This discussion will focus on a Wethersfield (PA) condo but is intended to inform generally for a one story type condo development in Pennsylvania. Installing a gen set at a condo is usually a bit more complicated than at a home: 1) HOA rules severely limit location of unit; 2) Usually a substantial distance between electric meter and gas supply; 3) HOA limitations on exterior conduit; 4) Most one story condo units are on a slab without a basement or crawl space; 5) Insurance for multi unit condo developments tend to be more risk adverse and detail focused.
My credentials regarding gen set installation include: BS in Mechanical Engineering; 1 year of study in commercial law at Univ. of Pennsylvania; 10 years of experience supervising commercial building construction and maintenance throughout North America; 6 years as CEO and Chief Engineer for electrical appliance manufacturer; 5 years as Luxury Custom Home Designer and “hands on” Builder in PA and MD; 3 years holding MD Master HVAC Contractor License.
In most cases, permission is required to install a whole house generator. First, permission from the Homeowner’s Association may be required but in any case is advisable. (Section 3213 of the PA Condo Act and 7.1.7 of the Wethersfield Declarations specifically grant unit owners the right to make alterations without damaging structure or thermal/acoustic characteristics. The HOA has right to control the exterior appearance.) Second, permission in the form of a Building Permit from the municipality is mandatory. Adherence to the Condo Declarations and the PA Condominium Act is required. Approval by the Codes Enforcement Officer of the municipality (and any of his designated persons) after inspections to insure good practice and compliance with building codes, is also required.
The interpretation of applicable building codes will vary depending on the municipality and inspector. The most important code is the National Fire Protection Association code NFPA 37 incorporated into the Uniform Building Code. This code requires the gen set to be located 5 feet from combustible walls and window openings. If the gen set is enclosed in a metal housing that has been tested for fire rating, the unit can be closer to the wall, according to manufacturers recommendations but no closer than 18 inches—assuming that local codes enforcement accepts this interpretation.
Generally, a conservative location would be having the unit be 5 feet away from any window and 5 feet away from any structure wall. Being “conservative” given insurance underwriters’ tendency to avoid risk seems wise in a condominium environment. A discussion may center around proximity of an AC unit that is considered an “ignition source” but generally more than 18 inches away from the AC unit will be approved. The best placement often will be for the generator exhaust to be pointing away from the home-perpendicular—placing the exhaust end of the unit at 10 feet + away from the home. In cases where the unit cannot protrude that far, the unit would need to be parallel to the home, with the front being slightly less than 8 feet away from the home. Note that due to the layout of a duplex, it may not be desirable to place the unit five feet away from building since it would create an area requiring maintenance—3 feet is probably optimum—consult HOA, Insurance Underwriter and Codes Enforcement Officer for permissions.
Keep in mind that the unit will start automatically periodically for test running, and it starts automatically within 10 seconds of a power outage. The unit generates significant heat and noise and should be far enough away from people seated on the patio area to avoid startling or otherwise harming them. If possible, it is better to avoid placing the gen set on a patio: 1) patio decks are generally not level so as to provide drainage; and 2) having the gen set separate from the patio/deck reduces possibility that guests would lean on or sit on the gen set.
The noise level near the Generac or Kohler gen set will be in the 65-67 decibels range—about the same as an AC unit. (See result of noise measurement next to AC)
See layout picture above and below.
The exhaust from the unit can in some instances contains dangerously high levels of carbon monoxide. (Bedroom windows near the generator should be closed when running and the bedroom should be equipped with a CO monitoring alarm.) In addition, the noise “trumpets” out of the exhaust end. So the ideal location is generally for the exhaust to point away from the home. But, generally the unit should not protrude past the edge of the adjacent patio—as lawn mowers will tend to follow the extended line of the patio edge and could impact the gen set.
