Heat Pumps: anyone have one/thought about it?

[b0rn2sk8]

The issue isn’t the costs of putting in the charger.

It’s the cost of retrofitting a 6mm cable nearly into a property which already exists.

The retrofit option inevitably involves lashing a cable across the outside of a house to get it to within a sensible location to plug a car into it. Or worse, you need to get it over to a detached garage or something and the developer just installed a 2.5mm under tarmac or block paving - yuck.

Put it in when the property is being built and it’s 1/4 cost and hidden in a wall.

Bidirectional charging isn’t going to be mainstream for awhile yet, there is a standard but it’s not ratified in the U.K. outside of a single pilot project ran by one energy provider, nothing supports it.

New builds should have at an absolute minimum the wiring installed to all parking spaces, even if they are detached from the property.

IIRC, they are all required now but anything that was approved before the law taking effect isn’t required to go back and modify the plan. That’s always been the case for electrical regulation changes.

For example, my old house was built after it was a requirement to have a metal consumer unit, it had a plastic one.

 

[Ron-ski]

Builders are very stuck in their ways, and they also want to maximise profit. Very few houses are built with solar, those that are usually have a stupidly small token system. Heat pumps when fitted to new builds are often over sized, and incorrectly installed.

New EVs may have a charger supplied, but secondhand don't, so that's a bit of a lame reason, we don't all waste a fortune on a new car, luckily some do which means there's a nice supply of second hand cars at a substantial discount, my three old car was half price.

 

[PermaChanged]

The issue isn’t the costs of putting in the charger.

It’s the cost of retrofitting a 6mm cable nearly into a property which already exists.

Which is why prior to a new bathroom being fitted, we routed the cable in the new stud for rear feed in to our EV charger.

Nothing worse than excessive trunking or externally routed SWA for a car charger IMO!

 

[relicalpha]

I'm moving into a house soon that has a 16kw heat pump, which is probably fair given the square footage.

With a 300l hot water tank, is a heat pump this big best just doing 1 reheat a day?

My main concern is that I really don't want to heat the whole house... If I turn off (frost protect) a number of unused zones and keep UFH to say 17/18 degrees over winter - is that something that might cause short cylcing given the size of the heat pump?

I'm just worried that 16kwh is going to cost a fortune to run as I'm used to having granular control with gas to keep things affordable. Or might it not be so bad?

 

[bimbleuk]

I'm moving into a house soon that has a 16kw heat pump, which is probably fair given the square footage.

With a 300l hot water tank, is a heat pump this big best just doing 1 reheat a day?

My main concern is that I really don't want to heat the whole house... If I turn off (frost protect) a number of unused zones and keep UFH to say 17/18 degrees over winter - is that something that might cause short cylcing given the size of the heat pump?

I'm just worried that 16kwh is going to cost a fortune to run as I'm used to having granular control with gas to keep things affordable. Or might it not be so bad?

Usually the best way to run a heat pump is low, slow and constant. Doesn't actually mean it will run 24/7 but will run the majority of the time at a low flow rate.

You may be effectively simulating a small house with a large HP which will likely cause short cycling. For general info a HP is typically rated by the number of starts not the continuous hours. Starting a cold HP causes the most wear though running all the time at max isn't great either.

Once the whole fabric of the house has settled to a steady temp the HP will be there to maintain that state. Having cold parts of the house will just make the HP work harder. Another benefit of a constant temp is the reduction in humidity throughout the house. My first winter is coming and I'm interested in seeing how much the condensation reduces (or disappears) on my windows in the morning. I was a bit miserly with the heating and that was one of the side affects.

Adjust the water heating to your routine so that may be once over night for the morning rush or several times a day. May also be adjusted to any smart tariffs. The only time I've heard the pump part of my smaller HP is when it was approaching 50C water temp. Being a low temp HP it was at it's upper efficiency range. I've adjusted down to 48C once a day with a minimum temp just in case it drops. Not a big demand in my house though. Lower temp more often may work better for you.

 

[b0rn2sk8]

I'm moving into a house soon that has a 16kw heat pump, which is probably fair given the square footage.

