts 🙂  We did find coding resistor available for £5 online though which someone bought and is using.

 

To clarify, if we had UFH in a screed above insulation then standard Vailant controls would work great for cooling.  The problem is that, as our UFH pipes are in the slab it self the very slow reaction time means the the Vaillant controller acting as a thermostat doesn't suffice.  The controls are there and work, but in my case (as with others with UFH in slab) you really need to control UFH based on slab temperature is posible.

Edited August 31, 2022 by Dan F

[JohnMo]

Don't think any thermostats are that good with a slow reaction heating system.  We are in 100mm concrete screed, thermostats just cause over and undershoot.  Smart controls cannot deal with the timings.  You just have to balance the energy going into the slab, low flow temp for long periods, or slightly higher flow temps for a set period.  Then balance the system room by room, to get the room temperature you want.

[HughF]

On 31/08/2022 at 15:20, joth said:

 

FWIW my biggest issue with Mixergy is having a hot water tank that's dependent on a Cloud hosted web service.  Honestly I just don't want that sort of complexity in my life, and I'm as early-adopter techie nerd as anyone. If they had a good story for local-only supported mode of working (software package or firmware controller, and local-only API to control it) I might have a very different opinion. [They have some tacit support for enabling this, maybe]

 

So FWIW the drawbacks I hear since this comment (mentioned elsewhere on this forum) with Valiant, and their controls specifically, are

- the need for an overpriced coding resistor to enable cooling mode. (Workaround posted elsewhere)

- lack of ability to enable cooling / call for cooling via API or Modbus, so manual intervention needed in otherwise fully automated M&E system. (Workaround not yet identified) 

@Dan F is the expert.

 

I'm a real fan of the concept of the Homely thermostat but the lack of non-cloud control and a decent in-home, physical front end is putting me off. It's either smartphone or smartphone...

 

Agree with you about the lack of cooling on the Vaillant - seems an oversight to make it so complicated to enable.

[JohnMo]

hope the homely thermostat isn't as clunky and slow to load as their website.  Doesn't fill you confidence.