The maximum requirement for make-up fluid in heating systems should be during the first few months of operation when air dissolved in the water is vented. This can be 2-3% of the total system volume. An allowance should be added for any free air that may have been trapped in the system.

The following feeder selections are based on losing 4% of the system volume due to venting, and not requiring the feeder to be refilled to get through the process. It is assumed that the feeder tank is full to start and that it is desired to have some fluid left above the pump cut-out level to handle ongoing make-up requirements.

For systems requiring a cold fill pressure no higher than 25 psig:

Feeder	Requirement
MF200	for system volume below 75 US gallons
MF300	for system volume 75-300 US gallons
SF100	for system volume 300-800 US gallons

 

For systems requiring a cold fill pressure higher than 25 psig and less than 55 psig:

Feeder	Requirement
SF100	for system volume below 800 US gallons
SF100L	for system volume above 800 US gallons

 

For systems requiring a cold fill pressure from 55 to 85 psig:

Feeder	Requirement
SF100-HP	for system volume below 800 US gallons
SF100L-HP	for system volume above 800 US gallons

 

If you have an application that requires either more storage or a higher fill pressure than is available from any of our standard models, please contact your sales representative or Axiom Industries directly for assistance with a custom built solution.

NOTE - the makeup requirements due to venting will be lower for chilled water systems. Makeup fluid may be required, however, to maintain pressure as the fluid is chilled and contracts, so the selection guidelines above are also recommended for these systems.