oil to air source heat pump

matelodave

I think we are confusing efficiency with cost - yes an ASHP can be more efficient than gas, in fact up to 300% more efficient insofar as 1kwh of gas = approx 900wh of heat whereas 1kwh of leccy through a heapump could produce around 3kwh of heat HOWEVER as gas is around 25% of the cost of leccy at the moment then it still costs more than gas.

I'm like shinytop, I dont have gas, I chose a heatpump and it was installed together with underfloor heating to try and get the most out of it. I also managed to get RHI which paid me £5k towards the cost. I have also have put quite a bit of effort into understanding how it works (our first winter cost me a fortune because I tried running it like a boiler) and I'll be doing a bit more tweaking this year to see how well I can optimise it..

We've done as much as we can afford to improve insulation - there's around 300-400 mm in the loft. The walls have rockwool cavity wall insulation which was installed in 1986 when the bungalow was built and we've got 1999 vintage double glazing.

My biggest problem is a wife who's a chilly mortal who will keep fiddling with the controls if she feels cold. TBH she will feel cold if she sees a thermometer that doesn't show at least 23 degrees.

Reed_Richards

born_again said:

Interesting thread.
So how does that work when your radiators are already to the point of covering all the under windows & available space in hallways. Do they have to go higher. Making them triple rads is not going to happen in hallways due to width. In most of our rooms there is no spare wall space that is not blocked by a piece of furniture. 

Would you end up having to go for say blown air heating?

Interesting times....

There are various types of radiators:

1.  Single panel (P1, type 10)
2.  Single panel with one set of convector fins (K1, type 11)
3.  Double panel (P2, type 20)
4.  Double panel, single set of convector fins (P+, type 21)
5.  Double panel, double set of convector fins (K2, type 22)
6.  Double panel, triple set of convector fins (K3, type33)

I looked up some widths (measuring projection from the wall)
K1 83 mm
K2 124 mm
K3 180 mm

If your radiators already occupy all available wall space then you have to make them wider.  Maybe K3 would be too wide in some locations but I only used two of these in my house, one because it fitted neatly under an unusually wide window ledge and the other because I did not want to use a horizontal radiator.  Mostly I replaced P2 with K2 so some new radiators occupied less wall space then the old ones had.

But you can always use a fan-assisted radiator to save space; some people like these, others don't. 

orbit500

The great thing with fan assisted is there’s actually few days a year when the boosted output is needed. 95% of the time it can run in passive mode.
The major trouble I see is the poor quality of the fan bearings leading to maddening squeaks after a few years!

QrizB

toadhall said:

I could have a gas tank installed, but again there is nowhere to put it.

I don;t know how big your property is but have you thought about 47kg cylinders? Easier to site than a bulk tank, but more expensive per litre of gas (still likely to be cheaper this winter than mains gas, though).

shinytop

Patrol said:

orbit500 said:

The biggest issue I faced was complete disinterest from ‘heating engineers’, aka Dave the plumber, in engineering solutions to long standing issues. I designed it from mainly German sources and my own physics background.

There's probably good reasons for this. Presumably a heating engineer goes on what they have been taught plus what they learn hands-on. Unless they like taking risks why try something new, or more complicated due to extra components or untried theories. If it goes wrong they are on the hook and their reputation or livelihood suffers.

Traditional gas and oil heating may well have been "good enough" for many years when fuel was cheaper. I do wonder how much more efficient they could be but doubt the average one man band or small company would want to invest time and money in trials. My GSHP was installed with no mention of options that I later learnt of  (do I want a buffer tank, should I have a shunt/pig valve for my upstairs radiators) and I suspect the same is true for many ASHP installations.

I could be wrong, there may be ongoing research about best practice for heating systems which in light of increasing fuel costs and environmental concerns would be nice to hear more about. It is interesting to read posts such as yours which describe a different way of thinking (oil plus buffer which may not be revolutionary but is to my simple mind almost the reverse direction to a combi boiler?)

Very good point there.  Gas has been so cheap over the last few years that efficiency measures and good heating engineering practices have simply been ignored.  Who needs to reduce gas usage when it's only 2p/kWh?  The result is we have under insulated homes, oversized condensing boilers that run too hot so they don't condense and crude on-off thermostats.  Note that these are the same factors that tend to make ASHPs expensive to run. 

The answers are all there because other countries (e.g. Germany) have much more advanced regulations for gas CH and for example boilers there do routinely use weather compensation. 

Patrol

Reed_Richards said:

The way their efficiency varies with operating conditions takes a bit of getting your head around but fundamentally they are just another heat source like a gas or oil boiler.

While that may be true is the performance difference between good-bad heat pump installation much larger than for gas / oil. Or does a heat pump require more fine-tuning compared to fit and forget for a boiler.

Reed_Richards

An oil boiler typically does not modulate; it's either full on or off.  If it's a condensing boiler all you can do to improve the efficiency is to reduce to output water temperature so it operates in condensing mode more of the time. And that only works if your radiators can give enough heat at the lower temperature to keep your house warm.

Likewise with gas boilers, you can reduce the output flow temperature to improve the efficiency.  But gas boilers can modulate and this gives scope for Weather Compensation and Load Compensation, both of which can can improve the operational efficiency a bit.  Weather Compensation automatically reduces the output water temperature when it's warmer outside so the radiators don't need to provide as much heat.

Modern heat pumps can also modulate, although the modulation range may not be as wide as for a gas boiler.  This also gives scope for Weather Compensation and Load Compensation.  Weather Compensation is a feature of all heat pumps that I know of, Load Compensation is much less common.  Weather Compensation, properly applied will give a much bigger improvement in efficiency than for a gas boiler, so if you have a heat pump it's important that you use it.

Whilst Weather Compensation should ideally be a fit and forget feature, the optimum compensation curve tends to be something you have to set manually.  My installer was guided to use very conservative values and I have had to fine-tune the curve in order to improve my efficiency.  This was not necessary to keep the house warm but it would have cost me money not to have done so.

Bad heat pump installation seems most often to be about trying to retrofit a heat pump where another type of heat source had been without changing the radiators to ensure that the new ones have enough output.       

  

Bianchiintenso

Our Ecodan is now up and running, one question to ashp users I have is, how important is an energy consumption meter to you? Our reports say estimated energy usage, which I guess can be pretty hit or miss. What would the average cost of having a meter that could talk to the MELCloud retro fitted to the system?

shinytop

Bianchiintenso said:

Our Ecodan is now up and running, one question to ashp users I have is, how important is an energy consumption meter to you? Our reports say estimated energy usage, which I guess can be pretty hit or miss. What would the average cost of having a meter that could talk to the MELCloud retro fitted to the system?

You'll need a MID compliant electricity meter connected to your ASHP supply and the FTC controller.  They're not expensive (<£50) but you'll need an electrician to fit it who knows what they're doing (or can read a manual!).  

The estimate for energy consumed should be OK. btw.  It's the energy delivered one that's a bit hit and miss (this would apply to other ASHPs too).

If you want the full monitoring of use and consumption that cost me about £1400 but was paid for by RHI.

Bianchiintenso

Ahh if the MELCloud report on consumption is fairly accurate (the split HW/heating is not correct, showing 50/50), that will do the job for now to keep an eye on performance. Thanks