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Old 06-10-13, 11:37 PM   #31
Xringer
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Now that's a nice system!

Since it's only for two people, why not use AC power right out of the enphase inverters?

But, only use 120vac. That way, it will only draw 1.1 kW of power. (13 ohm element 9.23A)
(Use a standard 120vac 15A circuit outlet).

Only apply power to the heater when the sun is bright and your Enphase system is putting out at least 2kW.

That way, your PV system will not send power out to the grid, but use it in real-time, heating your water.

Heck, I tested with 120AC once and it worked pretty well.
I might have used an X10 powehouse Appliance module.
It can handle a 15A resistive load.. ($10 to $15 on Ebay).

The hard part would be to build a fall-back device.
If there is no sun, and the tank is starting to cool off,
kick on the 1.1 kW anyways.. But limit it with a timer. Don't need hotwater at 2AM..
At that power level, won't cost much.. If the sun comes back out..

My tank has the A7 ASHP to use when the sun isn't out.
It's been rainy here, so the A7 ran yesterday and it's going to run again today.
Right now the tank isn't really hot, but it's good enough for a couple of showers.
At 13:00 the timer will send 120vac power to the A7, if the sun hasn't warmed it up,
the A7 will turn on and run for an hour or two. The timer removes AC power at night.
Since we are retired, we don't need real hot water in the early AM.

If my Solar panels disappeared, or were hail damaged, I would use 120AC
on a timer to run the A7. If the A7 died, I would use 120AC directly on the 13 ohm heating elements (via timer).
At 1.1kW, I figure usage would be 4 to 5 kWh per day max. That's still not a lot.

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Last edited by Xringer; 06-11-13 at 08:41 AM.. Reason: adding on. I can't help myself..
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Old 06-11-13, 06:57 PM   #32
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"That way, your PV system will not send power out to the grid, but use it in real-time, heating your water. "

Sorry but that would cost me $$$

I get $0.12 over the base rate of $0.10, thus $0.22 kw when I pump back into the grid.
I pay about $0.10 when I use it from the grid.

So far this year to date, my Electric Bill is $19.00 to date. Should be $0.00 or less at years end.
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Old 06-11-13, 07:56 PM   #33
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I'm not up to speed on how grid tie works in difference places,
but I've heard a few people say, they sell kWhs for less than they pay for them on cloudy days.
IIRC, there are places in Canada, where they pay you 2 or 3 times the price
that users next door pay for kWh. I'm pretty sure that can't last.
I guess they are trying to get everyone to install PV!

In your shoes, I would just use a timer to heat water when the Enphase system was asleep,
if I could do it at times where it wouldn't cause a big inconvenience.
Using 1.1 kW instead of 4.5 kW (& 240vac) might not make much difference in the bill.

Our tank isn't heated (with the A7) at all after 9PM.
(timer turns on at 1PM and off at 9PM).
Even if it's overcast for a couple of days, we don't have many problems.
I think once, my wife had a lukewarm shower (after my long hot shower).

Sometimes if I remember to, I'll bypass the timer during bad weather,
and let the A7 run during the morning hours, if it needs to.

That reminds me, I'm going to go take a shower now!
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Old 06-11-13, 07:59 PM   #34
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Quote:
Originally Posted by TackyTeddy View Post
I get $0.12 over the base rate of $0.10, thus $0.22 kw when I pump back into the grid. I pay about $0.10 when I use it from the grid.
If I had a deal like that, my house would be rigged to use the absolute bare minimum power between 10AM and 3PM, to maximize my thruput to the grid. Where I live, (South FL), there is only "net metering" with equivalent pricing both directions and no incentive to help the POCO reduce peak demand. I'll be happy to install a Geyser-RO and offset my cooling costs at mid-day.

Last edited by where2; 07-15-13 at 09:52 PM.. Reason: Fixed my poor editing
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Old 06-11-13, 08:25 PM   #35
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Quote:
Originally Posted by where2 View Post
If I had a deal like that, my house would be rigged to use the absolute bare minimum power between 10AM and 3PM, to maximize my thruput to the grid. Where I live, (South FL), there is only "net metering" with equivalent pricing both directions and no incentive to help the POCO reduce peak demand. I'll be happy to install a Geyser-RO and offset my cooling costs at mid-day.
That Geyser-RO is a very neat little machine.. The A7 is the cheaper version.

Geyser RO: Hot water with cooling as a byproduct! - YouTube
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Old 06-12-13, 01:32 PM   #36
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Hey Guys ...
More info how it's (Solar) works for me.

I have two meters (pic)
http://tackyted.com/storage/solar/So...rMetersTed.jpg
Really doesn't matter what I do at what time of day. Thankfully we don't have tiers or time of day rates.
Bill (pic)
http://tackyted.com/storage/solar/PowerMeterBilling.jpg

Hope this helps y'all understand my Solar Power and Billing.

I know this sounds so great and it is for me, but I got in 2010 on the pilot test program :-) :-) :-) That's now long gone.

