My Irish Heat Pump Odyssey - high SCOP monobloc install Heat Geek/Urban Plumber style

marcexec · 27-03-2026 08:58PM #1

Content warning: I compulsively over-research and am probaly addicted to the Heat Geek & Urban Plumber YT videos.

I'll document my experience with installers that I have for what should be the crowning upgrade to our house and probably have a bit of a rant as well.

The objectives:

True monobloc unit to minimize noise as the DHW cylinder and boiler are in the master bedroom.
System designed for a flow temperature of 45°C or lower
Open-loop system with no buffer tank
External monitoring for https://heatpumpmonitor.org/

Property:

1960s ex-council end of terrace, 115m2, MVHR (DIY'ed by myself)
5kW heat loss, have (DIY) heat loss calculation with Heat-Engineer.com
~10m pipe run to preferred location on top of kitchen extension
BER B1, HLI is 2.206 W/K·m2, so SEAI grant is possible
Relatively new condensing gas boiler from the Warmer Homes scheme
Radiators are mostly P+, so some will need to be replaced
5 people, ~200-250l cylinder for DHW
This will coincide with a dormer extension & chimney removal in the attic, so more intrusive works can be accommodated

From my research, the best option would likely be the refreshed Vaillant Arotherm Plus: https://renewableheatinghub.co.uk/forums/renewable-heating-air-source-heap-pumps-ashps/new-vaillant-arotherm-plus-in-black-when-will-it-come-to-the-uk/ , but others like

Daikin Altherma 4 MT, Samsung EHS Mono R290, Ideal HP290, Grant Aerona R290, Panasonic Aquarea L or even the Midea M Thermal Arctic (R290) should be OK. It has to be supported afterwards and I guess we're all used to a bit of compromise for being at the end of the supply chain…

Method:

I contacted installers that are SEAI registered, have a website and some reviews, don't just promote boilers and are close by
they got a version of the property details above and documents like the BER and HLC
I'm (naturally) tracking them in a spreadsheet
some only focus on brands that don't tick the boxes (like indoor units with the circulation pump), I tried to exclude them
others don't "have capacity" (likely not doing domestic installs), which is fair - so far #4 & #14

ECO_Mental · 28-03-2026 04:35AM

Hey I'm totally guilty of over researching things as well and it's good to learn about these things. My opinion is maybe you are better off getting one of the major manufacturers used here in Ireland that has a good service and support network. I'm thinking either Daiken or Joule Samsung for example.

My reasoning is... all these HPs are "theoretically" very efficient…the biggest factor in them not being efficient is not being used correctly or people not understanding how to use them. From what I can see you have this locked down😎 also not being sized correctly which also you have done your research. So next you want one that you won't have an issue with warranty or getting serviced, that might be an issue with some obscure high end German HP you import.

All HPs you can set flow temps, temp compensation curves etc. Some alright have fancy logging facility but I'm reality all you need to know if it's on or not and how much kW is drawing. A simple Shelly energy monitor linked to Home Assistant will give you this (and open other avenues for home automation and energy management)

So I would be looking for one of the major brands used here in Ireland for support purposes. From your research you understand how they work and how best to use them so I have no doubt you will get high SCOP no matter what. Oh yeah get a big HW tank, that way you can schedule your hearing of this to the night rates.

marcexec · 28-03-2026 03:59PM

https://www.boards.ie/discussion/comment/124346691#Comment_124346691

Yeah, agreed. I'll totally look into optimizing things further once the dust has settled. I already have HA, set up DHW priority and use Tado with OpenTherm to the boiler etc. I have added your suggestions above while I still can, thanks.

Heck, we even have Zypho WWHR units under bath and shower. I also plan to have them plumb in a duct mounted heater with the MVHR for heating and cooling for extra comfort and efficiency. Depending on the airflow it will add another 3-5kW emitter to the system.

