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richard_wardlaw
28-08-2009, 10:35 AM
Mt first post - we are set on using an ASHP in our new build (240m2) - integrated design incorporating DHW, UFH throughout and with an in-line 6kW back up electric boiler for the coldest days/peak HW demand. We were, until recently, considering a system using NIBE (Swedish pump) but were concerned as this did not use an Inverter Compressor that it would be less efficient than those that do (ECODAN/DAIKIN ALTHERMA etc). A relatively new player on the UK market appears to be the Hitachi YUTAKI - appears to offer competitive COPs at all temperatures (compared to other ASHPs), and is equally quiet to run - and may be cheaper than DAIKIN. Has anyone got experience of these, installed one, views on reliability versus the DAIKIN or ECODAN?

multisync
28-08-2009, 03:43 PM
Mt first post - we are set on using an ASHP in our new build (240m2) - integrated design incorporating DHW, UFH throughout and with an in-line 6kW back up electric boiler for the coldest days/peak HW demand. We were, until recently, considering a system using NIBE (Swedish pump) but were concerned as this did not use an Inverter Compressor that it would be less efficient than those that do (ECODAN/DAIKIN ALTHERMA etc). A relatively new player on the UK market appears to be the Hitachi YUTAKI - appears to offer competitive COPs at all temperatures (compared to other ASHPs), and is equally quiet to run - and may be cheaper than DAIKIN. Has anyone got experience of these, installed one, views on reliability versus the DAIKIN or ECODAN?


Can you please tell me what real time running costs data you have to show fixed speed non interters are less efficient in this situation?

nike123
28-08-2009, 04:12 PM
fixed speed interters

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richard_wardlaw
29-08-2009, 07:46 AM
Can you please tell me what real time running costs data you have to show fixed speed non interters are less efficient in this situation?

No I can't provide such data but as I understand it the additional cycling you get with non inverters leads to a comparatively less efficient performance and may also be responsible for the slightly lower COPs achieved. Using the NIBE we have reduced the impact of cycling by introducing buffers and limiting the number of thermostaticaly controlled zones to 40% of the overall UFH footprint. It may be that such an arrangement provides for a similar degree of efficiency as if we were to elect for the YUTAKI or DAIKIN or ECODAN for that matter, but I guess that goes back to my original question - how do ASHPs like the YUTAKI compare against the likes of NIBE using what appears to be 'older' technology.

John MacK
01-09-2009, 02:48 PM
Is an inverter an advantage or even necessary when heating water?

Thinking about it, maybe not. With a ASHP or GSHP you are heating a volume of water to a pre-set temp, and you want it done as quickly and efficiently as possible.

'Conventional' inverter A/C systems, ramp-down on approaching their set point and modulate around it. This is more efficient for cooling/or heating the air, but if for example you were heating water to 60 deg C, would having an inverter ramp down at 55deg C etc and then keep running at lowering speeds for longer to achieve 60 deg C be more efficient than it keeping going at full speed to 60?

richard_wardlaw
01-09-2009, 06:33 PM
You have a point although the problem with non inverters as I understand it is that they are less efficient in maintaining those temperatures without the use of buffers and restricting the number of thermostatic zones employed. Inverters self-evidently modulate their output to meet demand be that 35 degs for UFH or 60 for DHW.

What is noticeable is that most of the new ASHPs coming to the market are using inverter compressors over non-inverters - the DAIKIN MONOBLOC and MITSUBISHI ECODAN being the other two which have caught my eye - which would suggest they present real advantages?

multisync
01-09-2009, 09:37 PM
You have a point although the problem with non inverters as I understand it is that they are less efficient in maintaining those temperatures without the use of buffers and restricting the number of thermostatic zones employed. Inverters self-evidently modulate their output to meet demand be that 35 degs for UFH or 60 for DHW.

What is noticeable is that most of the new ASHPs coming to the market are using inverter compressors over non-inverters - the DAIKIN MONOBLOC and MITSUBISHI ECODAN being the other two which have caught my eye - which would suggest they present real advantages?

The problem with this 'suggest' is that we are into the old betamax VHS argument where the winner is the one who plays the market better not the one who serves the market better.
Virtually all Japanese equipment uses inverters these days, inverters are supposedly a higher efficiency way of moving refrigerant. However inverters have losses too. Plus they are at their least efficient when at full speed.(mid winter for example when it will be flat out 24/7)
However it is only the Japanese who are using inverters. The rest of the world (ASHP wise) still uses scroll standard compressors. Are they late to the market or have they tested inverters and found them not all they are cracked up to be?

