Air Source Heat Pump

[Christiez]

Evening all,

Appreciate this isn't Tesla related so forgive me but with you being such a helpful bunch I thought I'd try my luck.

As part of me getting a charger for my Model 3 I had to upgrade my amperage from 60 amps to 80 amps. I did ask Western Power at the time if they could put in 100 amps but they wouldn't entertain it. I didn't push that hard as 80 would suit my current needs.

3 months later and going through my first winter in the house I realised how much money I'm hemeriging on oil heating... After doing some research on alternative options I'm leaning towards a air source heat pump (saving my pocket and the environment) and recieved a few quotes. During conversation with an installer he mentioned the heat pump uses 40 amps and after doing the maths, having a EV charger and heat pump it doesn't leave much left over..

My question, has anyone got a heat pump plus charger and did you have any difficulties with amperage? For the life of me, I can't remember why Western Power refused 100amp but hoping it was something trivial. I will call them in the next couple of days but thought I'd learn from others experiences.

Again, apologies for the non related Tesla post!

 

[ItsNotAboutTheMoney]

Your circumstances have changed if you're thinking about a heat pump.
I suggest you ask again for an upgrade for the heat pump.
They should want your money.

 

[Christiez]

Your circumstances have changed if you're thinking about a heat pump.
I suggest you ask again for an upgrade for the heat pump.
They should want your money.

Frustratingly I already had to fork out £500 for the last upgrade so hope they take pity on me!

 

[ewoodrick]

If the power company limited you, that's because the transformer that you are sharing is already loaded. To provide higher service, they would have to replace that transformer, possibly the cable and more transformers upstream, could be a really expensive endeavor.

Even a 100A panel is questionable for high current EV charging.
How much are you needing to charge each evening? What if you reduced your charge speed, can you get it low enough?
For some folks, just basic 220V 15A service is more than needed.

Here in the states, a 200A or higher panel is common for most non-urban newer homes.

 

[Mr Miserable]

Evening all,

Appreciate this isn't Tesla related so forgive me but with you being such a helpful bunch I thought I'd try my luck.

As part of me getting a charger for my Model 3 I had to upgrade my amperage from 60 amps to 80 amps. I did ask Western Power at the time if they could put in 100 amps but they wouldn't entertain it. I didn't push that hard as 80 would suit my current needs.

3 months later and going through my first winter in the house I realised how much money I'm hemeriging on oil heating... After doing some research on alternative options I'm leaning towards a air source heat pump (saving my pocket and the environment) and recieved a few quotes. During conversation with an installer he mentioned the heat pump uses 40 amps and after doing the maths, having a EV charger and heat pump it doesn't leave much left over..

My question, has anyone got a heat pump plus charger and did you have any difficulties with amperage? For the life of me, I can't remember why Western Power refused 100amp but hoping it was something trivial. I will call them in the next couple of days but thought I'd learn from others experiences.

Again, apologies for the non related Tesla post!

Christiez, you need to put the bat signal out for @Jeremy Harris

 

[Christiez]

If the power company limited you, that's because the transformer that you are sharing is already loaded. To provide higher service, they would have to replace that transformer, possibly the cable and more transformers upstream, could be a really expensive endeavor.

Even a 100A panel is questionable for high current EV charging.
How much are you needing to charge each evening? What if you reduced your charge speed, can you get it low enough?
For some folks, just basic 220V 15A service is more than needed.

Here in the states, a 200A or higher panel is common for most non-urban newer homes.

On average I'm charging 3 1/2 hours each night adding roughly 26 kWh. I could potentially reduce the charge speed but in doing so would likely run into my peak electric rate which I'd quite like to avoid.

 

[ewoodrick]

On average I'm charging 3 1/2 hours each night adding roughly 26 kWh. I could potentially reduce the charge speed but in doing so would likely run into my peak electric rate which I'd quite like to avoid.

At what rate? Take a look when you plug in.

Well, you also have to take that heat pump into consideration with your electric usage. I guess that I'm assuming that you don't already have A/C??? If you did, the A/C would normally be replaced with a heat pump. (since they are basically the same thing) and you wouldn't need any additional power.

 

[Glan gluaisne]

We have a 7 kW ASHP, that is way too big for our heating needs (it was available at the right price...). It's absolute maximum input current (from the spec sheet) is 8.4 A. In practice, it tends to run at around 1.5 to 2 A almost all the time.

An ASHP that drew 40 A would be extremely large, way up into the realms of commercial units used to heat warehouses. A 40 A input is roughly equivalent to a heat output of around 28 kW, which is a heck of a lot of heat.

