Air Source Heat Pump - general question

[0llie]

Hi all this is my first post, i have recently moved into a property and due to the very low EPG rating (G which is the lowest rating) i may be able to get help regarding having an air source heat pump system installed using local funding

 

my question is this:

 

so for example with a gas combi boiler, or eg. an electric shower, when you need hot water you get it instantly, as the combi boiler or an electric shower just heats up the water fast when you need it, without needing a large amount of water always heated at the ready

 

but with air source heat pumps how do they work, as in, like above do they provide hot water fast only when you want/need it, eg. for doing the washing up, or doesnt it work that way, and if not, does that mean they are always on/active working away, and if so, is that not expensive regarding when the bills come in?   many thanks

[markc]

ASHP is not just a replacement and likely requires a lot of changes made to the existing.

they work slowly and at much lower temperatures so need a large water tank. They also work best with UFH or need much larger radiators.

how old is the property and how is it constructed? Loads of members on here are ASHP guru’s and can give specific advice with more info

[SteamyTea]

If can can remember when we all had copper cylinders in the airing cupboard that was heated by the boiler, that is how they work.

Combi boilers are a rather new invention, and hopelessly lacking in flow.

[LnP]

2 minutes ago, SteamyTea said:

 

Combi boilers are a rather new invention, and hopelessly lacking in flow.

So does that mean a combi boiler would be ok for a small house? How do you work out what flow you need?

[Jilly]

You need to put loads of insulation and some draft proofing in before installing a heat pump or the low temperature heat (about 35 degrees) will leak away quickly and your electricity bills will be huge. 

[SteamyTea]

1 minute ago, LnP said:

So does that mean a combi boiler would be ok for a small house? How do you work out what flow you need?

A combi, or several, can be fitted to any house assuming the gas supply is adequate.

Shower flow is worked out on how much water you want to come out the tap. Opinions vary, my shower is 10 litres a minute, other think 20 is needed, but you can get away with 8 quite happily.

A combi boiler is usually sized for the DHW supply, not the house heat load. An ASHP is sized differently usually for the maximum space heating load.

This is why a 24 kW combi may be swapped for a 8 kW ASHP.

A different sizing formula is used.

[JohnMo]

You can use a Combi in a small, medium or large house.  You can get very good flow out of a combi if it big enough and you choose the right one.  Performance varies quite a lot.

[0llie]

28 minutes ago, markc said:

ASHP is not just a replacement and likely requires a lot of changes made to the existing.

they work slowly and at much lower temperatures so need a large water tank. They also work best with UFH or need much larger radiators.

how old is the property and how is it constructed? Loads of members on here are ASHP guru’s and can give specific advice with more info

its an old property, kind of rural, a 2-storey house of small/medium size.  they told me on the phone that an assessor would come here first to determine if the ASHP would be viable here. they would insulate the house first and change the radiators, and look to see if there is somewhere for the large water tank

 

so it sounds like they are always running then?  i wonder how many watts we are talking.  i mean something like a regular fridge in a house is always running but not too expensive due to watts not being too high, but for an ASHP im wondering if they are expensive regarding running costs, especially if they are always running 24 hours a day

[JohnMo]

Are you asking them for quote or are they making contact with you - cold calling?

[markc]

@ollie be careful! Do not get sucked in by sales talk. See what they say, post it on here for comments and get a 2nd evaluation/quote. I have an old railway property and no way would a ASHP be suitable but my new oversized combi works well and pretty cheap to run I reckon (much lower than the old much lower powered combi I took out).

[0llie]

thanks for the replies,  i wont have to pay anything at all for having all of this done, as it is funded by the government/council and part of a scheme to improve homes with very poor EPG ratings for people on lower incomes or health issues etc

 

i contacted them rather than someone contacted me, this was the first point of contact:  https://buildingforhumanity.org.uk/

 

i forgot to mention that the option of mains gas to this property is not possible, hence my problem (otherwise i would have been happy to go with a regular gas combi boiler)

 

 

Edited September 14, 2022 by 0llie

[JohnMo]

Some heat pump basics

 CoP is the coefficient of performance, basically how much energy you put in compared to how much energy you get out.  The higher the temperature of the water the lower the CoP (not good).  So low temperature water flow is good.  For low water flow temps, you need big radiators or UFH.  You also need an oversized hot water cylinder as you only heat it to about 48degs.

 

The higher your home's heat demand, the more difficult it is to implement a high efficiency system.  It can be done.

 

Just be careful with sales men, you pay the bills when they've moved on and are nowhere to be found.

 

 

[JamesPa]

If your property is suitable and if the alternative is electric (resistance) heating, then ASHP may very well be a good choice.  Properly set up it should use about a third to a quarter the electricity that electric resistance heating will use.  However there is a substantial upfront cost, different behaviours to get used to and a poorly set up one will be expensive.

 

If mains gas is possible then that will probably be your cheapest install, and likely about the same cost to run (with current prices) as a well set up ASHP, albeit that many (including myself) feel that that is bound to change in favour of ASHP in time.

 

I don't know the prices of off-grid gas or oil so cant compare.  

