Every time I look into conventional ASHP for domestic heating I?m put off by the enormous complexity of the systems, the disruption of installation and the requirement to lose one?s gas boiler to get the grants.
It looks like like using air/air heat pumps would be less disruptive to install, and cheap enough to do without the aid of grants. I could also keep my gas boiler to ?top up? the heat output if required.
I?d also have the added benefit of air conditioning in hot weather.
We tend to find that we only need to heat a couple of rooms downstairs and sufficient heat normally percolates upstairs to keep it adequately warm so I think just a couple of adequately sized units could meet 90% of our heating needs.
The problem with heating systems which heat blown air (whether from burning gas or from a heat pump) is that they don't work (they don't keep the house warm enough), they blow dust around and they make a godawful whining noise.
My parents' old house, which they bought new in 1972, had gas-fired ducted-air heating and the house was always cold (the air coming out of the ducts was barely tepid at the end of a long run of ducting) and everything was covered in dust - not from the air itself which was fed through a sponge filter in the boiler but because the air disturbed dust that was already in the room and which would normally be removed by hoovering.
When we were looking for a house a couple of years ago we were shown one house which had a heat pump and air heating. The house was cold, there was a cold draught from the ducts, and everywhere throughout the whole house there was a very infuriating moaning/whining noise which we were told was the heating. The vendor was a heating engineer and he thought the system that he had fitted to his house was the dog's bollocks, but in fact it was the system that was bollocks!
I would say that the best heating system is one that uses a boiler to heat hot water to radiators. How you heat that water is debatable: gas, electricity, heat pump, using waste water from a power station (*), burning fairy farts, or whatever, but the end result needs to be nice hot radiators that heat by convection (radiators produce very little heating by true radiation) rather than by forcing warm air around where it stirs up dust and goes cold.
Also, heating needs to be flexible and immediate: any heating system which requires you to anticipate several hours in advance that there will be a cold spell or that someone will feel cold, is not fit for purpose. We stayed in a holiday cottage which had under-floor heat-pump heating. The house was either too hot or too cold. Also, we were told, you couldn't have carpets with underfloor - so all the floors were shiny (and exceptionally slippery) polished stone - lethal in the bathroom where wet feet or the bathmat would skid across the polished floor: that room at the very least needed the surface roughening to avoid wet feet going flying.
(*) As described by a report on Tomorrow's World in the 70s or 80s - brilliant as long as you live close to a power station... as we all do ;-)
I had some of my factories heated by air exchange heat pumps. One used a central unit with ducting to provide HEPA filtered, humidity controlled air to a clean room. A couple of others used individual units in each room, run from a communal external heat exchanger. They all worked very well, but the individual room units did hum constantly and the three phase external heat exchangers had a footprint about the size of a Mini, although half the height. They also needed a fork truck to shift them.
If you go down that route, check that the heat exchanger is designed for the British climate. Some of the ones designed for Japan freeze up when the weather is cool and they are trying to suck warmth out of the air. I had a small unit in another factory that kept doing that every winter. We had to add an extra heater for cold weather.
I had a gas-powered warm air system in a small town house nearly
50 years ago. Warm-up was fast, lack of radiators made room layout easier.
Every room was heated, including kitchen and bathroom, but these two had no direct return duct.
The system was noisy, both air movement and fan vibrations; cleaning filters, adjusting dampers and fan speeds never made much difference. In three years we got through two transformers and a fan motor.
In a family house, noise transmission along the ducts could have been a problem, conversations could be heard around the house.
Water heating was by a large instantaneous gas heater, which gave no trouble.
I have worked in offices with an air to air heat exchanger system as the only heat source. It appeared to operate quite well through the winter. There are defrost cycles, during which the mode reverses, in order to melt frost on the external heat exchanger. This means that the internal kit blows cool for a while, but not to the extent that it compromised overall heating performance. It might be less acceptable in a smaller space.
Yes, my sister and I, in adjacent bedrooms, used to chat late at night by talking/listening at the floor duct. When my sister was little, she could sit with her feet through the hole in the floor (having pulled out the metal grille) to keep warm. On day I started getting a strange smell in my room, which was downstream of hers, and after a few days we traced it to a bit of cheese that she'd (accidentally? deliberately?) dropped down her grill when she'd been sitting there.
The living room was below my bedroom. Late one night I heard my parents having a blazing row (a very rare occurrence), so I got down on the floor to listen. My sister then came through. She couldn't hear much through the floor, but she said "you can hear them so much better through the heating grille". I remember we were awarding points for how "hard" mum's and dad's
*verbal* blows were to each other ;-) (AFAIK they never hit each other, though mum did once throw a stiletto-heeled shoe at dad early in their marriage, and left a hole in the kitchen door - good thing he ducked).
