Going Green – Solar Water Heater Installation

SchicksSolar Water Heating0 Comments

Dual Geyser Configuration

Solar Water Heating Components

At last! After a long process of arranging financing and sourcing the right components for my solar water heating system, the parts were delivered and ready for installation.

What I got:

  • 2 x 2.4m2 Flat Plate Solar Collectors
  • 1 x 150 litre geyser to add as additional storage
  • Geyser controller
  • Circulation pump
  • Copper pipe and fittings to plumb the system in.
  • Non-return valve to fit after the circulation pump.
  • Ball valves to install both sides of the panels.
  • Some lagging for the hot water pipes.

Solar Water Heating System Design

Figuring out to put the system together proved a little more difficult than I thought. I knew exactly what the system should do, but didn’t have clue how to do it.

Seeing as I have very little experience in plumbing, I chose to use a professional installer to put everything together. What I didn’t realise was that the installer also didn’t have much experience in putting a system together like what I wanted. They have a lot of experience in heat pump installations and single geyser installations but not with a dual geyser system like I wanted.

After lots of discussions and eventually calling in a friend to assist with the design, we agreed on the setup below.

After all the debating and discussions, the setup is actually quite simple and logical.

Cold water to the panels is taken from the cold water supply and pumped through the flat plate collectors and returned to the existing geyser via the hot water outlet. During circulation, hot water is pushed through the existing geyser via the cold water inlet into the new geyser’s hot water outlet. This process is repeated as necessary to heat water while the sun shining.

When hot water is used in the house, water goes out the hot water outlet on the existing geyser. The only change here is to install a Banjo valve on the hot water outlet to allow flow in from the panels and flow out to the house.

When hot water is used, the geyser is filled with hot water from the new geyser / storage tank. The storage tank gets filled with cold water from the mains cold water supply.

A tempering valve (anti-scald valve) is added on the hot water outlet to regulate the temperature of the hot water being used in the house. On a really hot day, you could end up with water in excess of 70 – 80 degrees C which could cause a nasty burn.

The system is controlled via a geyser controller with three thermal probes connected.

Probe T1 is connected to the hot water outlet side of the flat plate collectors.

Probe T2 is installed in the storage tank. When the temperature in the storage tank is 8 degrees C below the panel temperature, the controller activates the pump to circulate water through the system. Circulation continues until the temperature difference is 4 degrees C. This process continues throughout the day and gradually raises the temperature in both geysers.

Probe T3 is installed in the existing geyser and controls the element. If the temperature is below a set temperature at a set time, the element will be switched on to heat the water. I have times and temperatures set close to what I had before, i.e. heating in the morning for the morning showers, heating in the late afternoon for the early evening showers and a last time later at night for the adult bedtime showers.

Solar Water Heater Installation

These are just a few pictures of the installation underway. (The installation was scheduled for one day, but ran on to three days eventually due to a couple of snags.)

Solar Water Heater Performance

Before I started with the installation, I moved my Efergy monitor onto the geyser supply to monitor my usage. The results may be slightly skewed as the measurement was done during August when we had some really cold days, so heat loss during the day and night was fairly high. Below is a snapshot of a typical day which shows when the geyser is switched on and the duration. Total energy consumption was in the region of 10kWh per day for electric water heating to maintain a maximum temperature of 55 degrees C.

Below is a snapshot of my current consumption. We have been blessed with nice clear, hot weather over the past few days, so this is probably a bit skewed as well. Over the last few days the temperature in both geysers has reached around 65 degrees C by 5pm.

Energy consumption for the day shown below is down to 1kWh, 10% of what it was before the conversion. As you can see, the element only switched on the morning for a total of around 20 minutes to reheat the water to the set point of 55 degrees C. The pump starts running and cycling from around 8:45am until around 4:00pm.

At this point there is 300 litres of hot water in both geysers sitting at 65 degrees C. This is enough for the early evening showers and the later shower without any need for the element to operate. I should be able to reduce the set point temperature for the mornings to eliminate the need for the geyser to run and still have enough hot water.

The important thing for me is that the installation hasn’t required a lifestyle adjustment of any kind to achieve the savings.