using excess power to heat water (For Dummies)

Started by kauaisolarman, October 25, 2016, 10:52:23 PM

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Westbranch

I would bet on the Slaves power being used to supply the '' WN Hi'' demand.
That being correct, the array that has the higher output latest in the day should be the one to tap... Do you agree?
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CL150 29032 FW V.2126-NW2097-GP2133 175A E-Panel WBjr, 3Px4s 140W > 24V 900Ah AGM,
2 Cisco WRT54GL i/c DD-WRT Rtr, NetGr DS104Hub
Cotek ST1500 Inv  want a 24V  ROSIE Inverter
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West Chilcotin 1680+W to come

kauaisolarman

#16
too bad only would be taking power from 1 array.

here's another question about the heating element.

if you have a AC 240V 4800 watt heating element can you just hook that to your 120V inverter and still work?  i know it will not use the entire 4800 watts but just want to know if that is possible or do you need a 240V capable inverter for that to work?

just trying to determine the best route for choosing to power the heating element AC vs DC.  i like AC just because i can use the stock thermostat/wiring that came with the heater, only problem is the heater is AC 240V and my inverter is only 120V capable. i'm assuming this is possible as if you can run it off other lower voltage power sources i dont see why not 120V also.

in this thread it seems they are running AC power using AUX 2 Waste Not HI PWM and it seems the inverter is fine with the SSR pulsing on/off not letting the element pull full power but only the excess power that the panels are providing. can anyone confirm this is OK? 

http://www.fieldlines.com/index.php/topic,147132.0.html

can i assume for a 240VAC 4500 watt heating element powered by 120VAC source
240V/4500W = 18.75A
240V/18.75A = 12.8 ohms
120V/12.8 ohms = 9.37A
120V x 9.37A = 1125 watts

so can someone confirm i can use my 120V inverter with this 240V heating element and the heating element will have a max draw of 1125 watts!

sorry 2 questions 1 post
2 solar systems in progress;
1. 24V interstate battery; 5x sanyo hit 190Watt in parallel to classic 150-SL + 8x Shell 140 watt series/parallel to classic 150-Sl (follow me).

2. 48V aquion battery; 6x panasonic HIT 325, 6x suniva 315,  CC TBD.

WillEert

I do AC diversion using an SSR. I found with the Magnum inverters I have that the Classic PWM frequency was so fast that the Magnums could not keep up and my lighting etc flickered like a discoteque (sp?). I ended up dedicating an inverter to only diversion and battery charging but then ran into other issues that caused me to search for a different method. Bob has posted that the Midnite PWM frequency can be dropped in a wind mode of some kind but I had already built my own diversion control when I learned that.

The power used by heating elements is dependant on ( among other things) the voltage. If you half the voltage you will use 1/4 the power. So that means 4000 watt 240 V elements will use 1000W at 120 V. This is one of the problems with diverting power - the heating elements must match the voltage supplied reasonably closely. You can source 120V elements and could put a lower element with a suitable wattage rating  in your tank. Install a 120V thermostat to control this element. Leave your upper as a 240. Set the temperature on the 120 higher than the 240. When diverting using the 12O the HW will rize to top of the tank and "push" your 240 element off. I have a large collection of heating elements now. I found what worked for me when using the Midnite AUX 1 system waste not Hi was an element that was about 1/2 or less of my array STC rating.

Will
(1)24 ET 185 mono, Classic 150,8x Surrette 6CS25p, 4x Magnum 4448, homecooked diversion system;(2)15 Heliene 330 mono,Classic 150;(3)2X6 Hansol345mono, 2 stand alone Hotspot ACDC12C Minisplit heat pumps.(4)15 Hanwha Q cell 400 1/2 cell, Classic 200: (5)1X6 HanwhaQcell 400 1 Hotspot minisplit ACDC18C

WillEert

More - If you are using AC diversion from your inverter then you will be using the excess power from both arrays as both Classics are wired into  common + & -  buses on the output side. These buses supplies both your batteries and the inverter. So the diversion controlled by one Classic will effectively divert the excess power from both arrays.

