Multi split heat pump

Sandwich567

We recently moved in to a 1930s semi. We have an old boiler with an immersion tank that is expensive to run, and rooms are often still quite cold. Local gas engineers have advised replacing it with an efficient combi boiler and said we’d also need new radiators as ours likely couldn’t cope with a pressurised system. They’ve said heat pumps don’t work in older houses. 

I’d ideally like to do better for the environment and get a heat pump. I presumed we’d do radiators etc but  a friend from the US has suggested getting a multi split system from an air source heat pump - he says the are common there and should cope with about -5 for heating, plus could do cooling, and reckons they are efficient. Cooling is quite tempting given how hot last summer was, if we could do it in an efficient way. 

We’d ideally like to get solar pv in the future, so this sounds like a good idea if the solar pv could eventually help power the heating/cooling system - is this possible?
Our EPC is currently a D, we have double glazing, loft insulation and some cavity wall, but not the whole house - would this work? 

Also what would we do for hot water? Keep the old immersion tank?
Im also worried about noise from the units, our garden is pretty small and we’re close to neighbours. 

Any advice would be great! 

Sandwich567

My friend also warned that electrical capacity could be an issue and potentially expensive to sort - how do I find this out? 

Reed_Richards

Sandwich567 said:

They’ve said heat pumps don’t work in older houses. 

Hogwash!  Older houses tend to be less well insulated and so more expensive to heat.  That applies whatever heating system you have.  At current prices the running costs of a well-installed air source heat pump system should be similar to the running costs of a gas boiler.

Solar PV would make little impact on your heating costs because you get very little solar power when you need the most heating.  But it might be able to provide much of your hot water in summer, and cooling if you get what your friend recommends, which I presume is a form of air conditioning based on an air-to-air heat pump.  

ecraig

Sounds like your gas engineers are purposefully trying to put you off getting a heat pump because they, rightly so, don't want to be out of a gas job.

Sounds like you need to contact a professional renewables company and understand if your rads, cylinder and pipes are up for it.

1961Nick

The latest air/air multi splits achieve an SCOP of around 4.5 so heat energy will cost around 7.5p/kWh compared to gas at about 12.5p/kWh for an 80% efficient boiler/heating system.

Solar would make a useful contribution towards running the heat pump(s) from February through to October.

Screwdriva

Sandwich567 said:

We recently moved in to a 1930s semi. We have an old boiler with an immersion tank that is expensive to run, and rooms are often still quite cold. Local gas engineers have advised replacing it with an efficient combi boiler and said we’d also need new radiators as ours likely couldn’t cope with a pressurised system. They’ve said heat pumps don’t work in older houses. 

I’d ideally like to do better for the environment and get a heat pump. I presumed we’d do radiators etc but  a friend from the US has suggested getting a multi split system from an air source heat pump - he says the are common there and should cope with about -5 for heating, plus could do cooling, and reckons they are efficient. Cooling is quite tempting given how hot last summer was, if we could do it in an efficient way. 

We’d ideally like to get solar pv in the future, so this sounds like a good idea if the solar pv could eventually help power the heating/cooling system - is this possible?
Our EPC is currently a D, we have double glazing, loft insulation and some cavity wall, but not the whole house - would this work? 

Also what would we do for hot water? Keep the old immersion tank?
Im also worried about noise from the units, our garden is pretty small and we’re close to neighbours. 

Any advice would be great! 

Hi - A few thoughts:

1) Solar PV will not power any high draw appliance in the winter. However, if you have a South facing roof that can accommodate 12+ panels, you will receive an heating "subsidy" via your PV panels for A-A heating. A discount from your roof, which will still generate 10-15% of their peak power produced during the summer months. If you export your excess energy (vs. store it in a battery), you will generate a credit in your Octopus account which can be used to pay for future energy consumption. 

2) Air to Air Heat Pumps can work "better" in less insulated homes compared to Air-to Water Heat Pumps, which rely on the more traditional heat emitters (radiators). You'll still need electric tower rail warmers for the bathrooms etc.

3) Daikin is on the verge of launching a UK market specific Air to Air Heat Pump that can also heat a hot water cylinder (via a dedicated port). This will allow you to remove your boiler entirely and save on gas standing charges. Alternatively, you can invest in a seperate heat pump hot water cylinder like the Vaillant AroStore. This unit has a 1.2kW immersion as a backup (vs. 3kW) and can run on solar PV for 8-9 months of the year. 

4) Modern A-A heat pumps are really silent. 

5) If you want to reduce your running costs further, you can always purchase a quality battery solution to power your heat pump using only PV/ cheap import tariffs. (£5-10K on top of your costs for a heat pump and Solar PV)

ispookie666

Fascinating time in the field of heating as we are nearing the cross-over point for ASHP, including alternate fuel for conventional boilers.  

There are advantages and disadvantages to ASHP (A2A) 

Advantages 

• Cheaper to install than Air 2 Water 
• Quick heating 
• Highly controllable 
• Quiet 
• Cheap to run compared to any other form of heating, COP (it goes by various names for the season) is highly dependent on the outside temperature and humidity!  

Disadvantages 

• Noise - the outdoor unit, if it's 3dB more than the ambient, you will run into problems if you are in a quiet neighbourhood. This will be an issue for multi-split and worse in colder months.
• The rooms will have to be on the same mode or off; this can be a problem in shoulder months (especially if the rooms are North and south facing)
• Planning permission - You need planning permission for any system which can cool. Unfortunately, that is the law/rules, and there are no permitted development rights for the Air 2 Air system, all of which have cooling mode.
• Ducting - can be unsightly. 
• Low-frequency vibrations - if the units are fixed to the outside wall.
• For larger units, you will need dedicated circuits.

Also, the ability of the unit to track the set temperature depends on the units - I have found Daikins to be useless compared to Mitsubishi.    

tacpot12

The Planning Permission point is interesting. Perhaps the Planning departments might lobby for a change on this if they start getting more requests for permisson.  

1961Nick

tacpot12 said:

The Planning Permission point is interesting. Perhaps the Planning departments might lobby for a change on this if they start getting more requests for permisson.  

If 1% of domestic A2A installations had planning permission I’d be surprised.

shinytop

tacpot12 said:

The Planning Permission point is interesting. Perhaps the Planning departments might lobby for a change on this if they start getting more requests for permission.  

I certainly hope not.  We don't need AC in UK homes as it's a waste of energy, puts unnecessarily strain on the grid and is anti-social.  A bit like hot tubs.

IMO of course. 

michaels

A2A does not use the existing rads so the op plumber is probably thinking about A2W systems. These are what is being pushed in the UK as they get the 5k grant whereas A2A gets nowt.