- Electric Calorifiers
- Materials of Manufacture
- Insulation
- Ancillary Equipment
- Ormandy Type References
- Sizes and Dimensions
- Hot Water Demand Requirements
- Immersion Heaters
- Control Panels
- Unvented Systems
- Immersion Heater Maintenance
- Element Failure Checks
- Fault Finding Chart
Sealed systems require careful consideration with regard to the design pressure of the calorifier shell. An appropriate pressure increase must be allowed for in order to accommodate expansion during the heating process. Generally, 0.5 bar is used as a measure between the cold feed pressure and the maximum working pressure.
The design pressure is calculated from the maximum allowable working pressure. A minimum margin of 10% or 0.5 bar, whichever is the greater, should be used to avoid nuisance lifting of the safety devices.
Systems can be offered with the appropriate safety devices together with expansion vessels, expansion relief valves and calorifier safety valve. Pressure Booster Sets can also be incorporated as a stand alone item, or as part of a skid mounted package.
Typical Unvented Electric Calorifier System
Unvented Systems – Expansion Vessel Sizing for DHW
STEP 1
Determine the booster set cold feed pressure in Bar absolute. It is important to ensure adequate provision is made for the highest point in the system.
STEP 2
Determine the required maximum working pressure. Generally this pressure will not be greater than the cold feed pressure +0.5 Bar.
STEP 3
Calculate the system volume in litres. The following table can be used to determine pipe run volumes:
STEP 4
Determine the required expansion factor from the following table.
For temperatures above 85°C, vapour pressures must be considered.
STEP 5
Calculate the required expansion vessel from the following formula:
Select next largest Ormandy expansion vessel from the table below:
Expansion vessels shown above are suitable for a maximum working pressure of 10 Bar g.
- Temperature range –10°C to +100°C.
- EPDM membrane
- WRC Approved