Solar PV panel Hot Water System

[JohnnyMX]

Simple mechanical timer maybe like for a pool pump (which would assume you have power available or stored to run a low) or a digital timer to a relay or something. I'm not a pro on this stuff but it seems reasonable.

https://www.amazon.com/JVR-Programmable-Digital-Battery-Powered/dp/B00WR0ELCO/ref=asc_df_B00WR0ELCO?tag=bngsmtphsnus-20&linkCode=df0&hvadid=79989588513681&hvnetw=s&hvqmt=e&hvbmt=be&hvdev=c&hvlocint=&hvlocphy=&hvtargid=pla-4583589115061805&psc=1

 

[camshawn]

for your electronic thermostat, can you supply power to it via a battery to keep the brain alive overnight? ( or use an old school thermostat to turn off the heater when it is up to temparture like used an an electric hot water tank). Cam

 

[FordnMassey]

for your electronic thermostat, can you supply power to it via a battery to keep the brain alive overnight? ( or use an old school thermostat to turn off the heater when it is up to temparture like used an an electric hot water tank). Cam

Hi Cam,

Yes, I've considered the battery option. My son will take a look at the circuit board soon and see if the "brain" is isolated to allow it to be kept on 24/7. A simple "battery as supply" solution fails of course as the supply to the heating element would flatten the battery fast.

Old school mechanical thermostats are for AC, and DC does odd things to the contacts at higher amps and burns them out. I will consider this as a plan b, as the thermostat will rarely be switched if set for 70C/160F and so it may last long enough to be useful.

 

[FordnMassey]

Hi,
Just updating this post with some outcomes:

Lpg/propane gas consumption reduced by 50% across a whole year.
Came through a summer with no thermostat controlling the 500W electrical heat input with no issues, tho I saw the expansion valve weeping a few times.

Overall, a successful project by my reckoning.

 

[jwmorris]

There's also the issue with solar water heaters failure to perform on cold or windy days or days without direct sun.

Kind of a problem with lots of stuff that relies on the Sun.

 

[Williy]

IMHO I would say they never tested a wind generator
from MO wind & solar as the 12 volt 1500 watt really
helped to keep my batteries up in the night use of the
window a/c unit for my wife in the evening

willy

 

[FordnMassey]

For anyone seeing this thread down the track....

Now had a full year go by with this system in place and LPG/propane usage reduced from 180kg/year (400 lb) to 80kg (180lb). Our cooking has remained LPG/propane all thru this time, meaning we're now using v little gas to heat water. Its was worth the trouble.

Also useful to know I have no thermostat on it. 500W element cannot boil the 80 L (25galUS) tank and it has a safety release anyway so I decided to skip the thermostat.

 

[kenmbz]

I have solar panels running antifreeze through an 80 gallon pre-heat tank with a small Taco pump.
During the summer I can get by with the Oil furnace almost never firing but had to go to 2 tanks, one off the furnace as the "sense" tank for the heat supply as the furnace does heat and hot water.
Using PV is interesting, I don't think we could ever get the panels that cheap here in NE US, but the idea of using PV panels to heat the pool water is interesting, it would take a lot of power to do that.

Do you have to sacrifice annode the heating coil to keep it from breaking down ?

 

[Williy]

This is a very easy way to get hot water! Purchase 150 ft if black plastic
pipe and lay it in the sun and hook up to a hot water tank you will be
amazed at how hot the water will get, you can actually burn yourself from
the water being so hot in my neck of the woods

willy

 

[FordnMassey]

I have solar panels running antifreeze through an 80 gallon pre-heat tank with a small Taco pump.
During the summer I can get by with the Oil furnace almost never firing but had to go to 2 tanks, one off the furnace as the "sense" tank for the heat supply as the furnace does heat and hot water.
Using PV is interesting, I don't think we could ever get the panels that cheap here in NE US, but the idea of using PV panels to heat the pool water is interesting, it would take a lot of power to do that.

Do you have to sacrifice annode the heating coil to keep it from breaking down ?

Hi,

The tank has a sacrificial anode in it which I renewed a few years ago and I'm allowing that to protect the DC heating element.

FordnMassey