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Author Topic: Controlling appliances  (Read 22787 times)
Baz
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« Reply #15 on: April 09, 2010, 06:21:21 PM »

A switched mode power controller won't try to smooth the current although the inductance of the circuit will make it something other than purely square. The power involved makes smoothing impractical. This is not the same a switched mode power supply (eg as used for laptop) which  is low power and needs to smooth things out to avoid upsetting the thing it is powering.
If you have a big enough battery attached then during the space period the power goes to the battery, and in mark period the battery supplies the shortfall. however it will radiate RF likethe clappers and destroy your ability to listen to the long wave radio test match comentary so obviously a really bad idea.
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climber
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« Reply #16 on: April 09, 2010, 07:25:00 PM »

Any way of using the pulse output from the KWh total generation/ROC meter?

Once the number of pulses reaches a certain frequency, an appliance/immersion heater is switched on?
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8 x SolarWorld 245W Mono Black Panels and Power One PVI-2000 Inverter (FIT)
4 x Solar Kinve 235 W Panels and Growatt 1000S Inverter (Non FIT!!!)
Alan
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« Reply #17 on: April 09, 2010, 10:22:41 PM »

Not for the faint hearted but the bare bones to get you going with out tooo much soldering / programming of Gizmoids. Proportional control system with less rocket science. Easy to add to in the future.

( Disclaimer- You still need a good under standing of whats going On )

If the D.C. voltage measured after the diode is

0.005 volts the grid inverter will be exporting about 500 watts. Probably about the house base load ? So no power will be out putted from the Triac control unit.

1.25 volts will be about 2.3 K.W. exported

If you loop the grid inverter wire through the current transformer twice the voltage at the diode will double. Which means twice the amount of power out put from the Triac unit.

The triac controller has got offset and span adjustment for setting the 0 and 5 volt range.
 
The 0 volt setting could be adjusted to allow a bigger base house load so that you only use power when available.

The 5 volt span adjustment could be adjusted for what ever power range your grid inverter  gives or if you use a large heater this would allow you to set the maximum power you would like to send to the heater.
 
If you have more than one grid inverter you need to pass both brown wires through the current transformer.

You can also size the heater more appropriable for the amount of power you will have available.


Current transformer here.

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0351106


Fitted here.



You need

One



http://www.united-automation.com/_ProductDetail.phuse?PhuseAction=PyrUUhn1O8sELPSFzFKQvF2fptvIHFGbmMb4An06h9CTdmMLrle8uqrtGZI6eaYm

http://www.united-automation.com/res/media/pdf/X10532EVR25A_Bpdf.pdf

http://uk.farnell.com/united-automation/evr-25pa/power-regulator-25a-ac/dp/1213105

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=searchProducts&searchTerm=EVR-25PA+&x=12&y=13

If you use a germanium diode instead of a silicon diode ( Less volts drop across a germanium diode ) it will allow you to start sending power to the proportional controller  /  heater with the house base load less than 500w

This will give up to 6 K.W. proportional out put in relation to a 0 to 5 volt opto isolated input.

Regards

Alan
« Last Edit: April 11, 2010, 10:14:33 AM by Alan » Logged
Alan
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« Reply #18 on: April 09, 2010, 10:31:26 PM »

Quote from Mr Climber Any way of using the pulse output from the KWh total generation/ROC meter?

Once the number of pulses reaches a certain frequency, an appliance/immersion heater is switched on?

The problem is while you are counting that is history and not real time. You could have counted some pulses and switched on the load, but then a cloud comes along or the grid inverter trips out and your paying for the electric used.

Quote from Mr Baz A switched mode power controller won't try to smooth the current

Not sure what you mean by a switched mode power controller.

Regards

Alan
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Kombi
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« Reply #19 on: April 10, 2010, 03:24:56 PM »

So, if I try to summarise what has been said so far there are 2 ways to go about:

- a current control unit which diverts power to one or more appliances according to certain criteria
- a set up with a battery bank, charger and inverter.

The first solution seems reasonably simple; the second one far more expensive but if done correctly should ensure virtually 100% on site use of any electricity produced.
Did I get the summary right?

Whilst investigating deeper both possibilities, I think it would be quite useful if I can monitoring and recording the power consumption for the household. Any suggestion on how best to do this?

Nicolas
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climber
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« Reply #20 on: April 11, 2010, 08:49:27 AM »

Alan, I reckon I'll have a go at the proportional control method - thanks for your explanation and schematic!
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8 x SolarWorld 245W Mono Black Panels and Power One PVI-2000 Inverter (FIT)
4 x Solar Kinve 235 W Panels and Growatt 1000S Inverter (Non FIT!!!)
Mostie
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« Reply #21 on: April 12, 2010, 12:15:03 AM »

I'm going down this route also, I'll let you know how I get on.
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2x Solis PV = 1.875 kW, Mitsubishi inverter heat pump. Yorkshire Boiler Stove.
Alan
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« Reply #22 on: April 20, 2010, 08:14:09 AM »

Try and run the current transformer cable so that it is not parallel to existing cables. It is best to use two core screened cable.
Only earth the screened brade at one end only.
If the current transformer sits next to the controller there will not be any problems.
The proportional controller works very well.
They did not get it quite right with one cable gland that has to get four double insulated 2.5 mm cores and an earth through. Use a round file and do away with the stuffing gland, gets over the problem.

