You're right to be cautious and question this! Let's break down the situation and the relevant code considerations.

The Situation: Infratech 240V Heater and Double-Pole Disconnect Infratech's Recommendation

Infratech specifying a two-pole (double-pole) disconnect means they want both hot legs of the 240V circuit completely de-energized when the heater is off.

Single-Pole vs. Double-Pole



Single-pole

Only interrupts one of the hot legs. The other hot leg is still connected, carrying 120V potential to ground even when "off".

Double-pole

Interrupts both hot legs. Completely isolates the heater from the 240V supply.

NEC Requirements - Why Double-Pole is Important (and likely Required)

The NEC (National Electrical Code) doesn't explicitly say every 240V heater must have a double-pole disconnect in all situations, BUT several clauses point towards the need.1. General Safety & Maintenance

The primary reason for double-pole disconnects on 240V appliances is safety for service personnel. If you have a single-pole switch, one leg of the circuit is always hot, creating a potential shock hazard even with the heater "off". Anyone working on the heater assumes it's safe when switched off, but that single-pole switch doesn't guarantee isolation.2.

NEC 422.31 (A) Disconnection

This section covers the disconnection of appliances and states: "Means shall be provided to disconnect appliances from all ungrounded conductors in accordance with the following: (A) From More Than One Circuit. Additional means of disconnection shall be provided for appliances connected to more than one circuit or appliance having more than one source of supply." While not explicitly about 240V heaters, it establishes the principle that you must be able to disconnect all ungrounded (hot) conductors.3.

Article 110.3(B) Installation and Use

Equipment must be installed and used per the manufacturer's instructions. If Infratech requires a double-pole disconnect for safe operation and warranty compliance, that is a Code requirement by reference to this article.4.

Potential Leakage/Fault Currents

Some appliances, even when "off," can have slight leakage currents through internal components. A double-pole disconnect completely eliminates this path, preventing nuisance tripping of GFCI breakers (if on a GFCI circuit) or other issues.5.

Listed Equipment

If the heater is listed (e.g., by UL, ETL) and the listing requirements specify a double-pole disconnect, then you must follow that requirement. The listing is part of the overall safety standard for the product.

Why Single-Pole is Not Usually Acceptable Safety Hazard

Leaving one leg of the 240V circuit energized poses a serious shock risk during maintenance or troubleshooting.

Code Compliance

It violates the spirit of the NEC, if not the letter, regarding safe disconnection of appliances. An inspector could easily argue it violates 422.31.

Manufacturer's Requirement

Going against Infratech's recommendation could void the warranty.

Lampholders (410.93)

You're correct, 410.93 applies to lampholders. It's not directly relevant to the heater, but it illustrates the general principle that switched conductors should not leave the load energized.

Conclusion Follow Infratech's Instructions

If they require a double-pole disconnect, you must install one.

Consult Local Inspector

Discuss the installation with your local electrical inspector before you begin the work. They have the final say on Code compliance in your jurisdiction.

Install a Double-Pole Disconnect

This is the safest and most compliant solution. It ensures complete isolation of the heater and avoids potential code violations.

In summary: Although there may not be one NEC section stating that a 240V heater must use a DP switch to disconnect power, manufacturers’ instructions are a key part of an installations, which will cause an inspector to require it, if the manufacturer demands it. There are also safety implications for a single pole switch, which would not turn off the power to both legs of the circuit. Flag for review