PV Hot Water Controller

[Graham Hilton]

Has anyone got any experiences with all these new products that are coming out to direct excess generated electricity from a PV system to your immersion? I'm getting a few of my customers asking about them. The ones I've found seem to just use a relay switch once there is a certain amount available (usual a minimum of at least 1kW). I would have thought there would be a more efficient method. They also seem quite expensive for what they actually are.

Any thoughts would be much appreciated. Seems hard to sell something that might only save the customer maybe £30-40 a year.

 

[sambotc]

I've looked into these as well. The 2 options seem to be a parson switch, which is a very crude solution which may end up costing you more money than it saves, or the EMMA unit which is to expensive to appeal to the majority and over engineered for an immersion alone.

There have been various DIY methods created on this site that sound like they do the job just fine, but none seem to have gone to market, maybe due to patent?

 

[Graham Hilton]

Thanks sambotc

I disregarded the Parson switch as when I spoke to them they basically told me it was just a relay switch in a box AND you needed to drain the hot water cylinder down AND replace with a 1kW immersion - can't see many people going for that.

The EMMA seemed to tick all the boxes until I finally got a price from a supplier and they were quoting £2500-£3000!!

The best option I can see at the moment is immerSUN :: Use 100% generated free electricity :: A 4eco Product . It sounds like it works in a similar way to the EMMA (it modulates the power, doesn't just switch it on when a predetermined amount is generated). When I contacted them they said the RRP was going to be in the region of £300. Not due to be available for another couple of months, but might just be worth waiting for if nothing else comes up.

 

[Gary K]

You could try one of these
Water Heating with Surplus Solar PV - Solar

Not as sophisicated as some but only £30.99

 

[li150pacemaker]

You could try this:
Chris Rudge Renewable Energy Systems

 

[yellowvanman]

Or this one:

SolarDivert Solar PV Immersion heater controller

 

[Earthstore]

Or this one.......

 

[Gary K]

Or this one.....

forget it

 

[Earthstore]

No Link

I know, but it is there now...

 

[Gary K]

Lol.....

 

[arwooldridge]

This is the controller you need :-
www.sgwooldridge.co.uk/solarpvswitch
Its unique in that it actually senses the net power available for export and diverts it, however small, to the heater, normally a hot water heater.

No need to fit a smaller immersion heater it uses the standard 3Kwatt one ,and never imports power for the heater. It just patienly waits for net surplus of pv generated over consumed power.

Will even power additional loads like towel rail heaters etc if purely resistive.
Operates even at 50 watts surplus power! These are great devices and should save its cost in less than a year.

I have three running on my properties heating background heaters, hot water, towel rails.

The secret to paying back quickly is to ensure that all surplus power is used, even when the water is up to temperature.
You can do this by parrallelling loads, as the maximum output power will not exceeed your peak Solar PV power.
It will even work with a 3Kwatt oil filled electric heater in parrallel with the immersion heater.
You must make sure though you do not import power which this controller won't, but other simpler switches do.

A simple calculation based on say 4Kwatt Solar PV generating 3500kwatt hours per year at say 11p per kwHr could save £385 if you used all the surplus power.
Also factor in you can switch of the central heating from around now, due to the back ground heating, which otherwise I would have kept on just to do the hot water.

Has anyone got any experiences with all these new products that are coming out to direct excess generated electricity from a PV system to your immersion? I'm getting a few of my customers asking about them. The ones I've found seem to just use a relay switch once there is a certain amount available (usual a minimum of at least 1kW). I would have thought there would be a more efficient method. They also seem quite expensive for what they actually are.

Any thoughts would be much appreciated. Seems hard to sell something that might only save the customer maybe £30-40 a year.

 

[Gavin A]

hmm... how many switching cycles is that rated for?

 

[arwooldridge]

Its not an electro mechanical switch, its solid state so it will outlast all the other switches.
Its rated at 30 amps but only ever takes 16 amps given a 4kwatt solar PV system.
It therefore operates well within its rating.

 

[arwooldridge]

I 've had it running over 6 months, and I expect it to last least as long as the Solar PV inverters.

 

[Mr.Shing-A-Ling]

@arwoolridge - does your system work in the same way as the immersun?

 

[Worcester]

Yes basically, at the simplisic level they are very similar, however the Immersun has roll-over / duel load facilities and timer controls also built in.

 

[Mr.Shing-A-Ling]

Yes basically, at the simplisic level they are very similar, however the Immersun has roll-over / duel load facilities and timer controls also built in.

What are the timer controls for? I thought the idea was to dump all export generation into a water store instead of the grid?

 

[Worcester]

Yep, however if the system isn't up to temperature by the end of day due to either usage or lack of sun, the the system can then control your normal (or backup source) of heating to provide the nescessary boost.

For example most of our oil customers switch their whole oil systems off from May to October, so rely on the immersion, and the ability for it to ensure that whatever the sun's output that day they have ho****er is invaluable. This is even more important if someone is at home during the day and so has some kind of existing 'base load' and also if they don't have a roof or capital enought to have installed a 4kWp system. So whatever the sun's output and your consumption you are ensured hot water at the cheapest possible cost, even if there hasn't been enough 'free'. To do this with other systems other systems would be far more complicated and far more costly in installtions / controls / eergy consumed.

 

[Mr.Shing-A-Ling]

Yep, however if the system isn't up to temperature by the end of day due to either usage or lack of sun, the the system can then control your normal (or backup source) of heating to provide the nescessary boost.

For example most of our oil customers switch their whole oil systems off from May to October, so rely on the immersion, and the ability for it to ensure that whatever the sun's output that day they have ho****er is invaluable. This is even more important if someone is at home during the day and so has some kind of existing 'base load' and also if they don't have a roof or capital enought to have installed a 4kWp system. So whatever the sun's output and your consumption you are ensured hot water at the cheapest possible cost, even if there hasn't been enough 'free'. To do this with other systems other systems would be far more complicated and far more costly in installtions / controls / eergy consumed.

Thanks Worcester, I see. So the Immersun system could be coupled with a gas boiler to give the necessary boost or top when needed?

 

[Gavin A]

ho****er

lol.

also, thanks for the info - after checking out all the options, we're signing up with Immersun as well.