Will
(1)24 ET 185 mono, Classic 150,8x Surrette 6CS25p, 4x Magnum 4448, homecooked diversion system;(2)15 Heliene 330 mono,Classic 150;(3)2X6 Hansol345mono, 2 stand alone Hotspot ACDC12C Minisplit heat pumps.(4)15 Hanwha Q cell 400 1/2 cell, Classic 200: (5)1X6 HanwhaQcell 400 1 Hotspot minisplit ACDC18C

ClassicCrazy

Today there is a guy out here doing a workshop on connecting series solar panels directly to an ordinary AC water heater so you don't need any inverter or batteries, etc. You would only need an SSR to turn off DC power to lower heating element if water gets too hot . He keeps upper heating element connected to AC . Makes sense in a lot of ways for heating water -  I know it is a bit off topic to this diversion subject. Though maybe it makes more sense to take a string of panels off the batteries in the summer when there is extra power and send it directly to hot water heater using this method.

Larry
system 1
Classic 150 , 5s3p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system 2
 5s 135w Kyocero , 3s3p 270w Kyocera  to Classic 150 ,   8s Kyocera 225w to Hawkes Bay Jakiper 48v 15kwh LiFePO4 , Outback VFX 3648 inverter
system 3
KID / Brat portable

Westbranch

Larry, like Joe Friday (Dragnet) said....  Facts, mam, we just need the facts....  Let us know a link or two if you get them...

that array 'diversion'' in summer would be simple. Just need a lock out switch setup to keep the 2 DC/Ac separate
KID FW1811 560W >C&D 24V 900Ah AGM
CL150 29032 FW V.2126-NW2097-GP2133 175A E-Panel WBjr, 3Px4s 140W > 24V 900Ah AGM,
2 Cisco WRT54GL i/c DD-WRT Rtr, NetGr DS104Hub
Cotek ST1500 Inv  want a 24V  ROSIE Inverter
OmniCharge3024  Eu1/2/3000iGens
West Chilcotin 1680+W to come

kauaisolarman

Quote from: WillEert on October 29, 2016, 11:13:25 AM
I do AC diversion using an SSR. I found with the Magnum inverters I have that the Classic PWM frequency was so fast that the Magnums could not keep up and my lighting etc flickered like a discoteque (sp?). I ended up dedicating an inverter to only diversion and battery charging but then ran into other issues that caused me to search for a different method. Bob has posted that the Midnite PWM frequency can be dropped in a wind mode of some kind but I had already built my own diversion control when I learned that.

The power used by heating elements is dependant on ( among other things) the voltage. If you half the voltage you will use 1/4 the power. So that means 4000 watt 240 V elements will use 1000W at 120 V. This is one of the problems with diverting power - the heating elements must match the voltage supplied reasonably closely. You can source 120V elements and could put a lower element with a suitable wattage rating  in your tank. Install a 120V thermostat to control this element. Leave your upper as a 240. Set the temperature on the 120 higher than the 240. When diverting using the 12O the HW will rize to top of the tank and "push" your 240 element off. I have a large collection of heating elements now. I found what worked for me when using the Midnite AUX 1 system waste not Hi was an element that was about 1/2 or less of my array STC rating.

Will

thanks for the reply.

i am using a cheap samlex 2000W inverter so i hope that it can handle the SSR pulse guess i will have to just try and find out myself.

what method did you end up going with since the AC inverter route was giving you problems?

I understand that i will not get the Full 4500W out of the 240V heating element if i only put 120V to it, but my question is, is it possible to connect my 120V inverter to this 240V heating element?  i actually only need about 1000W of diversion power anyway.

would i need to change the thermostats/wiring to make it happen or can i just plug and play with the black and red wire?  i was planning to only hook up the bottom heating element.

thanks again for any help

2 solar systems in progress;
1. 24V interstate battery; 5x sanyo hit 190Watt in parallel to classic 150-SL + 8x Shell 140 watt series/parallel to classic 150-Sl (follow me).

2. 48V aquion battery; 6x panasonic HIT 325, 6x suniva 315,  CC TBD.