For comparison, at our last house (a pretty typical 1980's 3 bed) we had a gas boiler that was rated at about 10 kW when heating the house, and it managed just fine, even in really cold weather. If we had increased the size of the radiators (to allow the use of an ASHP) we could have replaced that boiler with an ASHP of about the same rating, which would have drawn a maximum of around 14 A.

It sounds to me as if someone has got output power and input power mixed up. As a general rule of thumb, output power from a heat pump will be between 3 times and 3.5 times the input power. Since being installed ours has averaged an output power that's about 3.6 times the input power.

 

[Mr Miserable]

Christiez, I told you!

 

[Christiez]

At what rate? Take a look when you plug in.

Well, you also have to take that heat pump into consideration with your electric usage. I guess that I'm assuming that you don't already have A/C??? If you did, the A/C would normally be replaced with a heat pump. (since they are basically the same thing) and you wouldn't need any additional power.

That's charging at 32A.

I appreciate the heat pump would add to the electric usage but 'should' be considerably less expensive than what I'm paying for oil and a lot cleaner.

Good point on the a/c but isn't something I have.

 

[Christiez]

We have a 7 kW ASHP, that is way too big for our heating needs (it was available at the right price...). It's absolute maximum input current (from the spec sheet) is 8.4 A. In practice, it tends to run at around 1.5 to 2 A almost all the time.

An ASHP that drew 40 A would be extremely large, way up into the realms of commercial units used to heat warehouses. A 40 A input is roughly equivalent to a heat output of around 28 kW, which is a heck of a lot of heat.

For comparison, at our last house (a pretty typical 1980's 3 bed) we had a gas boiler that was rated at about 10 kW when heating the house, and it managed just fine, even in really cold weather. If we had increased the size of the radiators (to allow the use of an ASHP) we could have replaced that boiler with an ASHP of about the same rating, which would have drawn a maximum of around 14 A.

It sounds to me as if someone has got output power and input power mixed up. As a general rule of thumb, output power from a heat pump will be between 3 times and 3.5 times the input power. Since being installed ours has averaged an output power that's about 3.6 times the input power.

Thanks for this, is really useful.

We live in a 1900s 4 bedroom farmhouse and being quoted for a 12 kw Nibe f2040. I must admit 40A seemed quite high but couldn't find any real info online.

So would you suggest this being overkill based on your experience?

 

[Christiez]

Christiez, I told you!

Was a great shout!

 

[Glan gluaisne]

Thanks for this, is really useful.

We live in a 1900s 4 bedroom farmhouse and being quoted for a 12 kw Nibe f2040. I must admit 40A seemed quite high but couldn't find any real info online.

So would you suggest this being overkill based on your experience?

The Nibe is an expensive unit, but OK. You can get better value heat pumps at around the same output at a better price. Any of the big names, like Daikin, Mitsubishi, Panasonic etc are pretty reliable and easily serviced if they need it, as they are essentially much the same internally as the air con units those companies have been making for decades.

A 12 kW inverter controlled unit will draw a maximum of maybe 4 kW from the supply, so roughly 17 A to 18 A. Because all decent heat pumps are now inverter controlled (have been for several years) there's no high startup current, in fact they start at a low current and ramp up to maximum, specifically to get around the startup surge that used to be an issue years ago, with non-inverter drive heat pumps.

Not sure where your installer got the idea that a 12 kW heat pump would need a 40 A supply from, as it won't need even half of this, and most of the time would be running at maybe 5 A to 8 A or so, if that.

If it's running radiators, then the radiators will need to be larger in order to work well at the lower flow temperature from a heat pump. Best efficiency for an ASHP is when the flow temperature is kept at or below about 40°C, which is maybe 15°C cooler than the typical flow temperature from an oil or gas boiler running radiators. If you have underfloor heating then a heat pump is ideal, as that rarely needs a flow temperature higher than about 35°C.

Hot water can be an issue with a heat pump, as they don't really like working above about 50°C, and even then they will be fairly inefficient. 45°C to 50°C is fine for hot water, but it does usually mean having a bigger hot water tank, as more hot water will be used, because there will be less mixing with cold water to get to the right temperature for a bath or shower (shower temperature is usually around 38° to 40°C). An alternative is to use the heat pump to heat your existing hot tank to, say, 45° to 50°C and then boost that overnight to around 65°C with an immersion heater run on off-peak electricity.

We have the advantage of underfloor heating set inside a well insulated concrete floor slab, so use that rather like a storage heater. We only run our ASHP at night, during the off-peak E7 period, and that charges the floor up with heat that easily lasts the whole day. This works out at about 2.4 to 2.5 p/kWh, so a fair bit cheaper than oil or LPG, that were the only other two options we have here.

