Electric panel resistive element water heating

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Re: Electric panel resistive element water heating

Postby Gordon-Loomberah » Wed Oct 26, 2016 10:40 am

Apologies for the lack of a response Kurt, I'm told that since Flex took over EM the old agreement with Apricus is no longer operating. There will be a notice placed on the quote page until a new agreement is in place.
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Re: Electric panel resistive element water heating

Postby offgridQLD » Wed Nov 02, 2016 7:09 pm

No problem the Apricus brand was most likely a bit out of my budget anyhow.

How do you find off center performance of the vac tubes?

playing with a tube outside they look like they would still work very well with the sun off center. Well at least until the sun was so low that one tube started to shadow the one beside it.

In a effort to not install my 30 tube collector on the house roof. I am thinking of installing it on my power room roof as all pipework can run down a cinder block wall to the tank bellow (no need for roof penetrations, very short pipe run and tank can be is sheltered from rain- wind) Power is already in the location along with it being close to the old system's hot/cold pipes.

The collector frame that the system has can be setup to sit flat on the roof or at about 45deg or so. Depending how you configure it. (it could be modified for any inclination) The power room faces North east and the roof is only at about 15deg.

We all shower in the mornings so I'm thinking this could be ok ....depending in how forgiving they are to being off center to the sun. My thinking is that most SHW system if anything work to well in summer so is of little concern.
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Re: Electric panel resistive element water heating

Postby Gordon-Loomberah » Wed Nov 02, 2016 7:15 pm

My tubes face a bit E of north, as I'm at the base of a large hill, and they work just fine. I have them tilted at about 40 deg.
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Re: Electric panel resistive element water heating

Postby australsolarier » Fri Nov 04, 2016 6:20 am

Kurt,
15 degrees off the solar north is only 1 hour off. i don't think you would be able to measure losses there.

when you connect the tank make sure all the pipes point downwards for the first 20cm or so. this creates a siphon break. (connecting vertically or horizontally the warm water creeps out and creates its own circuit. also if it runs up to the heat pipe manifold it might start the pump at night ......)
also, tanks have large losses. in my case the estimation is so 4kw/h a day. on a sunny day this is quickly returned. however when the sun is not shining this loss becomes very important. after installation add another insulation blanket over the whole thing. avoid glass fibre, if you need to work on the tank you won't get itchy hands.

just wondering what you are planning for backup water heating when the weather is not sunny.

in my solahart 300l tank bringing up the temperatur from 45 to 59 degrees uses 5kw/h heating via the resistive element. so using the battery is probably not a good option. but you could probably do something with the spare inverter you are using in the shed when everything is in float.

in my case the water tank is also looped with a thermo siphon to the wood cooking stove. and has a loop to the space heating hot water tanks. as a matter of fact i am thinking of just cutting out the solahart altogether and using the heat exachanger inside the space heating tank directly for domestic hot water. the solahart is still going well after 24years use. one of the panels is 32 years old, the galvanized framing has a bit of rust and some water ingress markings on the black bottom, but still going well too. water must have gone into the insulation of the tank and expanded out at the ends, pushing out the black side covers over the ends of the aluminium frame. this i fixed with alu tape. ??? works well. needs replacing so every 5 years.
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Re: Electric panel resistive element water heating

Postby offgridQLD » Fri Nov 04, 2016 7:00 am

Thanks for the tips. I have a few options for boosting.

One would be to keep the instantaneous gas heater in the loop that would kick in if the water was under 50C.

The other would be to use the 2400w element in the tank. I have a set of batterys 50kwh worth in the shed that I use for night time charging of my EV. With only a small amount of pv connected to them. The bank tops up slowly and is ready on bad days to see things through.(kind of like a totally quiet generator with a smallish fuel tank) :lol: Not that we have a lot of bad days in a row in QLD.

I also have this little pv inverter unit to try out that a friend is developing. That can power a element straight through from PV. Though if there isn't enough sun to heat the water in the tubes I would assume there isn't sun for PV.

Then there is the 8kva generator that could polish things off on a really bad day. Though I don't like that idea. I would prefer to use the instantaneous and LPG 9kg bottle if I am going to burn a fossil fuel over that.

It all boils down to how often in my location with the system I have chosen and hot water needs that I would need boosting.

Then there is the issue with meeting heath guidelines having the tank water reach 60C every 24hr. I don't now how seriously to take that not the 60c part but the how often to reach that temp part. As that has a lot of systems on the grid using more power than they need to (if they could have just pushed the time limit out to 48hr or so and got the next sunny day.

I played around with our 315lt SHW system on Brisbane house. It just has two north facing flat panel collectors that are a bit dirty and get a little bit of shad in the morning. Along with the pipes and valves not being very well insulated. I need very minimal boosting on that system to maintain 60 C

I have some time to get this system in and running As I have 4x 40lt full LPG bottles strapped to the house 500kwh or so each of energy to burn through before I hand them back.