TomW



I would NOT PWM an SSR on either the A.C. or the D.C. side of an inverter as it would likely not work as expected and may well release the magic smoke they put into the equipment at the factory. It can be expensive getting it all back in after a catastrophic release of said smoke.

Tom

Do NOT mistake me for any kind of "expert".

( ͡° ͜ʖ ͡°)


24 Trina 310 watt modules, SMA SunnyBoy 7.7 KW Grid Tie inverter.

I thought that they were angels, but much to my surprise, We climbed aboard their starship and headed for the skies

kitestrings

#23
You've just reinforced for me why DC makes more sense.  It's worked well for us since ~2007.  If you only need 1,000 watts then your only talking 40A when it is fully engaged.  Much of the time it will be something less than that.  They are readily available in the 900-1200 w range IIRC.  With DC elements you're not affecting the inverter at all, and you can use excess power from both of your arrays - well, assuming they are both tied to the one bank - you really are just taking would be lost energy once the bank is satisfied.  I can imagine buzzing LED lights, and potential noise on audio & electronics with AC, not to mention what toll it might take on the inverter long-term.

For us, on a sunny weekday when the kids are off to school and my wife and I are working, the batteries might be well into absorb cycle by late morning.  If they're calling for only ~500 watts, there is another 2.5 kW available for diversion.  There's something to be said for the KIS approach IMO.

The direct array approach sounds promising, and should be interesting to follow, but in my mind it's more of an alternative approach, say like considering a solar (thermal) water heating system.  Here you already have the investment in panels based on the electrical needs, and you're just looking to leverage more of the available energy.

~ks

ClassicCrazy

Quote from: Westbranch on October 29, 2016, 02:02:09 PM
Larry, like Joe Friday (Dragnet) said....  Facts, mam, we just need the facts....  Let us know a link or two if you get them...

that array 'diversion'' in summer would be simple. Just need a lock out switch setup to keep the 2 DC/Ac separate

Attached is an article Pete wrote about direct PV to AC hot water heater element  - he may have more up to date info - email him - his address is at end of paper.

He had a paper today with equivalent ohm ratings of various AC hot water heating elements. I was not able to stay for his whole talk.

Larry



system 1
Classic 150 , 5s3p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system 2
 5s 135w Kyocero , 3s3p 270w Kyocera  to Classic 150 ,   8s Kyocera 225w to Hawkes Bay Jakiper 48v 15kwh LiFePO4 , Outback VFX 3648 inverter
system 3
KID / Brat portable

ClassicCrazy

Quote from: kitestrings on October 29, 2016, 07:47:35 PM

The direct array approach sounds promising, and should be interesting to follow, but in my mind it's more of an alternative approach, say like considering a solar (thermal) water heating system.  Here you already have the investment in panels based on the electrical needs, and you're just looking to leverage more of the available energy.

~ks
True what you say about if you already have PV electric system in.
One of the presenters at the talk didn't have any  PV and wanted to see if it was less to install PV direct to water heater than to install solar thermal system. He showed all the numbers he crunched and PV was less and do it  yourself easier.  The big benefits for him were just being able to run a wire in to the house instead of insulated pipes full of glycol , pumps, etc.
So he ended up buying a kilowatt of panels and making his own rack in the back yard  to put them on. He had some data he collected from past summer. So without the cost of batteries or inverter it does seem to make sense for water heating.

Larry

system 1
Classic 150 , 5s3p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system 2
 5s 135w Kyocero , 3s3p 270w Kyocera  to Classic 150 ,   8s Kyocera 225w to Hawkes Bay Jakiper 48v 15kwh LiFePO4 , Outback VFX 3648 inverter
system 3
KID / Brat portable

WillEert

I run my AC PWM diversion system at 10 hz and the MS4448 PAE inverter just happily hums along as the load changes. It did not like the fast frequency of the Midnite PWM at all - it seemed very unhappy. I think the magic smoke would have leaked out quite quickly at the high PWM frequency. The inverter could fail tomorrow I guess but so far it seems ok after 14 months or so. I vent the heat generated from the efficiency loss into my garage and do not worry too much about efficiency. I run two 2kw 240V elements in my tank using simultaneous control - first the lower element PWMs up to full load and then the upper one turns on and takes any additional power available. Fun. The standard thermostat gave me problems as it did not turn on quickly enough after it opened. This meant that the tank would have to cool down about 15F before I could divert again. So I configured an electronic thermostat which I run at 5F differential. The thermosdisc thermostats I turn the set point up above the electronic one as backup in case my system decides to try to run amok. If the electronic thermostat stops diversion by the next day the tank has cooled down the 5F and the diversion starts as soon as power is available.

