Solar Expansion Vessel Sizing

As the liquid heats up and expands the pressure of the system increase to an amount greater than the air pressure inside the expansion vessel and causes the membrane to take up more liquid to the air side.

Solar expansion vessel sizing. This is the total capacity of the flexcon expansion vessel. Static pressure p st. Sizing an expansion vessel for a solar thermal system with the following technical specifications. The primary solar vessel in order to lower the temperature of the liquid in direct contact with the solar plus membrane.

The appropriate size of vsg vessel is proportional to the main. Part ii of this discussion will appear in an. 520 146 0056 5 litre heating vessel click to view. Sizing the appropriate sizing of an expansion vessel must be undertaken by qualified or appropriately trained engineers.

Simon expansion vessel are sized at 4 of the system content on heating systems but over sized on solar heating sytems in case of stagnation and so some use an 18ltr vessel however in practise most installs only need 12ltr vessels and a good arguement could be made for using an 8ltr vessel as most domestic installation would have less than 11ltr s water antifreeze mix. The guide provided is to assist with the sizing of a heating vessel and we would always recommend if unsure then refer to the system manufacturers. The sizing of this tank is similar yet different from siz ing an expansion tank in a typical hydronic heating system. Vapour pressure p d.

Determining the size of this tank requires knowledge of how hot the solar collector circuit can become. Vessel size litres static head metres boiler rating kw btu. An expansion vessel must ensure the solar system can work safely particularly during periods when hot water is not being drawn off. Vp content of medium in the solar panels 4 l va content of water in the system vp volume in the pipes 20 l e medium expansion coefficient for glycol solutions 0 07 at 120 c and 30 glycol pvs safety relief valve setting.

During this period modern solar collectors may reach temperatures up to 200 c and consequently the fluid within the system can either evaporate or reach levels that can damage all the components within the solar energy system over time. This is the pressure created by the static height hst of the system between the connection point of the flexcon expansion vessel and the highest point in metres of water column 1 metre water column 0 1 bar. The solar expansion tanks has a rubber membrane which separates the solar liquid loop and the other side is filled with pressurized air. The following has been prepared as an aid to correctly size a sealed system expansion vessel.

A short guide to assist in the sizing of a heating expansion vessel using just a few system calculations you can more accurately choose the correct size heating expansion vessel for your system.