 

[MrBadger]

Before going for a heat pump, you need a detailed energy survey for the property. Heat pumps in houses not designed or upgraded to use one is a recipe for disappointment. Heat pumps work in a completely different way to a normal boiler heating (fundamentally low heat output for long periods of time vs high output for short periods) wise and that does not work well in spaces that cannot cope with that, ie the majority of UK homes. I worked with someone who did exactly what you are proposing, they were never happy even after several attempts to fix. I looked into this too and still running on gas even though I have done a reasonable amount to our house to make it thermally more efficient and still more to do but there is only so much you can do to regular UK housing stock - enough though to run MVHR well which needs good air control. Jeremys heat uses are not typical because his house was designed specifically for low energy use, so his numbers will not be typical. A heat pump is not a silver bullet although some installers may try and paint that picture.

You put your head down the heat pump rabbit hole, you may never return. Ask the same question on Navitron Renewable Energy and Sustainability Forum - Index - they know about EV's, electrical, insulation, batteries etc etc and quite a few are off grid. That is full of helpful people who have tons of experience doing this on regular UK building stock and what works, what doesn't and what installers do get wrong. And remember, insulate, insulate, insulate, thats the best saving you can make.

 

[Christiez]

Haven't had chance to digest the feedback yet as I should be working but the support on this forum is incredible. Thanks guys.

 

[Andywil]

The Nibe is an expensive unit, but OK. You can get better value heat pumps at around the same output at a better price. Any of the big names, like Daikin, Mitsubishi, Panasonic etc are pretty reliable and easily serviced if they need it, as they are essentially much the same internally as the air con units those companies have been making for decades.

A 12 kW inverter controlled unit will draw a maximum of maybe 4 kW from the supply, so roughly 17 A to 18 A. Because all decent heat pumps are now inverter controlled (have been for several years) there's no high startup current, in fact they start at a low current and ramp up to maximum, specifically to get around the startup surge that used to be an issue years ago, with non-inverter drive heat pumps.

Not sure where your installer got the idea that a 12 kW heat pump would need a 40 A supply from, as it won't need even half of this, and most of the time would be running at maybe 5 A to 8 A or so, if that.

If it's running radiators, then the radiators will need to be larger in order to work well at the lower flow temperature from a heat pump. Best efficiency for an ASHP is when the flow temperature is kept at or below about 40°C, which is maybe 15°C cooler than the typical flow temperature from an oil or gas boiler running radiators. If you have underfloor heating then a heat pump is ideal, as that rarely needs a flow temperature higher than about 35°C.

Hot water can be an issue with a heat pump, as they don't really like working above about 50°C, and even then they will be fairly inefficient. 45°C to 50°C is fine for hot water, but it does usually mean having a bigger hot water tank, as more hot water will be used, because there will be less mixing with cold water to get to the right temperature for a bath or shower (shower temperature is usually around 38° to 40°C). An alternative is to use the heat pump to heat your existing hot tank to, say, 45° to 50°C and then boost that overnight to around 65°C with an immersion heater run on off-peak electricity.

We have the advantage of underfloor heating set inside a well insulated concrete floor slab, so use that rather like a storage heater. We only run our ASHP at night, during the off-peak E7 period, and that charges the floor up with heat that easily lasts the whole day. This works out at about 2.4 to 2.5 p/kWh, so a fair bit cheaper than oil or LPG, that were the only other two options we have here.

Hot water temperature in a storage tank should be >60°C for at least 30mins per week to remove the risk of Legionella which easily survives 50°C.
This can be a significant risk for tank fed showers for the young and elderly.

 

[Glan gluaisne]

I'd absolutely agree that a heat pump cannot ever be a straight one-for-one swap with a gas or oil boiler, as other changes need to be made to enable the heat pump to work efficiently. In terms of cost saving over oil, then a lot depends on the age of the oil boiler, as well as how much the change to a heat pump is going to cost. Some older oil boilers are only around 80% efficient, maybe less, whereas a heat pump will be typically around 300% efficient, maybe more. If you know how much oil you use per year, in terms of kWh of heat provided (so kWh per litre used less boiler efficiency) you can work out how much heating and hot water energy you're using, and then use that to work out how much a heat pump might cost to run. If the heat pump is run all the time on peak rate electricity then the running costs may not be a lot different.

There's a chap on another forum I'm a member of, that has recently converted his old Welsh farmhouse from oil to a heat pump (goes by the user name Home Farm). I'm not convinced he's making much of an overall saving, but he has also fitted a PV system as well, so is getting the benefit of being able to use some of that energy. He has a thread on his experiences with the heat pump here: Caernarfon 18kW ASHP review

I'd say that his ASHP set up is very far from being optimal, though, largely because he was, IMHO, badly advised as to what he needed. That's not uncommon, there are a lot of heat pump installers around who are treating these things as if they were boiler replacements, when a lot more thought needs to go into planning and implementing a successful heat pump installation than needs to go into installing a new boiler. There are a lot more members of the Buildhub forum with practical experience of installing and living with heat pumps than there are on the Navitron forum, and it's worth looking through the dozens of ASHP posts from members that are getting some pretty impressive performance figures from their installations.

