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brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548
Posted: 09:52pm 31 Jan 2009
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Hi Crew,
Yesterday ,I had to buy a replacement electric hot water system,the previous night itdeveloped a huge leak in the internal cylinder---probably caused by my brand new constant pressure water pump ,sad.
Anyhow, we visited 3 big dealers(wholesalers) and this is what I foundout.
A Top of the range 250 ltr Rheem replacement $900,all the suppliers within $10.
We bought that because 1, 2 pipes to fit exactly where the existing ones are, very simple electrical,no mods.
2. Solar , Even with the Govt. rebates was much more expensive overall, with roof works,new plumbing of feeders, new Electric, new pressure safety valves, disruption to house looks and also the week or more delay without hot water.
So, not bad if building a new house , but reto fitting is a nightmare.
3. Heat pump. Now these are good and will come into law in 2010 for ALL new and replacement systems.
Cost , at present ,yesterday, around $1200 more than a replacement electric hot water system, even with the Govt. rebate.
Plumbing ,different,so an added cost.
Now the cruncher,,, Off-Peak tarrif does NOT apply to heat pumps ---, so ,probably sparkie or supplier has to remove off-peak meter,added cost??maybe.
Now , off-peak , say 9 cents per Kw ,, normal , say 18 cents per Kw,, so ,my mind says , the off peak would have to be on TWICE as long as the heat pump to break even on the monthly bill,plus remember the $ 1200 or more that was incurred in the replacement.
So, thats why we went with the ordinary replacement,
Food for thought.
Interesting to see what you think
Bruce
BruceBushboy
oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686
Posted: 01:40am 01 Feb 2009
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Interesting stuff Bruce.
I have had nothing to do with heat pump hot water, but I assume it is the usual compressor cycle.... somewhere it must have an evaporator, (I assume the condenser IS the hot water cylinder)....... I wonder if you could use the evaporator to cool your beer.??... maybe hook it up to the fridge..
In short, I wonder if the next thing will be a refrigerator with hot water heating in the one device. (kill two birds with one stone.. or hot water heaters with beer fridge built in???
... or for you queenslanders using air conditioning all day, if you put a heat exchanger on the condenser line to supplement the hot water... food for thought??
Must have island fever I guess
........oztules
Edit: On thinking about this a hot water unit using about 2kwh/day (heat pump type) would make for a very aggressive freezer. The freezer coils could be the primary evaporator, with a secondary evaporator outside to take care of it when the temp is reached in the freezer... I wonder... cheaper hot water and free freezer/fridgeEdited by oztules 2009-02-02Village idiot...or... just another hack out of his depth
KiwiJohn Guru Joined: 01/12/2005 Location: New ZealandPosts: 691
Posted: 07:45am 01 Feb 2009
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[quote]On thinking about this a hot water unit using about 2kwh/day (heat pump type) would make for a very aggressive freezer. [/quote]
Hmmmmmm... I need to think about this, the high pressure side needs to be >100C and the low pressure side <-4C, is that temperature difference range feasible?
oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686
Posted: 11:20am 01 Feb 2009
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KiwiJohn,
The current range of heat pump hot water units already have the condenser temperature sorted out. They use the cylinder as the condenser to liquefy the hot gas.... then you have to change it's state back to a gas again, so you will easily achieve -20C doing this... in the evaporator in our add on beer fridge. It must currently have a heat exchanger to do this anyway.
It would be like running a petrol genny, using the kilowatts for power and using the exhaust (via heat exchange) to heat the house in winter, or heating hot water with the exhaust gases.
...........oztules
Village idiot...or... just another hack out of his depth
sPuDd Senior Member Joined: 10/07/2007 Location: AustraliaPosts: 251
Posted: 12:58pm 01 Feb 2009
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The heat pump systems coming into play will be like having another fridge in the house.
So I wonder how many units will fry in the next power surge. Also wondering if you need
to call a sparky, fridgy & plumber to fix one...
