You cannot balance a manifold you cannot read.
A radiant system with a fogged, stuck, or missing flow meter forces the installer to balance by feel — adjusting a circuit, waiting for the floor to respond, and guessing at the result. The meter is what turns that into a measurement, showing the GPM through each loop while the valve is being set.
The Caleffi NA669250 is the replacement meter for that job on older manifolds. Caleffi identifies the NA669 series as replacement flow meters for 663 and older 668 series manifolds, with the NA669250 covering the ½–2 GPM range.
What Is the Caleffi NA669250?
The NA669250 is a self-cleaning, high-temperature flow meter for radiant heating manifolds. It gives a visual indication of flow through an individual circuit, which is what makes circuit-by-circuit balancing possible rather than approximate.
The meter uses a ½–2 GPM scale with a dual reading and a brass body. Caleffi specifies a maximum operating pressure of 85 psi (6 bar) and a maximum fluid temperature of 210°F (98°C) for the NA669 series.
Why Flow Measurement Matters in Radiant Heating
A radiant system is several circuits fed from one manifold, and each needs its share of the flow. When one loop takes more than its share, the loops downstream of the imbalance run short — and the symptoms show up in the finished space, not at the manifold.
What Poor Balancing Looks Like
- Uneven heating between rooms or zones
- Cold areas within a single floor
- Reduced overall system efficiency
- Difficult, iterative balancing
- Higher pump requirements than the design calls for
- Unnecessary energy consumption
A manifold flow meter shortens that process considerably: the installer sets a circuit, reads the actual rate, and moves to the next one. Caleffi's 668S1 TwistFlow manifolds build the same idea in, using integrated meters with a ¼–2 GPM scale for balancing.
A Replacement, Not a Manifold Rebuild
The NA669250's main value is that it services an existing installation. When a meter on a 663 or older 668 manifold fails or clouds over, the assembly does not have to come out — the meter does.
Caleffi offers the series in two ranges, so the replacement has to match the circuit:
| Caleffi Part | Flow Range |
|---|---|
| NA669150 | ¼–1 GPM |
| NA669250 | ½–2 GPM |
Check the range printed on the meter being replaced before ordering — a mismatched scale still installs, but it will not read usefully at the circuit's design flow.
High-Temperature Design
Standard flow indicators are not always rated for the temperatures hydronic systems actually see. Caleffi specifies a maximum medium temperature of 210°F (98°C) for the NA669 series, which covers most radiant and hydronic applications where reliable indication is needed at elevated supply temperatures.
Key Specifications
| Specification | NA669250 |
|---|---|
| Brand | Caleffi |
| Part Number (MPN) | NA669250 |
| Product Type | Self-cleaning flow meter |
| Flow Range | ½–2 GPM |
| Connection | ¾" straight male × ¾" straight female nut |
| Maximum Operating Pressure | 85 psi / 6 bar |
| Maximum Temperature | 210°F / 98°C |
| Accuracy | ±10% |
| Body Material | Brass |
| Application | Radiant heating / hydronic manifolds |
| Compatible Manifolds | Caleffi 663 and older 668 series |
| GTIN | 8016615964196 |
These specifications are based on Caleffi's current technical documentation for the NA669 series.
Who Uses the NA669250?
The meter is a sensible stock item for anyone maintaining radiant systems installed on Caleffi manifolds:
- Radiant heating installers
- Hydronic and plumbing contractors
- HVAC service technicians
- Building and facility maintenance teams
- System commissioning and balancing crews
- Mechanical contractors servicing existing manifolds
For crews balancing or re-commissioning an older manifold, a spare meter on hand keeps a cloudy sight glass from stalling the whole job.
Why Buy from KPaul Industrial?
KPaul Industrial supplies contractors and facility maintenance teams with genuine replacement components, valves, and hydronic accessories built for dependable service work.
Customers benefit from:
- Genuine Caleffi replacement components
- Competitive contractor pricing
- Support for hydronic, radiant, and plumbing applications
- Assistance with RFQs, bulk orders, and recurring purchasing
- A growing catalog of manifolds, mixing stations, and accessories
Availability on individual parts changes — the sidebar above reflects live stock status, and our team can confirm lead times before you commit to a customer's schedule.
Final Takeaway
The Caleffi NA669250 is a practical replacement flow meter for radiant and hydronic manifold work where a ½–2 GPM range, ¾-inch connections, and high-temperature capability are needed. Its value is straightforward: it lets a technician measure and balance individual circuits without touching the rest of the manifold assembly.
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