My parents said that never again would they have a house with blown-air heating - cold, dusty and noisy. Our old neighbours eventually had theirs replaced with radiators - probably when the boiler was due for replacement, they went for a big change rather than just replacing the boiler and keeping the ducts.
I have an electric Daikin hot water boiler system, with a heat pump that drives 8 radiators. Currently I only use 3 radiators on low @ £1.20/day. Thats obviously going to change very soon now Symbio has collapsed.
Cheap enough to dip your toe in the water with something like this:
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COP is under 3 when heating but it draws from the room and dumps cold air via the hose, I wonder what the effect of the cold air infiltration would be compared with a split system.
Noise would be an issue, I have a 150W max centrifugal ventilation fan on its lowest setting transferring 25-35C air from a 5kW stove via two
50mm diameter pipes into another sitting room and it is a bit noisy. I provides enough warmth to inhibit the gas central heating most winter days.
- you wouldn't get hot water, so you'd need to run that some other way
- air to air needs either refrigerant pipework (small) or fairly large ducts. If you have a multisplit you can put one fan coil in each room, or a central unit blowing air into ducts.
- air2air units are often fairly small - eg if a whole house needs 10kWh of heat that's 34000 BTU, which is a big unit. If you go for multiple smaller units you may find they're underpowered - if you're trying to heat a room with a 9K BTU unit and the heat is leaking to other rooms.
- cooling is harder work than heating (lots of heat sources are 'free' - solar gain, people, pets, appliances - but there are no free cold sources in hot weather unless you go GSHP). You might find you need more cooling capacity than you think.
- fans in the indoor units can be bothersome, since it will need to run anytime you want heat, including at night. DC motor fans can be quieter and more efficient (efficiency is important when cooling, since the unit has to pump its own electrical losses on top of the room heat) but they're less common and more expensive
- you would have to check the planning situation. ASHP installation can be permitted development, but perhaps not if you need multiple outdoor units. I think technically if cooling is possible it's not PD. Also check noise limits and locations relative to neighbours.
- if you're doing cooling you'll need condensate drain pipework too
My parents lived in a one-bedroom flat which had a (centrally distributed) warm-air heating system. It wasn't noisy and was very efficient. They had no problem with it.
The first house I bought had a gas-fired warm-air heating system (Johnson & Starley with a separate gravity-fed hot water boiler). I loved it. I could come in on a cold day, turn it on and within two minutes the air in the rooms was already getting warm. I didn't find it noisy or dusty. No maintenance other than a quick vacuum of the filter now and again and a check of the centrifugal motor were required. Other than that motor there were no moving parts. Nothing to go wrong and nothing ever went wrong in the 14 years I was there. Just a block of iron to heat and a fan to push the warm air around.
Unlike the idiotic, expensive, complicated, maintenance-driven conventional hot-water system I now have. Want to warm a room? Well, heat a lump of iron, use that to heat water, pump that water round, use it to heat another block of iron (the radiator), and use that to heat the air in the room. Oh, and you have to somehow get the air to circulate in the room. Is convection sufficient? Yes, of course if you want to heat the ceiling. The warm air system has vents almost at ground level, and as the air is moved by the fan, it doesn't stagnate at ceiling level. Instead of ducting, you need water pipes and radiators, possibly valves to control them, and of course the water pump. It's a system designed to /need/ maintenance. Even with inhibitors the radiators will slowly fill with sludge and eventually need power flushing. If you're lucky, that won't find any leaks in the system.
Looks to me that it wasn't installed properly, and the ducting wasn't insulated. We get plenty of dust with our conventional radiators. Unless you're not going to move around, dust is a fact of life.
Maybe your bias against the system was showing? If you don't like warm-air heating why did you bother to view the house? Or were you thinking of ripping it out and replacing it with radiators?
Of course you would, because that's what you like. I'm completely the opposite (I know I'm in a minority). If you think about it, just about all commercial properties use warm air (and the ability to have cooling air in summer) to warm their properties. I don't remember ever visiting modern offices where there were radiators. Why do they use that rather than circulating hot water like residential properties?
How you heat that water is debatable: gas,
That shows your bias. The warm air coming up is warm where you want it, not on the ceiling.
For once we are in agreement. I've never seen the sense in underfloor heating except as low-level background heat which can be topped-up with, for example, a fan heater. Oh - don't those blow air around and increase dust too much. How about an old-fashioned radiant bar heater then?
With gas currently at 4p/kWh and electricity at 25p/kWh for new contracts, the ASHP would need a massive gain of >6 to overcome the difference.