They might be more efficient than resistive heating, but it still baffles me why new homes
in the tropics where I live are fitting them instead of solar. Mareeba, the town close to
where I live boasts "300 Sunny Days A Year" as you drive in, but there's not a solar system
to be seen anywhere. I can understand a heat pump where I live (Atherton). Its "300 Rainy
Cold Days A Year".
Also I see the odd place going up using the solar systems where only the collectors are on
the roof, not the cylinder. Seem like a nice unobtrusive alternative. Shame solar is
such an over inflated choice.
sPuDd..
It should work ...in theory
Jarbar Senior Member Joined: 03/02/2008 Location: AustraliaPosts: 224
Posted: 05:55am 06 Feb 2009
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Oztules,
Now you've got me thinking.I was looking at making a heat sink for the hot part of my fridge.Which currently has a fan cooling it down.But the idea of maybe a copper coil around it connected to my hot water header tank might be worth attempting.Then using thermo syphoning to dissipate the heat.Thanks for the idea.
Thanks Bruce for the fiscal break down.
Anthony.Edited by Jarbar 2009-02-07"Creativity is detirmined by the way you hold your tounge".My Father
"Your generation will have to correct the problems made by mine".My Grandfather.
oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686
Posted: 11:15pm 06 Feb 2009
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Jarbar,
If you can find a way to harvest the heat from the condenser then it is a win... you've paid to get the gas hot anyway. If you can shift a few BTU's into the hot water then good on you.... doesn't look easy though.
..........oztules Village idiot...or... just another hack out of his depth
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 12:29am 07 Feb 2009
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Hi jarbar,
All these ways of using waste heat, rely on proximity to each other of the components. If the hot water storage is close to the fridge, then plumbing to utilise the waste heat of the fridge would be viable.
The condenser of a fridge is a critical component in its operation. Most use a capillary type line between the condenser and the evaporator. This relies on a certain condenser pressure/temperature to function optimally. There is the minimum gas volume used these days and if the condenser is too cold, then gas flow rates and oil transfer are affected. This can reduce compressor lubrication and service lifetime.
take care to not overdo things.
Gordon.
become more energy aware
KiwiJohn Guru Joined: 01/12/2005 Location: New ZealandPosts: 691
Posted: 02:05am 07 Feb 2009
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While we are on this subject, (Gordon?) would a water spray on the condenser of my practicually useless Ford air conditioner in my ute help it to cope with the three days of summer we get each year here in Wellington?
No, there is nothing 'wrong' with the unit, it has been next to useless since the ute was new, recently checked out and regassed but still not really up to the job I want it do do.
(Actually, the problem might be I drive too slow and the engine is never over 1800 RPM)
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 02:46am 07 Feb 2009
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Hi kiwijohn,
I would not bother with a water spray just yet. This will consume many litres of water in operation to be effective.
A long time ago I installed Mark4 car aircons. On some cars, we had to increase the radiator fan sizing. A simple solution these days is an add on thermatic radiator fan. The biggest problem with poor condensing is high compressor head pressure and the problems this causes with flex hosing.
additional thermostatic fans could be left all year.
Gordon.become more energy aware
oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686
Posted: 04:45am 08 Feb 2009
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Well,
We could of course just fashion yourself up a good ole solar refrigerator like this one from Julius Kewir Tanga (Ph.D).....
Interesting simplicity. Don't get much more basic than that. Solar collector for the compressor, some home brew heatsinks on the line for the condenser, a collector and one assumes a capillary line to a similar evaporator in the box.... neat
...........oztules Village idiot...or... just another hack out of his depth
sPuDd Senior Member Joined: 10/07/2007 Location: AustraliaPosts: 251
Posted: 07:54am 12 Mar 2009
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My Electric HWS just failed and the plumber came to take a look at replacing it. I asked him about the heat pump units and he laughed. He maintains a very large installation feeding ~600 users, which was changed from gas fired to heat pump recently. Since then, he spends most days fixing and replacing heat pump units.
