Heat pump SEER rating

[Andy Bennet]

Its a longitude thing. High ratings are only achieved between about 70 and 120 degrees west. A bit like music power really.

[alan_m]

I'll bet that in the USA they may not be quoting the spec for heating, just cooling

[Robert]

Glad I could complete your useful and relevant post.

[Robert]

A quick skim read also suggests that there is a difference in units used. in the States the ratios are based on BTU of cooling divided by electrical power in WATTS And in Europe WATTS divided by WATTS

I may be wrong though!

[alan_m]

Probably in the UK the heating cycle figures are more important as its more likely to be fitted for winter heating rather than the few weeks during the summer where you may benifit from AC to cool the air.

Try searching for Coefficient of Performance (COP) for heat pumps and you may get some clues why different figures may be quoted and/or why some of the claims made for the use of heat pumps in the rest of the world may not directly apply to the UK. This doesn't stop companies in the UK from making some of these rest of world claims.

Consider the average monthly temperatures in the UK and you may find some of the higher quoted figures can never be achieved in our climate - or possibly not achievable without a more specialised design which may not have a payback period in a domestic environment. I do appreciate that for some people saving the planet rather that saving on energy bills is more important and cost is not a factor.

COP rises with a higher input temperature COP falls with a higher differential temperature (higher output temperature)

In the UK the (air) source heat pump becomes less efficient as the temperature falls during the winter AND if you attempt to have a higher output temperature to run an existing "conventional" radiator system or hot water the efficiency also falls. Hence why lower temperature under floor heating and/or much larger radiators are recommended. In this real world scenario you may be looking at (SEER/Heating) figures of 2 to 5 rather than the top line 14 minimum for the USA.

Even sites promoting heat pumps suggest that insulating the house is an important part for the installation.

[Max Demian]

Megapixels (and megabytes) are less than they used to be. 1,000,000 rather than 1,048,576.

[alan_m]

Hard disks have always have always been 1MB = 1,000,000 Bytes

[The Natural Philosopher]

I dont think so

[gfretwell]

What is this "heating" thing? ;-)

[The Other Mike]

60Hz vs 50Hz?

For several manufacturers they all come off the the same production line, using the same refrigerant, most now use a multiphase inverter driven compressor.

The result is there is essentially bugger all difference in thermal performance and certainly none related to the mains input voltage and frequency.

[trader_4]

Certainly not true here in the US. Manufacturers have a product line that goes from 13 SEER to maybe 20, the higher efficiency units costing substantially more.

[The Natural Philosopher]

No one with a monniker like "A noiseless patient Spider" van possibly have an IQ over 50

[Commander Kinsey]

If UK SEER is different, then they should call it something else, eg India SEER is called ISEER.

Anyway, as long as I can compare like with like, I can get a rough idea of the relative efficiencies. Any rating that's double the same rating on another model means it's about twice as good.

Just had a reply elsewhere that said the USA 13 minimum SEER only applies to split units, and that most single units are much lower. Any reason why split units would be more efficient?

[Clare Snyder]

Derfinitely not - what makes the uneducated think so is the FACT that formatting eats up a portion of the drive capacity - so you do not get a full 1,048,576 bytes of useable space out of a megabyte of hard drive capacity. Not just hard drives - memory sticks as well.

[danny burstein]

A bunch of reasons:

1: "mini split" units tend to be inverter controlled, with variable output cooling/heating. There's more efficiency with a five degree temperature drop [a] than a 20 degree one.

2: the mini splits aren't wasting energy pumping all that air around through ducts. Also, less leakage in places where, well, the conditioned air is leaking..

[a] standard units have the compressor (cooling part) fully on or off. The thermostat will kick it on and, well, off as needed.

Hence if you only (for simplified example) need 5,000 BTUs/hr to keep your place cooled down (let's say it's only a tad warm outisde) and your system is rated with a 24,000 BTU (two ton) output, it'll cycle on for one minute, then off for four, on for 1, off for 4. Rinse, cycle, repeat.

A variable output unit will drop its output to 6,000 BTU, so stay "on" for 4.5 minutes out of five.

The air temperature drop (the "delta") will only be a few degrees instead of the 25 F typical of a full power operation.

NOTE: there are now a _few_ window units that are finally available in a variable output model.

So far _only_ for cooling, none yet with heating.

I picked one up earlier this year. It is, indeed, much quieter, no "ker-thunk" when coming on, and a gentler air flow. More efficient, too.

They're available from LG (formerly Lucky Goldstar). In the US the _only_ general purpose retailet that handles them is Home Depot. Others might, soon.

There's a _minor_ feature/annoyance/get used to it... change.

With a standard, say, 10,000 BTU unit, if you left it off then came back to a 90 degree F room, then turned it on, you'd get a nice blast of cool air in your face

30 seconds later.

With the LG's, since they're inverter units which measure how much cooling is needed, they start off with just a bit of chilling... so you don't get that refreshing and icy flow.

[A noiseless patient Spider]

And the IQ requirement to type accurately?

[Commander Kinsey]

The single unit I was looking at was a single, but using an invertor.

I assumed the single one I was looking at wasn't allowing for ducts. It shows it as heating/cooling a single area.

Ah! I never thought about the air temperature drop. So that's why they use less power.

So does that mean if you need 5000 BTU/hr and buy a 5000 BTU/hr unit, you use way more power than if you buy a 20000 BTU/hr one which never taxes itself? If so, how much difference does this make? Eg. if you run one at 50% power, how more efficient does it tend to become?

I knew them as "Life's Good", but the latest thing I got from them says "Best Choice" which er.... is the wrong set of letters.

Strange, you would think they'd adjust their power by how much too hot the room is. If it's marginally over, they should run on low power, but if the room's way too hot, they should give it a good boost. Are you sure it's working right? What on earth would make it think a lot of cooling is needed then? Does it wait to see if it can cool the room in an hour, then only later ramp up the power? Pretty daft really, it's nothing like what you'd actually want.

[gfretwell]

I think he is talking about comparable models, just rated different here than in UK.

[gfretwell]

temperature

"Single units" are typically window shakers and they get sold dirt cheap, You can find higher efficiencies in window shakers, wall packs and package units but they cost more.

[Commander Kinsey]

Irrelevant. If you both keep your house at the same temperature, but one of you has a different outdoor temperature, then one of the AC units will be more efficient, as the thermal gradient is different.

I don't understand the fuss people make about temperature. Especially in a shared office where one wants it to be 18C and one wants it 23C. Ever heard of changing your clothing to suit?!