Regards

Alan
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Kombi
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« Reply #23 on: April 23, 2010, 10:19:43 PM »

I have progressed in my investigation and have decided which way I want to go.
First I have acquired a Current Cost energy meter. I am still struggling a bit with the data/software recording but I have 4 sensors in place:
- whole house
- lighting circuit 1
- lighting circuit 2
- office sockets
For the next few weeks I shall be monitoring the power consumption of those 4 circuits.
My idea is to set up an Inverter/charger (Victron MultiPlus) and a battery bank system and use it to power the lighting circuits and the office sockets, subject of course to enough power being available.

The important bit is the integration of the system into the house supply and PV set up. This is what I envisage:
- First the PV system should supply the house load, with help from the grid if needs be
- when PV production > house load then
          1) first priority is to charge the batteries
          2) when batteries are fully charged current is diverted to the immersion heater
- In case of grid failure then PV production should be diverted to the MultiPlus who will balance the load and supply power to the whole house in this case only.

At night, when the PV system no longer produces, the MultiPlus should provide power to the lighting circuit 1&2 and to the office. When the batteries have reached a pre-set discharge level, supply is reverted back to the grid until such time as the batteries have had enough recharge.

What do you think of the "rules"? Can they work? Have I missed any possible scenario? As usual any views or comments are greatly appreciated.

Nicolas
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Adiethesailor
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« Reply #24 on: May 10, 2010, 11:07:08 PM »

Kombi,
Our PV system being fitted at the end of the month.  I totally comply with your aims.  Would you let me know how you are getting on.
Many thanks,
Adie
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sandyrainyb
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« Reply #25 on: May 30, 2010, 10:41:09 AM »

I have just put in a 5kW pV array as well and am planning to try and control the immersion heater in the same way when producing too much. I hope to have a log boiler (to replace oil) soon as well so will switch control to the immersion in the accumulator tank so I don't have to fire it up often over the summer.

This thread is what I have been looking for without much success until now

Cheers
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hernibles
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« Reply #26 on: January 30, 2011, 03:12:41 PM »

Not for the faint hearted but the bare bones to get you going with out tooo much soldering / programming of Gizmoids. Proportional control system with less rocket science. Easy to add to in the future.

****snip****

This will give up to 6 K.W. proportional out put in relation to a 0 to 5 volt opto isolated input.

Regards

Alan


Thanks for the inspiration Alan, I found this old thread, acquired the bits and today tested my first "Mark 1" smart load for my PV.

In my case I have a 3.98 kWp system, with maximum output about 3.4kW =~ 14 Amps.

It all works nicely and exactly as you describe it should.

My first issue is that I only have a 3kW immersion and it's not possible to drive this at at the desired power without a higher control voltage, so I am going to have to either take an extra turn around the current transformer OR add some amplification.  Actually I am inclined to do both for max flexibility.

Today I have experimented with a LT1013 op amp, which can operate with a single sided 5V supply.  Seems to work fine....and of course can be powered from the load controller.

Next step is to install a second current transformer so I can inhibit the load when high demand appliances like cooker/kettle are running.

Hopefully will be sorted by next weekend.

David

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Alan
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« Reply #27 on: March 12, 2011, 02:10:33 PM »

Hello David.

Just got round to trying the second EVR controller here.
This one only out puts 9.5 amps to a 3 K.W. Heater with
a control voltage of 5.04 volts D.C.
That's with the greatest range on the offset and span adjustments.

I had some spare 4 to 20 milli amp opto isolated converters so
just increased the D.C. Voltage on the supply to the EVR.

The first EVR controller quite happily sends 12 amps to a 3 K.W.
Heater with a 5 volt D.C. Input signal.

Could you post your details of the LT1013 op amp circuit. It may
be of use to others.

Regards

Alan
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BlueNev
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« Reply #28 on: May 13, 2011, 09:32:59 PM »

this sounds great...
I'm looking to install 4kw peak on the roof but have the option to fit a 2kw60) or a 3kw(20) immersion heater? Obviously 3kw version is cheaper and would mean being able to use the maximum generation when available.
Have I got this right, the application uses a PIC processor board (30)(+Power supply) with programming to compare the generation and house load current using current transformers (2 x 25) and supplies anything from 0 to 5V to an EVR (98) like United Automation's EVR-25PA, which in turn supplies 0 to 12 Amps to the Immersion heater for 0-3kw? Approx cost 180? with 3kw heater 200?

I love the idea of having a go at setting up my first PIC implimentation but are the costs as above correct or is there a cheaper option on the EVR/Triac? surrender
I'll be adding a few LED arrays or an LCD!
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echase
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« Reply #29 on: July 25, 2011, 01:09:17 PM »

In doing experiments on this I tried pulsing a 3kW immersion with a cycle of 1 second on and 0.1 sec off. The element failed after 10 minutes.  I am assuming that whilst 50Hz is OK, as the thermal time constant is presumably >> 50Hz, when I use a 1 second cycle (1 Hz) the element just fatigues rapidly due to it heating up and cooling down too much/quickly. Anyone else had this problem?

I am not suggesting that such a low pulse rate is a good way to do this control of export, It was just a by-product of other experiments.
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