Air to Air Heatpumps / Air conditioning

[JIBYC]

Seeing as we have threads discussing solar and batteries I thought I'd start one about air-to-air heat pumps, aka air conditioning.

I've got a solar setup that generates a significant amount of extra energy even when it's cold outside. With the CoP of a heat pump, it looks one of the best uses for solar is to heat the house and reduce some of my gas consumption, and then use it for cooling in the summer.

I'd probably want it fitted to four rooms on the south facing end of my house - anyone want to hazard at a ROM cost for the South East?

 

[Jonstorm]

I've had air to air heat pumps in my last 2 homes primarily for air conn in bedrooms and 1 living space. We hate sleeping in the heat in summer and modern houses are insufferable for this nowadays. People think UK is not necessary but recent summers have had way more hot weather. Best decision we ever made. Our current house is all electric with air to water ashp for heating and hot water. I have a separate external unit fitted after we moved in to power a/c in 2 bedrooms and our large open plan living area.
I have 7.2kw solar on the roof with 19kwh batteries so if its hot then likely we also run them for free. Works a treat.
You are looking at around £1.2- 1.4k per room I guess cost wise

 

[qwickshot]

I’ve been doing some research and weighing up doing an air to water using the existing wet heating system or going a full air to air route.

I’ll be honest, I don’t know why more people do t go air to air or why it’s not that common in new builds.

It’s more efficient and if you use ducted units, basically invisible.

 

[WannabeOwner]

I've got a solar setup that generates a significant amount of extra energy even when it's cold outside.

I'm surprised that you get much PV Nov-Jan in UK, Feb (and Oct) gives me a few sunny days that generates me more PV than I can use, but the house is warmed significantly by the sun on those days so not much heat input needed. March has better PV (stronger mid day, but also long hours from Dawn-to-Dusk), but (for me) hardly any heating required.

So usually PV doesn't contribute much at UK latitude during the winter - other than the occasional day when its wall-to-wall sunshine.

In Summer I have an excess of PV most days ... and driving AirCon is a good combination - need more Air Con on (hot) days and those days have more PV too.

anyone want to hazard at a ROM cost for the South East?

Might be worth starting with PVWatts - Put in your postcode, then on the System Info page you can draw (zoom right in on / drag the satellite map) a rectangle for one face of your roof (i.e. repeat for each roof surface facing a different direction) and that would give you an idea, month by month, what your roof will generate. Accuracy improved if you can provide the "tilt" angle of your roof

 

[JIBYC]

I'm surprised that you get much PV Nov-Jan in UK, Feb (and Oct) gives me a few sunny days that generates me more PV than I can use, but the house is warmed significantly by the sun on those days so not much heat input needed. March has better PV (stronger mid day, but also long hours from Dawn-to-Dusk), but (for me) hardly any heating required.

So usually PV doesn't contribute much at UK latitude during the winter - other than the occasional day when its wall-to-wall sunshine.

In Summer I have an excess of PV most days ... and driving AirCon is a good combination - need more Air Con on (hot) days and those days have more PV too.



Might be worth starting with PVWatts - Put in your postcode, then on the System Info page you can draw (zoom right in on / drag the satellite map) a rectangle for one face of your roof (i.e. repeat for each roof surface facing a different direction) and that would give you an idea, month by month, what your roof will generate. Accuracy improved if you can provide the "tilt" angle of your roof

I'd suggest it's the result of poor insulation and being in a terrace. Household usage is about 6kWh a day so even in February there was a bit of excess.

7.5p/kWh off peak electricity divided by the CoP is still cheaper than my 6.5p/kWh of gas so it seems it would have some use all year.

 

[WannabeOwner]

using the existing wet heating system

Do you mean a wet system that is heated separately, and add a heat pump to it just for summer cooling? (as distinct from already having a heat pump and just making that do "cooling" in Summer, in addition to existing heating in Winter)

I've been trying to find someone who will do that and they seem to think it would be a problem.

I have UFH (heated from biomass boiler) and I'd like to just put some cold water through it in summer. The objection is "You'd get condensation on the floor which would be a hazard". I say "I only want the water to be, say, no colder than 16C" and they don't believe that would be enough ... the house is well insulated, needs a tiny amount of heating (and cooling ...) and (I assume) it would be a lot easier and less intrusive to retro-fit than individual units added into each room.

 

[WannabeOwner]

Household usage is about 6kWh a day so even in February there was a bit of excess

I have 48 panels - sunny days in Feb were between 35 - 45kWh. There were 16 such days. So 0.7 - 0.9 kWh per panel

The rest of the 12 days were 10-20kWh - 0.2 - 0.4kWh / panel.

