How to correctly install heat pumps so that they work properly and efficiently

I guess it very much depends how well insulated and airtight the house is. A passive house for example could have a 5kW or smaller HP. From spring to autumn it wouldn't come on if a big enough solar array and eddi was part of the setup.

How does having the heat pump off for 6 months affect the longevity of the unit? Instinctively I'd say it would increase the life of it but maybe not if sitting idle.

Another option is go down the air con mini split route. That’s still an air to air heatpump afaik so supposed to have decent COP. And costs wayyyyy less than a normal heat pump. Cost is closer to gas boiler price afaik.  Heats and cools air only, not water. Not connected to rads, and not connected to hot water (so won’t heat water). So same setup as the air con in apartments in europe. Compressor out the back which connects to one of more wall mounted units inside. Plus handy for the (seldom) warm weather in Ireland to reduce the temp at night. We live beside a busy road so can’t open the windows at night (for noise more than fumes).

I’ll likely look into that when the gas boiler dies or is close to it. Won’t cover the whole house but the remainder could be electric rads. Need a lot of battery capacity for any electric heating so not running on expensive day rate.

Was a good Heat Geek video but can’t find it now. They did one on air con which I didn’t watch. But they did a follow up with an air con guru to correct some of their misconceptions. Difference is heating companies don’t fit them as air con uses refrigerants, not  gas mains, and there are no water pipes. So need to be refrigerant qualified afaik. Heat Geeks fella didn’t realise air con = air to air heatpump, nor did I.

This fella got one to supplement his other heating and raves about it. He’s electric rads in places and replaces his oil boiler. Toshiba Air to Air Heat pump (A2A) - Probably one of the best heating systems you can install - YouTube

Seems a decent setup if you’re ok to have more than 1 type of heating (which I would be as using electric rads in parts of the house for 1st time this year as well as gas boiler).

@unkel, did you get a mini split air con unit last year? Think I remember you saying you might or where looking at it

I looked at a similar system - albeit water based - from Panasonic. An ASHP connected to a cylinder for hot water and a fan assisted radiator for space heating. For passive or NZEB houses 1 fan assisted radiator could do the job depending on the size of the home. It too can work in reverse in the summer to provide cooling.

Interesting. Never saw that type of rad before. Looks like an electric one but is water rad with 4 speed fans. Fan assisting would help boost the convection. So even at the lower temp the rad runs, it would be getting moving more hot air upwards from the rad. And says it can cool too.

Heat Geeks did something on that afaik. Normal rad with fans at bottom to try cool a room. Did sfa as far as I recall, but was only half paying attention. But was a very cheap and cheerful stab at it. They did it in a small bathroom.

For cooling how would it work? Put cool water in rad and then it that 'radiates' into the room colling the warm air? But if a rad takes up a tiny % of volume in a room, I struggle to see how it’s gonna do much. Not being critical, just don’t get how it’s supposed to work. Difference with an air con unit is the amount of air it pushes out per min would be higher. And if it cools from the roof down, the air at the top causes a cool convention of air dropping downwards.   

I've already completely dismissed the idea of installing a full heat pump system. Lots and lots of money wasted on labour (and profit) retro-fitting. Then you end up with a system that will cost you more to run than gas / oil, if we end up paying 50c day rate electricity.

No way Jose, I'll have 45kWh of batteries within the next couple months, but even that simply isn't anywhere near big enough for heating on a cold day (never mind the rest of my electricity needs) On new (passive) houses and on very well insulated / retrofitted houses, it's a no brainer. For the rest of us not so much

+1 for me on that. Our leaky gaff was 'born' in 1940s. So heatpump 'readiness' is wild money. I'd love an A rated new build, but that's not what we have :) We're using a mix of far IR panel, electric rads and gas boiler at mo. And house is at perfect temp in each room and we've halved our gas usage V last winter. So we're trying stuff and finding what works. It's a little clunky as don't just have a single Nest app to change the heating. But works for us

It would be very hard for me to move away from the comforts of a combi boiler, for the likes of instant (and fresh) hot water for showers.