Note: the TVA serves 9 million people in the South East

Now (new program) the TVA has only so much Solar KW per year open and it's first come first to get in. After that it's closed, so you have to wait till the next year to get in. This fills up in the first two months of the year. So if your in the TVA area think about this!

You can't hook into the grid without that program. That's right no Solar for you (unless your into batteries) !!!

So Yes I'm thankful I'm in for 10 years. So grab it (solar tie in) when you can.
As it seems like part of the movement across sections of our country to SLOW SOLAR.

Randy (the guy I got my self install solar from) (also a friend) wrote this about the TVA.
TVA is killing the solar industry with 3 easy steps |
and my post
Life On The Plateau - Editoral - I'll take Coal Ash over Clean Renewable Power
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Old 06-12-13, 09:45 PM   #37
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Quote:
Originally Posted by Xringer View Post
That Geyser-RO is a very neat little machine.. The A7 is the cheaper version.[\QUOTE]

My understanding is the A7 is a non-US made device providing similar utility. I have read your reviews, and other reviews on the A7, and would choose the added expense of a USA made product in this instance. (My wife has family that lives within 3 miles of the Nyle facility in Maine, an economy hard hit by the recession.)

QUOTE=TackyTeddy;30302]Hey Guys ...
TVA is killing the solar industry with 3 easy steps
WOW! That TVA Program really insults the intelligence of the PV system purchasers and would-be purchasers. Before reading that, I thought the friends of mine that had moved to TVA served areas had made a pretty good choice. Not that $0.10/kWh electricity is ridiculously expensive, but those two options are absolute deal breakers for me to even consider moving to any area served by TVA. I'll move to the great white north first.

Outlawing Net Metering is begging for outlaws to illegally back feed grid-tied PV systems with anything and everything they can purchase off the internet. (whether it is UL1741 compliant, or not).

My utility has a PV incentive program that offers $2/W toward a PV system, IF you can get into their very limited waiting list, and IF you want to pay an installer to install the system. I chose to purchase my own system, and self-install it, skipping their incentive.
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Old 06-12-13, 10:04 PM   #38
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Here in the state of MA, you could get a nice $1200 hybrid (ASHP+elements) hotwater heater for free.

But, to get the state rebate, you had to use a state approved installer..
I'm not sure, but I have a suspicion the install labor would end up being about $1199.99
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Old 07-15-13, 12:48 PM   #39
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Thanks for the thread, Xringer.
I do enjoy a novel idea

I calculated some time ago that my shower consumes about 20 kW while running, so ~ 1.2 kWh of DC PV a day is good for about 3.6 minutes of shower time a day.

Not bad, but I wonder if you have exhausted conservation ideas that are more efficient and less expensive ?

1. Low flow shower head. I switched out our old 2.5 gallon/min head with a 1.8 gallon/min. My wife *likes* the new one more, so I was a hero for a day, and cut my shower energy consumption by 28%. I paid about $25 if IIRC. Lower flow devices also are on the market but I have read complaints that the spray stings. ymmv.

2. If you have a shower that is often used on the second floor and some plumbing skills, check out drain heat exchangers. I think they cost under $400 and conserve about 50% of the hot water energy.
Drain Water Heat Recovery | Department of Energy
Here is a DIY . I am not sure if the installation can be horizontal, or what the heat recovery is. Seems like the tubes should be sized to match the shower flow rate.

3. I am a wimp in the winter, but in the summer I turn off the water stream while I am soaping and shampooing. I think I keep the flow time to under 5 minutes.

4. If not done, well insulate your tank and pipes. I find that setting the hot water thermostat to about 120F is more than enough.

5. Wash clothes in cold water.

------
Lastly ...
For your situation, comparing alternatives to oil heating is completely reasonable since that is what you have, but also consider whether spending your money on completely unrelated energy savings projects would give you a better return -- pollution and/or money wise. E.g., in our home I decided to replace our electric DWH heater. I considered ASHP, natural gas, condensing NG (high efficiency), and solar heating. In the end, I chose cheap tank natural gas and used the money saved to self-install windows. The windows cut my winter home heating bill by over half -- much more important than my DHW after conservation. In short, take a wide view of your home's energy use.

Good luck, and thanks again for the interesting thread.

Last edited by ELGo; 07-15-13 at 02:46 PM..
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Old 07-15-13, 02:58 PM   #40
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Default Save trees cancel your daily newspaper!

No gas lines on my street. So, it's not on the selection list.
This month, the A7 is using 0.412 kWh per day from the grid.
At 16.63 cents per kWh, that comes to 6.85 cents per day. ($2 per month).
Considering we've been taking twice as many showers, I think that's pretty good.
Solar PV DHW works!


This week, at long last, we've finally canceled our daily newspaper delivery.
Now saving $5 a week! ($261 per year, $21.75 per month).

So, we now get our DHW for free, and have money left over for Pizza!!

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