Page last updated Jul 6, 2022 @ 06:37pm

PowerShelter II
Complete Plans, Parts List &
Assembly Instructions

psk2-exhfan.jpg (51494 bytes) psk2-damper.jpg (52905 bytes) psk2seethru.gif (4738 bytes) PSK2-BMS2500-fanoutside.jpg (38957 bytes) PSK2-BMS2500-inletoutside.jpg (42827 bytes) PSK2-BMS2500-open.jpg (56598 bytes) PSK2-BMS2500clearance.gif (16616 bytes) BMS4700.jpg (30035 bytes)
outlet shutter fan inlet shutter open inside clearances dimensions outside dimensions
Installation in walk-in shed
(up to 15,000 watt generators)
Installation in Suncast BMS2500 & BMS3400 garden sheds
(7,999 watt generators maximum)
Suncast BMS4700 shed (15,000 Watt generators maximum)
Click thumbnail images above to enlarge
(NOTE: Kit includes parts to convert shed.  Shed must be purchased separately. Fully assembled version includes shed.)

DIY Generator Enclosure
Converts most garden sheds
into an enclosure for your portable generator.
Works with Suncast model BMS2500 storage shed available from Lowes and BMS3400 from Home Depot.
Also works with larger BMS4700 shed. 

The PowerShelter™ II is designed to convert most garden sheds so they can house your portable generator outdoors for both storage and operation.


Design Features

  • Weather protected design for storage, maintenance and operation of generator
  • High temperature cutout to automatically shutdown generator if fan cooling is lost (reduces chance for engine damage or fire if fan stops running or air intake is blocked)
  • Large ventilation openings to dissipate engine and exhaust heat
  • Digital carbon monoxide detector and alarm to warn of ventilation malfunctions (for walk-in sheds)
  • Vents with louvers to keep out rain, birds, rodents and most insects.
  • Suitable for air-cooled gasoline, diesel, natural gas or propane fueled generators.
  • High capacity fan to cool engine
  • PowerShelter can be used with recoil or electric start generators
  • Fan powered from spare 120VAC outlet on generator
  • Exhaust adapter/extension option to redirect exhaust toward outlet fan
  • Wire cage fan guard that meets OSHA requirements is provided inside shed to reduce possibility for personal injury due to moving fan blades
  • High temperature furnace refractory board option for mounting to inside wall to deflect hot exhaust gasses
  • Optional second screen guard can be installed sandwiched between fan and outlet shutter to prevent reaching through shutter from outside when fan is running

  • Most sheds can be locked to keep your generator secure from theft
Storing your generator in this shelter frees up storage space in your garage, shed or basement for other uses
  • Electrical plug connections are made in a dry weather-protected environment which reduces shock hazards during bad weather

Makes it easier to startup and connect your generator during a power outage because it is always ready to go -- no dragging generator outside during the outage or bad weather to use it.


These PowerShelter™ instructions provide all the information for you to purchase the shed and small parts locally, order the fan and shutter online or by mail, and perform the modifications and installation. The installation normally takes a day.  The major installation steps are:

  1. Select proper location of generator and vents in shed.

  2. Select method for routing power cable out of shed.

  3. Cut two square vent holes in shed walls (if possible before assembling shed).

  4. Install outlet shutter fan.

  5. Install intake shutter and holding clip.

  6. Route and connect all power wiring.

  7. Install high temperature cutout on generator and test for proper operation.

  8. Mount exhaust deflector or exhaust adapter if required.

  9. Test generator along with fan and intake shutter.


Technical Details

  Small non-walk-in Sheds
(and BMS2500, BMS3400)
Large Walk-in Sheds Large non-walk-in Sheds
(and BMS4700)

Generator ratings

up to 7kW up to 7kW 8-15kW 8-15kW

Exhaust Fan Rating

1/10 hp 1/10 hp 1/3 hp 1/3 hp
Exhaust Fan
Shutter Size (nominal)*
16" square 16" square 20" square 20" square
Intake Shutter
Size (nominal)* 
20" square 24" square 30" square 30" square
Approx Rated
Air Flow (cfm@ 0" SP) 
2,900 2,900 5,000 5,000
Fan Amps @ 120V 1.0 1.0 3.5 3.5
Power Required (VA)** 120 120 420 420

CO Monitor Required?

no yes yes no

** Power requirements for fan motor.  Derate generator Wattage by this figure.
  * When framing a rough opening add 1/2" to these dimensions.  So, for a 16" square shutter frame the opening at 16.5" x 16.5".
     When cutting a tight opening in BMS shed wall add 1/8" to these dimensions.  So, for a 16" square shutter frame the opening at 16.125" x 16.125".


We have designed this PowerShelter with safety in mind.  However, whenever fuel is used to operate an engine generator there is always a risk due to fire, exhaust gases and electric shock.  This kit will not completely eliminate those risks.  If a fire develops, metal sheds will not contribute to the spread of the fire but sheds made of flammable materials could feed a fire.  Therefore we recommend the use of sheds made of non-flammable materials if possible.   WARNING -- failure to follow the directions for construction and use of this product can cause serious injury to persons and property.  Read all directions fully before attempting to modify your shed and use only as directed.  We DO NOT recommend that this kit be installed in any space that is part of a dwelling or attached to a dwelling.

You will need to prepare the mounting pad for the shed. Locate the pad as follows:
  * within easy wiring distance to your transfer switch or breaker panel with panel interlock
  * away from bedrooms and other rooms where engine noise could be annoying
  * at least 5 feet from any building opening such as windows, doors, vents, soffit vents, etc.
  * at least 5 feet from structures having combustible walls
  * at least 5 feet from combustible material
  * at least 5 feet clearance to any overhead structure, overhang, or tree
  * not under a deck
  * where exhaust cannot accumulate in any nearby occupied area
  * allows space to open front doors and to move generator in and out
  * meets any additional requirements of your local codes and Fire Marshal

Metal garden sheds can be purchased locally at some home improvement centers.  Costs start at about $300.00.  The Suncast BMS2500 storage shed can be purchased at Lowes.  The similar Suncast BMS3400 can be purchased at Home Depot.  But these are limited to generator sizes up to 7999 watts.  Note also that the Suncast sheds are made of plastic resin and will burn if exposed to fire. However they will usually first melt to a liquid before starting to burn.  Even though most sheds have provision for a padlock they are not very theft resistant.  A determined thief during a power outage could break into the shed and steal the generator. Therefore we recommend the additional theft prevention measures described in the instructions.

If you do not already have a transfer switch, transfer panel you may click here to order one from our wide selection.  You will also need to obtain any necessary building wire and a junction box locally if you wish to hard wire from the transfer switch to the PowerShelter. As an economical alternative we also sell panel interlock kits here.

If you do not already have a portable generator, view our selection online by clicking here.



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Item Number: PSPLANS
Price: $20
Price last updated 5/14/2021
Shipping Weight: 1 lbs.
This item ships with free ground freight to the USA 48 states.
This item normally ships in approximately 2 days or less.


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