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.