Electric panel resistive element water heating

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Re: Electric panel resistive element water heating

Postby 34by151 » Sat Jun 10, 2017 11:57 am

The tank is a Rheem Stellar Electric Stainless Steel 315L, dual element and we have 4 people using it daily

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Re: Electric panel resistive element water heating

Postby huntercg » Sat Jun 10, 2017 12:46 pm

I am also in South East QLD also and have a high hot water requirement with 2-3 adults in the house along with 3 kids. I like the idea of solar hot water but have been quoted $3-4k for a new evacuated tube system. I looked into the evac tube systems you retrofit to existing electric tanks and from my research an 18 tube system was equivalent to 1.5kw of panels (let me know if this is not correct). The kit costs ~$1600 + freight so I then looked at the techluck and sunflux units. The Techluck is $400 and I acquired the 2nd hand panels for $200. With BOS for the panels, mounting box, breakers etc this system on an existing hot water system will come to `$800 of gear (even if you didn't have an electric hot water system you could pick a 2nd hand one off gumtree for $100). I know I have not included installation by a sparky but from my estimates I could have 2 solar panel systems which should provide with with ample hot water even in winter for a lot less then a brand new evac tube/ plate collector system. I know I have compared a new system to a retrofitted system with 2nd hand panels but their would be quite a few people considering solar in a similar position to me.
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Re: Electric panel resistive element water heating

Postby huntercg » Sat Jun 10, 2017 12:47 pm

34by151 wrote:both the solar panel rails and the hater tank body are connected to earth.
The element is fed by the DC and is isolated from the tank body
The mechanical thermostat has been removed and replaced by a Resol controller

The solar panels connect to the tech luck controller.
The output goes to the element via a contactor
The contactor is controlled by the Resol controoler

I only use the resol for a thermostat. I dont have a solar tubes in the system or water pump connected to the controller.

For the enclosure i used one like this as I had it lying around the shed.
http://www.ebay.com.au/itm/400-x-400-x- ... ZdQjC8tdcQ

It houses the techluck, contactor, resol controller, 240v light switch and power point.

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34by151


34by151 did you use the Resol controller and contactor because you didn't think the thermostat could handle the DC input?
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Re: Electric panel resistive element water heating

Postby australsolarier » Sat Jun 10, 2017 1:06 pm

the thermostat on a water tank is for ac only. it will burn out or weld together very quickly
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Re: Electric panel resistive element water heating

Postby huntercg » Sat Jun 10, 2017 1:42 pm

australsolarier wrote:the thermostat on a water tank is for ac only. it will burn out or weld together very quickly

From talking to the guys at sharp energy the the Sun flux outputs a modified DC sine wave to protect the standard AC thermostat and element of a standard electric hot water tank. I can only assume that the techluck controller uses a similar methodology. Here is a video on the sun flux from a guy in WA which shows it in action.
https://www.youtube.com/watch?v=Dvib1FxBEvc
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Re: Electric panel resistive element water heating

Postby australsolarier » Sat Jun 10, 2017 1:48 pm

i don't think there is such a thing like "dc sine wave" . the sunflux hacks the dc current into small pulses. so when the thermostat disconnects, it will interrupt arcing like it does ac currents.
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Re: Electric panel resistive element water heating

Postby 34by151 » Sat Jun 10, 2017 1:55 pm

huntercg wrote: 34by151 did you use the Resol controller and contactor because you didn't think the thermostat could handle the DC input?


No the techluck supplies square wave AC to the element so the standard thermostat is fine.

I fitted the resol before the solar+techluck as the plan was to fit evac tubes on the west roof.
In the middle of that we had a broken panel and insurance replace one string. The next result was I had a bunch of panels in the shed. This led to using the techluck which was a lot cheaper considering the parts were basicly free.

If I had planned to go this way Id still have the standard thermostat and no need for the contactors.
As it ends up the having the resol was good thing as I have the RS482 data feeding into my monitoring and control system.

What it has done is remove about 6kwh of load from our daily use.
Im running 5, 230W panels though the techluck.

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