With a 300l hot water tank, is a heat pump this big best just doing 1 reheat a day?

My main concern is that I really don't want to heat the whole house... If I turn off (frost protect) a number of unused zones and keep UFH to say 17/18 degrees over winter - is that something that might cause short cylcing given the size of the heat pump?

I'm just worried that 16kwh is going to cost a fortune to run as I'm used to having granular control with gas to keep things affordable. Or might it not be so bad?

A 16kw heat pump is very big for a house. What brand is it?

How big is the house and how old is it and has it had any improvements since it was built (insulation, windows etc)?

The issue with large heat pumps isn’t the top end, it’s the minimum output. If that’s too high, it will cycle a lot.

What you are suggesting regarding zoning is counter productive, particularly if the heat pump is correctly configured. It’s likely to increase your running costs compared to running the whole house at the same temperature, particularly with underfloor heating which is designed to heat the fabric of the building which then heats the air (radiators heat the air which then heats the fabric).

As the above poster said, the most efficient way to run the system is to run the house at the same temperature and the heat pump with as low flow temperature as possible and constantly.

Have a look at this (and all their other videos):

This is a great channel if you want to learn about heat pumps - a lot of the information is trickled into their videos so you you’ll not be able to target specific ones based on the title:

As for hot water- it depends how much you use but yes heating it as few times as possible is usually the way forward - ideally once per day during an off peak period.

I’ve got a 180 litre tank and I heat it once per day to 50c.

I run my heating fully open, all my TRVs are set to max so they can never restrict the flow. My heating is ‘on’ all the time but I drop the thermostat by 2c at 21:00 to 02:00 so the heat pump naturally turns off. From 02:00 to 05:30 the heat pump is working pretty hard doing hot water and heating the house back up to the day time temperature (the target is higher to ‘store heat in the house).

My electric is only 7p/kwh over night so I focus a lot of energy consumption in this period including heating. This is less efficient but it works out cheaper because the cost of electric is very low.

 

[relicalpha]

A 16kw heat pump is very big for a house. What brand is it?

How big is the house and how old is it and has it had any improvements since it was built (insulation, windows etc)?

The issue with large heat pumps isn’t the top end, it’s the minimum output. If that’s too high, it will cycle a lot.

What you are suggesting regarding zoning is counter productive, particularly if the heat pump is correctly configured. It’s likely to increase your running costs compared to running the whole house at the same temperature, particularly with underfloor heating which is designed to heat the fabric of the building which then heats the air (radiators heat the air which then heats the fabric).

As the above poster said, the most efficient way to run the system is to run the house at the same temperature and the heat pump with as low flow temperature as possible and constantly.

Have a look at this (and all their other videos):

This is a great channel if you want to learn about heat pumps - a lot of the information is trickled into their videos so you you’ll not be able to target specific ones based on the title:

As for hot water- it depends how much you use but yes heating it as few times as possible is usually the way forward - ideally once per day during an off peak period.

I’ve got a 180 litre tank and I heat it once per day to 50c.

I run my heating fully open, all my TRVs are set to max so they can never restrict the flow. My heating is ‘on’ all the time but I drop the thermostat by 2c at 21:00 to 02:00 so the heat pump naturally turns off. From 02:00 to 05:30 the heat pump is working pretty hard doing hot water and heating the house back up to the day time temperature (the target is higher to ‘store heat in the house).

My electric is only 7p/kwh over night so I focus a lot of energy consumption in this period including heating. This is less efficient but it works out cheaper because the cost of electric is very low.

Thanks that's super helpful. It's a 16kw Samsung AE160 for about 3000 sq ft, fairly decent insulation, downstairs UFH and upstairs radiators. The spec lists the output at W45/A-2 12.67kW, is that what you mean by minimum output?

I think my main concern is that's obviously a big space to heat, and we're only going to use a small % of the living space day to day hence why i'd like to zone it - but I get the point about turning off zones potentially being even more inefficient. I guess I'll have to see how it goes trying to keep to a constant temperature and monitor the data.

I'm hoping if we were to drop it to 35 degree flow temp, and keep thermostats at about 18, then maybe it will be affordable. I don't really want to use more than 40-50kwh/day in the worst of winter.

