Newbie
Joined: 23/07/2023
Location: AustraliaPosts: 1
| Posted: 01:44pm 18 Mar 2024 |
My 180 litre hot water system works well. Two strings of 3 x 260Watt panels provide about 90V DC@ about 18A into a 1.9kw heater element that was a 48V model but moved the 2 links to be a 90V element. Probablly best resistance matching.
I did some experiments to evaluate the 90 V and discovered the 3 panels as described
Didn't want to burn up the contacts of the existing mechanical thermostat with DC current so it only handles 12v @ about 100ma to switch the input of a D.C. Solid State Relay rated about 40A DC x 400V Dc. Cheap. A main 25A isolating CCB in series, and a very small c/o switch controls the SSR on, or bypass the thermostat.
Regardless of any thermostat hysteresis it is set for 95degrees and of course a tempering device is on the output that mixes cold with the very hot water to give about 40 degrees max at the output.
I didnt trust the old thermal insulation to take advantage of the higher stored level of thermal mass so took the tank out of its old steel drum and replaced it with good R factor closed cell thick foam rubber sheet insulation.
The SSR is mounted on an ordered heat sink and only needs backup 50V supply about twice in 5 years. Small gas shower heater is on standby.
The small bypass switch will easily take the temp up another 5 degrees to boil the tank.
Is still ok after 5 days of set in rain for shower being a bit careful with usage, and the return of partial sun can be a bit slow to recover tank temp to above 40 degrees shower water temp but would be helped with another string of 3 panels.
No copyright. :-)