A whole house gen set can be fueled with propane, but most condo units have a natural gas supply. The natural gas supply line needs to be run from the gas meter to the gen set. The gen set requires a pressure of 5-10 inches of water. Some gas supply service is provided from the gas meter’ s regulator at pressure of 7-10 inches of water. In this case, the gas meter may be too small to handle the additional 280,000 btu’s required by the gen set at max 18KW output—the “standard” gas meter is rated for 1/2 inch water column pressure loss at 250,000 btu flow rate. (In this case the meter would need to be upgraded to a residential/commercial version.) Most modern condo gas supply however is a 2 psi high pressure system and this “standard” gas meter is “rated” for 540,000 btu’s at that higher pressure. (This is according to Columbia Gas “new service” dept. on 8/16/23 and their “Plumbers Guide”. )
With gas heat and electric hot water, max btu’s excluding the generator are only 150,000 btu’s. With gas heat and a gas fired “tankless” hot water heater, the maximum btu’s are almost 250,000. In either case, according to Columbia Gas, a “standard” gas meter in a 2 psi system can handle an 18,000 KW gen set. (540,000 btu’s capacity at 2 psi output—it is doubtful that this max would ever be required as it would only be if ALL gas appliances were running AND the electric demand was the full 75 amp output of the gen set.) There will be a second pressure regulator for the gen set supply—the gas pipe size from that regulator to the gen set should be more than 10 feet of 1 1/4 “ NPT pipe or equivalent.
Before digging a trench for the gas line, Columbia Gas as part of PA “one call” will mark where their supply line is. ( see yellow line and flag-white line is area where possible trenching is planned.)
Apparently, the HOA will allow iron pipe attached to the stone wall for the gas line, but the buried line is much safer and less noticeable.
A substantial electric connection will run from the gen set to the 200 amp transfer switch, generally in the garage next to the 200 amp panel. (Usually around 100 feet of wire for a “quad” unit-less for a “duplex” depending on location chosen-duplex units have a choice of long electrical run and short gas line or vice-versa.) The output of an 20/18KW gen set is 75 amps. According to the National Electrical Code (NEC 310.16) this requires #3 copper or #2 aluminum wire. An additional 120 volt, 15 amp circuit needs to be run from the panel to the generator to power the battery charger. There is a supply of special “Generac” cable that combines all necessary circuits in one sheathed cable. Kohler gen sets require an additional run of low voltage shielded wiring in separate conduit to allow the transfer switch to control the gen set. All of this wiring and installation must meet the National Electrical Code.
The gen set will be set on a pre-fabricated “pad”, most times made from concrete, but sometimes out of composite filled on site with a liquid that cures into a gel. (The gen set is bolted to the pad and the additional weight provides more wind resistance and protection from being moved if bumped.) The gen set should set at least 3 inches above the adjacent grade and well above (10 inches +) any possible flooded area. The pad should be placed on a compacted, stable level area, with a base of crushed stone. (In coastal areas the unit may need to be mounted on an elevated stand several feet above grade) Since generally, the area adjacent to the home is sloped, preparation of part of this base will require significant fill and compaction. (In the pictures shown the pad base is 2” higher than the patio deck at the outer edge, so the gen set would be 5-7” higher—more than 10 inches higher than any possible pooled water.) The more crushed stone, the more noise and vibration is absorbed by the base. The composite pad absorbs noise as well.
 |
During heavy rain water pooled near location of gen set. Homeowner Association failed to remedy despite homeowner request. Gen set base raised up sufficiently to be well above this puddle. Maximum height of puddle shown as it drains at this level around side and front to grated runoff drain in driveway in front of home.
. |
To contain and stabilize the raised portion of the base, some form of retaining material (retaining wall stone or 14” CoreTen steel edging) should be placed and further supported with a tapered, well compacted supporting berm of reasonable angle to reduce erosion. In addition, concrete blocks can be placed as “footers” with drainage paths filled with 1/2 inch stone.
Once the perimeter is prepared, and a solid soil base is exposed, a 1 inch layer of 3/4 in stone “paver base” should be spread and compacted. A final layer of 3 inches of 1/2 inch stone (600 pounds +) should be spread and heavily compacted. The gen set will create a load of 100 pounds per square foot. The compacted base is designed to support more than 300 pounds per square foot. Below is a pic showing the generator placement (cardboard template-click to enlarge to see more details)
Above is the final prepared “base” ready for the pad and gen set. The final layer of 1/2” stone is sprinkled with stone “screenings” to bind the stone during final compaction. 6 feet from window and 5-6 feet from structure wall/s. Intake side is 24” plus from AC unit. Exhaust is more than 10 feet from window/s.
The following pics show the details of the wall cavity designated for wiring.
Note that the conduit with 10 ga wire, other than foam and silicone is completely unsupported. This would not be in compliance with 300.4 of the NEC for large #3 wire. It is far less than ideal even for the smaller wire.
Watch this video. Click on it.