Will
(1)24 ET 185 mono, Classic 150,8x Surrette 6CS25p, 4x Magnum 4448, homecooked diversion system;(2)15 Heliene 330 mono,Classic 150;(3)2X6 Hansol345mono, 2 stand alone Hotspot ACDC12C Minisplit heat pumps.(4)15 Hanwha Q cell 400 1/2 cell, Classic 200: (5)1X6 HanwhaQcell 400 1 Hotspot minisplit ACDC18C

dgd

Quote from: ClassicCrazy on October 29, 2016, 08:28:37 PM

He had a paper today with equivalent ohm ratings of various AC hot water heating elements. I was not able to stay for his whole talk.


Thankfully the ohm value of an element is easy to calculate, just divide the wattage rating by voltage to get current draw, so a 120v 2Kw element is 2000/120 or 16.66 amps,  the ohm value is then 120/16.66 or 7.2ohms

A problem with using a 120 vac rated element with lower voltage DC is that the power of the element is significantly reduced.  So the 2Kw element connected to a 48v battery would take 48/7.2 or 9.26 amps of current from the battery
Power output would then be 48*9.26 or 445 watts.
That would take a long time to heat a 200 litre tank.

Hence the need for a 48v rated element, although these tend to be rated 300 to 600watts and be expensive.

OTOH if a higher DC voltage direct from PV array can rerouted to the element then lower cost AV rated elements can be used and respectable watts power used to heat water.
In my home system I use 90volt mpv PV strings (either 5 by 18v 140W or 3 by 250W 30v PVs).
To keep things simple when float is reached two 750w PV strings are diverted to the element using AUX1 float high to enable an SSR that connects the element to the PVs outputs.  A diode commoned 3phase rectifier between the SSR and Classic prevents the Classic trying to feed power to the element.

dgd
Classic 250, 150,  20 140w, 6 250w PVs, 2Kw turbine, MN ac Clipper, Epanel/MNdc, Trace SW3024E (1997), Century 1050Ah 24V FLA (1999). Arduino power monitoring and web server.  Off grid since 4/2000
West Auckland, New Zealand

Westbranch

DGD, how or why does a 3 phase rectifier work on a single phase setup?
KID FW1811 560W >C&D 24V 900Ah AGM
CL150 29032 FW V.2126-NW2097-GP2133 175A E-Panel WBjr, 3Px4s 140W > 24V 900Ah AGM,
2 Cisco WRT54GL i/c DD-WRT Rtr, NetGr DS104Hub
Cotek ST1500 Inv  want a 24V  ROSIE Inverter
OmniCharge3024  Eu1/2/3000iGens
West Chilcotin 1680+W to come

kauaisolarman

Quote from: TomW on October 29, 2016, 05:11:07 PM


I would NOT PWM an SSR on either the A.C. or the D.C. side of an inverter as it would likely not work as expected and may well release the magic smoke they put into the equipment at the factory.

Tom

sorry tom i dont understand exactly what you are referring to.  are you recommending not running a SSR with either AC or DC power?  i though the only way for AC is through the inverter and only way for DC was directly from the battery bank?

what exactly do you mean by "A.C. or the D.C. side of the inverter"?
2 solar systems in progress;
1. 24V interstate battery; 5x sanyo hit 190Watt in parallel to classic 150-SL + 8x Shell 140 watt series/parallel to classic 150-Sl (follow me).

2. 48V aquion battery; 6x panasonic HIT 325, 6x suniva 315,  CC TBD.