replace large outdoor unit with smaller one
I have a complex issue with the heat pump that was fitted to my house - far too big and unaffordable to run. There are many reasons for this but the main one is that I was not given a choice. The six heat pump installers who have visited since disengaging from the cashmachine that did the intitial work, have all tried to make decisions for me - they know best and they quote £7k, £4k and £1.2k, without showing any proof that they know what they are talking about. Most do not seem to have any credentials regarding the environment etc. and two out the six were intent of selling biofuels or lpg systems.
I am reasonably convinced that a heat pump is the right solution for my house, especially as there is one fitted! I cannot solve all its problems in one post so I have reduced my question to this:
If I disconnect the 16KW Samsung out door unit and replace it with a 5Kw unit, will the rest of the system accept the new device without needing an expensive installer?
I have many spreadsheets full of heat loss data, all diffferent, all dependent on the guess work of experts, none of which are trustworthy or beleaveable. I have 55sq mtrs of living space that I want to heat with ufh in most of the space that requires heat. I have followed discussionsand the MCS spreadsheet is an excuse to oversize the hp and laugh all the way to the bank.
This one makes sense and suggests that 5kw would be sufficient.
55m2 is a very small heated area, a 5kW unit would provide 90W/m2, which is at the higher end of the 65-85W/m2 'typical installed heating load' for a home, especially underfloor. You have spent a lot more time researching your requirements than any of the professionals you've engaged with, and you know best how you want to heat the property, what heating profile (24/7, timed, etc.) and what works for you.
I asked my MCS installer to drop from their calculated 13kW ASHP (Heat Engineer software) to my calculated 10kW. My calculations took in some diversity - we don't heat all the rooms in the house all the time to 22 or 23degC. This winter has validated my 10kW ASHP as 'right sized' not oversized. The practical difference meaning the ASHP can modulate down to 20% without cycling on and off on low load.
It coped, just, during the very cold two weeks before Christmas, but that was due to spending so much time in defrost, which all ASHPs are similarly afflicted with. I would sooner have the system a little slow to warm up and maybe struggle a little for 3-4 weeks a year than be oversized for the remaining 18-20 weeks of a typical UK heating season. I can always put the log burner on if I need to boost the downstairs quickly, and we prefer cooler bedrooms upstairs.
In my mind, oversizing plant is just as bad as under-sizing. Others on here have a view which may differ. It certainly costs more to run oversized heating plant, whether gas, oil, ASHP or whatever. It's inefficient too. In my day job I calculate, size and specify custom build HVAC equipment for projects that cost several millions of pounds to purchase, so maybe I'm a little more sensitive to adding contingencies and factors of ignorance onto equipment capacities than most. 😉
- 22 Forums
- 2,049 Topics
- 44.7 K Posts
- 61 Online
- 3,277 Members
Join Us!
Trusted Installers
Struggling to find a reliable heat pump installer? A poor installation can lead to inefficiencies and high running costs. We now connect homeowners with top-rated installers who deliver quality work and excellent service.
✅ Verified, trusted & experienced installers
✅ Nationwide coverage expanding
✅ Special offers available
Latest Posts
-
RE: How to disable radiator heating in LG HM161MR
Easy way just set your hopefully single thermostat to m...
By Johnmo , 44 seconds ago
-
RE: Warm weather and heat pumps.
We just switch it to either heat or cool. Had it on coo...
By Johnmo , 15 minutes ago
-
A buffer is a legacy issue, they were never used on gas...
By Johnmo , 19 minutes ago
-
RE: Yes, the "zoning with ASHP" topic again...
I agree (that it's overthinking). I think people forg...
By JamesPa , 31 minutes ago
-
RE: Solar Power Output – Let’s Compare Generation Figures
@julianc I don't have the fit payments like you, but it...
By Andris , 41 minutes ago
-
RE: Hydronic plinth heaters and ASHPs
Thanks. I suspected I was overthinking that part. ...
By benson , 1 hour ago
-
RE: Renewables & Heat Pumps in the News
Let me add two other points to what @lucia has just pos...
By Transparent , 4 hours ago
-
RE: Help optimising my system!
@wh0am3ye you’re absolutely right that what you’re seei...
By Mars , 6 hours ago
-
RE: Additional Battery v Wind Turbine v Ripple
There was a call today for Ripple investors and amongst...
By Judith , 23 hours ago
-
-
RE: Commencing on an ASHP Installation Process
I think you may very well be right and of course A2A ca...
By JamesPa , 2 days ago
-
-
RE: Agile: average import cost vs other tariffs?
@old_scientist We are with SSEN and our G99 application...
By Toodles , 3 days ago
-
RE: ASHP Ecodan L9 error - No Heating but Hot Water
@phoenix15, @heacol cover your area… I’d strongly recom...
By Mars , 3 days ago
-
RE: Potentially more choice including air to air heat pump grants
@jeff Such documents are far too wordy for my ‘daily re...
By Toodles , 4 days ago
-
RE: Getting the best out of a heat pump - is Homely a possible answer?
@grahaml I cannot agree that it is a small percentage o...
By benson , 5 days ago
-
RE: Samsung Gen6 16kW tribulations
@emceed, can you please give us an update on your syste...
By Mars , 6 days ago
-
What's the problem you are trying to solve. The answer...
By JamesPa , 1 week ago
-
Good luck. For what it is worth my system was very def...
By JamesPa , 1 week ago