The electric lines will run into the wall cavity adjacent to AC wiring and refrigerant lines-according to HOA rules. (Or, at least the conditions associated with my request for HOA approval.) At our Wethersfield condos, this can be a challenge as the walls were sheathed with 1/2” insulating foam board without wood sheathing. (See above video for better understanding of this controversial method of sheathing.) Foam board sheathing provides no structure or substrate behind the flimsy vinyl siding, making mounting of junction box or disconnect housings difficult. Large penetrations thru the foam board is ill advised. (A junction box for a 18-20KW gen set is generally 10”x10”— considerably larger than the smaller 60 amp AC disconnect. The conduit running to the 18-20KW gen set needs to be 1 1/4” and code requires the box to be 8x the 1 1/4” size = 10 inches. Some interpret code requiring only an 8”x8” box. In addition, generator wiring is considerably larger (more than 1” diameter) stiffer and more dangerous and is usually run inside rigid conduit when inside walls. (It is a violation of the electrical code to “fish” a large wire inside a wall behind drywall without being attached to the stud every 30”.) The wall cavity containing the AC wiring in our quad unit is located adjacent to the powder room. Drilling a large diameter hole in the 2x6 top plate (weakening it) for the large cable along with a second hole for an additional collection of wires (gen set control and battery charger circuit) and risking catastrophic damage to the insulated AC line set while fishing the several wires (not in conduit) through the narrow wall space full of insulation is not optimum and probably in violation of the Condo Declaration prohibiting the diminishing of the building’s structure and thermal character. (HOA guidelines specifically stated permission to drill holes in structure, e.g. the 2x6 too plate, would not be granted.) We chose a different route. Fishing high amperage wire in a wall cavity without conduit can be dangerous if anyone drills a hole in the wall. (For example if installing shelving)
When there is a long distance between the generator and the main service panel (gen set in back of home and service panel in front) a rather large SER (#2 aluminum or #3 copper) service entry cable is run thru the attic and down thru or along side walls. It is good practice (and required depending on interpretation of the building code) to run the cable thru conduit wherever it could be damaged-like when running thru or vertically down walls or in the attic where it could be stepped on.
It should be possible and much cheaper to run the wiring thru a rigid pvc conduit (hopefully painted to match siding) along the exterior of the wall, tightly next to a gutter downspout, and then into the attic, but interpretation of HOA rules by some prohibit this because it is deemed to change the appearance of the building—and contrary to my understanding of HOA guidelines, wiring does not enter adjacent to AC wiring. This based on recent instance where unit owner was required to redo AC wiring that had been run up exterior wall in conduit. (Kohler installs would require two conduits, where Generac can be wired using only one cable and conduit. One unit owner apparently received HOA approval for his Generac install running one conduit up exterior wall into soffit. Remarkably, later the HOA made the unit owner move the conduit 6 inches closer to the gutter downspout! It would have been cheaper and easier to move the downspout.) Running wire thru lower portion of wall has a better, less industrial appearance, especially for a Kohler install that would require two separate conduits. Beauty is in the eye of the beholder and opinions/approvals of HOA regarding “exterior appearance” can seem quite arbitrary—it pays to communicate clearly and in writing to avoid misunderstandings.
 |
| Generac install with conduit up exterior |
 |
| With conduit moved and painted |
 |
| Generac unit at duplex-gas line and electrical conduit up exterior wall approved prior to 2020 |
In our unit the tub had been removed and the space converted to a storage closet. With little lost space we were able to run the wires safely and according to code thru conduit placed in the corner of the closet up the wall, into the attic without drilling (weakening) any structural members and without potentially damaging the AC system plumbing or wiring and without disturbing the insulation in the wall. It also allows an install that essentially does not significantly alter the exterior appearance of the unit. A substantial amount of carpentry was required to support the conduit while maintaining access to the inspection service panel for the outside water faucet supply shutoff valve.
 |
| Access panel for water shutoff still accessible |
 |
| New 8x8” Inspection Opening with 10x10” cover |
 |
| With removable cover in place |
It is possible, if your Codes Enforcement Officer and electrician interpret the code as allowing the SER cable to run inside the wall without conduit as a branch circuit. It would be possible to cut access holes in the drywall every 30 inches to allow attachment in the middle of the 2x6 wall—2 1/4 inches away from drywall and sheathing. Making the access holes large enough to allow a person to guide the wire might minimize damage to insulation. The holes could be patched, and repainted. (One would have to be very careful not to damage other wiring and AC lines while cutting the drywall for the access holes. This is still not ideal as a large hole in the top plate would be drilled, reducing the cross section by 40%, weakening the structure-against HOA rules.) For units with a tub in this area, another option would be to run the wire in conduit above the tub inside a corner chase covered with drywall-preserving the thermal character and structure. Or, wiring could be run inside wall cavity then entering into a small section of exposed conduit to go around top plate into attic.
