Fan flow synchronizer

Abstract

The fan synchronizer is a small flow tube 5, 2″ IPS or smaller, connected between the supply fan 13 duct and return and/or exhaust fan 16 duct that allows flow through the tube 5 to issue a signal from an in line flow meter device 2 that will control the supply fan 13 and return/exhaust fan 16 to be synchronized to hold a set flow difference throughout the system flow range without series flow instability. The purpose is to maintain, in a variable flow system, a positive or negative building or room pressure difference to atmosphere, avoiding series flow instability of the fans.

Description

No cross references to related applications.

No federally sponsored development is involved.

No reference to sequence listing or computer program listing or computer disc appendix.

BACKGROUND OF THE INVENTION

This invention is involved in the moving of supply and exhaust/return air under low pressure, maximum of 10 inches water column, for the purpose of conditioning of space and space pressurization, positive or negative. To date other methods have been attempted that are either very expensive or don't perform or both in the stable controlled decoupling of the fans at a low cost.

BRIEF SUMMARY OF THE INVENTION

The purpose of the invention is to synchronize supply fan 15 and exhaust fan 16 flows so that a set flow differential is maintained between the two fans without one fan or the other affecting the stability of the flow difference desired and set between the fans allowing the fans to be decoupled and prevented from series flow operation.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF DRAWINGS

FIG. 1 Exhaust/return fan 16 synchronized to a variable flow static pressure controlled supply fan 15. Positive building pressure.

FIG. 2 Supply fan 15 synchronized to a variable flow static pressure controlled exhaust/return fan 16. Negative building pressure.

FIG. 3 Room pressurization. Positive to atmosphere.

FIG. 4 Room pressurization. Negative to atmosphere.

FIG. 5 Detail of invention.

REFERENCE NUMBERS FOR DRAWINGS

Reference
Number Name of Part
2      Flow Sensor - Pitot tube, orifice plate,
       venturi or turbine
3      Static Pressure Sensor - Top hat design
4      Full port ball type adjustment valve
5      Air flow tube - 2″ IPS max size
6      Differential Sensor Cell - Pressure
7      Differential Pressure Transmitter
8      Proportional, integral, derivative controller
9      Signal output from controller to speed
       control/inlet vanes/vortex damper of fan
10     Static Pressure Sensor
11     Static Pressure Transmitter
12     Static Pressure Controller
13     Flow Synchronizer Controller
14     Vari-Speed motor or inlet vane or vortex
       damper
15     Supply air fan
16     Exhaust air fan and/or recirc/exhaust
17     Variable flow room or space-typical
18     Fresh, return and exhaust dampers
19     Damper Actuator
20     Air supply to room or space
21     Air exhaust from room or space
22     Controlled damper
23     Heating coil
24     Cooling coil
25     Variable flow inlet box

DETAILED DESCRIPTION OF THE INVENTION

The fan flow synchronizer invention receives air flow input from the supply duct static pressure receiver 3 into a small tube 5, 2″ IPS maximum, and allows flow through the tube 5 past an adjustable ball valve 4 to the pitot tube 2 mounted in line 5. The pitot sensor 2 produces a differential flow signal which is sent to the differential receiver 6 then to the differential transmitter 7.

A proportional, integral, derivative controller 8 sends a continuous output control signal 9 to the exhaust/recirc fan's 16 variable flow control device 13. This device can be a variable speed motor, inlet vanes, vortex vanes or outlet damper 14. This control is set to produce a CFM that is less than the supply fan 15 CFM and to hold the CFM difference through the full operating range of the system. This operation allows stable building positive pressure and prevents unstable series fan connection. The supply fan 15 is controlled from a static pressure sensor 10 which output transmitter 11 sends signal to the variable flow device 14 similar to those listed for the exhaust/recirc fan 16 above.

The supply fan 15 is set to control the system pressure at a constant point as it responds to the variable flow of the users 17 and maintains a positive building pressure compared to outside atmosphere.

To cause a negative building pressure see drawing 2/6 where the exhaust fan 16 draws air from the building and variable flow user 17 to produce a negative pressure versus atmosphere. Static pressure is sensed at static pressure sensor 3 in the exhaust fan 16 discharge duct. Air flow from sensor 3 through the full port ball valve 4 then through the 2′ IPS pipe 5 then through the pitot flow sensor 2 then into the supply fan 15 suction. A differential flow signal comes from pitot 2 to the differential sensor 6. A differential pressure transmitter 7 receives the signal and sends it to the proportional, integral, derivative controller 8 which outputs a control signal 9 to the variable speed motor 14 to control the supply fan 15 speed to synchronize the supply fan 15 to the exhaust fan 16 at a fixed CFM flow difference.

This prevents the fans 15 and 16 from operating in series which causes unstable system and building pressure conditions.

Claims

1. Synchronize and track return/exhaust fan 16 flow with supply fan 15 flow by sensing flow through a 2″ IPS maximum pilot line 5 and flow sensor 2 between the supply fan 15 discharge duct and the return/exhaust fan 16 inlet duct when static pressure controls supply fan 15 and variable flow system has a positive pressure to atmosphere.

2. Synchronize and track supply fan 15 flow with exhaust fan 16 flow by sensing flow through a 2″ IPS maximum pilot line 5 and flow sensor 2 between the exhaust fan outlet duct and supply fan inlet duct when static pressure 10 controls the exhaust fan 16 and the variable flow system is controlled to negative pressure versus the atmosphere.

3. Control room pressure positive to atmosphere by sensing flow through tube 5 flowing from room sensor 3 to atmosphere sensor 3 and air flowing into room from supply source 20 at a higher rate than controlled air leaving through the exhaust damper 22.

4. Control room pressure negative to atmosphere by sensing flow from atmosphere to room through tube 5 flowing from sensor 3 from atmosphere to sensor 3 in the room then out through controlled exhaust damper 22 at a rate higher than the air supplied by the inlet supply duct 20.