I suspect you'd wind up using your current gas boiler instead of the ASHP system, and it looks like the current energy situation is taking the edge off the Renewables dream. You might not want to be an early adopter lumbered with a white elephant.
I think you'll find noise is an issue. I have a 15-years old version of that device (it states it has 1.8kW of cooling power), and with the fan at full power is very noisy indeed. That airflex states it has a noise level of =<65dB(A), which would be around a normal conversation level. In my experience, trying to vent the hot air through a 1.5 metre hose can be awkward without a "hole in the wall" to take it. It is unfortunately lower down on the a/c body rather than at the top, and barely stretches to the bottom of an open window. I also find it necessary to wrap it in bubble-wrap or it just lets some of the heat back into the room.
The water will also have to be emptied or an arrangement made to pipe it out
Our Creda underfloor warm air heater unit caught fire and the smoke was ducted throughout the house very quickly. The PVC insulation melted off a pair of trailing wires which shorted and set the fan running at full speed.
Had something similar in an hotel that had been converted from a nunnery. They put one in each cell (aka room). It was impossible to sleep at night with it turned on.
I've worked in office environments with blown air heating. OK if the filters are cleaned or replaced regularly - if not after a while air vents in the ceiling drop dirt.
So temporarily "lose" it into a box in the garage, and hang it back up when done :-)
Not totally - at least for space heating / cooling. So of the offices I do work at have ceiling mounted cassette style heatpump aircon units, and the do dual service for heating and cooling. Noise is certainly ok is a small office environment.
Hmm. I'm sure there was something wrong with my parents' system. The boiler was as big as a wardrobe: about as wide and deep as a washing machine or fridge, but about 7 feet tall, which is big even allowing 1970s technology and for a big air blower on top of a gas-fired heat exchanger. And the air that came out of the vents was never warmer than vaguely tepid, even at a vent close to the boiler, and it cooled down more as you got further away. I wonder if the ducts were actually insulated...
For the five years that we lived in that house, we were always frozen in winter and huddled in the living room round the gas fire. And that was a
1972-built brick house with cavity walls and (installed by us) cavity wall foam insulation, so it wasn't a draughty 200-year old cottage. But a feeble puff of tepid air versus a radiator at about 70 deg C - no contest!
Talking of which, the coldest house I've ever lived in is my parents' holiday cottage in the Yorkshire Dales (my wife and I lived there for a year between selling our old house and buying our present one) which *is* 200+ years old. Heated by bottled-gas boiler/radiator, so it costs the earth to run, plus an anaemic little wood/coke stove with a very poor draught on the chimney so it's a bugger to light and to make it *burn* rather than smoulder. And the windows in the old house let in the draughts. There's no double glazing even in the 1990s-era extension. When the old boiler broke, my parents chose, for reasons best known to themselves, to replace it with another bottled-propane boiler rather than replacing it with an oil-fired one - oil is a *lot* cheaper to run than 47 kg propane cylinders. A year's worth of oil at our old house had cost about the same as three deliveries of
4x47 kg cylinders, and we went through those about every month.
Moral - avoid bottled gas boilers like the plague.
The irony is that the lane up to the hamlet where the cottage is located had to be dug up about 30 years ago, at great inconvenience to the farmers who used it, so a big gas main could be installed for the nearby town and army camp. The farms right on the roadside clubbed together to buy a pressure-reducer so household-pressure gas could be fed to them, but the cost of continuing the pipe about 300 metres to the hamlet itself (two farms and six cottages) was extortionate. One of the farmers got a detailed cost breakdown from British Gas to see where the money would have gone, and found that they were charging rip-off rates even for the unskilled, unqualified work like digging the trench. He offered to dig the trench himself with his JCB, leaving British Gas to do the skilled, have-to-be-qualified work of actually installing the pipe. It would have knocked several thousand off the cost, but BG just laughed at him - *everything*, even digging trenches, has to be done by their own contractors - who are on a nice little earner. So no mains gas there, even though it passes so close :-(
The main difference is there's a single unit, and you just need to cut holes through the wall. If you're in a flat you may not be able to mount anything outside. With one of these you can make the holes from the inside so you don't even need access, which means no scaffolding in a tower block (I think there's a cunning drill tool so you don't drop masonry on people below, and there's a way to feed the liner through from the inside).
The other advantage is you don't need a F-gas ticket to install, since all the refrigerant is contained within the monobloc unit. That cuts several hundred pounds off the install cost.
The problem is they're a single unit with a relatively small fan, so can be noisy. And if your vent pipes don't go directly outside you lose through the ductwork unless you can insulate it (unwieldy and expensive if pre-made).
The main advantage is they provide cooling, which gas won't.
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