ASHP's are still way too dear and too inefficient to be considered worth the investment. Get a new gas boiler, spend a grand on insulation and have a 2 week holiday in the sun.

richard_wardlaw
02-09-2009, 10:13 AM
Thanks - just the sort of insight I was looking for. I agree about gas boiler but sadly the only option for where we are building is oil or LPG, the latter doesn't work out a lot less after tank costs etc. We have over insulated against current regs so I expect demand to be much reduced but still no no where near Passive house levels - interestingly a number of other new houses in the area have elected for ASHP. One particular developer has been so impressed he has replaced his own oil boiler in his very grand house!

John MacK
02-09-2009, 02:30 PM
Inverters self-evidently modulate their output to meet demand be that 35 degs for UFH or 60 for DHW.

They don't need to modulate to meet that demand though. There is no reason for it, other than it is an inverter controlled compressor.

US, UK or Scandinavian heat pumps that I've worked on were all either scroll or hermetic compressors, no inverters in site, and the US and Scandinavia have been making and using HP's for decades, so surely if there was an advantage they would have introduced them when inverters were being introduced to AC nearly 20 years ago.


Good debtae though. :)

ace
13-09-2009, 07:28 PM
Hi
There are a few advantages to the inverter technology but then again there are some disadvantages. One of the main advantages is you do not need buffer tanks and all the gear that goes with them. This reduces the installation costs, running costs (fewer pumps), it makes them easier to install and they require less space. The performance at the rated capacity should be approximately the same as a fixed speed unit. The rated capacity should not be the maximum output. The efficiency a the maximum output will be lower. This is not a problem as when it gets extremely cold the inverter unit can up it's game and produce the heat if the design has been done correctly. Doing it this way is is cheaper than switching on a bank of electric elements to boost the power (generally common practice with fixed units) and provides a better overall annual performance, this is what is relay important.
The main disadvantages of this technology is the inverter itself. It can be susceptible to power fluctuations and brownouts. Fixed units are easier to repair as the technology is easily recognized by most refrigeration engineers, no special training will be required, therefore you will not be held by any manufacturer after your warranty runs out. Because of the complexity of some of the inverter units this is not always the case.

At the end of the day both systems have there advantages and disadvantages and will probably work equally as wellIF theoriginal heat loss calculations on your house and the design of the system has been done correctly. The variable units are a little more forgiving and can hide a poor design. This is often where a perceived performance increase is achieved.

I hope this has helped. If you wan to know more PM me and I will do what I can to help.

richard_wardlaw
21-09-2009, 04:18 PM
Hi
There are a few advantages to the inverter technology but then again there are some disadvantages. One of the main advantages is you do not need buffer tanks and all the gear that goes with them. This reduces the installation costs, running costs (fewer pumps), it makes them easier to install and they require less space. The performance at the rated capacity should be approximately the same as a fixed speed unit. The rated capacity should not be the maximum output. The efficiency a the maximum output will be lower. This is not a problem as when it gets extremely cold the inverter unit can up it's game and produce the heat if the design has been done correctly. Doing it this way is is cheaper than switching on a bank of electric elements to boost the power (generally common practice with fixed units) and provides a better overall annual performance, this is what is relay important.
The main disadvantages of this technology is the inverter itself. It can be susceptible to power fluctuations and brownouts. Fixed units are easier to repair as the technology is easily recognized by most refrigeration engineers, no special training will be required, therefore you will not be held by any manufacturer after your warranty runs out. Because of the complexity of some of the inverter units this is not always the case.

At the end of the day both systems have there advantages and disadvantages and will probably work equally as wellIF theoriginal heat loss calculations on your house and the design of the system has been done correctly. The variable units are a little more forgiving and can hide a poor design. This is often where a perceived performance increase is achieved.

I hope this has helped. If you wan to know more PM me and I will do what I can to help.

Thanks for your comments - your final comments regard heat losses are well made and will certainly be at the core of what we are planning. I think the variable units do provide for greater thermostatic control and may allow some savings in terms of buffer tanks (although my sense is that buffers may still be worth while?) and associated pumps.

I sense the debate has run its course on this one, although it has been interesting to see the pros and cons flushed out - especially given the onslaught from the Far East into this market versus the established N European players such as NIBE and others. Something I haven't been able to get an answer to is why the Scandanavians went for this technology and the rest of us until recently did not? Was it the cost of gas/oil vs electricity in these countries or something else?