1. What Is an EM HT Thermostat?
The term EM HT thermostat stands for Emergency Heat Thermostat, a key control device used in heat pump systems. Unlike standard thermostats that manage heating and cooling through compressor cycles, an EMHT thermostat directly activates backup or auxiliary heat sources—such as electric resistance heating or gas furnaces—when the main heat pump cannot meet the temperature demand.
In simple terms, the EM HT thermostat is the system’s “emergency override.” It ensures that when the outdoor temperature drops too low or the compressor fails, heating continues to operate safely and efficiently.
For OEMs, distributors, and HVAC integrators, understanding this thermostat type is essential when designing or sourcing thermostats for heat pump-based HVAC systems.
2. Key Functions: How It Works and How It Differs from “Aux Heat”
Many confuse Emergency Heat (EM HT) with Auxiliary Heat (Aux Heat), but they differ in control logic and usage:
| Function | Trigger | Heat Source | Control Type |
|---|---|---|---|
| Aux Heat | Automatically activated when the heat pump cannot maintain setpoint | Supplementary heating (resistance or furnace) | Automatic |
| Emergency Heat (EM HT) | Manually activated by user or installer | Bypasses compressor, uses backup heat only | Manual |
How it works:
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In normal conditions, the heat pump provides primary heating.
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When outdoor temperatures fall below efficiency thresholds (typically near 35°F / 2°C), the user or technician can switch the system to EM HT mode, forcing the backup heat source to run exclusively.
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The thermostat then ignores compressor signals, protecting the system and ensuring uninterrupted heating.
3. When to Use—and When Not to Use—EM HT Mode
Recommended Use Cases:
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Extreme cold climates (Northern U.S., Canada, or Middle East mountain regions).
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Compressor failure or maintenance periods.
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Emergency backup operation in commercial HVAC systems.
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Residential units where the user wants guaranteed heat output.
Avoid Using EM HT Mode When:
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The heat pump is working normally (unnecessary energy cost).
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For long periods—since EM HT mode consumes significantly more electricity.
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During cooling season or mild weather conditions.
For building operators, distributors, and system integrators, proper configuration of EM HT thermostats is critical to balance comfort, safety, and energy efficiency.
4. Common Operations and Visual Indicators
Most EM HT thermostats feature clear touchscreen or LED indicators to display system mode.
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When EM HT mode is active, the screen or LED typically glows red, or displays an “EM Heat On” message.
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On OWON’s PCT513 Wi-Fi thermostat, users can enable Emergency Heat directly through the 4.3” touchscreen or mobile app interface.
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When connected to a cloud platform, installers can remotely monitor or disable EM HT mode across multiple sites—ideal for OEM or property management applications.
Quick Operation Summary:
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Navigate to System Mode → Emergency Heat.
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Confirm activation (indicator turns red).
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System runs on secondary heat source only.
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To return to normal operation, switch back to Heat or Auto.
5. The Core Value of EM HT Thermostats for B2B Applications
For OEMs and system integrators, EM HT thermostats like OWON’s PCT513 bring measurable value:
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Safety & Reliability – Ensures continuous operation during extreme cold or system failure.
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Flexibility – Supports hybrid HVAC systems (heat pump + gas furnace).
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Remote Management – Wi-Fi and API access allow centralized monitoring.
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Customization – OWON provides OEM firmware and interface adjustments to meet project requirements.
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Regulatory Compliance – FCC-certified for North American markets, with cloud options for data privacy compliance.
These features make EM HT thermostats a preferred solution for HVAC equipment manufacturers, building automation providers, and distributors seeking reliable 24VAC control systems.
6. Does OWON PCT513 Qualify as an EM HT Thermostat?
Yes. The OWON PCT513 Wi-Fi Touchscreen Thermostat is fully compatible with heat pump systems and includes an Emergency Heat (EM HT) mode.
Key Technical Highlights:
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Supports 2H/2C conventional and 4H/2C heat pump systems.
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System modes: Heat, Cool, Auto, Off, Emergency Heat.
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Wi-Fi remote control, OTA firmware updates, and geofencing features.
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Compatible with voice assistants (Alexa, Google Home).
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Advanced protection functions: compressor short-cycle protection and automatic changeover.
This combination of connectivity and reliability makes the PCT513 an ideal EM HT solution for OEM, ODM, and B2B clients targeting North American HVAC projects.
7. FAQ – Common B2B Questions
Q1: Can I integrate the EM HT thermostat into an existing BMS?
A1: Yes. OWON provides both device-level and cloud-level APIs, allowing EM HT functions to be managed through third-party systems.
Q2: Does OWON support firmware customization for different heating logic?
A2: Absolutely. For OEM clients, we can rewrite control logic to match specific dual-fuel or hybrid HVAC systems.
Q3: What happens if the EM HT mode runs too long?
A3: The system continues heating safely but consumes more power. Integrators often set timer-based limitations via software.
Q4: Is the PCT513 suitable for multi-zone applications?
A4: Yes. It supports up to 16 remote zone sensors, ensuring consistent temperature control across large spaces.
8. Conclusion: The B2B Value of EM HT Thermostats
For HVAC OEMs, distributors, and system integrators, EM HT thermostats represent a critical component for system safety, energy management, and operational control.
The OWON PCT513 Wi-Fi Thermostat not only meets technical standards for EM HT functionality but also offers advanced IoT integration, customizable firmware, and proven manufacturing reliability.
Post time: Oct-05-2025