Heat Pumps, One for the engineers

[NewcastleFalcon]

Gas Boilers are soon to become persona non grata, and go the way of the internal combustion engine. The only alternative purported is either direct electric heating or heat pumps ground and air source, together with better insulation.

So what do I know about heat pumps. Not very much and its probably all wrong. Here is a back of a postage stamp summary of my current little knowledge thinking.

This is a heat pump

Heat pump installations are ridiculously and unnecessarily expensive.
I've seen some heat pumps they are just a small cabinet not a lot bigger than a gas boiler which sits outside the building with the minimum of pipework and electrical connection entering the house.
They are a glorified fridge in reverse, not really any cutting edge technology
I can't believe the components in those cabinets are any more complicated, or any more expensive materials wise than a gas boiler.
I suspect the pricing of them is inflated by unnecessary subsidies for installations.

I could go away and do a bit more research and I probably will, but give me an armchair ride with your own thoughts to get us started.

How do they work
Why are they currently so expensive
DIY could you make one in your shed what components would you need

Words are good, pictures, pen and pencil drawings better

I will regard the thread as a success with a single response, a page or two would be brilliant.

Join in if you can

Regards Neil

[Peter.N.]

Air conditioning/heat pumps are not all that expensive, at least not the air to air ones. An efficient heating installation requires a ground source for the input, which means digging a lot of trenches or drilling a very deep hole - that's what makes it expensive.

We used an air to air heat pump in our very cold downstairs bedroom for some years and it only cost a few hundred pounds and was fairly efficient until the temperature dropped below freezing - then it wasn't.

Peter

[myglaren]

My boiler is up for replacement this year (it was two years ago )
I dipped my toe into the heat pump pool and withdrew it rapidly when I saw the costs involved.

Short term thinking admittedly but
a) I am not likely to need it for all that long and
b) As with most things, the installation and over the counter prices will reduce as they become more mainstream.

[Dormouse]

the only drawbacks that I see that I don't like, other than the cost of installation, is that there is no backup if the electricity goes down and the limiting heat source parameters. That is why I and my wife both agree that having a Baxi gas fire in our open plan home and a gas hob in the kitchen is an essential we won't be doing without anytime soon, if ever. If push comes to shove, I even have replacement gas jets for both to run on LPG. The supposed benefits of heat pumps is completely wiped out by the practical issues surrounding the consistent source. On top of that you have the human factors. For instance, a local waste to heat facility in the Midlands kept overpowering the emergency heat release system that the company I worked for installed. Of course, it was all our fault til I discovered that the supervisor of the adjacent council industrial estate, which was far from being fully occupied, was turning off the heating in the unused units "to save wasting money"! So, instead of having to deal with a few occasional overloads our plant was running flat out to be the full load. Right hand, left hand! Operating instructions?

[white exec]

Most modest domestic heat pumps are no more than normal air conditioning systems.
The advantage is energy consumption. The three we have here are capable of knocking out around 3kW of heat, but with an electrical consumption of just 900W. They also cool in the summer, of course.

Price in UK has always been on the high side for this "luxury" item, but here you can find split (inside unit, outside unit) systems for just €200, or around €600-700 for a leading make like Panasonic, Daikin or Mitsubishi. Installation of one of these split systems costs about €200 extra. There are also 2+1 systems that use one outside unit, linked to two internal units for two separate rooms.

A heat pump system capable of providing heat to under-floor piping or conventional (or maybe existing) wet radiators will be considerably more expensive. As Peter says, ground-source heat capture lifts efficiency, but at increased initial cost.

Industrial waste heat trounces all of this. Battersea power station used to heat half of Pimlico with 'waste heat' piped under the Thames!

[Dormouse]

My wife and I considered a ground source heat pump for our old house. It was set in a very large plot in a wood and we had a septic tank for extra heat generated. We eventually plunked for LPG heating purely on initial costs. The house we have retired to could only have air to air heat pumps and, believe it or not, one of the issues for building warrant was going to be the noise of the unit! We ended up with gas central heating.

[xantia_v6]

Own photo

A house near us... I think I count 7 heat pumps.

We are currently thinking of converting our under- floor heating to have a heat pump. Probably a 9kW output air to water unit.

[NewcastleFalcon]

A house near us... I think I count 7 heat pumps.

We are currently thinking of converting our under- floor heating to have a heat pump. Probably a 9kW output air to water unit.

Good stuff thanks everyone for the responses so far that but keep them coming. I'll briefly get out of my armchair, as my ears pricked up to the air-water unit. More info on it gratefully absorbed.

Regards Neil

[Dormouse]

Air to water for underfloor (or ceiling) heating is quite good. The operating temperatures for underfloor heating are lower than wet radiators by a fair level. You can install a ceiling water tubing based heating system that also gives out infra red heat and, no, your ceiling doesn't need to glow orange! These lower operating temperature systems are well suited to heat pumps/extractors.

[myglaren]

Haven't seen him for years now but an old school mate with a huge garden designed and built his own heat pump using buried water pipes. He was an offshore oil platform engineer so well placed for such a task, a bit of an inventor too.

[NewcastleFalcon]

Haven't seen him for years now but an old school mate with a huge garden designed and built his own heat pump using buried water pipes. He was an offshore oil platform engineer so well placed for such a task, a bit of an inventor too.

That's refreshing Steve. I'm sure a bit of shed engineering Heat Pumps in a scrapyard challenge way is perfectly possible, and one of my original thread starter questions

How do they work
Why are they currently so expensive
DIY could you make one in your shed what components would you need
Words are good, pictures, pen and pencil drawings better

.
Regards Neil

[Peter.N.]

The main problem with heat pumps is they have to work on daytime electricity most of the time which is now about 18p per kwh. oil on the other hand works out at about 5p per kwh at the moment. My boiler I bought secondhand for about £12, its a Worcester and 85% efficient, as a litre of fuel contains 10kw worth of energy we are getting 8.5 kwh of heat for about 40p at current prices. I installed it myself so that cost very little.

The price of oil is very volatile but if you put in a large oil tank you can take advantage of oil price variations and top it up when its cheapest. The best priced fuel is mains gas, but unfortunately we don't have any here. LPG is cheaper than electricity but about twice the price of mains gas.

Peter

[mickthemaverick]

On a slightly different but similar subject I designed and built a simple pool heater for Ken's pool in Mallorca, using sunshine and copper pipes and making use of the existing filter pump system by diverting the output of the filter through the heat exchanger before returning to the pool. Control wasn't great but it did extend the pool usage period by a couple of months each side of the summer!! Not the greatest drawing but it should give you the idea!:-D

Own work

[white exec]

The same is often done here, Mick, but using 25mm black HDPE water pipe, laid out back and forth, or as a huge flat coil if there's room. The heat collected/transferred is considerable.
The coil, or laid-out pipe, can go somewhere less obvious, of course...

Black poly pipe can be as cheap as €30+ for 100m.
.
.
For DHW, these units sell for around €1000+. OK to put on any roof that doesn't get frost.
The unit then feeds a standard DHW (immersion heater) cylinder, which does little work.

[NewcastleFalcon]

I could go away and do a bit more research and I probably will, but give me an armchair ride with your own thoughts to get us started.

How do they work
Why are they currently so expensive
DIY could you make one in your shed what components would you need

Nearly onto page 2 so far so good.
So out the armchair for a brief moment with this...and you can see with the installation its pricy for even an air source system. £5,445 for the basic gubbins.



Regards Neil