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Wanderer ,

Air to air heat pumps are amazing. I’m completely converted, they are fair superior to gas.

But why the UK is pushing do hard for air to water is a mystery to me. Seems like betting on old inferior technology.

Also I don’t get why they aren’t pushing for a induction also conversion and disconnecting the gas line to the house entirely. Induction is magic, that is a way superior technology to gas cooking.

silence7 OP ,

The big reason somebody might want air to water is that it enables a low-cost retrofit of an existing heating system which uses water to distribute heat. Definitely not what I’d choose if designing from scratch, but I can see how it makes financial sense in a lot of homes.

And yes, induction is amazing, but there are a whole bunch of people who have been marketed into treating gas stoves as their personal identity.

Wanderer ,

I think most of those retrofits aren’t cheap because the pipes and radiators aren’t big enough for the colder water. So it ends up needing a whole now install anyway.

silence7 OP ,

I can see how that could happen for some homes. Worth doing the calculation though, since it can be cheaper if the pipes are adequate.

Wanderer ,

It’s probably always cheaper. The government is pushing for air to water. There are no subsidies for air to air which I think is a better way to heat a home.

Greyghoster ,

On the other hand, using a heat pump for replacing a hot water heater is definitely a good thing. Using a heat pump on an old water radiator system may not work well. Friends had to replace a gas heater for their water radiator system and were told that there wasn’t a heat pump unit hot enough for the retrofit.

Wanderer ,

Oh yea. I’ve been in houses (outside the UK). Had heat pump water tank and an air to air heating (and ac) system for the house.

I’ve always wondered if you could have an air to water system that fills the tank for the taps and then heats the radiators. But also have supplementary heating air to air. Maybe a big one downstairs in the hallway or in the main room of the house.

But with the UK it always comes back to having the worst insulation in the world. Fix that and we wouldn’t even be discussing heating systems.

tal ,
@tal@lemmy.today avatar

But with the UK it always comes back to having the worst insulation in the world.

Most of the UK has relatively-comfortable temperatures, so the impetus to add lots of insulation is relatively low.

en.wikipedia.org/…/Climate_of_the_British_Isles

Temperatures do not often switch between great extremes, with warm summers and mild winters.

The British Isles undergo very small temperature variations. This is due to its proximity to the Atlantic, which acts as a temperature buffer, warming the Isles in winter and cooling them in summer.

Over here, in the US, the places with the lowest temperature variations are also islands, like Hawaii. Extreme temperature swings happen in places like the Dakotas, far away from the ocean.

You’ve been cursed with fairly comfortable temperatures. :-)

tal , (edited )
@tal@lemmy.today avatar

why the UK is pushing do hard for air to water is a mystery to me.

I was a little confused when I followed a European forum. The transition to heat pumps has been a big deal, lot of discussion in the UK and Germany. It had a bunch of people talking about boilers and having heat pumps heat water, which confused me. I’d only heard about boilers in the US much in the context of large buildings with old steam heating systems.

In the US, I’ve seen plenty of air source heat pumps. Some water source heat pumps. But they both are used to heat (or chill) air, which is then blown into ducting and circulated through the house. Provides ventilation and such and humidity control. But it seemed to be overwhelmingly the case that people in Europe were talking about heating water and circulating that.

Small window or through-wall air conditioning units do obviously heat air, usually for one room. Split minis move refrigerant, which ultimately heats or cools air.

And it seems like you’d rather have ducting, as it can provide control over a given ratio of fresh air to an area of a building and filter it.

I was able to find a few companies in the UK dealing with ductwork, but they focused on new office buildings.

I eventually figured out what was going on.

A lot of houses in the US were built after the introduction of air conditioning. Not only that, but the US has more areas that get quite hot than Europe, so once air conditioning was an option, people really wanted it. The result is that a lot of US housing was built with central air conditioning.

This meant that when houses were designed, ductwork was built into the design.

Ducts are relatively-large. It takes a lot of space to move a given amount of heat.

It is not easy to retrofit ducting into an existing house. You have to have this big thing jammed into the house somewhere that runs to all rooms.

