New hot water system ideas

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New hot water system ideas

Postby stefancr » Wed Aug 20, 2014 11:14 pm

I live in the Adelaide Hills and am keen to replace my hot water system. I'd really like to go with an instant system so that I'm not heating water I don't use. I don't have gas connected (and changing gas cylinders would be a pain) but I'd really like to get an instant electric system. I only have two phase power - is this possible?

What are the other alternatives? I don't have a roof cavity so I'm not sure if solar is possible?

Cheers for your thoughts
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Re: New hot water system ideas

Postby davidg » Thu Aug 21, 2014 12:24 am

stefancr wrote:but I'd really like to get an instant electric system. I only have two phase power - is this possible? What are the other alternatives? I don't have a roof cavity so I'm not sure if solar is possible?

Yes, but not smart, they consume a lot power in short periods of time.

Frankly I'd go Solar with either electric or gas boosted. If the solar tubes are sized properly then you will use very little extra of either electricity or gas as the case maybe. You don't need to have the tank on the roof or in the roof it can be on the ground, the system then uses a small circulating pump to move the water from the roof to the storage tank.

Description
1. Non return isolation valve
2. Pressure limiting valve 500kPa (not specifically required depending on regs)
3. Expansion control valve
4. Solar 4-way converter fitting
5. Differential temperature controller
6. Solar circulating pump
7. Swing non return valve
8. Evacuated tube collector
9. Top of tank temp sensor
10. Tempering valve (depends on regs and when hot water system was originally installed)
11. Pressure Temperature Release (PTR) valve
Attachments
58066d82331012bd625b605e0f1cd3c6.jpg
Example of Solar tubes retro-fitted to existing hot water storage system
58066d82331012bd625b605e0f1cd3c6.jpg (28.31 KiB) Viewed 2354 times
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Re: New hot water system ideas

Postby stefancr » Thu Aug 21, 2014 12:38 am

That sounds like an expensive system to buy! What would something like that be worth? And surely instant electric would use less power than the overgrown kettle I've currently got?
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Re: New hot water system ideas

Postby Tracker » Thu Aug 21, 2014 8:20 am

..
Plus one... to David's comments, especially on the instant electric heating, given the general move to time-of-use billing...
Washing up in the evening could be most expensive..
. Waiting 'till 10pm would be a pest.. but obviously you could work with it to advantage..

The likely cheapest alternative is to retain the standard tank and add a Siddons-bolt-on heat pump...
These can be purchased for about 2000 plus install, and this should be much less labor intensive than a solar system..

Then you could consider a Solar PV system to help reduce the general power consumption , AND use this to power most of the heat-pump operation... Win-Win.... :idea:

We are still talking a deal of dosh.. Probably 2500 for the change to the Hot-Water, and then :?: 2000 for a SMALL PV system .... like. 1500W..

DON'T GET TALKED into larger systems, as what you need is to just cover the general background power during the day, AND that of the Heat Pump during the peak solar times..
..
.
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Re: New hot water system ideas

Postby davidg » Thu Aug 21, 2014 8:36 am

[quote="Tracker"]The likely cheapest alternative is to retain the standard tank and add a Siddons-bolt-on heat pump...These can be purchased for about 2000 plus install, and this should be much less labor intensive than a solar system..[quote]
That SolarVox retrofit is no more than that I posted a pic on, plus install


and can still add the solar PV as well with power diversion unit I now have :D
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Re: New hot water system ideas

Postby Tracker » Thu Aug 21, 2014 10:11 am

and can still add the solar PV as well with power diversion unit I now have :D


And that would be a double benefit..
The PV could power the HeatPump, AND, if there was excess power (NET exported), that could then be used to boost via the conventional electric element...
..
.
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Re: New hot water system ideas

Postby Smurf1976 » Thu Aug 21, 2014 10:41 pm

stefancr wrote:And surely instant electric would use less power than the overgrown kettle I've currently got?

Electricity heating water as such will use exactly the same amount of power whether instant or storage.

Storage will lose some heat however, but only a few % per day thus meaning it uses a bit more power overall. Offsetting this is that a storage system usually runs on much cheaper off-peak electricity whereas the instant system will be charged at peak rates. End result is that the storage system costs less to run than instant.

I'd be looking very seriously at either a good quality heat pump (Siddons, Sanden or Stiebel Eltron are all good products - forget the other brands in my view as there are some real duds out there) or alternatively a proven "off the shelf" solar system from a major manufacturer. Yes there's some complexity, but a decent system will work reliably.

My own system is a heat pump (Siddons) and it's been working just fine since installed in 2009. Even in the middle of winter here in Tasmania it has no problem heating the water properly. Energy consumption has dropped 65% compared to the electric water heater it replaced, as measured by the off-peak electricity meter (the "real" meter used for billing).

Cheapest option for you would probably be the Siddons "Bolt On" as someone else suggested. It simply connects to your existing tank and it's a straightforward installation that any plumber and electrician can do. Tank stays where it is now, the heat pump unit goes outside and connects to the tank via ordinary water pipes - just normal plumbing work to install it. I'd be looking seriously at this as an option. Alternatively - solar.
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Re: New hot water system ideas

Postby Tracker » Fri Aug 22, 2014 8:12 am

..
BTW.... HOW does that diagram work...
The hot and cold ends of the solar collector are both connected to the COLD port of the HW tank via "4. Solar 4-way converter fitting"... :oops:

And....
forget the other brands in my view as there are some real duds out there

Especially the cheaper ones with the heat pump built on top of the tank..
IMHO.... the pump should be totally separate to the tank, because tanks have a limited life and when you add the technical nature of the Heat-Pump, which is prone to normal malfunctions, you have a recipe for disaster..
I HAVE SEEN many integrated systems replaced prematurely because of either tank leaks or compressor failure or gas leaks ..

A standard type tank and a Bolt-On heat pump seems the likely jest compromise in my mind .. :-)
..
.
Retired Engineer and keen PV experimenter - Always ready to learn and share.
2 x CMS2000 (fan cooled) GCI and SE 170W panels
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Re: New hot water system ideas

Postby davidg » Fri Aug 22, 2014 9:04 am

Tracker wrote:BTW.... HOW does that diagram work...
The hot and cold ends of the solar collector are both connected to the COLD port of the HW tank via "4. Solar 4-way converter fitting"... :oops:

Pipe inside a pipe. Some tanks have 2 inlets so it's not required then. :D
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Re: New hot water system ideas

Postby Benny » Fri Aug 22, 2014 2:32 pm

I think everyones jumped the gun here with offering options. You really need to give more info' before we can advise as to the best option for you. And also specify what is "best" - cheapest ? Best for environment ? Lowest capital price or lowest on going costs ?

Are you a single person who's undemanding, i.e. can put up with a 2 min, 45C shower each day or a family of 5 with teenage kids who have 20min showers at 25L/min.

Specify your situation a bit more first and then we can discuss.
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