Re "obscure high end German HP", I found the Wolf unit but ignored that. The Vaillant is very successful on the UK market, "top of the SCOPs" and C&F Quadrant said they'd try to get a price at least.

now /rant (need to thank them for pushing me to post here already):

#1 experience so far:

friendly and responsive
good reviews on Google
local to me

But:

didn't read the brief, and they only install Viessmann HPs. The Vitocal 100A is R32 (disallowed to install from next year and less efficient than R290) and the current 150/151As must use a hydrobox. I had contacted the distributor Precision Heating (PH) before and they tried hard :)
they don't do the system design, that's done by PH. I doubt he's done a HLC in his life, see next point
we have 1/2" pipes on the rads, which is at least 2.3kW at DT5 and 40°C flow. They insist that all pipes in the whole bloody house get replaced with 1" ("for the flow rates, you know"). If any old pipes remain we'd have to sign a waiver regarding the performace of the system!
all radiators must be replaced with aluminium ones…

Bottom line is that they are - well draw your own conclusions, but they could benefit from a Heatgeek course, even a video…

It made me quite angry yesterday thinking that some people will fall for that and have to spend 10s of k plus their house ripped apart and we're all paying for it. They likely end up with a system that's working but overkill if not oversized. Plus another horror story to tell in the news.

Makes me wonder if the people that say that the SEAI grants are "all a scam" might have a point…

graememk · 28-03-2026 06:13PM

Oh yes, must have aluminium radiators, I have yet to see a spec sheet that shows a alu rad out perform a steel rad of similar size. They may heat up quicker due to lower water volume, but if running steady state, it doesnt matter.

Must find championC's thread in the plumbing forum where he self installed a valliant.

Ive installed an ecoforest 12kW, just dropped it in, replacing the oil boiler. I did end up upgrading 2 radiators where I found it to be lacking but that wasnt hard to do. Very happy with the ecoforest, The main distributor is up my part of the country, but they cover the whole island. I did have an inverter failure, but that was no issue getting it replaced. House is on tado TRV, with the hall thermostat deciding the call for heat, all other rooms are set as limits not targets.

https://emoncms.org/app/view?name=EcoAir&readkey=82a75750e2f56ccdc7e96768b9776268

background, 1980 house, mostly double rads, was able to heat it solely from solid fuel stove, but 24/7 fire.

main pipe from heatpump is 1" which drops to 3/4 before going to radiators, split into 2 circuits, pipes in floor is 3/4 until the last radiator or 2 where it drops to 1/2"

I started off running it on a schedule, but this winter i more or less went steady state, and was able to reduce the flow temperature (weather compensated), increasing efficiency. I think I possibly could reduce it a little bit more

marcexec · 28-03-2026 09:26PM

https://www.boards.ie/discussion/comment/124347648#Comment_124347648

Cheers, fair play to you.

Have you considered using FRVs (https://www.firepowerheating.co.uk/frv) instead of the Tados? It's fine on the boiler (especially with OpenTherm), but I expect to ditch my system and maybe go with one wifi-based one on HA for the sun room (often window open for clothes drying) and leave the rest in one big open loop. Thus the balancing valves.

graememk · 28-03-2026 09:39PM

https://www.boards.ie/discussion/comment/124347924#Comment_124347924

Seen Glyn Hudson use them in his last install. If blank slate yes, but now, juice not worth the squeeze.

Also got tado support to set a minimum call for heat time.

You might end up designing the system yourself!

marcexec · 29-03-2026 03:22PM

Thanks @graememk, I feel like I already have…

THE ALM · 29-03-2026 04:52PM

Like you, I do a lot of research.

I was going down the Valliant route but couldn't get anywhere with it in Ireland. Did contact CF Quadrant and even visited them at one of the home shows but never got any response from them despite following up several times.

I did contact nearly all the suppliers, Grant, Midea, Bosch, Heliotherm etc. and then whittled it down to Viessmann and Stiebel Eltron and would have been happy to go either or. I might have gone the new Grant R290 but it wasn't available at the time. They are local to me and the new unit and controls seem to be well regarded and a big improvement on the older unit.

Did my own heat loss calcs and sent the details to both. Both got back with sizing, similar to what I had, and both were happy to answer any queries I had.

Both have a presence in Ireland with Viessmann through Precision Heating and Stiebel, now, through Nutherm. Both are considered to be well made units. (Stiebel did have there own centre in Dublin, that seems to have changed, I did deal directly with them at the time).

Had to change three radiators to get the design flow temp down to 45° (I have never seen it anywhere near 45° in the 18 months we have been running it) but no mention of changing pipes or aluminium rads. Like graememk, I think the whole aluminium rads things is a bit of a gimmick as once they are up to temp then that is it.

I came across the installer on a job I was on. He priced several different system, has an Ecodan himself, but was very impressed with the Viessmann.

