VAV Controller Drive Time Specifications

VAV Controller Drive Time Specifications

This article addresses actuator drive time specifications for VAV controllers and the practical realities of available products.

Understanding Drive Time

Drive time (also called stroke time) is the time required for an actuator to travel from fully closed to fully open (or vice versa).

Term	Definition
Drive Time	Full stroke duration (0-100%)
Stroke Time	Same as drive time
Travel Time	Time for partial movement
Response Time	Time to begin movement after signal

Typical Drive Times by Actuator Type

Integrated VAV Actuators (Built into Controller)

Manufacturer	Product	Typical Drive Time
Schneider	SpaceLogic VAV	150-180 seconds
Belimo	VAV compact	90-150 seconds
Johnson Controls	VMA	90-150 seconds
Honeywell	Spyder VAV	120-180 seconds
Distech	EC-VAV	120-150 seconds

Reality: Most integrated VAV actuators have drive times of 90-180 seconds.

Standalone Actuators (Faster Options)

Type	Drive Time Range	Notes
Standard 24V	90-180 sec	Most common
Spring Return	15-30 sec (close)	Spring-assisted one direction
Fast-Acting	35-90 sec	Available but more expensive
Electronic Fail-Safe	3-5 sec (close)	Emergency/safety applications

Addressing the <30 Second Requirement

Is <30 Second Drive Time Possible?

For integrated VAV: Generally no - standard products don't offer this.

For standalone actuator + controller: Yes, but with trade-offs.

Options for Fast Response

Option 1: Separate Fast Actuator

Use standalone controller with fast actuator:

• Belimo LF/NF series: 35-95 seconds
• Belimo AF/NF with spring return: ~15 seconds (closing)
• Siemens GDB series: 30-90 seconds

Trade-off: Higher cost, more wiring, larger physical size

Option 2: Spring Return Actuator

Spring return actuators close very fast (spring-assisted):

• Typical: 15-30 seconds to close
• Opening: Standard 90-150 seconds
• Good for: Fail-safe closed applications

Trade-off: Fast in one direction only

Option 3: Question the Specification

Before engineering alternatives, clarify the requirement:

Questions to ask the consultant:

1. What is the basis for <30 second requirement?
2. Is this for control response or safety?
3. Does it apply to full stroke or partial modulation?
4. Is the requirement negotiable with proper justification?

Why Fast Drive Time May Not Be Needed

For typical VAV applications:

Consideration	Why 150 sec is Usually OK
Zone response	Thermal mass of space is slow
Duct pressure	System response is gradual
Comfort	Slow changes feel more natural
Noise	Fast actuators can be louder
Wear	Slower = longer life

Exception: Fast response needed for:

• Laboratory pressure control
• Clean room applications
• Process control with tight tolerances
• Safety/isolation dampers

Engineering Response to Unrealistic Specs

Document the Issue

Prepare technical submittal noting:

1. Industry-standard drive times
2. No integrated products meet <30 sec requirement
3. Alternative solutions available (at cost premium)
4. Recommendation for specification revision

Propose Alternatives

Option	Drive Time	Cost Impact	Recommendation
Standard integrated	150 sec	Baseline	Most applications
Fast standalone	35-90 sec	+50-100%	Special requirements
Spring return	~20 sec (close)	+30%	Fail-safe needs

Request Variance

Submit RFI (Request for Information) to design team:

• Reference specific spec section
• Cite industry norms
• Request clarification or variance
• Offer alternatives if requirement stands

Product Research Resources

When searching for specific actuator capabilities:

• Belimo product selector tool
• Siemens damper actuator catalog
• Honeywell actuator specifications
• Johnson Controls product data sheets

Tip: Drive time is typically listed under "Timing" or "Operating Time" in actuator specifications.

Summary

• Standard integrated VAV controllers: 90-180 second drive time
• <30 second is unusual and expensive to achieve
• Question the basis for such requirements
• Document alternatives and cost impacts
• Spring return offers fast close if one direction is critical