shorting out solar panels

[Gilligan]

I think this would help you with your quest:

https://www.youtube.com/watch?v=kVaxAfXQPDU

[Nidge]

I all ready have a tiny system at home
iv got 2 very small panels one controller and one car battery this powers my 16inch tv in the dinning room
for ten monthes of the year I don't expect it to power the house
I all so don't expect the water heater to heat the water up to that degree
if it heats the water up by 40% it is still 40% more than it is now as we don't use the 240v one that is in there
I have not got a battery in this heater project as if I did then the heater would proberbly just drain the battery over night
Iv built control panels for 40 years so I know how to limit the time the heaters on but there is no need as the sun is a natural timer

iv since been looking into just getting one 275w solar panel all though the voltage on this is about 30v the currant output is
only about 9A
iv been talking to the tester at work and he seems to agree with me that the extra voltage should not hurt the 24v heater
its current that will kill it and 9A should not kill it
but if some one has all ready done this and it has not worked I could all ways get a 15A Dc to Dc step down buck converter
I know a controller does a simarlar thing but I thought that the heater would be more robust with it not needing a more controlled supply and charging currant
like a battery does

[PNPmacnab]

What are you expecting to do with this hot water? Nothing serious I hope. For most of the day the heating element will look like a dead short to the panels. Direct connect is popular because it is easy, it just doesn't work well. You have made about the best match with that element. I heat water off panel voltage with a power point controller and it is amazing how well it works.

[Nidge]

Yes in parallel

[bcroe]

the heating element is 24v 300w which will take about 12.5amps and is 1.92 ohms
the solar panels vmp is 19.2v and the imp is 5.23 amps
so in series 2 solar panels should give you about 10 amps which is what the heater will run on ???

Perhaps you meant IN PARALLEL? Bruce Roe

[Nidge]

yes pn junction no controller just directly
my existing heater is 3ooow 240v and uses 12.5 amps
all ac

[PNjunction]

Is your plan direct-connection of the panels? I see no battery nor controller in your plans. That usually ends up going badly.

[Nidge]

the heating element is 24v 300w which will take about 12.5amps and is 1.92 ohms
the solar panels vmp is 19.2v and the imp is 5.23 amps
so in series 2 solar panels should give you about 10 amps which is what the heater will run on ???
and there is no thermostat in the heater as it is only an element
I might need to fit a over tempreture stat but as it is only like a pre heat system I don't think it will get that
hot especially with our English weather.

[Mike90250]

On the panel, will be a value called Vmp=_____ That number is the max power voltage of the panel. you need a single panel or combination of panels, where that number adds up to 24V. But 100w panels will not work well, with a 300w load on them, their voltage will collapse and you will not get a lot of heating.

And the thermostat in the heater, must be changed to a DC thermostat.

[Nidge]

iv just realised im six hours in front of you so thanks for replying
I have a 240v water element and I want to replace the element with a 24v 300w
so I can connect it up to the solar panles
im told it can be connected up to a 24v solar panel
would that be 2 in series or what

[Mike90250]

Shorting solar panels does not hurt the panel, but the gold plate on the MC4 connectors will be spoiled if they are connected/opened under load.

Water heaters generally have AC voltage thermostats, which will quickly be ruined with the DC from solar panels. If your heater has DC thermostat, you should be OK

[Nidge]

hi this is my first time on a forum so im new to all this
I want to connect 2 100w solar panels to a 24vdc 300w water heater
can this be done without a regulator but would this create a dead short on the solar panels
with ohms law the heater has an impedence of about 2 ohms
is this enough not to create a dead short ?????