ASHP sizing

[Dan F]

1 hour ago, Thorfun said:

I spoke to Enhabit about our cooling requirements and we are having the cooling modelling done (awaiting the results). we can use fan coils and it's something they would design but they say it complicates things and they've recommended keeping it simple and having the cooling as a separate system. plus the fan coils they've suggested aren't amazingly cheap and it's something that I just don't have time to play with as there's too much else to do.

 

We are indeed having external blinds on the FF (and many GF) windows and we think our cooling requirements will be very low but we both can't sleep if it's too hot and if we can have an 'invisible' ducted AC system in the bedrooms for the occasional use we both think that it's a price worth paying. The AC company we've spoken to are happy to simply first fix for AC now and then we can just live in the house and see if we even need it and then if we do second fix the AC units with minimal disruption if we can't find the funds in the budget to fit it now.

 

There are many options I'm finding with self-building and you have to, at some point, just make a decision and stick with it otherwise you could end up going around in circles. There's no reason why an AC cooling system can't be controlled from Loxone and so we can have a centrally managed temperature controlling system that can deal with hot and cold weather and whatever climate change throws at us, albeit for a price.

 

I'm having to choose my battles with the build and decide which to attack myself and which to delegate out, and cooling is one of those I'm delegating.

 

I know the feeling.  We are also using enhabit who did calculations.  In our case they specified UFH + Comfopost for cooling.  This approach isn't for every build (e.g. if you don't have lots of automated blinds or not very well insulated), but when it's suitable it is nice and simple as no first floor pipes (other than MVHR) at all.  They calculated our total cooling load as 335W,  with the UFH able to supply 3.6kW (ground floor) and MVHR ComfoPost (first-floor) 1.1kW.

[Thorfun]

7 hours ago, Dan F said:

 

I know the feeling.  We are also using enhabit who did calculations.  In our case they specified UFH + Comfopost for cooling.  This approach isn't for every build (e.g. if you don't have lots of automated blinds or not very well insulated), but when it's suitable it is nice and simple as no first floor pipes (other than MVHR) at all.  They calculated our total cooling load as 335W,  with the UFH able to supply 3.6kW (ground floor) and MVHR ComfoPost (first-floor) 1.1kW.

 

it's interesting that they suggested UFH cooling for your cooling needs. I'm pretty sure I talked about that with them (or it may have been another company I can't remember now!) and they said it's not allowed. now I know that's not true and I was thinking of just doing it myself post-installation but if they've designed that for you then I will just ask them again.

 

What ASHP do you have? they've said that the Ecodans aren't reversible and so if I wanted to use the ASHP for cooling using fan coils then I'd need to 'upgrade' to a Daikin. 

[joe90]

45 minutes ago, Thorfun said:

it's interesting that they suggested UFH cooling for your cooling needs. I'm pretty sure I talked about that with them (or it may have been another company I can't remember now!)

If I remember correctly you can’t claim RHI if you use the ASHP fir cooling!!!. Read. Jeremy Harris,s blog, he reverse engineered his ASHP to give cooling and it worked well.

[Thorfun]

36 minutes ago, joe90 said:

If I remember correctly you can’t claim RHI if you use the ASHP fir cooling!!!. Read. Jeremy Harris,s blog, he reverse engineered his ASHP to give cooling and it worked well.

I thought someone here has shown that the rules changed in 2017 for cooling and RHI? can't remember who or on which thread though but I remember reading it somewhere!

[Dan F]

37 minutes ago, joe90 said:

If I remember correctly you can’t claim RHI if you use the ASHP fir cooling!!!. Read. Jeremy Harris,s blog, he reverse engineered his ASHP to give cooling and it worked well.

This might have been the case previously but its not any more. 

[Dan F]

@Thorfun I doubt Enhabit would have said it's not allowed. We're using Vaillant.  I thought other people on forun were doing cooling with ecodan ( @joth? ), I might be wrong though.

 

Happy to share our m&e spec with you for comparison. 

[IanR]

5 minutes ago, Thorfun said:

I thought someone here has shown that the rules changed in 2017 for cooling and RHI? can't remember who or on which thread though but I remember reading it somewhere!

 

Yep, rules changed at end of 2017. HP "water" cooling is now allowed on RHI

 

[Thorfun]

2 minutes ago, Dan F said:

@Thorfun I doubt Enhabit would have said it's not allowed. We're using Vaillant.  I thought other people on forun were doing cooling with ecodan ( @joth? ), I might be wrong though.

 

Happy to share our m&e spec with you for comparison. 

yeah, like I said it could've been another company as it was quite a while ago and my memory is pants.

 

they've said the Ecodan isn't reversible but, as you say, others have done so by switching a dip switch so I do know it's possible. I'll try and find the manual that says how to do it and go back to Enhabit. it might be that changing the dip switch isn't supported in the UK by Mitsubishi and so they might not be able to do it but what an individual does to their system post-install is another matter. but I will have the conversation with them.

 

I'm still waiting for our cooling demand calculations to come back (will chase the company up today about it) and once I have that figure I can make a more informed decision about it all. Comfopost is still an option if the demand is low enough.