 

Iyf you haven't got many rooms it might just be worth considering the solution often adopted in commercial properties namely 'air to air' ASHP.  Basically you have a wall mounted fan unit in each room  (or (instead of radiators) connected to an external unit.  These are easier to set up, cheaper to install and by and large they just work.  However fans make a noise and you might not find that tolerable, particularly in a bedroom.  Its not a common configuration for a domestic situation, but probably shouldn't be ruled out.  It really does depend on what you have, what sources of fuel you can get, and whether you can stomach/afford a large upfront cost.  As others say, don't get sucked in by sales talk. 

 

Having said that, if someone else  is funding it, they will have some set criteria and types of install and your concern is just to minimise the running costs (which presumably they aren't funding). 

 

Post some stuff here (including more information about the house/fuel availability) and I am sure you will get useful comments.

[Marvin]

Hi @ollie

 

We have an ASHP which is designed to be on standby (monitoring) all the time. It runs at about 80Wh measured over 2 days.

 

Our freezer runs at about 70Wh and our Fridge freezer  about 160Wh.

 

So freezer a year = 70 Watts * 24 hours * 365 days is 61,320Wh or 61.32kWh a year.

ASHP 80 *24*365 70kWh a year.

Fridge freezer 160 * 24 * 365=  140kWh a year.

 

Edited September 14, 2022 by Marvin

[SteamyTea]

4 minutes ago, Marvin said:

Our freezer consumes 70Watts per hour and our Fridge freezer consumes about 160Watts per hour.

It is Wh, not watt per hour.

Watt is power, Wh is energy, though we should really deal in joules as it would save all this confusion.

There are 3,600 joules in a Wh, 3,600,000 J in a kWh.

[JohnMo]

48 minutes ago, Marvin said:

Hi @ollie

 

We have an ASHP which is designed to be on standby (monitoring) all the time. It runs at about 80Wh measured over 2 days.

 

Our freezer runs at about 70Wh and our Fridge freezer  about 160Wh.

 

So freezer a year = 70 Watts * 24 hours * 365 days is 61,320Wh or 61.32kWh a year.

ASHP 80 *24*365 70kWh a year.

Fridge freezer 160 * 24 * 365=  140kWh a year.

 

Confused, you have an ASHP sat on standby all year, why?

[Marvin]

23 minutes ago, JohnMo said:

Confused, you have an ASHP sat on standby all year, why?

Its supposed to be, however I have chosen to have this changed because of the amount of power it uses all the time.  Having a contactor installed, governed by a timer and a digital external thermostat to protect from frost in the winter.

 

 

[ProDave]

11 hours ago, Marvin said:

We have an ASHP which is designed to be on standby (monitoring) all the time. It runs at about 80Wh measured over 2 days.

 

This is proving to be a question that should be asked of the manufacturer BEFORE you buy an ASHP as some are proving to have high standby power use.

 

My own, a 5kW LG Therma V use used 1kWh in the last 6 months of standby.  That's 1kWh in about 4000 hours which is an unbelievably low standby power level.  Yours would have used 320kWh in the same time.

[ProDave]

10 hours ago, Marvin said:

Its supposed to be, however I have chosen to have this changed because of the amount of power it uses all the time.  Having a contactor installed, governed by a timer and a digital external thermostat to protect from frost in the winter.

 

 

Be careful.  There is a long thread about this with Ecodan units.  Some use a sump heater, and the manufacturer said something like the sump heater should be turned on for a few hours before starting the unit.  So your simple timer might end up doing harm if the cause of the high consumption is a sump heater.

[joe90]

Just now, ProDave said:

Be careful.  There is a long thread about this with Ecodan units.  Some use a sump heater, and the manufacturer said something like the sump heater should be turned on for a few hours before starting the unit.  So your simple timer might end up doing harm if the cause of the high consumption is a sump heater.

Ooh er, didn’t realise this so I must check my spec on my Cartier unit!

[ProDave]

3 minutes ago, joe90 said:

Ooh er, didn’t realise this so I must check my spec on my Cartier unit!

Dies yours have high standby power consumption as well then?

[joe90]

2 minutes ago, ProDave said:

Dies yours have high standby power consumption as well then?

Never checked, it’s on my “to do list”, I only have a 13 amp plug in monitor and the unit is wired direct to the CU so without a clamp devise not sure how to monitor it 🤔

 

[SteamyTea]

5 minutes ago, joe90 said:

Never checked, it’s on my “to do list”, I only have a 13 amp plug in monitor and the unit is wired direct to the CU so without a clamp devise not sure how to monitor it 🤔

 

I wonder if the logger I put on years ago is still logging, that should show if it is drawing silly amounts of power.

[joe90]

1 hour ago, SteamyTea said:

I wonder if the logger I put on years ago is still logging, that should show if it is drawing silly amounts of power.

I took the clamp off recently as had to work on the CU, but can put it back on I guess, but will it tell the difference from other stuff (STP)?

[SteamyTea]

3 minutes ago, joe90 said:

I took the clamp off recently as had to work on the CU, but can put it back on I guess, but will it tell the difference from other stuff (STP)?

Yes, if I can disaggregate the data.

Memory card is probably full as I think it was only a 4GB one, so on top of the OS, it has been adding half a MB of data every day at least, for the last 6 years or so.

If you lived further away I would come and pick it up and see what is on the here.

I never travel unless it is at least 300 miles it seems these days