Could I replace my gas boiler with split aircon that does cooling and heating?

[Derek M]

At the moment, the non-combi gas boiler in my kitchen pumps hot water into my hall cupboard, from where it gets distributed to the radiators for heating and into an immersion tank for hot water, so I only get about 30 minutes of hot water out of that. There's an electric backup for the immersion tank, which I've never needed to use, and there's a cold water tank in the cupboard as well.

I'm investigating options which would allow me to remove everything from the hall cupboard so I can expand the bathroom into that space (I'd probably use it for a walk in shower). I also need to get aircon, because it reaches over 30c in my flat in the summer, so I was going to get a split aircon system, with the compressor unit on my balcony and then two wall units in the bedroom and living room. I only need cooling for a couple of months in the summer, and heating for a couple of months in the winter. I don't need any heating/cooling in the kitchen or hall, and I'm thinking of using an infrared panel on the wall or ceiling in the bathroom to provide heating in there, which I'll only need for half an hour in the mornings in the colder months (it doesn't get very cold in there anyway as it doesn't have any external walls, but it has an extractor fan/vent which lets in some cold air). I could put an aircon unit in there instead, which would have the benefit of also being able to dehumidify the room as it obviously gets damp in there, but the compressor units that support more than 2 internal units tend to be quite a bit more expensive, so it will come down to which option works out cheaper to buy and install.

I'm not sure why some places say that the difference between aircon and an ASHP is that aircon can only provide cooling whilst an ASHP can provide cooling and heating, because there's load of aircon units that also provide heating. This is just one example. Looking at the figures on p.4, it says that it uses 164kWh/a when cooling and 922kWh/a when heating. https://www.airconditioningworld.co.uk/global/media/pdf/1625133638-5855.pdf

I know aircon units can't provide hot water, although I'm not sure why when they're able to provide heating. So I'd need another option for that. I could probably fit a hot water tank somewhere in my kitchen. I know it would be more expensive to heat the water with electric rather than gas (and I'd still have the same problem that I have now, where I don't have hot water available all the time as I have to wait for the tank to fill and it runs out in about 30 minutes, which wouldn't be a problem if I removed the tank and replaced my existing boiler with a combi boiler), but maybe being able to disconnect the gas and thus avoid the standing charge would cancel that out?

Alternatively, could I get an ASHP that provides air to air heating/cooling/dehumidifying via wall units like an aircon unit, but can also do air-water for the hot water tank? Or one that does air-water for the tank and the existing radiators, but can also do air-air to provide aircon in the summer? From what I've read, it seems that there are some units called Variable Refrigerant Flow that can do this, but they can only do cooling or heating at one time (so it would be fine in the winter when I want heating and hot water, but not in the summer when I want cooling and hot water), unless you get a 3-pipe version which can do cooling and heating at the same time, but I think they're only available in big units for commercial premises (hotels, etc.) and not for residential use.

 

[stem]

These days the terms Air Conditioning and Heat Pump tend to be used interchangeably. So, it would be the functional specification of the unit that you are interested in that matters, not what it's called.

Air Conditioning, the shortened version of 'Air Conditioning System' originally described a complete system that dehumidifies, heats, cools and filters the air inside a building, as the term suggests it 'conditions' the air to maintain a pleasant environment.

A heat pump is part of an air-conditioning system it's the device that transfers the heat collected from a cool area to warm another area. Some heat pumps, as used in a fridge will only work in one direction, others (i.e. the split units you mention) can work in reverse, so in a domestic setting, in the winter the outdoor unit gets cold and the indoor unit gets warm, then in the summer it can be reversed so that the outdoor unit gets warm and the outdoor unit cold.

When it comes to heating domestic hot water, heat pumps only generate a temperature of around 40C which is too low for hot water which should be 60C minimum, so a supplementary heating system for hot water is required. Usually a hot water cylinder heated by an immersion heater.

When heat pumps are used for space heating because of the low temperatures they produce they are best used either directly to heat (or cool) the air using a split unit. Or, to warm water for underfloor heating which emits heat from a big area but at a low temperature. If a heat pump is connected to an existing wet radiator system the radiators will only get warm and not hot, so new larger radiators are required to heat most properties satisfactorily. UFH and radiators are used for heating only as the emitters themselves are not suitable for cooling a building.

 

[ericmark]

As far as I can understand it is the legal bit which causes problems complying with government rules which means heat pumps are often one directional units, there is nothing to stop a heat pump being manufactured to work in both directions, it is just getting grants etc which stop it.

In 1980 I worked in Algeria and back then we had units that worked in reverse to heat the accommodation when required.

The Myson iVector fan assisted radiator comes in two versions one with single matrix and one with twin matrixes, the single one the whole building is either heat or cool, the twin one room can be heated and another room cooled, since heat raises you can only have heat and cool with fan assisted radiators.

The fan assisted radiator does not control flow of the coolant, it adjusts output by adjusting fan speed, this works well with a series plumbed system, but most domestic systems are parallel plumbed, the problem was the gas condensing boiler, where if the water returned too hot it would auto turn down the output of the boiler, so the whole system used TRV heads and lock shield valves with a by-pass valve, so the old system does not lend itself to simply having a heat pump replace the gas boiler, nor does a heat pump work at maximum efficiency if heating the domestic hot water.

So for a new build there is no good reason not to fit a heat pump to heat and cool, and also have roofs orientated to use the solar panels with walk ways to clean them, there is a disadvantage in that if there is a loss of electric power in the winter the central heating does not work, but if one wanted one could install a oil or gas powered generator, is summer for cooling the solar panels would power it.

But we do not buy land then get a builder to build our house, it is the builder who buys the land and builds the houses, so we buy the house ready built, so the only way to get homes designed to have solar panels in the correct orientation and with maintenance access is to force the builders to do it.

There is a lot of why do you do that? Answered with because we have always done it that way, homes are not designed, they are little boxes built nearly the same way for 100's of years.

 

[vulcancontinental]

Speak to an expert contractor regarding AC, it's perfectly possible to have the condenser on the balcony and the internal unit supply hot water, a split system. I work for Vokera, part of the Carrier group which includes Toshiba AC. I've no expertise in AC personally. Ring Toshiba on 01372 220 240, they can put you in touch with an approved installer in your area.