Active Closed Loop Solar Water Heating Systems
Example of a Multiple Application Custom Design

A Closed Loop system can be used to link domestic hot water (DHW), space heating, and swimming pool to the same collector. It is normal to include domestic hot water in any multiple application as it is a year round requirement.

When plumbing a swimming pool or spa heat exchanger a bypass should be included. This is to avoid putting too much back-pressure on the pool/spa pump.
An example of a custom design is shown above. It combines linking methods which can be used independently in a variety of ways.

• The solar collector heats the solar storage tank through the bottom coil in the tank.
• When the tank reaches 135ºF, zone valves switch the flow to the pool heat exchanger.
• When the temperature at the tank bottom coil falls below 120ºF, the flow is directed back.
• Backup is provided for the DHW by the combination boiler. The top coil is plumbed as a zone of the radiant  heating system, and the boiler will add heat if the temperature in the top half of the solar tank falls below 130ºF.

• The pool is winterized and the power switched off to the radiant heating controlling the zone valves on the solar loop side. All solar heat will now go to the storage tank only.
• When the water in the storage tank reaches 130ºF:
• If the radiant  system is calling for heat it will draw it from the top coil, or
• If the radiant system is not calling for heat, the temperature in the tank will continue to rise until the high limit temperature is reached. The solar system will then switch off, safe because of the self-limiting maximum temperature feature in the collector.

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