Solar thermal system maintenance

Do not believe that the solar system does not require maintenance. Of course, it works without it, fortunately for many years, but with a little care, its lifespan and efficiency can be significantly improved.

Checking the antifreeze mixture

Take a few centiliters of the mixed antifreeze into a plastic container through the safety or drain valve. Check with an indicator strip pH.

The pH can be read in the middle on the color-coded indicator paper, which must be between 6.9 and 7.5.

 The pH of the rinsing water is strongly acidic

The pH of the rinsing water is strongly acidic
I assume you don’t have a refractometer at home to measure your freezing point, so take a few drops of the sample to one of the gas stations and look there. Tell the wellman to look at the propylene glycol scale.

Checking the expansion vessel

The pressure in the expansion tank during operation is the same as the air and antifreeze. There is only a membrane between the two. However, it doesn’t matter how much liquid is in the tank.

If there is too much fluid, that is, little air, if the system heats up, there will be little space left for the expanding antifreeze, so the pressure will increase greatly.

If, on the other hand, there is too little liquid, that is, a lot of air, if the system cools down, the shrinking antifreeze may run out of the tank, and the system pressure will drop.

The ideal condition is between the two, That is, if the tank is half antifreeze and half air during operation.

This can be achieved as follows:

  • Relieve the antifreeze circuit. To do this, drain several liters of antifreeze until the pressure gauge shows zero.
  • Remove the plastic cap from the expansion tank
  • Measure air pressure with a wheel pressure gauge
  • The pressure must be set to half the operating pressure. That is, if the system operates on 2 bars, then on 1 bar. If there is more pressure, it should be drained, if less, it should be pumped up.
  • If you don’t have a car pump, remove the tank and pump it up at a gas station.
  • Fill the system with antifreeze to operating pressure.

This expansion tank has not worked since the initial commissioning

This expansion tank has not been operational since the initial commissioning. The system operating pressure was 3 bar, but the air in the expansion tank was inflated to 4 bar. Therefore, the antifreeze could not enter the expansion tank. It was as if it weren’t.

Leak Check

The pressure drop is relatively large (above 0.5 bar)

If you find that the pressure in the system is much lower than normal operating pressure, it can be assumed that the antifreeze is leaking somewhere.

Also check for leaks. Swipe your finger along the bottom of the connectors. If your finger gets wet, there is an error.

  • Hollanders
  • Other seals, soldering
  • Motorized valves, if any
  • The pressure drop is small (max. 0.5 bar)

    This is such a small loss, the source of which you are unlikely to find. What’s more, there may be no leaks, just some steam escaping in high heat through the automatic deaerator.

    Replacing the Antifreeze

    With hand pump

    This is only required if the antifreeze test has indicated that it is too acidic or too alkaline. The freezing point must be -23°C or below. If the pH and the freezing point is adequate and the liquid appears clear, the antifreeze can remain in the system for up to 5-10 years. Or until demolition.

    Drain the old antifreeze

    Most of the antifreeze can be drained with the drain tap at the bottom of the system. However, the non-return valve may retain some fluid, so it is advisable to break the circuit on the other side of the valve so that the residue also drains.

    If there is no drain plug at the lowest point, one of the detachable joints must be broken there.

    Mix in the new antifreeze

    If you have purchased antifreeze concentrate , it must be diluted. If you bought it from us, you have to mix one and a half times as much water with it. This will give a concentration of 40% and a freezing point of about -23°C. It is advisable to use a clean plastic container (bucket).

    Load and refill the antifreeze

    • Solar collector with station-mounted charge pump
      We also install a charging pump for our systems, so there is no need to call a specialist for charging. If we did not install the system and do not have a pump, ask us for one. The plastic hose must be placed on the bottom of the pump and the antifreeze must be pumped in. Make sure that the hose does not suck in air during pumping. Pumping should be continued until the pressure is 2 bar.
    • Order your charge pump
      This charge pump is connected to the system with a 2 meter hose and can be stored separately. Therefore, when you start to fill the system, the whole pump unit is full of air. It is not advisable to pump this air into the system, so do the following:

      1. Wind the end of the pump’s 2 meter hose to the connection point of this system, but do not pull the hose end completely
      2. Try to position the pump unit so that it is completely below the level of the connection point on the system
      3. Insert the 0.5 meter pump hose into the antifreeze container
      4. Start pumping
      5. If the pump has hardened, meaning you can barely push the piston, loosen the hose end on the 2-meter hose end and bleed the air
      6. If you feel that not all the air has come out yet, continue from step 4
      7. Open the tap on the connection point on the system
      8. Pump in the required amount. In the meantime, make sure that the 0.5 meter hose does not breathe air.
      9. Close the tap on the system
      10. Preserve the pump

      Bleed the system

      Don’t forget to bleed the system. After deaeration, if the pressure has dropped slightly, pump in a little more antifreeze mixture. Only then remove the hose from the pump.

      Pump flushing the system

      You need

      • Pump with tap and hoses
      • Dish for antifreeze
      • A pot of clean water
      • Approximately 50 liters of deionized or purified water
      • The amount of antifreeze
      • Appropriate connection points on the system

      Washing process:

      1. Slightly open the clean water taps to bleed the pump
      2. Open the dirty antifreeze tap to release the pressure
      3. Fully open the clean water taps
      4. When starting the pump, fill the system with clean water until the outgoing water is clear
      5. Stop the pump and open the taps to allow the rinsing water to drain.

      Magnesium Anode Replacement

      Against the common misconception, the function of the anode is not to protect against limescale.
      The anode is responsible for protecting the boiler from punctures. If a damage, such as a hairline crack, occurs somewhere on the internal enamel, the iron wall of the boiler may start to rust and puncture over time. This is prevented by the anode forming a galvanic cell with the iron under the crack. As a result, it is not the iron that is oxidized, but the anode wear.

      Therefore, if you see that the anode is badly worn during disassembly, be sure to replace it.

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