Useful PV generation only between 09:30 and 14:30 (and, within that, only when no clouds )

Fair bit of generalisation in there - a couple of days with close to nothing, and one day with 50kWh.

January 15-20kWh on 10 days, then rest were around 10kWh and the useful PV generation window is narrower

December 10-15kWh on 13 days, the rest were 5kWh-ish

7.5p/kWh off peak electricity divided by the CoP is still cheaper than my 6.5p/kWh of gas

You'd need to run the Heat Pump Off Peak to get that price which (if I've understood correctly?) the nature of your house is that it is poorly insulated ... so I'm not sure you'd be able to "keep" that generated heat for the day?

 

[JIBYC]

I have 48 panels - sunny days in Feb were between 35 - 45kWh. There were 16 such days. So 0.7 - 0.9 kWh per panel

The rest of the 12 days were 10-20kWh - 0.2 - 0.4kWh / panel.

Useful PV generation only between 09:30 and 14:30 (and, within that, only when no clouds )

Fair bit of generalisation in there - a couple of days with close to nothing, and one day with 50kWh.

January 15-20kWh on 10 days, then rest were around 10kWh and the useful PV generation window is narrower

December 10-15kWh on 13 days, the rest were 5kWh-ish



You'd need to run the Heat Pump Off Peak to get that price which (if I've understood correctly?) the nature of your house is that it is poorly insulated ... so I'm not sure you'd be able to "keep" that generated heat for the day?

It'd come from the batteries in the loft.

 

[WannabeOwner]

It'd come from the batteries in the loft.

Ah, OK.

Need to allow say?? 10% loss for "Charge battery" and then "Discharge to Heat Pump", so there is a little bit to consider on the electricity cost Off / On Peak.

Other than that batteries will, of course, allow time-shift of usage from low tariff purchase (or excess PV) to high tariff consumption

 

[JIBYC]

Ah, OK.

Need to allow say?? 10% loss for "Charge battery" and then "Discharge to Heat Pump", so there is a little bit to consider on the electricity cost Off / On Peak.

Other than that batteries will, of course, allow time-shift of usage from low tariff purchase (or excess PV) to high tariff consumption

Yes understood, but it will augment a gas combi boiler so it won't be taking on all the heating duties.

 

[qwickshot]

Do you mean a wet system that is heated separately, and add a heat pump to it just for summer cooling? (as distinct from already having a heat pump and just making that do "cooling" in Summer, in addition to existing heating in Winter)

I've been trying to find someone who will do that and they seem to think it would be a problem.

I have UFH (heated from biomass boiler) and I'd like to just put some cold water through it in summer. The objection is "You'd get condensation on the floor which would be a hazard". I say "I only want the water to be, say, no colder than 16C" and they don't believe that would be enough ... the house is well insulated, needs a tiny amount of heating (and cooling ...) and (I assume) it would be a lot easier and less intrusive to retro-fit than individual units added into each room.

When I say wet system, I mean the existing radiator based central heating system which is currently gas fired. The air to water heat pump would be for heating only.

Realistically using a traditional wet heating system for cooling probably wouldn’t work as well as you think it would.

The reason rads and UFH heating work is because you get natural convection from the rising heat. Pumping cold water through then will just mean the air at the level of your radiator (or floor) gets cooled and the rest of it will stay the same.

The air in the room will stratify in the same way hot water does in a hot water cylinder. I suppose you could install ceiling fans to mix the air. That is why they have a cooling effect, it’s because they mix the layers of air, pushing the hot air down to mix with the cooler air below.

When you have air to air heat pumps you have to change the settings for the vents depending on if you are heating or cooling. When cooling you want the vents pointed up so it mixes the with the hot air in the highest points of the room. When heating you want the opposite, point the vents down so the output mixes with the cool air at floor level.

 

[spon88]

Seeing as we have threads discussing solar and batteries I thought I'd start one about air-to-air heat pumps, aka air conditioning.

I've got a solar setup that generates a significant amount of extra energy even when it's cold outside. With the CoP of a heat pump, it looks one of the best uses for solar is to heat the house and reduce some of my gas consumption, and then use it for cooling in the summer.

I'd probably want it fitted to four rooms on the south facing end of my house - anyone want to hazard at a ROM cost for the South East?

We're finalising plans for air-to-air at moment. Probably Daikin 5 port external unit with 4 indoor units, so one spare. Still waiting on the final prices but I'm predicting £7-8k for their "Stylish" system.

All indoor units are on external walls but to reach one of them we need to duct through the loft.

We have 10.2kwp of solar and 19kwh of batteries so seems like a logical next step. They are very, very efficient. However, it does look like we need to replace 3 bathroom rads with electric units and modify the hot water system (Eddi, immersion and de-strat pump) to make best use of generation and cheap battery top ups.