[joth]

13 hours ago, Dan F said:

@Thorfun I doubt Enhabit would have said it's not allowed. We're using Vaillant.  I thought other people on forun were doing cooling with ecodan ( @joth? ), I might be wrong though.

 

Happy to share our m&e spec with you for comparison. 

Yep ecodan supports it fine, just a dip switch and a bit of fiddling in the controller menus. (and for me, messing around in the loxone program)

 

To be generous to installers, when they say it's not supported they may not be referring to the ASHP or RHI, but just the lack of gap-free insulation they applied to pipes, pumps, valves etc which will guarantee puddles of condensation everywhere. A system has to be designed and installed with cooling in mind if it's going to be usable, and our UK installers are just not trained to do this. Nor do they seem willing to charge a premium for the bit of extra effort this takes. 

Edited September 29, 2021 by joth

[Thorfun]

I received my cooling modelling back @Dan F and this is what it says:

 

 

I only got it late on Friday so didn't get a chance to ask questions as it looks like it doesn't take the shading of the external blinds in to consideration but I'll ask that on Monday. just seems quite a high cooling load.

 

anyone got any comments on this? 

 

(probably should start my own thread on this subject but ho-hum)

[joth]

1 hour ago, Thorfun said:

load.

 

anyone got any comments on this? 

Hope you installing 3 phase, and got enough space for a serious outdoor heat exchanger.

Over 30kW of cooling? on a UK domestic home sounds insane.

https://www.orionairsales.co.uk/daikin-air-conditioning-rooftop-packaged-uatyq30abay1-heat-pump-30kw100000btu-415v50hz-10214-p.asp

[Thorfun]

1 hour ago, joth said:

Hope you installing 3 phase, and got enough space for a serious outdoor heat exchanger.

Over 30kW of cooling? on a UK domestic home sounds insane.

https://www.orionairsales.co.uk/daikin-air-conditioning-rooftop-packaged-uatyq30abay1-heat-pump-30kw100000btu-415v50hz-10214-p.asp

yeah, that's what I thought. makes me think they didn't take any of our solar gain mitigation strategies into consideration. in fact, I think I've literally thrown money down the toilet for that cooling demand report.

[Dan F]

3 hours ago, Thorfun said:

yeah, that's what I thought. makes me think they didn't take any of our solar gain mitigation strategies into consideration. in fact, I think I've literally thrown money down the toilet for that cooling demand report.

 

Wow!  Agree, that doesn't seem to make much sense!  Did they tell you what method they used for this or what their assumptions and inputs were? Are they considering MVHR (on summer bypass), opening of doors/window? What heat inputs are being used (people, cooking, UVC/recirculation losses)?

 

Our PHPP calculation gave 1.1W/m2  (4.2W/m2 without blinds).  We do have 750mm overhangs and a large canopy on south elevation though.

[Thorfun]

10 hours ago, Dan F said:

 

Wow!  Agree, that doesn't seem to make much sense!  Did they tell you what method they used for this or what their assumptions and inputs were? Are they considering MVHR (on summer bypass), opening of doors/window? What heat inputs are being used (people, cooking, UVC/recirculation losses)?

 

Our PHPP calculation gave 1.1W/m2  (4.2W/m2 without blinds).  We do have 750mm overhangs and a large canopy on south elevation though.

they didn't give any details at all! (this wasn't Enhabit btw). the report was a couple of tables with no explanation of how the model was achieved etc and I have sent them an email asking for details and telling them how unhappy I am with their 'report'. one table seems to allude to them using occupancy and equipment to determine the cooling demand. no mention of blinds, MVHR or anything else. 

 

really think I wasted my money on this one but will see what they respond with when they get back to work tomorrow.

[Dan F]

4 hours ago, Thorfun said:

they didn't give any details at all! (this wasn't Enhabit btw). the report was a couple of tables with no explanation of how the model was achieved etc and I have sent them an email asking for details and telling them how unhappy I am with their 'report'. one table seems to allude to them using occupancy and equipment to determine the cooling demand. no mention of blinds, MVHR or anything else. 

 

really think I wasted my money on this one but will see what they respond with when they get back to work tomorrow.

 

Ask them if you should get 30kW heat pump based on this, see what they say.  Enhabit couldn't do this?  Not sure how much you paid, but might have been worth getting PHPP.

[Thorfun]

2 hours ago, Dan F said:

 

Ask them if you should get 30kW heat pump based on this, see what they say.  Enhabit couldn't do this?  Not sure how much you paid, but might have been worth getting PHPP.

Enhabit could do PHPP for me but said it has limitations in that it's whole house rather than room by room. Also, I'd already paid the other company for the thermal modelling and SAP report so the cooling demand wasn't as much as getting Enhabit to do a whole new thermal/cooling/phpp modelling.

 

in for a penny, in for a pound as they say!

 

I'll see what they say in response to my snotty email.

[Dan F]

35 minutes ago, Thorfun said:

Enhabit could do PHPP for me but said it has limitations in that it's whole house rather than room by room

Yeah.  Although if you know you have automated blinds in any rooms likely to have any significant solar gain then this limitation is less of an issue in my opinion.  That said, I would have done the same and not got PHPP if I'd already paid someone to do thermal modelling and wasnt certifying.