This https://sunamp.com/en-gb/products/thermino-ipv/ will do very nicely for pv/boiler/cheap night rate combo but installers in Ireland don't have a clue about the tech.

I was thinking about something like this alright https://www.buyitdirect.ie/p/multi-split-27000-btu-smartapp-wifi-inverter-wall-air-conditioner-with-3x-9000-btu-indoor-units-to-a-single-outdoor-unit-iqool-3ms9k9k9k but the A2A COP is way worse than A2W and I think you'll need two of these for the whole house probably but it will give you true zoned control and also help for those 2 scorching weeks we get once a year 😂

Each unit can pull 3kw so 18kw o'clock easily from these.

Spot on description of infrared heater. I’ve one for the WFH room and I like it. For me it’s more comfortable than other forms of heating including oil filled electric rad. It heats me, not the air. They really supplement heating, not replace it. Start from around €120 euro for the basic ones, more depending on the wattage and bells and whistles.

Uses a little less electricity than an oil filled electric rad in the WFH room. It’s a cold room with old windows that doesn’t see any solar gain and loses a lot of heat. Means I don’t need the room to be as warm as I’m in the line of the heat. And drafts don’t affect it. I can even open the window a crack and still be warm – which takes getting used to 😊

I got a 350W one and it’s fine. That’s likely on the small size for some but ok for me as it’s on the wall close to me.

Mine is on or off only, can’t adjust the wattage. But it does turn off when reaches the temp you set. Thermostat on it is a very crude. It’s not the temp it thinks it the sensor is on the side of it (so it’s hotter than the room). But once you work out the ‘offset’ it’s ok. I wanted a small wattages one as have solar but no battery so wanted to use the solar excess for heating.

They work for places you stand or sit at – as in you’re not moving so in the line of the heat. Only other place we could use one would be the sitting room. But would need to be roof mounted over the sofa due to the room setup. That’s the most efficient setup some manufactures suggest, but need to run a cable down the wall to a socket or get a spark to add a spur.

Some have them in the bathroom to replace the mirror over the sink. But that wouldn’t heat our shower area, so no gain for us there.

You can already get fans that can be added to existing radiators to increase the output, radfan and speedcomfort are 2 I've come across. I've looked into them a bit but havn't been able to find any decent figures on the output increase.

There are already stats on how the output decreases with lower deltaT, image below shows it.

It would be great to be able to see the increase based on forced convection. Lets say you have a rad with 2kW output at 50deltaT running off a conventional boiler than heats the room more than sufficiently. You want to put in Heat pump but the lower running temp means you have only a deltaT of 20 so the output is 600W, not enough for the room. What if using fans you could bring that back up to 1.2kW. That might be enough heat for the room without having to get a bigger rad if you run it constantly instead of cycling at 2kW. It could make Heat pumps much more attractive if you didn't have to replace the radiators.

I did try see how much of a difference it would make but trying to find the heat transfer coefficients for free convection and force convection is hard as I think the radiator geometry would come into play. Best way would probably be experiment measuring the temp in and temp out of radiator with a fixed deltaT and flow rate with fans and without. Bit much for me to bother but easy enough setup for a business or university with an interest in it.

Tbh I don't think that it's a case they aren't arsed, the installers aren't heating engineers, they're not really qualified to do the design to any degree of depth

From what I've seen, they seem to have a basic cookie cutter system design that they put into all houses. Bigger houses, scale the system up a bit, etc.

The manufacturers seem to try and support this, they make standard systems and fairly simple online calculators that just spit out a system spec

The problem is without someone qualified double checking the system, it can end up pretty poorly optimised. Installers could probably get away with this back in the days of oil and gas. You can kind of balls up an oil boiler to some degree but if it's putting out water at 70C then the house will be warm regardless and the customer probably won't know any better

With heat pumps, having an efficient design is critical. I think this has led to some pretty terrible design decisions and bad installations

Absolutely, people tend to compare the price of fuel but they don't compare the consumption. One person might be using 20l of oil a day and think it's fine until they see someone using 10l per day for a similar type of house

I'm starting to subscribe to the idea that the best thermal store is the house itself. There's a lot of stuff in the house which can absorb thermal energy, furniture, concrete flooring as well as the structure of the house itself

That should provide a reasonable buffer if the house is well insulated.