We'll also be keeping the gas boiler for a while until we're confident it's all working to plan.

With air-to-air, don't forget that you need planning permission.

 

[qwickshot]

We're finalising plans for air-to-air at moment. Probably Daikin 5 port external unit with 4 indoor units, so one spare. Still waiting on the final prices but I'm predicting £7-8k for their "Stylish" system.

All indoor units are on external walls but to reach one of them we need to duct through the loft.

We have 10.2kwp of solar and 19kwh of batteries so seems like a logical next step. They are very, very efficient. However, it does look like we need to replace 3 bathroom rads with electric units and modify the hot water system (Eddi, immersion and de-strat pump) to make best use of generation and cheap battery top ups.

We'll also be keeping the gas boiler for a while until we're confident it's all working to plan.

With air-to-air, don't forget that you need planning permission.

Isn’t planning only needed if you are installing more than 1 outdoor unit or you are in breach of the boundary rules?

I’m pretty sure Daikin now do a hot water cylinder which can also be heated from the heat pump. Nice piece of kit.

Any reason why you didn’t go for ducted units for the upstairs if you are going up to the loft already?

 

[spon88]

Isn’t planning only needed if you are installing more than 1 outdoor unit or you are in breach of the boundary rules?

I’m pretty sure Daikin now do a hot water cylinder which can also be heated from the heat pump. Nice piece of kit.

Any reason why you didn’t go for ducted units for the upstairs if you are going up to the loft already?

We were originally looking at two external units but it's a bit OTT - that's when we spotted that if the system can cool as well as heat, then it's subject to planning I believe. Plus we are just under a metre from a boundary.

Our preferred installer is back on Tuesday to look at ducting options for another bedroom and the hall. With regards to the loft, it would mean a lot of upheaval whereas the current plan has just a single duct running along the apex. I will have a quick revisit though, cheers.

 

[qwickshot]

All air to air heat pumps can heat as well as cool and pretty much always could. Planning is for multiple outdoor units and their location rather than their capabilities.

The reason I mentioned ducted units in the loft is because I’m pretty sure their output can be split so they cover multiple rooms, avoiding those electric radiators in the bathrooms. Sure you can’t individually control those rooms but for the most part you always want them heated alongside other bedrooms that you use daily. Aside from the air vents in the ceiling they are also invisible and silent as everything is contained in the roof space.

You are stuck with retrofitting wall units on the ground floor but at least upstairs you have the option to hide everything.

One issue we have is that in our kitchen, all the external walls are covered in kitchen units so there is no obvious place to install the wall unit without needing internal trunking. That’s going to need a ‘discussion’

 

[JIBYC]

One thing I'm struggling with is the ration of hardware costs to labor.

It seems very high for a job done by two in a day, especially as I have to make power available myself.

 

[PITA]

We have air to air heat pump.

Toshiba Haori wall units in all bedrooms, office & living room

2.5 kW cooling on each unit
3.5 kW heating on each unit
Plus each unit can be power throttled to 50% / 75% / 100% power.

- WiFi App controlled
- Plasma Air Purifying, dehumidifier, hot, cold
- Alexa Voice Controlled
- Extremely quiet units, perfect for bedrooms
- Back-lit guest remote control
- Wired onto Powerwall backup circuits

Highly recommended

 

[JIBYC]

We have air to air heat pump.

Toshiba Haori wall units in all bedrooms, office & living room

- WiFi App controlled
- Plasma Air Purifying, dehumidifier, hot, cold
- Alexa Voice Controlled
- Extremely quiet units, perfect for bedrooms
- Back-lit guest remote control
- Wired onto Powerwall backup circuits

Highly recommended

View attachment 917020

Cost in line with the above?

Annual servicing too?

 

[WannabeOwner]

The reason rads and UFH heating work is because you get natural convection from the rising heat. Pumping cold water through then will just mean the air at the level of your radiator (or floor) gets cooled and the rest of it will stay the same.

Thanks, that's useful to know.

I have Mechanical Ventilation (with Heat Recovery) so air is moved around the house ... dunno if that would be enough to shift the cold layer down near UFH ... but, for example, we have no heating at all in upstairs bedrooms and they never fall more than 3-4C lower than heated areas.

I need to revisit passive house consultant to see if there is an option. Can't use the MVHR as the ducts are not insulated - that would be the obvious route, if the designers / installers had drawn my attention to the opportunity at the time ...

 

[PITA]

Cost in line with the above?

Annual servicing too?

Cost me £6,500 installed

4 x Rooms
1 x External compressor
3 x Peristaltic Water Pumps