Frequently Asked Questions

Q: Why does the compressor not operate in heating mode?

A: The BULLDOG™ is an energy efficient hybrid heat pump which does not require compressor operation for heating. The BULLDOG™ unit utilizes a hydronic hot water coil for heating. The hot water can come from various sources such as heat rejected from other heat pumps operating in cooling mode, a boiler system, and/or a geothermal unit with our Compax Modular Chillers.

Q: What is the proper operating temperature?

A: The BULLDOG™ can safely operate in both cooling and/or heating mode with supply water temperatures from 85°F/30°C to 125°F/52°C.

Q: My thermostat is not bringing on the BULLDOG™ heat pump? This is one of the most common service issues.

A: The BULLDOG™ is a Hybrid Heat Pump and will not operate properly if the thermostat is set to “HP” (heat pump) mode. It must be programmed for electric or gas heating.

Q: Why does my BULLDOG™ heat pump take so long to start once the thermostat is calling?

A: Most programmable thermostats have an adjustable time delay (1-5 minutes) built into the thermostat program, and the BULLDOG™ heat pump has its own built in time delay of 10 minutes.

Helpful Hints

Home Owner Guide | Home Owner Bulldog Guide                                       

Service Troubleshooting Guide | Service Guide

Flash Code Diagnostics | Flash Code Diagnostics

Commission and Start Up

Commission and Start Up Form | Start Up Sheet

Bulldog Refrigerant Charge | Bulldog Refrigerant Charge

Compax Start Up Form | Compax Startup Form

Varipak Start Up Form | Varipak Startup Form

For all service questions please forward them to:

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