In any case, the best path for the wire is in conduit inside or outside the wall, with minimal disturbance to the insulation, entering the interior thru the vinyl soffit or the siding. Beauty is clearly “in the eye of beholder” but avoiding a 10 foot vertical run of large conduit up the exterior wall clearly “disturbs” the appearance of the home more than a properly mounted panel hidden behind the AC unit. This is particularly more important if installing a Kohler unit that requires TWO conduits.
Next issue regarding the electrical wiring is how the cable exits thru the wall or soffit and runs to the gen set. The conduit or “raceway” run from the wall to the gen set depends on the distance and the type of wire used. Common practice is to install a 10”x10”x4” junction box or disconnect on the wall. (As an alternative to two large LB’s or “pull boxes”. ) Inside the metal or PVC box, the SER cable is connected to a different wire type, allowing for smaller 1 1/4” conduit to the gen set. Mounting this junction box, like the mounting of an AC disconnect and frost free faucets, is often done incorrectly—resulting in the vinyl siding being crushed and distorted. (See pic below)
A junction box or disconnect is essentially a large electrical outlet—similar in function, but larger than the typical exterior duplex outlets.
Note that wiring enters the “box” from the rear thru a sealed “penetration” in the wall sheathing and siding. The outlet itself is mounted on a smooth panel “on top of” the siding in a way that the siding is not deformed, with the panel sealed to restrict moisture entering behind the panel. The panel is sealed to the siding and the outlet is sealed to the panel. The “penetration” is not visible. Generally this is best practice for all exterior electrical “outlets”,
 |
Interpretation of code varies from 6x or 8x the 1 1/4” conduit exiting the box.
|
Where there is OSB rigid substrate, one method would be to cut the siding out, attach the box to the substrate and using j-channel around the box, reinstall the siding. Absent major and a bit ugly surgery to the siding, the correct installation requires 1/2”-5/8” standoffs that position the box solidly to the rigid substrate without crushing the siding. If there is no rigid substrate (like where insulating foam boards were used without rigid substrate) then a 3/4” PVC panel board can be attached to the studs using 1”-1 1/8” standoffs with the junction box attached to the panel. (NEC 314.23 requires this method.) Attachment of the PVC Board requires precise carpentry to exactly match the mounting holes in the board with the studs and the circular cut outs in the siding. The ideal standoffs (sealed with generous amounts of silicone sealant) would have some “cushion” (using 1/8” neoprene/nitrile discs) to allow the panel and siding to expand and contract together with temperature changes. The PVC board and vinyl siding expand and contract at approximately the same amount with temperature. The board is sealed where it contacts the siding.
This panel and junction box could be mounted above or beside the AC disconnect. Mounting beside the AC box is most consistent with HOA rules as the new box would be lower and generally concealed behind the shadow of the AC unit. The white PVC panel should be painted to match the siding so that the panel does not materially change the appearance of the building.
The height of the hole/s in the wall for the cabling should be 20” above grade to minimize water entering with melting snow. (Same height as faucet and electrical outlets) They should be circular with little gap. Another reason not to pass cabling by enlarging the existing irregular shaped, poorly sealed hole used by the AC is that it is significantly less than 20 inches above grade—15 inches to be exact. (Because of the lack of rigid substrate, the AC installer chose to mount the disconnect to the stud rather than using a panel for support, running the input into the bottom of the disconnect, rather than the rear—this resulted in a much larger irregular shaped hole in the siding-a less than ideal practice and generally not optimizing the thermal character of the building. AC lines sets should be run inside a round tube sealed to the wall penetration and sealed inside the tube. The wiring should be run thru another round tube into a disconnect or j-box. Encouraging the AC and gen set wiring to be combined (with a goal of limiting “penetrations”) and run thru an irregular shaped hole is not consistent with optimizing the thermal and acoustic character of the structure. Encouraging the enlargement of this irregular shaped opening in flexible foam board to accommodate the gen set wiring makes a poor installation substantially worse.
