Where Can You Actually Put a Hot Water Heat Pump Cylinder?

This is the question that decides more installations than price does, and yet it is the one people research last. A hot water heat pump cylinder needs air to do its job. Choose the wrong location and it will underperform no matter how good the unit is. Before you browse models or compare prices, read this. 

It Takes Heat Out of the Air Around It

That is the whole principle. The unit draws air, extracts heat from it, transfers the heat into the water, and blows the now cooler air back out. The space it sits in must be able to supply enough air, and you need to be comfortable with that space becoming cooler and drier over time. 

Good locations: a garage, utility room, plant room, basement, outbuilding, or a large ventilated store. Somewhere with decide air volume that you are not deliberately heating. 

Bad locations: a sealed airing cupboard, a small windowless store, or at the centre of a heated living space. In a heating room you are simply reclaiming heat you already paid to produce, which defeats the purpose entirely. 

The Airing Cupboard Problem

This catches people out constantly. The old cylinder lived in the airing cupboard, so the assumption is the new one should too. It does not work like that. A heat pump cylinder placed in a sealed cupboard will rapidly chill the small volume of air available, run out of heat to extract, and fall back on its immersion heater. At that point, you have spent a great deal of money on what is effectively a direct cylinder. 

The solution is ducting, which is exactly why manufacturers supply dedicated kits for this purpose. For the Edel units, we stock two ducting options: Dimplex Edel 170L Vent Kit and the Dimplex Edel 170L Vent Extention Kit. If the only available position is a confined space, budget for the ducting at the outset rather than discvoering the need on installation day. 

Space and Dimensions

 These are tall appliaces. You need clearance above for the heat pump section and additional headroom for service access. The bare dimensions are not the hole the unit fits into. Always add clearance before you committ to a space. 

Here is our full range from the current catelogue, with mounting type noted. 

Two things worth noting. The Project Curv 80, 110, 150 are wall mounted, which is the answer when the floor area is the constraint. And the Dimplex Edel 200L at 1460mm is the shortest 200L unit we stock, at the cost of being wider and deeper, which makes it the right choice when height is the problem, such as beneath a sloping ceiling. 

Noise

There is a compressor and a fan, so there is noise. Manufacturers describe models like the Dimplex Edel as ultra quiet, and modern units are significantly better than early designs, but they are not silent. This rules out positions that otherwise look ideal, particularly anything sharing a wall with a bedroom or a stud wall adjoining a living room. A garage or dedicated plant room removes that problem entirely. 

Condensate

Extracting heat from air produces condensate, just as a condensing boiler or dehumidifier does. It needs a drain. Confirm where that drain is before installation day, especially in a garage or basement where a suitable outlet may not be nearby. It is a small detail that can cause a large headache if left to the last minute. 

Electrical Supply and Building Regulations G3

Each of these units requires suitable and dedicated electrical supply. Every model is also an unvented cylinder, which means installation is goverened by Building Regulations G3 and must be carried out by a suitably qualified installer. This is not a formality. It is the law, and it directly affects your building control sign off and your insurance position. 

Five Checks Before You Order

1. Is there enough air volume in the intended space, or can the unit be ducted to somewhere that has it (like an outside wall?)
2. Are you comfortable with the space becoming cooler and drier during operations? 
3. Does the unit physically fit, with adequate clearance above and around it for service access? 
4. Is there a condensate drain close enough to be practical? 
5. Is there a suitable electrical supply, and do you have a G3 qualified installer confirmed? 

What This Guide Does Not Cover

• Minimum room volumes and ducting limits are model specific. Always refer to the manufacturer figures, not general guidance. 
• This guide does not cover exhaust air units that also ventilate properly, which follow a different design principle
• Dimensions are taken from our range as of the 24th August 2026. Always confirm against the product data sheet before committing to a space.