Glycol Solar Panel Loop

Glycol closed loop solar thermal systems.

Glycol solar panel loop.

A closed loop often referred to as a glycol or anti freeze system a drainback system. Glycol or some equivalent antifreeze fluid fills the collector and associated routing pipes. Are there advantages to running at 30 versus 20 psi. My system is two stiebel eltron sol 25 collectors a stiebl eltron sbb300 tank and new grundfos.

When commissioning a pressurized glycol solar hot water system it is essential that all the air in the solar loop is removed. Always mix in as little glycol as possible to keep optimum efficiency but never risk burst pipes. This glycol mixture is a non toxic food grade anti freeze. This is obviously catastrophic for any solar thermal installation and must be avoided.

There are two main types of solar hot water systems. The process of filling the plumbing system with this antifreeze while purging all the air out must be done systematically and in the right order. In all three scenarios if a glycol fluid is used the residual glycol remaining in the panels becomes acidic and can cause corrosion issues. Never use less than 20 glycol in the mix.

Perhaps higher boiling temperature. The primary difference between the two system types is that water is used for heat transfer in a drainback system and a glycol solution is used for heat transfer in a closed loop system. This is known as charging the system. This type of system uses solar panels also known as solar collectors that heat a propylene glycol mixture.

I ve been running at 30 psi for years but it s now working fine at 16 20 psi. Closed loop active antifreeze systems are the most versatile and failsafe of all the solar supplemental water heating systems. In the case of the closed loop solar heating system the htf is typically a mixture of water and propylene glycol. Propylene glycol pg has become the most common heat transfer fluid used in closed loop solar heating systems that contain antifreeze.

While stagnation situations do not happen often or for extended periods of time when they occur glycol degradation potentially can do enough damage that early replacement of the fluid and parts of the panel might be necessary. When you re choosing a glycol bear in mind the following. The type of system affects overall system design and each type of system has strengths and weaknesses. It has a long track record over many decades in this application and is widely available from a number of sources.

Most new solar homes feature a variation of one kind or another. Never use more than 60 glycol in the mix.