Kurt.
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Re: Electric panel resistive element water heating

Postby australsolarier » Fri Nov 04, 2016 7:35 am

the 60 degrees part, 57 degrees to be exact, is because of legionella. this temperature is suppose to kill it, stopping mass breeding. however i think once a week is enough to keep it in check.
there are some people that keep the temperature in their hot water tanks super low (45 degrees) to save energy and once a week they crank it up to 60 degrees for that very reason.

the instantaneous gas heater is really good. just was talking to a bloke having installed one to his solar hot water. seemingly they need mains voltage, but he was talking about his that just uses a battery.(saves a large chunk of installation cost for the wiring) i suppose the electricity is needed to ignite the gas.
there are also electric instantaneous heaters. keeping in mind they only need to heat the difference, so say from 35/40 degrees to say 50 degrees. this would tie into the solar pv much better than heating up a whole tank at one go. i have seen little devices for the kitchen sink and the shower. they are quite cheap.

just doing the maths for a shower:
say your water is 30 degrees in the tank and you are using 50 liters for the shower, that equals to about 0.75kw/h top up energy. i suppose still a hefty draw, particularly with an extended household.
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Re: Electric panel resistive element water heating

Postby australsolarier » Fri Nov 04, 2016 7:46 am

incidentally my small everhot wood cooking stove ties in quite neatly when solar is low. it takes over heating, hot water and cooking (part of electricity).
the draw backs are it is messy and somewhat polluting. and more work. and needs forward planning when cooking.
have yet to see how the pv ties in. so far i greed feeded all the electricity. but that will change end of this year.
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Re: Electric panel resistive element water heating

Postby offgridQLD » Fri Nov 04, 2016 8:02 am

We have a wood oven/heater but its location is not practical due to distance to tie in with the hot water system. In QLD I don't think the expense to tie it in would be worth the short time it is needed potentially.

Yes the legionella can end up in water anything from 25 - 50C though like you say I'm not sure how pedantic to be and if the health recommendations are a bit like the recommended speed limit for road bends in country roads (you don't often take them at 45kph)

That said making yourself or family and friends sick potentially very sick just so save some energy isn't ideal. My gas instantaneous heater is already installed and yes it has 240v power as they don't burn a pilot light but ignite on each use. The issue is that would help with the water being comfortable and no cold showers if it ever got that low. Though it would not help keeping the tank to 60C as its plumbed in after the tank as part of the hot feed to the house.

My concern isn't cold showers it's more how many days is safe to go with a tank that's under 60C .

Though I would have thought that tanks would have a portion that was under 60C most of the time as the boosters elements even on mains are only in the top section of the tank and unless the thermostat trigger was sitting on the bottom of the tank a lot of the time there would be only warm water in that lower section.

My system included a little display that I will mount on the other side of the wall to the tank/pump. In the laundry. this displays 3 temp readings tank in two positions and the collector temp. It also has a manual boost button. I have already start to work on how I am going to data log this info to see how often the tank reaches 60C.
Last edited by offgridQLD on Fri Nov 04, 2016 8:35 am, edited 2 times in total.
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Re: Electric panel resistive element water heating

Postby offgridQLD » Fri Nov 04, 2016 8:08 am

What are you doing Gordon to deal with legionella? Just sucking it up and getting use to the chesty cough :lol:..joke

From what I remember you had a lot of collector area two or three ground mounted 30 tube collectors and a large storage tank 500lt?. Though wasn't sure if you were just using the tank as a heat exchanger with a coil or using the water directly.

boosting?

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Re: Electric panel resistive element water heating

Postby australsolarier » Fri Nov 04, 2016 8:25 am

as i understand the legionella, there is an optimum temperature for it to breed. so at the bottom you have that cold water inlet area (where the legionella can live, but is extremly slow at multiplying), at the top the hot and somewhere in between that intermediate layer that is temperate conducing to the legionella breeding. as it gets sucked up higher in the tank it then gets killed. or at least gets into an area of slow breeding again.

that is the theory of it. in practical terms i do not know of an incidence where the legionella came out of the hot water tank.(even from the 45 degree tank people worrying about it) so, i think it is not worth worrying about it. there are all kinds of things in the water, they only pose a problem if there are large amounts of it.
my hot water tank hoovers around lower than 57 degrees for months at a time during winter. (until the wood stove cranks it up to 80degrees in low solar insolation)
so, i suggest, you enjoy taking showers with the free solar generated hot water to the full and don't worry about legionella. every time i have a shower, there is this appreciation of that hot water generated by the sun and all the water pipes that enables such luxurious pleasures. (i remember when growing up we had neither shower nor bath tub and went for weeks or even months without shower, mind you in a different country with more temperate climate than here. )
i think the possibility about getting injured when you drive your imiev is infinitely higher than getting sick from legionella.
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