PV immersion heater proportional control

[rjd]

I joined the forum to investigate proportional (immersion) heater control to try to make better use of spare power generated by my PV installation. Thanks for the help that I've found so far. I would still be interested in hearing from anyone who knows of a ready made board offering proportional control, rated at >3kW so suitable for an immersion heater, which I could then interface to the output of a micro-controller.

 

[Spudnik]

Hi rjd and welcome to www.electriciansforums.net!

 

[CRAGS]

Hi and welcome

 

[fredfred2]

I joined the forum to investigate proportional (immersion) heater control to try to make better use of spare power generated by my PV installation. Thanks for the help that I've found so far. I would still be interested in hearing from anyone who knows of a ready made board offering proportional control, rated at >3kW so suitable for an immersion heater, which I could then interface to the output of a micro-controller.

On a recent job I saw this thing that looks rather clever. But I know not who makes it... Owners were out while I was working. Anyone know who it's made by? 2kW panels, connected to 3kW heater. Nothing in between the box and the heater, so me thinks it modulates the power somehow.

Sorry about the pic quality- taken by my phone.

cheers,

fred

 

[brian wright22]

View attachment Solar PV Heating Switch S&G Wooldridge Ltd.doc

This device looks interesting I have spoken to their technical and they confirm that it Bi directional detects the import & export power with ONE SENSOR and feeds all of the exported pV power to and immersion heater.Priced at £395 +vat it makes the similar performing EMMA device look very over priced!


Regards Brian Wright

 

[fredfred2]

Thanks for the info Brian. Looked at that link, and that product looks good too, but works differently I think. This heating switch you mention uses some sort of optical sensor that tracks the 1/1000 kWh pulse LED on a typical meter, and only switches on at two levels- half and full power.
The box that I spotted has a single current sensor insode the consumer unit which presumably monitors house or solar current. When I had curiously put a clamp meter around the cables, I noticed that it tracks the power precisely and the grid return feed was about zero. Really efficient, using every last drop of PV power. The owners of the house don't know much about the thing, but they say it works really well even on cloudy days. It was installed by their MCS installer back in May 2011- The MCS installer has now gone out of business...

I've noticed that there are quite a few devices on the market. The EMMA from Ireland is ridiculously expensive, but appears to do exactly what I want, but looks complicated and you probably need a scientist to set it up.

There are quite a few solar switches or solar immersion diverters out there, some being kits or real DIY circuits, but most need plumbing and a change of element to a lower power one.

I don't like the idea of a lower power element purely because when your boiler packs up (ours did in November), you need to operate only on the immersion. And it's soooo slow.... I'd say at least an hour and a half for a bath load of water, and then you have to wait ages again for it to reheat. If you have a lower power immersion the wait would be much longer.
I've also noticed that for most of the time since we've had our 4kW PV system, the 'average power' output is only about 600W (daylight hours). Using a switched system would probably mean that the immersion would hardly ever come on, except on the sunniest days. That's the main reason I'm looking for a proportional or tracked type solar immersion heater controller.
If I get called back to the house I'll have a look inside the unit and report back, unless someone else has seen the same one on their travels...

 

[brian wright22]

Hi Fred ,
You have opened and looked at my word attachment for the S & R Wooldridge ltd document have you?

This device does not use an optical sensor, I think you are relating to device called SOLAR DIVERT that senses the led on some of the Domestic Electric Meters.

The S & R Wooldridge device sensor clamps around the incoming mains and is more sophisticated to determin the ac current is either importing or exporting and if it is exporting I am told by Anthony Wooldridge that the circuitry within the device controls the feed to the immersion to supply the same power that is exported, therfore it should be as efficient as the very expensive EMMA device.
My main concern I have with the Wooldridge device is that they have not supplied me with any printed technical details of their device.The total information is exactly as I have given in my attachment!

Anthony Wooldridge has been very helpful but has only supplied me the attached information.

At the moment I am not prepaired to spend £500 for a device that I have no technical details,electrical performance or installation information.
As far as I'm concerned if they want to promote this device they need to have some marketing literature and technical details

Has anyone else enquired after the Wooldridge Immersion Heater proportional Control device?. If it does what Anthony Wooldridge say's then it would be well worth considering

Regards Brian

 

[Worcester]

Have a look at this thread also: http://www.electriciansforums.net/s...ral-heating-linked-monitoring.html#post551986

As far as I WAS aware, the only commercially available proportional control system is the EMMA,

However just spoken with Wooldriges' SG Wooldridge, Fabrication,Machinery, YES it is a proportional control system - I understand how he's doing it and he's doing it the right way! (Solar PV Controller type SPVHC/1 4Kwatt rated £395 plus 20% VAT recorded delivery £10)

You won't get it much cheaper than that though because of the component costs.

 

[jbella]

Hi

The link you are referring to

Have a look at this thread also: http://www.electriciansforums.net/s...ral-heating-linked-monitoring.html#post551986

appears to be broken.

However just spoken with Wooldriges' SG Wooldridge, Fabrication,Machinery, YES it is a proportional control system - I understand how he's doing it and he's doing it the right way! (Solar PV Controller type SPVHC/1 4Kwatt rated £395 plus 20% VAT recorded delivery £10)

You won't get it much cheaper than that though because of the component costs.

First of all I am not an electrician. I am using proportional controllers in my job (so got some ideas about them) and following http://www.electriciansforums.net/c...23969-immersion-heater-pv-electricity-34.html thread discussing a lot proportional energy controllers but I am completely lost to understand how one can monitor the direction (export/import) of the current by one induction clamp around the incoming mains. Could somebody explain this to me?
Anyway I agree with Brian that without any documentation it would be too risky. And what about the oscillations around the 0?
The controller which Fred has spotted seems be much more professional. Shame there are no more info about it.

Juraj

 

[Worcester]

You have to monitor the voltage and phase angle also - commercial meters using CT's have to be plascd a particular way round, and also have a cable attached to the phase 'live' for monitoring purposes.

If you want more info about the Wooldrdige device and how it works, pm me.

Sorry the link wasn;t broken - it's in the Sun lounge and you have to join that