It's interesting how a buffer tank is supposed to stop the heat pump cycling but has been shown to actually increase it

I still think there's value in using a buffer that you can zone out using valves for a heating system that can't provide heating on demand, like solar. That'll give you the ability to store energy when it's abundant and you can cut it off from the heat pump when it isn't needed

100% agree, people would often say that gas is more cost effective that electric for cooking. It's easy to say that when the fuel is just really cheap, no reason to be efficient then

I suspect a lot of those folks with the huge fuel bills are not switching providers and are getting f!cked at the standard rates

I cannot understand people not doing that. I've known people who would drive across town for cheap petrol but won't spend 20 mins finding a cheaper energy tariff and switching

There's really a lot of disinformation around this. I remember a colleague of mine from India was complaining about the electricity bill in the house share he was in. I asked why they didn't switch provider and he said the landlord told them it would cost €300 to change

It's BS like that which keeps Electric Ireland and Bord Gais in business 🙄

I'm continuously shaking my head when I see new builds with insulated plasterboard fixed to the inside face of a cavity wall. It shows a real ignorance towards the thermodynamic properties of a building.

Put whatever insulation you need into the cavity to achieve the necessary u value and just plaster with sand cement and a skim the inside face of the wall. That way you get a thermal store, a more comfortable room - as it won't heat up and cool down rapidly - and the air tightness task is simplified significantly.

chasing is not bad if you have the correct equipment and airtightness is easy and quick with the use of airtight paint.

Plasterboard on the other hand is notoriously difficult to make airtight as heat can escape from a multitude of places.

That would be dripping with condensation though

I thought the idea then was to put the airtight layer on other side of the cavity to the plasterboard?

So the cross section from outside to inside of a timber frame would look a bit like this

Cladding (blocks or render) -> External cavity -> OSB with vapour barrier -> Structural timber with insulation in between -> Insulation panels -> Airtight barrier -> Services cavity with thin studs -> Plasterboard and plaster

I would agree with insulating on the outside but to do a full house is very silly money even with "grants"

The house already had interior insulation but it was that white crap they used in the 90s (before kingspan) stuck to plaster board (60mm or so) and then stuck to the wall with 2-4cm blobs of tile adhesive or something (max cowboys), no wood studs or anything (except in batrooms), which I'm sure for air circulation the empty space behind the pb helped but house was an igloo once the heating off and you could hear the wind.

Replaced it with kingspan and it made a big difference for sure.

I have a GSHP in a 2011 build house (A2 rated) all block build (internal & external walls) with concrete slabs on 1st floor Its a 12kw HP which is on all year but only heats the water from May to Nov. I have a meter attached and just checked it there and it has used 551 units in total over the last 36 days (av 15kw per day) all of which were used at night rate. I have ufh throughout and only have 2 stats, one on each floor. I think thermal mass is essential with HPs as you can heat the house overnight and it will pretty much last all day. I have no other heat source in house except for a log stove which I lit probably 5 evenings this winter to-date and that was only for the added comfort late in the evening. As for heat loss from hot cylinder, I have a 500l cylinder in the attic which has been kitted out as a large 'hot press'. I heat the tank every night to 50 deg c, which from memory only takes about 3 units of electricity (must check that again), and this lasts all day for all hot water use incl showers. The minor heat loss works great to keep the area 'aired' so I don't consider it to be heat lost.

So for me the HP has been a great success but the system was designed and installed as part of the new build by a guy who obviously knew what he was doing - unfortunately he's out of the game now so I woudnt even know where to start looking for someone to install a system. A couple of neighbours, who were very skeptical of HPs when I was installing given the high installation costs, are now considering retrospectively installing a HP given the low running costs of my set up but I have cautioned against simply drop kicking a HP into an older house with rads. It simply wont work as well and they will be hugely disappointed when the expected savings wont materialise.

Btw thats some battery capacity you have, I wouldnt mind drop kicking some of those into my ever degrading Leaf!!

Anyone want to learn how to install a heat pump?

Unfortunately I think you have to be a UK citizen to get it for the discounted price 😭