I'd urge a bit of caution with regard to the Navitron forum. It's owned by a supplier of heat pumps and other renewable stuff for a start, so discussion is often limited by the moderation team if it starts to veer off into the merits of products that Navitron don't sell. It's also very heavily moderated, or was, last time I looked in there a few years ago. It also has a subset of hard core, long term members who are, shall we say, a bit extreme in their views. I got thrown off there by an extremely obnoxious moderator for simply being honest about my many years of real, hands on, practical experience with a particular battery chemistry, for no other reason than the prat just didn't want anyone coming along and injecting a bit of honesty into a discussion. It seemed to me that all they wanted was to have a bit of a rant to reinforce their own highly biased views, led by another respected member there who clearly didn't know his arse from his elbow. Navitron lost around £12k of business from me as a direct consequence, as I cancelled my order for solar panels and other stuff that I was buying from them, solely because of the attitude and rudeness of their staff.

 

[Glan gluaisne]

Hot water temperature in a storage tank should be >60°C for at least 30mins per week to remove the risk of Legionella which easily survives 50°C.
This can be a significant risk for tank fed showers for the young and elderly.

This has been looked into in depth, now, and the risk of legionella growth only really exists for a vented hot water system. The reason being that the bacteria are airborne and can get into the cold feed tank, usually up in the loft, and so get passed to the hot tank, where they can multiply.

If the hot water system is closed, i.e. uses either an unvented tank or a thermal store fed from a mains supply with no air break, then there is zero legionella risk, as the bacteria cannot enter the hot water system. The incoming cold mains water will be legionella free (has to be, as there is a zero tolerance for bacteria in drinking water), so as long as there's no part of the hot water system open to air there's no requirement to run a legionella cycle every two weeks.

In addition, when I spent a week or so researching this last year, I could not find one single case where a legionella infection had been traced to a domestic hot water system in the UK. So far it has never happened. It seems that almost all cases of legionella in the UK come from poorly maintained air conditioning systems that use evaporative cooling systems, with a few coming from badly maintained systems in care homes and hospitals.

The system I described earlier, of using an immersion to boost the hot water temperature during the E7 period gets around the miniscule risk, anyway, by heating the water to around 65°C.

The simplest solution, and the one that yields the best efficiency in terms of hot water storage and use, it to replace any vented hot water cylinder and associated cold feed tank with a sealed unvented cylinder. Not only does this remove the legionella risk, but it also significantly reduces heat losses and gives mains pressure hot water. It also removes the other, more serious, bacterial, viral and spore-related risks from having cold water in the bathroom fed from an open loft tank. Having see a fair few dead creatures inside loft cold water tanks, getting rid of them seems to be a good thing.

 

[tsh2]

I swapped from electric storage heaters to ASHP/radiators in a 2 bed bungalow, and achieved a COP of about 2. The biggest problem was that the heat pump was slightly oversized for the load (from radiators and DHW tank), and the control electronics wanted to ramp up the output to full power faster than heat would flow round the house - meaning it went off,ramp,full-power,over-temp in a continuous 20 min cycle (and couldn't heat the hot water in the summer without tripping the over-temp failsafe).

Still an improvement on the old system, but emphasises the risk of getting a badly specified install. Hopefully standard practice has moved on in the past 8 years too.

 

[p_iv]

Looked into this myself recently as I have an old, inefficient oil boiler. The running costs of an ASHP don't stack up, especially in winter when its actually cold outside when even my existing boiler beats it for price/kwh heat produced - a modern oil boiler would easily seem to beat an ASHP. One idea I do quite like though is a 'hybrid' system, e.g. something like this;

Grant VortexAir Range | Grant UK

This uses a combination of AHSP, modern oil boiler and immersion heater to make best use of heat sources depending on inside/outside temperatures, and will work with existing radiators - heat pump can bring the system up to its max temperatures, then the boiler can take over to top it up. Running costs should thus be lower than either a boiler or an AHSP running on their own.

Expect it'll be expensive, but has the option that you can just put a new boiler in now and then bolt on the heat pump later on.

In the short term I recon I can do better by keeping my existing boiler and getting some solar/powerwall and just using my existing immersion heater to heat water during the summer months, meaning I don't have to burn oil at all unless I need heating, but YMMV.