The Viessmann might be out for you with the indoor unit, we have this in a utility room and there is a slight hum from the pump. The 150-A Compact as an Integral Cylinder that might work for you, but again this as an internal circulation pump that may give a hum.

marcexec · 29-03-2026 07:24PM

Cheers @THE ALM, yeah the Viessmann is out. I didn't have the SE on the radar yet, but they look very nice and seem quiet as well. Certainly no objection to them, just checked the RHH video. Just one question, if you went that far with the SE, is the Hydraulic Module (HM) Trend mandatory? From what I can see online it contains the circulation pump as well:

"The following are integrated into the appliance: a diaphragm expansion vessel with 24 litre capacity, a high efficiency [HE heating circuit pump sized in line with heating output, an electric emergency/booster heater and a WPM heat pump manager."

see picture for the proximity of the hot press to the master bedroom bed (and it's "guardian")

THE ALM · 30-03-2026 09:53AM

When I looked at the SE it was with the Integral cylinder which, again, had the circulation pump built in so may lead to a noise issue in your bedroom. The look to have added a new cylinder which may mean a circulation pump could be installed elsewhere?

Looking at your photo the hot press looks tight for a modern cylinder, I'd say the one there is about 450mm, so will be worth checking the size of a new assuming you are replacing it.

micks_address · 30-03-2026 10:11AM

ok, so we are in as simillar boat and are going with the Grant r290. We have been tipping away at changing out gunmetal pipework and microbore over the last few years and in december we swapped out our relatively new hot water cylinder for a joule 200 litre heat pump ready cylinder. We needed a bigger tank anyway as the old one was only 120 litres and running a shower off it with four adults was tight. Watched a lot of urban plumbers and youtube etc and tried contacting few installers. One or two just sent me quotes without even visiting the house or talking about heat loss which was a big red flag. Once the grant got bumped up it seems like a relative no brainer as with us already having the cylinder in place the grant will cover a lot of the cost. We are replacing a gas boiler. Adding one extra rad downstairs. Moving a bedroom k2 to the bathroom which has a single panel and installing a k3 in that bedroom. Lad is actually here this morning putting in the base for the heatpump with the install scheduled for next week. Excited and a little nervous about it. Our HLI is 1.91 - attic insulated few years ago, and last year we replaced all the windows and external doors with triple glazing etc. We have hollow block construction so our only insulation path would be to add external insulation. With the amount of windows we have it might not be worth it. We might do the cable wall at some point but will see how we get on.

Have solar and battery storage (32kw) I dont expect to be able to run the house during december / jan without using some peak electricity usage. Currently on the pinergy 3 hour ev tarrif which is silly cheap. Will see how it goes. Getting the 9kw grant. I calculated heatloss using heatpump at 5.6, google did the same based on hli from ber and the installer came in at 5.5 with his calculations as well. Will let folks know how it goes.

graememk · 30-03-2026 11:05AM

https://www.boards.ie/discussion/comment/124350376#Comment_124350376

How much of the install would the grant cover?

Is there as much hoops to jump though now?

micks_address · 30-03-2026 11:30AM

https://www.boards.ie/discussion/comment/124350494#Comment_124350494

it should cover 90% of it.. process so far has been fairly painless but i guess its after the works done and application goes in we will see.. i need to arrange a ber assessment and had to request a tax clearance cert from revenue.

marcexec · 30-03-2026 02:57PM

@micks_address are you getting the 9kW because the 6.5 only produces 5.98kW at -7°C vs. your 5.6 calculation?
Will look into Joule, though we have WWHR - showers aren't even a problem with the small tank we have.

marcexec · 30-03-2026 03:07PM

@THE ALM, thanks, will wait if anyone recommends SE, only very few replies so far. The DHW cylinder will be replaced and we can expand the hot press. We'll have some works going on anyway as we're getting rid of the (remaining) bits of chimney in the MB, attic and external. Don't need that heat sink, also allows for an additional PV panel ;).

micks_address · 30-03-2026 03:19PM

https://www.boards.ie/discussion/comment/124351053#Comment_124351053

well from what ive researched there's no penalty going for the 9kw as it modulates down really well.. at -2 it does 7.x i think and then if you have a defrost cycle might be tight to.. glyn hudson had a slide on it at the start of his video (grant r290 fit). https://www.youtube.com/watch?v=Tz0W9xCBxS0&pp=ygUQZ3JhbnQgYWVyb25hIDI5MA%3D%3D

marcexec · 30-03-2026 06:01PM

https://www.boards.ie/discussion/comment/124351111#Comment_124351111

Fair enough, I'd actually seen the video when it came out, seems reasonable.