The correct way to install the electrical box would be for wiring to enter into the box from the rear. Then the AC line set would go thru a separate more easily sealed round hole—ideally with a well designed housing to completely seal the opening and the line set.
Running large #3 electrical lines >2 1/2” diameter conduit plus a second 1 1/4 “ diameter thru a non rigid foam board wall with unsupported flexible vinyl siding would not meet the Uniform Building Code as it would be impossible to seal it to maintain the thermal integrity of the building—and it would not properly support the heavy wiring. It would be a violation of NEC 300.4(g).
Maintenance of the thermal character and integrity of the building structure is the requirement of the HOA Declarations—enlarging this existing hole used by the AC lines would be in violation of 10.1.2 of Wethersfield’s Declarations as well as the PA Condo Act and the National Electric Code. It would require an additional irregular shaped opening larger than that of precise round holes into the junction box. The waterproof junction box must be mounted on a rigid “board” mounted properly to studs and wiring should enter thru the rear of this box.)
In other words, maintaining the structural integrity of the building by NOT drilling a large hole in top plate; and minimizing disturbance of insulation in the wall cavity; protecting water line from cold temps by making round, tightly fitted and easily sealed penetrations, and routing wiring into a waterproof junction box, mounted properly, i.e. best maintaining the thermal and acoustical character of the building—all most consistent with HOA Declarations and Rules and Regulations. (See 10.1.2 and 7.1.7 a,b and the PA Act.)
The HOA “guidelines” still contain an ill advised clause of “no drilling thru siding” but any installation would require drilling or cutting siding. Running exterior conduit requires drilling holes to mount a junction box, and at least four clamps—all thru vinyl siding PLUS a hole thru the vinyl “siding” in the soffit. As mentioned, it is impossible and very unwise to push wire thru the siding without sawing or cutting the siding to enlarge the opening next to the AC power and line set opening.
The holes in the wall where the cable and wiring go thru the wall need to be carefully sealed, and the insulation with vapor barrier need to be repaired and properly reinstalled inside the wall cavity—this is especially important since the water line for the outside faucet runs horizontally inside the wall at almost the exact same elevation as the wiring path. An 8”x8” opening for a spring loaded 10” x10” plastic cover provides good access for this purpose. (See pic above) Another advantage of a rigid panel for mounting is the seam between the panel and the vinyl siding (if the panel is correctly positioned) is sealed with silicone providing double protection to prevent water or air protrusion into the building.
Here is a video explaining the wiring to the gen set and transfer switch.
The “logistics” of getting a whole house gen set is not simple. Planning takes a few days. Permissions take two weeks. Then preparation can take another few days. Typically, the installer will have a backlog of 4 weeks! (Getting building permit and preparation can overlap this time.) Finally, the gen set, pad, special wiring, misc supplies all have to be on hand. It is not unusual for the distribution supply chain to fail on its promises resulting in a key component to be late. (In our case installation was delayed by 2 weeks because the gen set distributor failed to coordinate—having the gen set but running out of concrete pads. The installer did not anticipate delays, waiting until the scheduled date of install to learn that the pad and wiring were not yet available.) From the decision to get a gen set installed to the completion of the install can take nearly two months!
In order to insure against further delays, instead of Kohler concrete pad, we will go with the QuikPad QT8200 composite pad that is available now. Still will be delayed. (Will fill 80% with 20 gal water for total weight of 200 pounds—more than the 190 pound 3” composite concrete pad from Kohler.)
The pad is a bit larger (56”x38”) but will fit the 60”x42” stone base area. This places the gen set: 27 in. from AC unit; 6 ft. from closest window; 5 ft. 10 in. from parallel combustible wall; 5 ft. from diagonal to corner of stone wall. All within a conservative interpretation of code.
22.4” front/ 26.4” mounting is one of several options with QwikPad threaded anchors.
The QwikPad is in place and filled per instructions to 3 in. Tipped and shaked during filling to dissolve polymer antifreeze into water. Estimated weight is now 210+ pounds. Ready for the gen set to be placed.
The QwikPad is made from LDPE with UV stabilization/resistance (carbon black) formulation. The load bearing portions are covered and not exposed to UV. There is five years of UV exposure history in Florida. Painting may increase life but some aging would be required before paint would likely adhere. Life of pad in PA is expected to exceed life of the genset.
