[SHL-Kelso]

Would you be happy with much larger, over-sized radiators so that they meet your winter heat losses at lower flow temperature suitable for a heat pump? if not then you may well want to consider other heat sources/designs.

 

[JDleaf]

Would you be happy with much larger, over-sized radiators so that they meet your winter heat losses at lower flow temperature suitable for a heat pump? if not then you may well want to consider other heat sources/designs.

This is something we are considering, im still not sure how big oversized radiators will be compared to the existing storage heaters. What other electric heat sources/designs would you suggest looking at?

 

[JDleaf]

Personally I'd just go for ducting if there aren't any radiators anyway. You can use the ASHP to best and cool effectively then. Also MVHR will be an option.

I presume this ducting would be for air to air. It’s a shame to RHI isn’t available for that.

 

[Ralkbirdy]

Panasonic Air Conditioning 5 x Etherea Wall Mounted Multi CS-Z35TKEW A+ 9Kw/ 31000Btu 240V~50Hz

5 of Panasonic Etherea wall indoor units on 1 outdoor R32 heat pump inverter air conditioning condensing unit Kit Includes 1 x Panasonic Air

www.orionairsales.co.uk

These air conditioning units are good for efficiency, they warm quickly, but no hot water with them. Choosing the Ethrea units they can operate at 18db which is very quiet. Quicker to install, less space needed (no new DHW cylinder) but no grant. We have a single unit in a 60m2 bungalow and it keeps it warm. Advantage for us is there is no water to freeze while away.

 

[BornAgainEcoWarrior]

Thanks both for your thoughts. Yes there is a separate circuit for the storage heaters on the low period electric. It would be a complete pipe work/radiator instal, and I know nothing of alternatives to ‘wet heating’. I’ll look into ducting/MVHR as well then. any other thoughts gratefully received.

In the UK we generally think of heating involving heating water to subsequently heat the house. If you go for a ducted system or even straight forward aircon style units it should be very efficient. Aircon style units should be a much low install cost than an air to water system even without grants, but remember you'll still need something additional to heat up your domestic hot water.

Heat pumps are most efficient when the difference between the heat source temperature and output temperature is smallest. That's why you'd want oversized radiators for an air to water heat pump so the water is heated to a lower temperature than conventional CH. You'll only get that COP of >3 by running radiators at something like 35-40C, so they need to be relatively bigger for efficiency. If you heat the water to 55-60C the efficiency is lower.

But it's going more efficient to directly heat the room air to a comfortable temperature rather than heat water to a higher temperature - to then subsequently use that hot water to heat the room air to a comfortable temperature. An air to air heat pump (aircon style units) can achieve COP of 4-5.

 

[JDleaf]

In the UK we generally think of heating involving heating water to subsequently heat the house. If you go for a ducted system or even straight forward aircon style units it should be very efficient. Aircon style units should be a much low install cost than an air to water system even without grants, but remember you'll still need something additional to heat up your domestic hot water.

Heat pumps are most efficient when the difference between the heat source temperature and output temperature is smallest. That's why you'd want oversized radiators for an air to water heat pump so the water is heated to a lower temperature than conventional CH. You'll only get that COP of >3 by running radiators at something like 35-40C, so they need to be relatively bigger for efficiency. If you heat the water to 55-60C the efficiency is lower.

But it's going more efficient to directly heat the room air to a comfortable temperature rather than heat water to a higher temperature - to then subsequently use that hot water to heat the room air to a comfortable temperature. An air to air heat pump (aircon style units) can achieve COP of 4-5.

thanks very much, lots to think on, like the sound of air to air the way you’ve explained it. I’ll definitely give that some more thought.

 

[booms]

Very interesting.

What kind of cost was the install? How about maintenance costs?

Trying to get a feel for the all in cost

 

[BornAgainEcoWarrior]

thanks very much, lots to think on, like the sound of air to air the way you’ve explained it. I’ll definitely give that some more thought.

The up sides of air 2 air
Efficiency can be close to 5 SCOP so cost per kWh is relatively cheap even if we are cynical about ever achieving the claimed efficiency.
Cools as well as heats, though as we're likely to use that it eats into the energy saving.
Each unit is relatively cheap
Easy control over individual units
Total install cost for 5 unit Daikin multi split system is coming in at £5500

The downsides
Multi split systems typically do up to 5 units Mitsubishi do 6, but your likely leaving e.g. the box room and bathroom unheated and relying on door open or passive heat. Otherwise bigger systems in a larger house are going to be close to Air to water cost, and then that heats the hot water too.
Many people don't like the indoor units appearance, though for me they are no uglier than radiators
House buyers maybe put off by the unfamiliar not sure it'll add value.
You've still got to heat the hot water somehow

Also : We're still using a refrigerant in R32 that has considerable global warming potential. Less of a concern than R410 or older HFCs but I wish the industry would get on with moving to R290 which is far better.
Still Fgas regulations mean refrigerants are well managed in the UK and EU and rarely allowed to escape, so probably I shouldn't worry that much about that.

 

[jmacneil]

For what it's worth, our primary heating in a fairly sizeable bungalow is three "mini split" single-unit A2A air conditioners (Daikin Ururu Sarara, R32). Mostly there's just the two of us in the house, though my Dad has stayed with us quite a bit through the last year and a bit of COVID. We also have a very high efficiency wood burning stove (and well seasoned wood) in the lounge - which doesn't have one of the A2A units, which gets used on cold evenings/weekends.

I chose these, despite "No RHI" because the install cost was quite reasonable (about £7k) compared to the cost for an efficient "Wet" central heating system (using Jaga low-temperature radiators) which I was quoted at about £23k, and because the A2A units can be way more efficient than the Air-to-water units for which you do get paid by the RHI.
The government really isn't keen to encourage installation of "Air conditioning" because they are concerned about the energy usage for cooling - but on the few days of the year when I use the units for cooling, my oversized Solar PV system is still busy exporting to the grid even when running the cooling.

 

[booms]

For what it's worth, our primary heating in a fairly sizeable bungalow is three "mini split" single-unit A2A air conditioners (Daikin Ururu Sarara, R32). Mostly there's just the two of us in the house, though my Dad has stayed with us quite a bit through the last year and a bit of COVID. We also have a very high efficiency wood burning stove (and well seasoned wood) in the lounge - which doesn't have one of the A2A units, which gets used on cold evenings/weekends.

I chose these, despite "No RHI" because the install cost was quite reasonable (about £7k) compared to the cost for an efficient "Wet" central heating system (using Jaga low-temperature radiators) which I was quoted at about £23k, and because the A2A units can be way more efficient than the Air-to-water units for which you do get paid by the RHI.
The government really isn't keen to encourage installation of "Air conditioning" because they are concerned about the energy usage for cooling - but on the few days of the year when I use the units for cooling, my oversized Solar PV system is still busy exporting to the grid even when running the cooling.

Very interesting.

I think this is the clear bang for buck option if you don't want to get into a multi year financial arrangement with the government.

Out of interest, why did you go for this model? What power output do they have, and how do you heat your hot water?

Haven't seen many detailed examples of people running their heating off A2A.

 

[Ralkbirdy]

70m2 bungalow with electric gel radiators and an immersion DHW. A single Panasonic unit in the hall facing through the lounge door. Easy installation through the loft. Is great when no previous central heating has been installed.

No wet system to freeze in the winter.
Used about 10kWh power in the winter, max of 15kWh when at 0C.
COP is about 4.5, so we were getting 45-60kWh of heat.
Very responsive, if we have been away, it will send a blast of warm air within minutes.
Quiet indoor unit running at 18db for the majority of the time.

A great system for the right environment.