# Relay to control hot water vessel



## Banshee (3/4/15)

Hi,

I currently have an old digital timer on my outside wall which I use to turn on the electric booster for my Solar Hot Water System (SHWS). Problem is that the only thing that functions on it is the manual over ride switch so I can basically only turn the element on and off. What I wish to do is use the retic programmable control box to set on and off times for the SHWS. So here is my idea. Remove the old timer from wall and replace it with a SSR and an over ride switch with an on/off LED on the 240v side. The circuit breaker is 10amp so I can assume the element is 1800w.
What I need help with is the SSR type and heat sink size?
Would a 10amp SSR get hotter than a 25 or 40amp SSR? 
So if I went for a larger amp SSR I could reduce the heat sink size??
Also because the SSR is always on 240v I have heard that there is leakage across the switch which can be up to 5% but there is a way to eliminate this. Anyone know how??
I can only guess it is as simple as running a resistor across the poles or to netural but not quit sure.

I would like to get this info before I get the electrician out to do the job. Why?
Because last year I had an electrician rebuild my metre box and they had to return 3 times to finally do the job correctly.
What did or didn't they do you ask?
Well they wired the 3 phase bore incorrectly so it was running in reverse. (Glad I checked it so the timer didn't turn it on and screw up the bore)
Put multiple circuits into single breakers.
They did not test the system after finishing the job.

I could also use the information gathered latter in my brew system build.

Thanks


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## Ducatiboy stu (3/4/15)

Why not just use a conventional relay. Will the same job.. Bit like buying a Range Rover just so you can park on the grass nature strip.


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## Adr_0 (3/4/15)

Yeah just use a normal 240/400V electromechanical relay. An SSR is great when you are switching multiple times every few seconds where a traditional relay will quickly fail. Sounds like you are switching on only one or twice a day which is absolutely fine for a traditional relay.


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## Banshee (3/4/15)

Ok. Cheers. During my search for relays I stumbled across ebay pages which have units similar to the one I already have on the wall. Be a lot easier to replace what I have with something similar as I wont have to run the wires from retic box to relay.
Thanks for your responses guys.


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