Is there a slimline heat pump?

matt_drummer

The laws of physics demand that the evaporator needs sufficient surface area in order to extract the required amount of energy from the outside air and transfer it to the circulating refrigerant in order to be able to transfer enough energy to the circulating water in the heating system to heat your house.

The fan heater you have shown has an electrically heated element inside it and the fan blows air across it to distribute the heated air over a wider area.

That fan heater does not contain refrigerant and does not have an evaporator.

For your `design' to work a tall thin evaporator would be required and in order to be thin enough for your alleyway the heat pump would need to be very tall. It would also need multiple fans as their diameter would be limited by the width of your heat pump.

If the evaporator on your design was 300mm wide then it would need to be over 3m tall to get the required surface area and need 10 of more fans with a 300mm diameter to mover the air.

It would be very noisy.

If you look at a heat pump you will see that the evaporator actually takes up most of the rear and one side of the unit.

Then there is another part that houses the heat exchanger, circulation pump and electronics. This would all need to be housed on top of or below your tall thin evaporator.

There is no such design, it is not commercially viable and unnecessary.

paul991

Is there space for a wall mounted unit

Alnat1

Still hasn't said why a heat pump can't go front or back of the property.

prowla

https://forums.moneysavingexpert.com/discussion/comment/81988821#Comment_81988821

I'm not sure why you seem to be pushing that point; it's irrelevant because it's not my requirement.

But anyway, since you're so insistent…

• The front of my house has doors and windows across the entire width and no place to run pipes into the house.
• The front of the house faces directly onto the road/sidewalk, via an open lawn.
• I am intending to have a full-width extension built onto the front of the house.
• The wall space under my office window at the front has a car charger and a fibe broadband connection there.
• The bottom of the lounge window at the front is 4 bricks off the gound.
• Between the lounge and office windows is the front door.
• It would be unsightly to place a heat pump at the front of the house and no other properties in the area have done so.
• The back of my house has doors and windows across the entire width and no place to run pipes into the house.
• The through-lounge window at the back of the house is a set of patio doors; they're about two bricks in from the adjoining other half of the semi-detached property.
• The patio doors open onto a patio with a garden table and chairs.
• Next along the back is the kitchen window, which has a drain directly below it.
• Then there's the back door.
• And then about 2ft to the corner of the house, where the guttering drainpipe runs.
• I am intending to have a full-width extension built onto the back of the house.
• Both sides of my gardent have wooden fences and they have been known to be blown down on occasion.
• My back garden is about 10m long and at the end there's a brick wall with ivy growing over it.
• The recommended maximum length of piping for a heat pump is 15m; siting one down the garden and connecting it to my upstairs boiler would likely exceed that limit.
• I have a solar inverter and battery attached to the side of my house and would be happy for a similar-sized unit to go alongside them.
• I would not like a heat pump plonked in my back garden.

In summary:

• Yes, I have thought through the front and back options and rejected them.
• The space down the side of the house doesn't meet the siting requirements of the back-to-front airflow heatpumps and placing one there would impede access to my front gate.
• If there is a lateral-flow unit which will fit into a 1.3m wide space and leave 0.9m space then I'd like to know.
• If there isn't then a heat pump is not suitable for my use-case.
• If a suitable one comes up at some point later then I will be able to reconsider.

I hope that answers your questions and satisfies your curiosity, but if it doesn't then I won't answer again.

prowla

https://forums.moneysavingexpert.com/discussion/comment/81988606#Comment_81988606

Sure - the laws of physics and all that.

I merely did the picture of the fan to demostrate that airflow doesn't have to be across the larger face of the unit, rather than presenting it as an all-encompassing "design" of a heat pump.

Similar other examples are:

• Water-cooled computers which fit into a 4U rack where the front and back are the smallest faces of the unit.
• Rear-engined cars which have side ducts to route the air to the radiator in the engine bay.
• Car air-conditioning, which does not require the radiator to be placed upright across the front of the vehicle.
• Aeroplanes, which don't have a huge air-intake plonked across the front of them, but seem to operate alright.
• Wind turbines can be large propellers or more compact rotary mechanisms, such as spirals or vaned cylinders; there is no law of physics which says only the propeller will work.
• "Blade" fans and hand dryers.
• Refrigerators and Freezers, where the piping is at the back against a wall and the airflow is therefore lateral.

So, an alternative layout is actively used and established in several applications, but just not in the current offerings for domestic heat pumps.

I assume your 3m tall thin evaporator reductio ad absurdium postulation wasn't serious, but it was vaguely amusing; of course, the airflow doesn't have to be at 90° to the coolant piping/evaporator and there is no reason why it would need to be any larger than in the current models.

The requirement is that there is sufficient airflow across the system; how it gets there is the design choice.

As to whether a lateral-flow layout is viable or necessary is something which the manufacturers and markets will decide.

At the moment it appears that they're all sticking to the same basic design, which is fine for them.

If it never changes then I'm out.

MWT

Given all of those points, it feels like you are working on this project in the wrong order.

I'd be inclined to figure out at least the rear extension and plan the heat-pump into that work and place it at the back of the house.

There are no fully lateral flow A2W heat-pumps at the moment, and even with the Aerotherm Pro which has side intake but front output, you are not going to get it installed in 1.3m with 0.9m left over.

The Aerotherm Pro does have a hugely reduced protective zone so it makes it very tolerant of adjacent doors, windows and drains, but if the rear just isn't going to work for you then I suspect A2W is not a solution you can use.

QrizB

Similar other examples are:

I don't think any of the examples you've given stand up to scrutiny. Rear-engined cars, for example, are well known for having heat dissipation problems (I owned one once). Jet aircraft really do have great gaping forward-facinf air intakes. And 90%+ of wind turbines are horizontal-axis fans; vertical axis turbines are much less efficient.

But I can tell I'm not going to be able to convince you otherwise.

Yarrows

When I had my heat pump installed, I did tell the installer that I planned to have a small extension built on that wall of the house in the future (though not the very near future or I would have done that work first/at the same time). I was told it wouldn't be a very big job to have the heat pump moved at the time of building the extension.

I haven't put it to the test yet of course!

matt_drummer

https://forums.moneysavingexpert.com/discussion/comment/81989522#Comment_81989522

My heat pump, like most others, has about 1 square metre of evaporator surface area.

I was not joking.

How are you going to get 1 square metre of surface area from something 300 mm wide without making it over 3m tall?

They do need to be how they are in order for them to work properly.

No other examples you give are the same thing for varying reasons.

The evaporator and fan could be smaller but then the air would need to move faster to compensate for the lack of surface area.

Do you really want the equivalent of a small jet engine bolted to the side of your house?

prowla

https://forums.moneysavingexpert.com/discussion/comment/81989634#Comment_81989634

Ah - I thought you were joking; apologies!

You are inherently making the assumption that the 1m square surface area of the heat pump evaporator has to directly face the air inputs and outputs, as opposed to the air has to flow over it.

The examples I gave demonstrate that this is not the case: there are many millions of operational implementations of evaportator/radiator units which do not directly face the air inputs/exhausts.

A real-world household example where the airflow in-out is not back-to-front is blade fans: the fan is upright in the base and the air is directed out at the top; they don't sound like a small jet engine.

In other words, the fact that there is a surface across which air has to flow does not dictate the path the air has to take to achieve that effect; they are separate considerations.