The Caleffi 548102A is a hydraulic separator with 4" ANSI B16.5 Class 150 flanged connections, rated for 247 gpm at a maximum working pressure of 150 psi. It installs between the heat source circuit and the distribution circuits of a hydronic heating or chilled water system to provide hydraulic separation.
Caleffi specifies this series for hydronic heating and chilled water systems containing a primary production circuit with its own pump and a secondary user circuit with one or more distribution pumps, where pump interaction would otherwise cause abnormal variations in circuit flow rates and pressures. Caleffi states the separator should be sized to the greater of the primary or secondary circuit flow rate; this model is rated for 247 gpm. Source: 01076/24 NA, Operating principle and Hydraulic characteristics.
Key Features
Primary/Secondary Hydraulic Decoupling
A low pressure-loss zone lets the boiler circuit and the distribution circuits operate independently, so neither pump interferes with the other. Rated for 247 gpm.
High-Capacity Automatic Air Vent
A float-operated brass automatic air vent continuously discharges air that collects at the top of the vessel, with no manual venting routine required.
Blowdown Drain Valve
A brass drain valve at the base of the vessel purges settled impurities without taking the system offline.
Insulation Shell Included
Supplied with a rigid closed-cell expanded polyurethane foam shell under an embossed aluminum cover, rated to 220 °F and suitable for chilled water service without surface condensation.
Technical Specifications
| Product Line | Hydro Separator |
| Series | 548 |
| Connection Size | 4" |
| Connection Type | ANSI Flange |
| Connection Style | Flanged |
| Separation Functions | Hydraulic separation |
| Rated Flow | 247 gpm |
| Fluid Volume | 8.0 gal |
| Maximum Working Pressure | 150 psi (10 bar) |
| Vessel Working Temperature Range | 32 - 270 °F (0 - 132 °C) |
| Working Temperature Range, Insulated | 32 - 220 °F (0 - 105 °C) |
| Suitable Fluids | Water and non-hazardous glycol solution to 50% |
| Body Material | Epoxy resin painted steel |
| Internal Element Material | 304 stainless steel |
| Flange Standard | ANSI B16.5 Class 150 RF |
| Drain Valve Connection | 1-1/4" NPT Female |
| Insulation | Rigid closed-cell polyurethane foam shell with embossed aluminum cover, included |
| Product Weight | 117 lb |
Specifications on this page are taken from Caleffi North America technical brochure 01076/24 NA and the associated submittal and installation documents linked below. Last verified July 2026.
Documentation
Design Resources
Related Products
- Caleffi NA548102A : Hydro Separator 4" ANSI Flanged, ASME/CRN
- Caleffi 549510A : SEP4 4" ANSI Flanged
- Caleffi 501502A : MAXCAL Automatic Air Vent 3/4" NPT Female
- Caleffi NA39589 : Ball Valve 3/4" Female-Female
Frequently Asked Questions
What does the Caleffi 548102A do in a hydronic system?
The Caleffi 548102A is a hydraulic separator with 4" ANSI B16.5 Class 150 flanged connections. It creates a low pressure-loss zone between the boiler circuit and the distribution circuits so that each pump works only against its own loop, which eliminates pump conflict without relying on closely spaced tees. It is rated for 247 gpm and holds 8.0 gallons.
Does the Caleffi 548102A separate air and dirt?
The 548102A is a hydraulic separator. It includes a high-capacity automatic air vent to discharge accumulated air and a blowdown drain valve to purge settled impurities, but it does not carry the coalescing dirt element rated to 5 microns or the magnetic element found on the Caleffi HydroCal and SEP4 series.
What flow rate is the Caleffi 548102A rated for?
Caleffi rates the 4" 548102A at 247 gpm with a fluid volume of 8.0 gallons. A hydraulic separator should be sized to the greater of the primary or secondary circuit design flow rate, not to the pipe size alone.
Is the Caleffi 548102A ASME code stamped?
No. The 548102A is rated for 150 psi maximum working pressure but is not ASME code stamped. Where a project specification calls for an ASME stamped and National Board registered vessel, use the corresponding Caleffi NA-prefix model.
Does the Caleffi 548102A come with insulation?
Yes. Flanged sizes through 4" are supplied with a rigid closed-cell expanded polyurethane foam shell under an embossed aluminum cover, rated for 32 to 220 °F. The shell also prevents surface condensation in chilled water service.
- Type:
- Hydraulic Separator
- Separation Functions:
- Hydraulic
- Product Line:
- Hydro Separator
- Series:
- 548
- Connection Style:
- Flanged
- ASME Code Stamped:
- No
- CRN Registered:
- No
- Insulation Included:
- Yes
- Connection Type:
- ANSI Flange
- Connection Size:
- 4 inch
- Max Operating Pressure:
- 150 psi
