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Newbie out of her depth – Samsung AE120RXYDEG 12kW heat pump

BAMi · 2025-03-09T10:58:59Z

Hi Long post, apologies!I had an ASHP (details below) with new tank and solar installed start November as part of the free gvt HUG scheme. Previously had oil CH but boiler was 25 yrs old and kept cutting out – I don’t have the money for a new oil boiler as on a low income, hence only option was ASHP as it was free. Previous Dec & Jan combined oil & elec bill was £165. Dec & Jan elec bill since ASHP was £350 & £400 😲 I can’t afford those kind of figures! I’m in a detached 1970s bungalow in the Lake District. Floor area 120 square metres. Pre-existing cavity wall insulation & loft insulation. Double glazing, not too old with trickle vents. Concrete floors. Extractors in bathroom, kitchen, utility. Pump is keeping house nice and warm, apart from lounge which is chilly. Bungalow is an L shape and lounge is in the L. It’s a north facing room and is the coldest room in the house. 2 new rads in there but it also has a huge 3m picture window. Setup: Installers: ASI Group (via contractor Rothwells) ASHP: Samsung AE120RXYDEG 12kw. Flow temp 47. SCOP 3.84. Sited on side of bungalow. Tank: Kodiak Joule 236L. Sited in former integral garage, which is now a wind & water tight room. Inverter: Solis hybrid. Currently can’t afford batteries, but requested hybrid for future batteries. 9 solar panels, total capacity 3.78kw on a South West facing roof. All new Stelrad K2 rads. All CH pipes are in loft, not concrete floor. Loft insulation was “to standard” but was topped up and is now 40cm thick. Water law is in action. Low (15C)=37C High (2C)=50C Current COP attached. DHW is set to 47C (was 50C but I turned it down as it was too hot), cycling to 60C on Tuesdays for legionella. TRVs are fully open, except in the room I work out in as it’s too hot (middle room in bungalow) which is set to 3 and also set to 3 in tiny en suite bathroom. No TRV on hall rad. Programmer & thermostat in hall. Set to 20C from 5am-9pm, then 15C overnight (installer recommended 18C but I can’t sleep in a hot room). I wasn’t given the heat loss calculation or design specification, but having read this forum have just requested both (no idea if I’ll get them though, had to chase & chase for MCS cert & DNO approval!) I’m with EON at 22.6p pkwh flat rate. SEG 16.5p (without a battery this was my best rate). I’m at home all the time as suffering from a brain tumour so bare that in mind. A cheaper night rate and higher day rate didn’t seem like a good option with no batteries. I’m frugal with electricity, trying to only use washing machine etc. on sunny/bright days timed to come on at noon. Don’t use much hot water so a huge tank being heated all the time seems wasteful, though I do have a mains pressure shower fed from the tank 🤷🏻♀️ QUESTIONS There seemed to be a mix up with the size of the pump. Installer wasn’t expecting a 12kw to arrive and to me it seems overkill for a 120m square bungalow? Install looks OK but what do I know?! Why are my bills so humongous?! What can I do to bring them down? Can't currently afford to add any extras to the system so need to work with what I have. I was given no instructions on the most efficient way of using the system. How does it work in summer? Do I need to alter anything in summer to stop heating coming on but still have hot water? Should the programmer with the thermostat be in the lounge as this is the coldest room? Or kept in hall as the hall rad has no TRV? Have read through some posts saying TRVs irrelevant and don't need thermostat, but don't understand why not as I don't want all rooms at max temp and need to be able to tell the heating when to step down at night. Confused.com! I have no clue re ASHPs etc. so any advice needs to be aimed at a child and not using technical jargon I don’t understand 🙏🏻

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Air Source Heat Pumps (ASHPs)

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bontwoody

(@bontwoody)

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Joined: 3 years ago

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11/03/2025 6:44 pm

@jamespa @bami

Just to clarify, I have already done what James has suggested. My water law settings are as low as I can use.

House-2 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
6.9 kWp of PV
5kWh DC coupled battery
Blog: https://thegreeningofrosecottage.weebly.com/
Heatpump Stats: http://heatpumpmonitor.org/system/view?id=60

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BAMi

(@bami)

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Posts: 29

Topic starter 11/03/2025 6:45 pm

@jamespa I haven't forgotten 🙂 But I want to talk to the tech chap at the installers before I start altering the system, just so they can't accuse ME of being the reason the system isn't running efficiently.

Apart from putting the DHW on a timer, and altering the low end of the weather comp to -2C from 2C the system is as it was commissioned - for now at any rate.

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JamesPa

(@jamespa)

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Posts: 2708

11/03/2025 7:06 pm

Posted by: @bami

↑

@jamespa I haven't forgotten 🙂 But I want to talk to the tech chap at the installers before I start altering the system, just so they can't accuse ME of being the reason the system isn't running efficiently.

Apart from putting the DHW on a timer, and altering the low end of the weather comp to -2C from 2C the system is as it was commissioned - for now at any rate.

No pressure or obligation, this discussion has moved on so much I felt it worth restating in case you had missed it.

Installers will probably say touch nothing, which eventually you may have to ignore, but you are imho right to be cautious while you are trying to get them to change things!

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.

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BAMi

(@bami)

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Joined: 5 months ago

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Topic starter 22/03/2025 11:00 am

Update for those following this thread.

Finally got the 'tech guy' from the installers to email me. I sent him the plan the surveyor had done, which was completely wrong, and the plan I've done which is correct.

He is trying to tell me that the plan I was sent was just to show the rad sizes and pipe positions and has nothing to do with the heat loss calculation (which I haven't been sent).

I told him that if the BTU for rad sizes has been calculated off the surveyor plan he sent me, in which the room sizes are incorrect, windows are missing and it shows a heat loss outside wall which doesn't exist, how on earth can the rad sizes be correct. He's still saying they are - which is nonsense. For starters, the utility is 6.48 m2 and has a 70cm x 80cm radiator, while BR3 is twice the size at 12.24 m2 but only has a 70 x 50cm radiator. BR3 is always cold.

I asked if the heat loss calculation was done via a different house floor plan and if so why? No response to that! I've now asked for the heat loss calc and the house plan that was done off. Will see if I receive it.

He has arranged to come for a visit this Friday, so I'll report back after that.

I don't want to tamper with too much until he's been, but did check the rad valves in the lounge (which is always chilly) and they were closed by a 4.5 turns! So I've opened both up to max and the rads are definitely getting warmer in there - thanks for this advice.

This post was modified 5 months ago by BAMi

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