Water is much denser. If you use water to move your heat around, you don’t require that much space. So if you retrofit an existing house, you don’t have to mess the house up. Not only that, but a lot of buildings in the UK had apparently already been set up with systems that heated water with natural gas and then moved it around the building to heat it, so putting in a heat pump could use that existing system.

My guess is that people did the math and decided that it didn’t make sense to massively go rip up existing houses when they could stick comparatively-unobtrusive additional water pipe in.

My guess is that what will happen is that new buildings will incorporate ductwork, so there will be a very slow transition to ductwork. But it won’t happen overnight, just as buildings age out and are demolished.

The current transition to heat pumps that they’re doing is on a much shorter timeline than that.

Rade0nfighter ,
@Rade0nfighter@lemmy.world avatar

Okay so we’ll need a new boiler in a couple of years and to be honest the idea of pumping gas through a pipe into my house seems kinda archaic. Like oil lamp kind of technology.

I really want a eco friendly alternative and modern, cost efficient technology instead.

However heat pumps just don’t seem to make any sense, and the more marketing materials I read critically, the less convinced I am of their practicality, nor the integrity of the vendors - if they work similarly to air conditioning units or refrigerators why do they cost 20x as much as those devices?

Anecdotally, an electrician I know has been involved with decommissioning more than one heat pump in new builds so that the owners could replace them with gas combi boilers because the heat pumps were so slow - taking a day or so to heat the house up after eg children leaving windows open, or forgetting to close doors when bringing in shopping etc. Never mind running out of hot water.

There are some very insightful comments in this thread from people who are clearly more clued up than me, so I wondering if anyone could change my perception - which I will be the first to concede is likely ignorant.

So…. Thinking about the UK implementation where one is supposed to swap out a gas boiler and replace it with a heat pump…

My understanding - as an admittedly ignorant layman - is that:

  • They are cheaper to run in an ideal environment - a super insulated building, that is often a very high bar even for a relatively modern (less than 30 year old building say) with all the insulation one can achieve. For the sake of argument let’s say this is doable for the individual and they have achieved a C level EPC rating, the most you can get before your house begins to generate its own energy eg with solar panels.
  • They cost 4x the price of a gas boiler (approx 3k vs 12k). A few hundred quid a year off the gas bill doesn’t justify that difference.
  • They take incredibly long (by comparison) to heat a home from perceivably “cold” to “warm”. Eg 24 hours to go from 14 degrees C to 21 degrees C, vs an hour with a gas boiler.
  • Hot water on demand is impossible, so you’re back to the olden days of having to plan life around a hot water tank, and praying no one takes a slightly longer shower than usual, or guests don’t want a bath

So then, what is the upside for a rational (ie selfishly motivated) consumer? A pay off after 26 years assuming a failure rate of 0? How long are they expected/guaranteed to work for? If the anticipated lifespan is less than that then it doesn’t make sense from a financial point of view no? And if they are expected to last longer, how much longer? Is that a good investment vs savings? And during/beyond that time are people expected to not value the loss of a superior experience in terms of heating time when temps drop unintentionally?

Reading my post back I appreciate it sounds very critical and full of FUD but I’m genuinely not trolling - just looking for sense where I don’t see it, but really want to!

silence7 OP ,

However heat pumps just don’t seem to make any sense, and the more marketing materials I read critically, the less convinced I am of their practicality, nor the integrity of the vendors - if they work similarly to air conditioning units or refrigerators why do they cost 20x as much as those devices?

A refrigerator cools a fairly small volume with excellent insulation, which allows it to use a fairly small compressor running at a single speed. This is cheap.

The big differences between typical air conditioning units and heat pumps are:

  • they’re set up to move heat both ways (eg: both heating and cooling) which requires a tiny bit of additional hardware
  • They often have a more substantial compressor to handle the larger temperature difference associated with colder temperatures
  • They’re a lot more likely to be a system intended to support the whole home instead of a single room
  • People care about efficiency, which has variable-speed systems getting installed
  • There’s a lot of demand for them right now, and limited supply
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