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When you have solar heating installed, there are a few details which if not carried will stop your system working properly.
The number one most common complaint we see in systems badly installed (not by us!) are airlocked systems.

In most other areas of plumbing, it is a given that any high points in the system will have air vents, so that when the system is filled up, the plumber will go to the air vents and vent the system - getting all the air out.
So why not do the same with solar thermal? Well thats what most plumbers and even some suppliers recommend - an air vent at the highest point of the system eg the top of the solar panels on the roof. Problems solved?!

Unfortunately not.

Firstly, if you use a normal plumbing air vent, it will be melt (thats right, melt!) when the system stagnates for the first time. Even solar rated air vents cannot withstand some tube collector stagnattion temperatures (up to 300C).

Secondly, even if you use the correct high temp air vent, and the plumber can get back to the top of the collector to vent the system during commisioning (i.e. the scaffolding is still up and the panel is not hot), you will still not get all the air out. The problems lies in the type of fluid in the system: Propelene Glycol mixed with water. This is a more viscous fluid and abosrbs air readily. This means that even after a week of normal running, you will still have air in the system, that is is slowly comming out of the fluid. This will build up and lead to either noisy opertion and poor heat transfer or even airlocking.

The solution? Use an experienced, well trained and qualified solar heating engineer. Who has the correct equipment for the job. The clue is in the picture....

So far in 2013 we have found 26 systems with air locking problems, most were installed less than three years ago and many by big nationwide companies.