If it ends up too expensive, and we go down the zoning route - would that typically mean downgrading to a smaller HP? Or changing to oil

 

[b0rn2sk8]

Well the good news is you can’t change to oil, that would breach the regs and that would probably be more expensive than fixing the issues with the sub optimal heat pump install anyway.

3000sqf is pretty big so that a positive sign.

I’m not familiar with the Samsung but I would expect that to be the units output at a 45c flow temperature.

It should be able to modulate its output, usually 4-5 levels between min and max. If its using proper Samsung controls that is, if its using anything but Samsung controls it won’t and it will be on/off only at max power (aka terrible efficiency).

For a 3000sqf house I’d be surprised if it didn’t use 50+kwh a day when it’s below freezing all day. Mine would consume ~25kwh (inc hot water) and my house is less than half the size. Luckily that is only a handful of days per year in reality and well in line with gas consumption.

The other thing to look at is time of use electricity tariffs. Ocotpus and others have tariffs designed for heat pumps and have 3 cheap periods and 1 expensive period every day.

Max out your energy consumption during the cheap periods (e.g. run anppliances) and turn off the heat pump off for 2-3 hours while it is expensive and you’ll probably cut your electricity bill by 20%-30% and it will be way cheaper than gas/oil.

Solar and/or just batteries will obviously drop that even further. My combination of an EV tariff, heat pumps, solar and a modest 13.5kwh battery mean I am paying absolutely nothing for any energy or fuel. In fact this year has been an extremely sunny year and Octopus energy are paying me. I’ve already built up more than enough credit to get me through to next March and I expect to build more in August and September.

It may be a silly question, but why buy such a large house if you are concerned about heating it? I can’t square that logic!

 

[relicalpha]

Thanks a lot, fair question on the size! I guess we loved the house but generally are used to living in fairly cold spaces, like always sleep with the window open type deal even in winter This does have solar (no battery) as well so that should help offset some cost, but I guess this is all a learning curve to optimize efficiency. It just feels like electric costs can probably only be optimized so much as long as there's a 16kw unit. It's probably oversized for our usage requirements sadly.

 

[b0rn2sk8]

I’m not saying all Samsung heat pumps are oversized or badly installed but there was a period of time when they and LG were the favoured units by the not so great grant scheme installers. There is a lot of ‘heat pump’ rescue content on the interwebs and most of them feature Samsung and LG installs. The benefit of said content is you can probably do a lot of the optimising they recommend yourself.

How old is the install? If the current owner is getting RHI payments, they should also transfer to you.

Get some batteries, they’ll literally pay for themselves. Given you are buying a 3000sqf house in the UK, you can probably afford it

 

[Ron-ski]

If you're staying long term, add more solar and a decent amount of batteries. When was the existing solar installed? It may be a FITS system and you could be due payments from that, you also need to make sure if upgrading it/adding batteries it's done correctly not to lose FITS payments.

It may be worth paying for a heat loss survey, and/or getting the system checked by a competent installer.

PS My 1970's 175m2 house required a 7kW heat pump, I have 29 kWh batteries, so in the winter for most days hope to be running on 7p electric.

 

[relicalpha]

Thanks yes, 4kw 2014 solar install with FITS, so I will definitely look at getting batteries if that will further offset heat pump costs. I guess then in winter you can then charge them at ~13p night tariffs rather than 25p and run some % of the HP off them - that sounds much more economical.

 

[Ron-ski]

I added a ninja edit in my last post, if you have an EV you can actually run on 7p electric, obviously the very coldest days you may use day time rate.

 

[Ron-ski]

Thanks yes, 4kw 2014 solar install with FITS, so I will definitely look at getting batteries if that will further offset heat pump costs

For advice on solar and batteries head to the thread below.

Solar panels and battery - any real world recommendations?

Morning all, I've started to look at the mind field that is Solar and wondering if anyone can offer real world reccomendations? I've got virtual consultations booked for today and tomorrow with another company coming to see me on Tuesday. I've got people offering GivEnergy systems, another...

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