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ProDave

Solar Pv Dump Controller And Two Immersion Heaters

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ProDave

A few weeks back I installed an optimmersion dump controller.

 

It's working so well, that the customer has "complained" that by 1PM the tank is up to temperature and the immersion has switched off, and there's still spare solar PV going to the grid waste.

 

So when his first tank is up to temperature he wants it to switch to heating his pre heat tank instead.

 

Before he bought the unit, optimmersion said it could handle multiple loads. I couldn't see how when I installed it, so asked them.

 

Simple a Cylinder thermostat with a changeover contact RATED 16A to switch it over to the other heater.

 

So if someone could find me a cylinder stat with a 16A changeover contact please.

 

Failing that, all I can see is a normal cylinder stat and two contactors.

 

Anyone got a better solution?

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steptoe

what about using the satisfied connection to fire a DP/DT contactor?

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Andy™

so they advertise something that can handle multiple loads, yet their 'solution' is external to the equipement and has to be DIY'd to fit?

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steptoe

ah, solution, 2 tank stats,

2nd tank tells the controller it needs heat,

controller feeds heat to unenergised contactor which feeds first tank,

satisfied stat on first tank throws contactor to feed 2nd tank,

if 2nd tank ever gets to temp it tells controller to stop.


:C

 

but I do agree with Andy, its a bit washy imo that they mislead you

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ProDave

Changeover contactor would be simpler, but I have plenty of NO contactors so that would be "cheaper" to use two.

 

Contactor must be powered independently (e.g from an FCU somewhere) It can't be powered from the output of the optimmersion, because at low sun levels it may only be producing a small output (burst firing I believe)

 

I did wonder about using the immersion heaters own thermostat, but that might be considered unsafe, introducing other control elements. They are both unvented tanks, and I don't want to be the one explaining to the judge how I interfered with one of the safety features of an unvented tank.

 

Mind you the hardest bit is probably going to be getting a secondary tank stat fitted. I need to go and have a look and see if there's a pocket to put a capillary stat into. Otherwise I don't relsih the thought of cutting a rectangular hole in the outer (i think) steel casing of an unvented tank.

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steptoe

I think using 2 NO contactors will be a right mash up of wiring TBH, more time than it would be worth simply buying a changeover for.

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binky

think your client is tight fisted wazzock and being daft, he's getting paid to generate not just for himself but for the benefit of us all ( FIT) .  However, I agree with Steps cos I hate mashed up wiring systems.

 

All these gadgets work by burst firing, unless panels are flying along - I have an Immesun and that is exactly what it does. Immersuns can be daisy chained for future reference. How about flogging tight fistted person bigger water tank or simple panel heater to warm the cockles of his heart. The feeder tank is mean't to be cold from memory, so think this plan is possibly flawed from start???

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ProDave

the second tank is just a buffer.

 

Sold water goes into the second tank, and the outlet from the second tank feeds the input to the main tank.

 

It was put there specifically for this purpose apparently as a pre heat tank.

 

I can see it might work occasionally, for a short time.

 

But in a prolonged spell of wall to wall sunshine it will reach the point when both tanks are hot. Will he then fit a third?

 

Don't forget, if the main tank is being fed with water already pre heated a bit, then it will take less to heat that to full temperature, so that one will cut out sooner in the day, sending more to the pre heat tank.

 

the only "solution" is to use more hot water.

 

Personally rather than faff about with two tanks, I would have changed the main one for a bigger tank.

Edited by ProDave

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kme

The 2013 version of Eric Ward`s circuit has a second output, switched in when the thermostat is satisfied :)

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ProDave

Yes, if designed properly, that's simple.

 

The software can switch on a load, and if there is STILL spare power switch on a second load.

 

This is what the guy was led to believe the Optimmersion would do, but once he got it, it became apparent there was only one output. 

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steptoe

mis-sold?

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binky

can't find anything in manual for controlling second element

Optimmersion Manual- Installation 1 1.pdf

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ProDave

The manual was about as useful as a chocolate tea pot.

 

Oh and did I tell you, I had to fix two faults with the unit before I got it working?

 

Add the miss selling issue, and I'm afraid I cannot recommend this one to anybody.

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