Solar PV Hot Water system Project

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Aredwood

3885 posts

Uber Geek
+1 received by user: 1749

#2126892 15-Nov-2018 01:47

argentum66:

Absolutely - solar panels are now $1 a Watt - I was wondering if I could use the grid tie inverter I have (never connected to grid ) which is rated to 2.5kw straight to the element

Grid Tie inverters are designed to only output power when they detect that they are connected to grid power. This is an important safety feature to reduce the risk of electric shocks to people working on the local lines network.

So your grid tie inverter can't be used for what you want. Unless it also has a UPS or battery backup mode. But even then, it will attempt to maintain a constant voltage on its output. Which it will never be able to do, as it will be attempting to supply a 2.5KW load from a source that can only supply max of 2.1KW.

argentum66

18 posts

Geek

#2127594 15-Nov-2018 22:30

How about wiring 7 x 280w panels in series and sending this directly to a 2kw element ?

Aredwood

3885 posts

Uber Geek
+1 received by user: 1749

#2128742 18-Nov-2018 09:34

argentum66: How about wiring 7 x 280w panels in series and sending this directly to a 2kw element ?

That will work. At least when there is enough sun to get the panels to run at max power. Other times, the voltage will drop too much, and the panels will output hardly anything, due to operating too far from the MPP.

You will also have to wire the panels directly to the element. As there is no way that a normal cylinder thermostat would be able to handle the DC from the panels.

Which way will the panels be pointing? As you said previously that you don't have much north facing roof space.

And have you considered just getting a sparky to install the panels and your grid connect inverter? Then add a PV diversion controller, to avoid exporting power and instead use that power to heat the hot water cylinder.

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