Our 30 year old off peak gravity feed HWS is due for replacement and I am seeking information about Heat Pump HWS's that are available - which one might be more reliable and durable etc - as well as the costs involved. Any info would be much appreciated. Ta.
Heat Pump HWS - which are the better brands?
(8 posts) (6 voices)-
Solgen
MemberI did a lot of testing of the Quantum heat pump HWS in the early 90's throughout NSW in various climatic conditions. They consistently produced a COP of 2 and sometimes as high as 3 (ie 200% to 300% efficiency). The higher efficiency was obtained where there was high hot water usage.
However, they did have a few issues.
Firstly, the flat panel concept was excellent in capturing heat and in fact they worked better in rain than during fine conditions (water is a better conductor than air). I even had one system at Glen Innes that was on the south side of the house, one cold July it was one great block of ice for a month but it was still producing plenty of hot water. However, the flat panels were prone to leak and lose refrigerant which meant over time their performance would deteriorate until they were regassed. Secondly, they used a standard mild steel tank which unless the anode was replaced regularly, would fail and the expensive hot water system would be useless.
Now there are fan units which address some of these issues but I don't know anything about their performance.Posted Thursday 2 Apr 2009 @ 11:53:00 am from IP # -
I installed mine in Rockhampton in July 06. After about 10 months it lost its refrigerant due to a loose connection on one of the pipes. However this may have been caused by the freight company dropping it on the deck when the pallet broke during delivery. Some crushing to one corner of the tank also happened but since it was regassed under warrabty it has performed flawlessly.
I keep all records and it consistently has averaged 3.5kwh/day over the year. It uses about 2kWh/day in summer and 6kWh/day in winter which drops to 2/4deg overnight in winter. We are in a warm climate so expect higher readings if you are down south.
Posted Thursday 2 Apr 2009 @ 9:10:36 pm from IP # -
Solgen
MemberOne of the problems with heatpump HWS is a fundamental problem of the refrigeration cycle. Heat pumps are fabulous for heating water to around 30-40degC because the temp differential between the hot gas off the compressor and the water is high and there is a good transfer of heat. However, once water starts getting up towards 50deg the differential becomes significantly smaller and they have to work much harder. For this reason heat pumps are fantastic pool heaters.
The ideal would be a heat pump as a preheater to instantaneous gas water heater. Unfortunately, the capital cost of this combination would be very high and probably not practical.
In most cases solar is probably better particularly the evacuated tube systems. The exception is where frost is a factor as heat pumps are unaffected whereas solar particularly flat plate collectors are very vulnerable. Even systems with "supposed" frost protection will eventually fail as anything that relies on a valve to operate in a water environment will eventually stop moving and then its goodbye to your solar panel.
Finally, make sure the system you purchase has a stainless steel tank.Posted Friday 3 Apr 2009 @ 4:39:30 am from IP # -
Sunshine
MemberThe Hills evacuated Tube Solar Hot Water system FAQ's http://www.hillssolar.com.au/arbitrage/pages/77 advises it is certified to -15 degress C.
I have had my system for around 6 months and have never used the electric boost yet.
My collector is facing west at a fairly steep angle but this doesn't seem to affect the performance.I am very happy with comes with stainless steel tank (ground mounted)
With the $1600 rebate from the Australian government to install solar hot water, there's not a better time to install one now.Posted Friday 3 Apr 2009 @ 5:01:27 am from IP #