Personal opinion is that they will be one of the biggest con jobs in the green trend.
sPuDd.. It should work ...in theory
windlight Guru Joined: 03/03/2007 Location: AustraliaPosts: 331
Posted: 01:09pm 26 Mar 2009
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If heat pump HWS become compulsory in Australia, it would make powering a home off solar and or wind that much more difficult.
I have opted for gas boosted solar for my new home, it will have a very good sun exposure as will my solar panels so we should not use too much gas.
Allan"I like this place and willingly could waste my time in it" - (Act II, Scene IV).
KarlJ Guru Joined: 19/05/2008 Location: AustraliaPosts: 1178
Posted: 04:43am 15 Apr 2009
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so now you have a new electric storage unit, put it to good use, can get an add on set of 20 evacuated tubes for around the $1200 mark, handful of extra dollars for some copper and whalah, 80% solar hot water, (only a handful of days over winter where it just doesnt cut it and rewarding to have a hot shower for free.
Did mine myself in half a day with about $300 for a PTR, some copper, handful of tee pieces and some lagging.Luck favours the well prepared
Jarbar Senior Member Joined: 03/02/2008 Location: AustraliaPosts: 224
Posted: 12:11pm 15 Apr 2009
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I have a flat plate panel that needs connection to my electric storage tank.With only one inlet (header tank) and one outlet hot water to house.How best to connect this up.I know the base of the storage tank needs to be higher than top of panel.Are tee connections adequate at hot water outlet and cold into header tank?.Or do new fittings need to be soldered onto tank.It's age might preclude this.Any help appreciated.
Also interested in pipe connections for heat pump to evacuated tubes as my brother just purchased one.
Anthony. Edited by Jarbar 2009-04-16"Creativity is detirmined by the way you hold your tounge".My Father
"Your generation will have to correct the problems made by mine".My Grandfather.
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 07:04am 16 Apr 2009
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I have seen the effects of someone opting for the Heat pump instead of direct solar HWS. The unit drained the 30kWh battery in under a week, off PV solar. If the unit was solar direct, the battery would probably still be full.
Gordon.become more energy aware
sPuDd Senior Member Joined: 10/07/2007 Location: AustraliaPosts: 251
Posted: 03:58am 17 Apr 2009
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What irks me about the heat pumps is they are marketed as "Solar without panels", which to the average consumer means the product is solar powered. I'm certain this is misleading advertising.
sPuDd.. It should work ...in theory
petanque don Senior Member Joined: 02/08/2006 Location: AustraliaPosts: 212
Posted: 06:25am 17 Apr 2009
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I know a person who owns on who stated it runs on air!!!!
Perhaps they should be renamed the Politian’s hot water service just ad hot air.
The heat pump hot water services I have seen are also noisy.
sPuDd Senior Member Joined: 10/07/2007 Location: AustraliaPosts: 251
Posted: 10:22am 17 Apr 2009
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Noise - that’s right, that was the other complaint from people. It sounds like a 20 year old wall aircon low on gas. Consumers are getting s$@'#&d in this country.
sPuDd..
It should work ...in theory
KarlJ Guru Joined: 19/05/2008 Location: AustraliaPosts: 1178
Posted: 05:25am 11 May 2009
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done a few, in both cases a pumped system with thermostatic controller works very efficiently and will yield more hot water, panel can be anywhere then.
New pressure system tanks have three connections, in/out/PTR valve, for your brothers system tee off the cold, run it through your pump, run the return into a tee pieve where the PTR valve is, also a cheap flap valve type one way valve on the cold side will prevent thermosyphoning of the hot water overnight (would only be losses in your pipework as the units themselves loose very little.
Reason for hooking the return in through the PTR side is when you turn on the hot tap it will flow through the collector as well as the tank thus at night you will get cold water and during the day may get scalded.
MUST run a tempering valve as in summer get 100degC hot which even if you are aware of it is dangerous.
Our family farm has a 300L storage tank and i can get boiling water out of the tap 15m away!!! (tempering valve did not work properly with gravity system)
Let me tell you I'm really careful-even the tap gets too hot to touch.
Evacuated tubes! -whatever did we do without them!Luck favours the well prepared
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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