#12 came back today asking some very good questions. MasterTherm seem to be good units as well, maybe a bit overkill with the backup heaters but let's see…

graememk · 30-03-2026 08:00PM

https://www.boards.ie/discussion/comment/124351111#Comment_124351111

Noticed that with the midea ones, a lot of them have a similar minimum output, (and compressor size etc) but the output changes, hints at the some of the range is somewhat software limited down to an output

marcexec · 04-04-2026 10:30PM

Happy Easter, got my first quote and it's even nicely itemised. They are suggesting the 26IP, which is oversized IMO as it can only modulate down to 4kW, but a safe bet for the average home I guess. The '22 is only 200 quid cheaper: https://www.mastertherm.eu/d-doc/1/700/638550146402066667/pricelist_R290_EN_INT.pdf - they are quoting list for the unit, €500 for the 2nd zone (?), €3,450 for installation, ~500 for control and connectivity, ~200 for energy meter, €675 for commissioning and support, ~1850 for the fitted cylinder (!) - €17k with VAT in total plus any radiator changes.

MT 17-18.pdf

al2025 · 05-04-2026 07:20PM

midsummer.ie might be worth considering, full package prices available if you want to DIY.

marcexec · 05-04-2026 09:44PM

Thanks @al2025,

I doubt I could wing that with the desired location on top of the kitchen extension in reasonable time (i.e. without the family revolting). The Telford cylinders though, they are very interesting and I didn't spot them before. Pretty good value as they have a decent coil size, so shouldn't be hindering efficiency.

eiritated · 12-04-2026 03:15PM

I love that these forums and discussions exist but is it also infuriating we don’t have something like Heat Geek here as an independent accreditation?

I’m also spending far too much time trying to figure how this should be done and meeting installers that have such differing opinions - is there not strong design rules from the premium manufacturers where everything is fed into software and the approved design implemented AND inspected?

I’m only at the start so maybe I’ve just not met the right people yet?

marcexec · 22-04-2026 05:50PM

I'm in the same boat @eiritated.

As we all like stats here, I have contacted 18 installers that (as per SEAI list) operate in my area. They all got an email from me with details of the house and I basically asked what brand/unit they would propose.

2 have sent me detailed quotes that I might consider.

3 have not replied after three attempts (24/03/2026, 31/03/2026 & 13/04/2026), while 5 replied they have no capacity only after those three emails. 3 others replied immediately that they can't/won't.

One only does Viessmann (mandatory indoor unit, i.e. fails basic requirements) and wants to replace all pipework, install all aluminium radiators and won't guarantee any performance if any existing plumbing remains. They don't even service or commission them and are leaving all that to Precision Heating? Absolutely no clue about hydronic design, i.e. a box-slinger…

One replied quickly but left me confused after I had the following exchange: "I noticed you have asked about a monobloc which is glycol, R290 is lpg gas on the outdoor unit. R290 are more expensive than monobloc heatpumps." I stated my confusion: "Is e.g. the Ecodan PUZ-WZ50VAA-BS not a monobloc with R290?" to which the reply was "You would be best off going monobloc, the R290 with Mitsubishi isn't going great for them currently they are currently revising the R290 I don't think any have been sold in Ireland as of yet they focused mainly on splits but by 2027 have to pull them from the market so monobloc is the primary replacement for split we have footed a few and they are going very well"
after which I didn't get a reply to my question if they have units with circulation pumps outside (they don't).

Which gets me to my current conundrum, if I insist on a unit with the circulation pump integrated I'm currently down to a single quote (the MasterTherm), which is overkill IMO.

Mitsubishi seem to have a range of installers and the controls are "discovered" (HomeAssistant etc.) if the standard controls are not sufficient at some point. Also, the SE rep suggested mounting a pump outdoors wouldn't be a problem if he can't find an option (no quote yet). What are your thoughts about having a pump outside? I checked online and there are some insulation jackets, but it would probably need an additional enclosure/cabinet for weatherproofing.

graememk · 22-04-2026 08:03PM

"I noticed you have asked about a monobloc which is glycol, R290 is lpg gas on the outdoor unit. R290 are more expensive than monobloc heatpumps."

