The Caleffi NA553366R is an NA553 boiler trim kit that packs eight boiler-room components into one box: a 1 in press DISCAL air separator (code 551066A), an AutoFill automatic filling valve pre-assembled with a ASSE 1013 testable reduced-pressure-zone (RPZ) backflow preventer (code 574002A, 1/2 in FNPT), a 4.4-gallon pre-pressurized expansion tank, an expansion tank check valve (code 561402A), two 3 in brass nipples and a brass NPT tee.
Product data compiled from Caleffi North America technical documentation. Last reviewed July 2026.
Key Features
Eight Components, One Box
DISCAL air separator 551066A (1 in press) · AutoFill + ASSE 1013 backflow combo 574002A (1/2 in FNPT) · 4.4 gal expansion tank · expansion tank check valve 561402A · two 3 in brass nipples · brass NPT tee. Caleffi matches every part for the installation, so nothing is sourced separately.
Testable ASSE 1013 RPZ Backflow
Includes a testable reduced-pressure-zone preventer for high-hazard applications such as glycol or chemically treated systems.
4.4-Gallon Expansion Tank
A pre-pressurized diaphragm expansion tank absorbs the expansion volume of the heated system fluid.
Fewer Joints, Faster Install
Factory-matched components cut sourcing time and field assembly on new boiler installations.
Technical Data
| Function | Boiler trim kit (filling valve, backflow preventer, expansion tank) |
| ASSE listing | ASSE 1013 |
| Air separator | Caleffi DISCAL 551066A, 1 in press |
| Fill / backflow combo | Caleffi 574002A, 1/2 in FNPT, ASSE 1013 |
| Expansion tank check valve | Caleffi 561402A |
| Connection | 1 in press (air separator); 1/2 in FNPT (fill / backflow) |
| Expansion tank | 4.4 gallon |
| Nipples and tee | Two 3 in brass nipples, one brass NPT tee |
Documentation
Technical brochureRelated Products
- Caleffi NA553362 1 in ASSE 1012 Boiler Trim Kit
- Caleffi NA553362R 1 in ASSE 1013 Boiler Trim Kit
- Caleffi NA553366 1 in ASSE 1012 Boiler Trim Kit
- Caleffi 535061A 1 in Auto Fill Valve
Frequently Asked Questions
What is included in the NA553366R kit?
Eight components: a 1 in press DISCAL air separator (551066A), an AutoFill filling valve pre-assembled with a ASSE 1013 backflow preventer (574002A, 1/2 in FNPT), a 4.4-gallon pre-pressurized expansion tank, an expansion tank check valve (561402A), two 3 in brass nipples and a brass NPT tee.
Which backflow preventer does it use?
A testable ASSE 1013 RPZ preventer for high-hazard (glycol / treated) systems.
What size is the expansion tank?
4.4 gallons, pre-pressurized, sized for typical residential boiler applications.
- Type:
- Boiler Trim Kit
- ASSE Standard:
- ASSE 1013
- Connection Type:
- Press
- Connection Size:
- 1 in
