Immersion Heater - PV electricity

[pmcalli]

emma circuit diagram shows a filter which appears to be mounted under the cylon controller. the crydom incorporates a PWM controller which switches at a high rate. this is necessary both to comply with the regs and to make sure that the inverter has enough power storage (hold up) to supply the 3kw load even though it might be generating a few watts on average.

 

[suntrap]

Thanks for clarifying, pmcalli - explains the Crydom's eye-watering cost, and it would be nice if the data sheet mentioned this (and talked about filtering too). Crydom also needs a low-voltage supply, which is irritating if operating it from a system designed to consume minimum power.

Interesting too about the problems of a spiky load for a solar inverter.

Would love to see the Emma circuit diagram!!

bradburts: I supposedly work in electronics but it's all software nowadays...

 

[bradburts]

bradburts: I supposedly work in electronics but it's all software nowadays...

You should ask for a pay rise then

I take it that the cylon controller is the industry standard energy management system (including a lighting controller?) rather than a evil scientist?

Which Crydom range are you refering too?
Did anyone find a FET capable of switching 3KW using AC? I didn't find anything. All I found had Amps dropping off very quickly as rating goes above 80V or so.
I am assuming that there is something (and with a high efficiency) as you can get 240V to 220V convertors fitted to your consummer unit for a few hundred pounds.

 

[suntrap]

You can put FETs in parallel as they self-regulate, so it possible this is done in some cases.

The Crydom range is here.

 

[bradburts]

Thanks.
Looked again, found loads. Must have been selecting gate voltage! What a numpty.
Lowest Rds was 70mOhm.
You sure that the linked Crydom switches at high frequency? I thought it was just a phase controller?

 

[suntrap]

I'm doubting that it can be high frequency, especially when the thermocouple version especially designed for heaters is zero crossing burst firing. pmcalli, which devices did you mean?

 

[Andysimm2000]

Would love to see the Emma circuit diagram!!

I have been on the Emma site and as well as a circuit diagram they show a full colour picture - the only bit that they are keeping under wraps is the software in the PLC.

Andy

 

[suntrap]

Sorry, I can't find the full circuit diagram - could you point me to it, please?

In the picture of the SP15 (smallest one) here there is a Kyotto KC2015AX (sadly apparently unavailable retail). This is definitely not a high frequency controller, and there is a nice big filter. (The black lump called Lambda is a DC power supply.)

In the PDF showing the wiring diagram, things are rather different. There is a Crydom 10PCV2440, similar to the Kyotto, but no filter. Unsure what unit this is, but as it's only a 40A controller and doesn't appear to have a heat sink, I assume it's also the smallest.

 

[bradburts]

(Posted as suntrap posted)
Checked the website & they show a schematic which is pretty much a circuit diagram as all the components seem to be COTS.
Think the Crydom shown is a 10PCV2440, which is a PFC.
There's a AC filter module. Cannot make it out though.
Any thoughts on what the DIN AC filter module is anyone?
Its clearly not designed for cost. Easy to build a DIN rail system but the components cost a packet.

So meeting regulations cannot be 2 hard if all you need is a COTS filter.

 

[suntrap]

Ah sorry, should have read pmcalli's post properly - yes, the high current wires disappear under the control unit, so presumably there is a filter there. I notice in the wiring diagram that you can't have your PV connected to the existing consumer unit - but then if the consumer unit is going to be full of relays it'll need replacing anyway.

 

[scoobiedoo]

Tryed to send a massage to see if you are still suppling your immersion units but get this massage (echase has exceeded their stored private messages quota and cannot accept further messages until they clear some space.)!

 

[pmcalli]

Ah sorry, should have read pmcalli's post properly - yes, the high current wires disappear under the control unit, so presumably there is a filter there. I notice in the wiring diagram that you can't have your PV connected to the existing consumer unit - but then if the consumer unit is going to be full of relays it'll need replacing anyway.

The emma unit uses a PID function in the cylon controller to balance the outputs of the two CT's which measure the power from the solar panels against the power consumed in the house including the variable load immersion heater. If the PV system is wired into a spare way in the consumer unit they recommend that it is seperated by fitting a henley block and a second consumer unit. This is not stricly necessary as there is a sneaky way to install the CT's without adding a second consumer unit. If you have 16mm2 meter tails then you can clip the CT around both the incoming meter tail and the PV wire. As the meter tail is carrying house load - pv gen putting both wires through the CT results in house load -pv +pv = house load. If you have 25mm2 tails then you may need to buy the bigger CT's.

 

[suntrap]

Someone on the openenergymonitor forums gave me that idea until I decided that one CT on the meter tail with a sniff of the voltage to determine the direction of current flow (not to mention give more accurate readings) would be a more elegant solution!

 

[pmcalli]

Accurate power readings are not necessary in a two ct set up as you are only make two things the same. the control function for this mode is very simple to implement. If you only sense the composite current you are trying to reduce the value to zero. current transformers are very inaccurate a low levels and the function is non trival to implement.

 

[suntrap]

Good points, although I was really considering a more sophisticated system based on a microprocessor so that I could log things. Maybe just keep it simple, although it might be difficult to stabilise the loop. It does require the solar feed T&E cable to be split.