Tech Support

Heat Flow

We get a lot of questions about the ‘R value’ of our damper doors, so we felt that it’s worth going over the basics.

The so called ‘R value’ is denominated in  the units of (square-feet x degree x hour/ BTU). Sounds complicated, but all you really need to know is:

Heat Flow  Q (in BTU per hour) = Area x (temperature differential) / R-value

[For you techies, this formula is valid for steady state, and assumes an infinite plane area.]

Let’s do the math for our whole house fan dampers.  We’ll assume VERY cold conditions in the attic (0° F) and 70° F inside.

Model length width Area (sq. feet) R value Q (BTUH)
1.0WHF 22.5 14.5 2.27 14 11.33
1.7WHF 22.5 14.5 2.27 7 22.66
2.5, 2.5eWHF 22.5 14.5 2.27 10 15.86
4.5WHF 26.5 22.5 4.14 10 28.98

Bottom line:  There is not much heat loss through a well insulated whole house fan damper door.  The question that you SHOULD be asking is: “How well sealed is the whole house fan damper door?”

Most residential windows will have R values of 1 to 3. Another question that we get all the time is : “What is a BTU ?”

BTU stands for British Thermal Unit.

1 BTU is approximately the energy released by burning 1 paper match.

100,000 BTU’s make up one therm – that’s how you purchase natural gas, and right now that costs about $1.50

A gallon of gas has about 114,000 BTU.

Where to find your AirScape model, version, and serial number

If you decide to add a remote kit after your initial purchase, the AirScape model, version, and serial number will be required in order to give you the correct remote for your unit. This information is also needed by our technical support staff to diagnose or troubleshoot an issue with your WHF.

4.5 Installation – Maximize Airflow, Minimize Noise

Recently we have been using our new and improved sound testing chamber to make sound comparison videos of our different models. The shooting of these videos reminded us that the set up of the ducted models will make a significant difference in the CFM and noise levels. Basically, improper installation will decrease the unit CFM and increase the amount of noise. Some numbers for comparison:

AirScape 4.5 improper installation –  high 59 dBA / low 50 dBA

AirScape 4.5 proper installation –  high 55 dBA /low 46 dBA ……A 4 dBA difference!

The photo above shows the correct install dimensions for the 4.5 WHF. You will notice that we have a nice even bend and the ductwork is fully extended (Note that we used an extra length of the provided chain to help support the bend). It is important to maintain the 20″ diameter of the duct through the 90 degree bend. This will ensure that you get unrestricted airflow through the duct and will help disrupt the sound waves. You also want to make sure the duct and fan are fully extended from the 90 degree bend. This moves the fan to the furthest point from the grill opening, thus decreasing the decibel level.

Airscape 2.5/2.5e installation: The install dimensions for the AirScape 2.5/2.5e are very similar. The duct should be 21″ from the attic floor. It should extend 44″ from the 90 degree bend to the fan (you may be able to extend it to 48″ if the bend is supported as shown in the photo above). The top of the fan should be 44″ from the attic floor.

Interlock / Master Override

interlock3The newest version of our control board has a master override or interlock. The interlock, which is now required by some building codes, effectively disables the WHF by closing the damper doors and turning off the fans. It is often used in conjunction with smoke detectors or mechanical systems located in the attic. The idea is that if the furnace turns on or the smoke detector goes off the WHF will shut down. This could slow down the spread of a fire or save $$$ if the furnace was accidentally turned on.


The interlock is integrated into our 24v digital controls on V4 of our control board. To use the interlock simply remove the two-pin shunt and run low voltage wire from the interlock screw terminals to the relay on the device that will disable the WHF. To activate the interlock the relay should interrupt the 24v current. Do not wire 120v to the interlock.


When activated a solid red LED will illuminate on the WHF control board. The fans will turn off and the damper doors will close. Once the interlock is disengaged, the LED will go out. The WHF can be restarted by flipping the wall switch off and on again or by using your remote.


interlock1

interlock2

Control Board Identification

When you call in with a tech support issue we will want to know which version of our control board is controlling your unit. This is important because it will help us properly diagnose what is going on with your WHF. In most cases we can determine the control board version if you give us the model information for your AirScape. The model is listed on a sticker found on the unit (near the junction box on the 1.7, 2.5, 4.5 and on the damper door of the 1.0). Occasionally the model sticker isn’t enough. If you are already going into the attic to write down the model information you might as well take a look at the control board as well.

The control board has had several different incarnations over the years. Please take a look at the photos below and identify your control board before you call tech support.

My control board looks most like: 1, 2, 3, 4, 5 or 6 (Differences between 3 and 4 circled in red)

1C1_blue_300x250 2C1_green_300x250

3B8_10_300x250 4B7_300x250

5B5_6_300x2506

Wiring A Timer To Your WHF

NOTE: The following instructions do not apply to the Kohilo 1.5 or 2.8

NOTE: The following instructions do not apply to units newer than July of 2013. Please call for compatibility

We often get asked how to use a timer with our whole house fans. The short answer is to purchase the optional wireless remote which has a built in timer. But for people who prefer a wall switch there is a solution for you. You can wire a mechanical turn dial timer to operate your WHF. We recommend a mechanical timer because most digital timers require 110v. Our controls are 24v and hooking up 110v would damage the AirScape control board. We also want the process to be a manual one so that you remember to open a window. The following shows two ways to wire a timer with your AirScape WHF:

OPTION 1: TIMER AND AIRSCAPE WALL SWITCH

OPERATION:

ON – Wall switch in on position, turn timer to desired time, chose fan speed

OFF – Switch wall switch to OFF or timer expires

timer_option1_1

OPTION 2: TIMER AND CUSTOMER SUPPLIED SINGLE POLE SWITCH

OPERATION:

ON – Turn timer to desired time, choose fan speed

OFF – Timer expires

timer_option2_2