I dispair… I dont think there is anything correct in that sentence. (bar the R290 is LPG…)

Re pump, How big is your house? Is it "Normalish" size? The intergrated pumps in most of these units are very good.

Ive had good experience with the sellers of Ecoforest heatpumps even though mine was a self install, I still got it from them, Main office is in the north of the country but cover nationwide i think. No issue with warranty on the machine itself when I had an inverter failure due to possibly a loose connection on the inductor as that had burnt out.

micks_address · 22-04-2026 09:39PM

https://www.boards.ie/discussion/comment/124414320#Comment_124414320

Have you looked at the grant units? I just had one installed. I can pm you the installer. They are very knowledgeable on design and installation was pretty good. I've a ber due next week and then the grant forms going in for processing.

marcexec · 23-04-2026 04:01PM

@graememk cheers, didn't have them on my radar yet. SCOP is a little lower but the documentation is very comprehensive with actual graphs and sizing is suitable. Not very open on the Home Assistant side though, but would work.

We have 115m2, so not massive, the issue is that only one (expensive) quote had one with a pump outside…

@micks_address cheers, yep, since the Urban Plumber video (https://youtu.be/2zznWycWnwA, check the comments as well) they are my "backup Vaillant", but no one had quoted it yet! I'm a bit concerned about actual noise, but the controls have apparently improved even more and as we'll need the 6.5kW unit (4 is way too small) it will likely not have to run full throttle ever. So, please, do forward it, TAI!

graememk · 23-04-2026 05:05PM

https://www.boards.ie/discussion/comment/124416575#Comment_124416575

My house is similar. 1980 bungalow, massive windows, have recently upgraded the 25+ yr old double glazing with triple in October.

Eco forest has modbus access, I've the modbus document and pull it in via a esp32 rs485 board through esphome.

My data

https://emoncms.org/app/view?name=EcoAir&readkey=82a75750e2f56ccdc7e96768b9776268&mode=daily&start=1774310400&end=1776988800

micks_address · 23-04-2026 06:39PM

https://www.boards.ie/discussion/comment/124416575#Comment_124416575

Yes indeed I asked urban plumber for his recommendation and he suggested either valiant, nibe or grant .. I guess each installer has their preference. The guy who did mine said the grant is very well priced and looks good. Mine was the first he has done. I know probably not the best idea but I asked for it. He said they are a good couple of k cheaper thank the likes of the viesman before you add the required indoor unit and fittings

marcexec · 24-04-2026 11:54AM

https://www.boards.ie/discussion/comment/124416966#Comment_124416966

Yep, looking at the controls they aren't reinventing the wheel and are going with something that's also used by others: https://community.openenergymonitor.org/t/econext-direct-local-control-of-grant-hp290-econet-replacement-plum-ecomax360i/29758
How's your COP in April going?

micks_address · 24-04-2026 08:25PM

https://www.boards.ie/discussion/comment/124418322#Comment_124418322

We only got the weather sensor up this week so cops etc all over the shop. Honestly don't think will have much meaningful data until autumn winter.

marcexec · 28-04-2026 09:09PM

For some fun bit, this is the current fan-assited rad under the kitchen cabinets. It's the only heating in the kitchen extension but someone in the house keeps turning the fans off (yes there is a HA automation…) because it's "too loud".

Heat loss at design temperature is 775W

The "dining room"(old kitchen) will get a K2 (K3 is too deep), likely 600x1200 but I'm still playing with sizes as the door is often open to the hallway.

Back to the extension I'm going to put in a passive solution, six of these shinies from Germany(https://www.killus-technik.de/de/ekowand-heizleiste-1m.html):

They should add a good 300W at design temperature and flow of 42°C, maybe 39°C if I'm allowed to move the old P+ from the hallway to the living room as an addition. It's the bottleneck if we're not upgrading any of the existing 3 500x1100s.

Heat Engineer does a (pessimistic I think) SCOP estimate of 3.4 at 42 and 3.8 at 39°C, based on the current Arotherm Plus:

I do realize I'm fiddling around within the margin of error here and have ignored balancing, but I think I'm in the ballpark. Under 45°C is pretty decent for a retrofit and easy with R290, but happy to discuss.

My Irish Heat Pump Odyssey - high SCOP monobloc install Heat Geek/Urban Plumber style

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