Samung 16kw 5 months in - Happy with heat and DHW but some questions

Air Source Heat Pumps (ASHPs)

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DowallyDrifter

(@dowallydrifter)

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Joined: 7 months ago

Posts: 14

Topic starter 18/10/2025 9:20 pm

Where to start?

In brief we are happy with the system, the house is warm enough for us but not too warm. DHW is fine for showers and washing up now we've got used to it at 50C rather than the 60C we had with the oil boiler.

Background

Rural Perthshire location where we had a very warm summer and temp just starting to hover around 8C - 12C.

Replaced dead oil boiler with a 16kW Samsung in May this year to heat 270m2 detached house with UFH on both floors. Reasonable levels of insulation in walls, and attic. One large vaulted ceiling living room with 5kw wood burner used in winter months. 5kw wood burner in entry hall used in winter months. Original system installed 1999 with manifold on lower floor that has aux pump, and manifold on upper floor that has no pump. Timer is in the large living room which turns on 3 sessions a day, morning, lunch, evening. Thermostat in each room. 3 bathrooms on open circuits so they are heated whenever heating is on somewhere else.

Installation

16kw mono bloc Samsung model AE160CXYDEK/EU, 300l DHW, 50l integral buffer tank (as a volumiser I was told).

I set DHW timing to off overnight 2200-0800.

All I have for data is what i've taken from the screens on the controller and put into Excel, plus some taken randomly during the day when passing!

I don't have flow rate data for the existing or new system but I can monitor temperature on the manifold in/out and it is roughly in line with the water outlet recorded on the controller.

(Guy did an impressive job of fitting into a tight space which required some intricate pipework. All well insulated and labelled).

FSV Values

I think these are the key ones from what I've seen from posts here.

201: 15 / -4

202: 25 / 45

203: 35 / 50

4013: 17

Operations

Over summer we had heating off and DHW on 50C which used max 6.1Kwh/day and min 2.7kwh/day during August (when we weren't away and DHW turned to AWAY).

Mid Sept we turned the heating on, set room thermostats to 25C throughout to get the house warmed up, and, as expected saw a huge spike in energy use (25kwh on the 3rd day). Soon the house was way too warm.

I set water law to -5C expecting that to reduce water output temp. Bedroom stats turned down to 15C (we never heat them). All other thermostats set to 20C which is comfortable. Kitchen still warm at 23C despite the stat turned down but the Aga contributes to that, though the floor still warm.

Water outlet temp recorded from observations, varies from 21.6C to 58.5C in Oct, average of readings ca. 30C.

October energy use has varied from min 5.83kwh/day to 15.97 kwh/day. (I'm ignoring days we've been away). House is now at comfortable temp though large living room fire has been on once or twice.

SCOP appears to vary week by week from around 3.8-4.0 over the summer to 4.5-5.2 in the last 6 weeks when the heating went on [ calculated as (energy in + energy out) / energy in ].

Total energy use for the last 20 weeks is 661.4kwh, average weekly 33.07kwh

Operating duration varies in Oct from 40hrs to 87hrs roughly.

Questions

1. I've seen on several occasions the water outlet temp on the HEAT screen is >60C. Should this happen? Is it the legionella cycle? Why is it on the HEAT screen if so?

2. What should we do, if anything, with the existing controls so that things run smoothly, efficiently, cheaply?

change the timer so it is "always on"?
open all the thermostats so system is "always open"? (the pump on the manifold may run 24/7?)
change the heat curve settings to moderate flow teamp but to what?
change the water law figure on the controller (to what?)

3. When we go away in winter months I plan to keep heating on and reduce DHW to 20C. the controller only allows a minimum of 40C for DHW when Heat is on as far as I can see in the (not particularly useful) Smarthings app. Am I right or is it user error?

4. Does the performance seem reasonable in terms of energy use and SCOP calculated? (I think it does btw)

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