Trying to wrap my head around a whole house generator

The #1 community for Gun Owners in Indiana

Member Benefits:

  • Fewer Ads!
  • Discuss all aspects of firearm ownership
  • Discuss anti-gun legislation
  • Buy, sell, and trade in the classified section
  • Chat with Local gun shops, ranges, trainers & other businesses
  • Discover free outdoor shooting areas
  • View up to date on firearm-related events
  • Share photos & video with other members
  • ...and so much more!
  • Kaneda13

    Adeptus Mechanicus
    Rating - 100%
    13   0   0
    Aug 13, 2013
    311
    18
    Indianapolis
    So, for quite a while I have wanted to install a whole house generator in my garage. I've got access to my chimney stack, so I can just vent it there (feel better with it inside than out). Anyway, I'm trying to get an idea of what size I would need. I'm an auto mechanic my trade, so i'm most likely looking at cobbling something together, and paying someone to wire it into my main breaker box (also in the garage, very near where I want it). Anyway, on to my question: I'm having trouble picking out what size generator I would need. I've been tracking my IPL kWh readings over the last year, and My peak was 1500 kWh in a month, with an average of 920 over the last year. So figuring my highest over the last year at 1500 kWh for the month of December, so my average would be 1600 kWh / 30 days * 24 hours = and average of 2.2 kWh. I understand this is an average, but I'm just trying to figure all this out in my head. Anyone with an understanding point me in the right direction if I'm off?
     

    Leo

    Grandmaster
    Rating - 100%
    30   0   0
    Mar 3, 2011
    9,733
    113
    Lafayette, IN
    I don't think you want to use your chimney. I would not vent it anywhere that fumes can mitigate back into the house. Chimneys work best when there is plenty of heat and volume to keep the fumes rising. Whatever size you think you need, buy the next size bigger. A big block engine at 50% load is better than a small engine at 100% load.
     
    Last edited:

    Butch627

    Master
    Rating - 100%
    24   0   0
    Jan 3, 2012
    1,698
    83
    NWI
    As an auto mechanic do you really think the heat, fumes, gasoline, etc of a engine running for hours or days at a time in your garage is a good idea?

    I would size the generator by my peak loads when operating it. What do you want powered up at any given time? work off of that load and add in power necessary for starting motors
     

    IndyDave1776

    Grandmaster
    Emeritus
    Rating - 100%
    12   0   0
    Jan 12, 2012
    27,286
    113
    If you feel that the garage is the place you want your generator, I would recommend that you remove either the muffler or the complete exhaust system, whichever is more convenient, and have a plate or plates if you have a twin cylinder made with a hole/holes in the center to which you weld new pipe and run that pipe through the wall like a dryer vent with a muffler installed somewhere in the assembly, either inside or outside. Several years ago, while outfitting a van as a service truck, I similarly had new exhaust pipes fabricated to bolt onto the heads of the welder and air compressor which I ran partway through a piece of flex pipe to accommodate vibration, and then out the floor into a side-inlet ag tractor type muffler. It worked beautifully with no fumes inside the van.
     

    Kaneda13

    Adeptus Mechanicus
    Rating - 100%
    13   0   0
    Aug 13, 2013
    311
    18
    Indianapolis
    Ok, some clarifications... By "my chimney" I should have referred to it as my furnace and water heater exhaust stack, not a chimney from a fireplace , that one is separate. As for getting the "next biggest size", that's what I'm trying to figure out. I was thinking that if my average is 2.2 at the highest time of the year, would a 3K get me most of the time. I'm not looking for something that will run everything in the house as if nothing had happened, just something we can still have water (well head), lights, some comforts, etc (I'm fine with the A/C and heat pump being off the circuit, we can use the whole house fan in the summer, and the fireplace in winter if needed). As a mechanic who regularly has cars running in the shop while hooked to proper ventilation, no, I don't have a problem with that. If I thought the fumes where building up for some reason, I could always just open the garage door (opens to the rear of the house if i needed to, or even leave it open). I'm not looking for something that is self starting even, I'd be fine going out to start it manually, or when I got home (I have enough friends and family nearby that I could have start it if I was away). If i wanted to cut through the outer brick wall, I would vent it right outside, but the the exhaust stack already in there, I think it would be easy enough just to tap into that.
     

    Cameramonkey

    www.thechosen.tv
    Staff member
    Moderator
    Site Supporter
    Rating - 100%
    35   0   0
    May 12, 2013
    31,682
    77
    Camby area
    [STRIKE]First, if you can do a sealed exhaust pipe all the way up the chimney, (using the space as a pathway, but still containing the gasses until they reach open air) I think that would suffice the fumes concern. I think folks were thinking you were just going to basically point the muffler exhaust at the flue opening and let the heat rise. I also like the idea of the welded plates. Only drawback is new fabrication when that one blows up. (everything breaks after all.)[/STRIKE]

    Edit: Disregard. I just noticed the clarification. That would take too much exhaust pipe volume away from your appliances. I thought you were using an unused chimney.

    Second to make a large dent in your household load, swap out all the incandescent bulbs to LED. You can greatly reduce the load that way. For example:

    40 bulbs in my house for an average wattage of 50 watts each= 2,000watts
    40 bulbs swapped out for equivalent LEDs @9* watts each (50w equiv)=360 watts (*I aimed high, could be as low as 280w in this example)

    That upgrade alone could save significant amounts on your utility bill as well.

    I know when I switched I saw big differences. ESPECIALLY at Christmas. Used to run C9 bulbs. Had to dedicate a 15a circuit to them to keep from blowing breakers because they would run at 12a. I was spending 20-50 bucks a season to run them. Now I run LEDs and pull less than 5a.

    I now am nearly 100% LED. I only have 2 traditional bulbs in the house; the one in the oven, and the one 20w in my garage to put enough load on the motion sensor circuit to keep the rest of the LEDs from glowing when they should be off due to the trickle of current that still leaks to the fixtures.

    It may not significantly reduce your generator size, but it should reduce the worry of "should I not turn too many lights on for fear of overloading the genny?
     

    churchmouse

    I still care....Really
    Emeritus
    Rating - 100%
    187   0   0
    Dec 7, 2011
    191,809
    152
    Speedway area
    Never tag into the stack you refer to. It is sizes for the appliances and not the addition of a forced exhaust from a mechanical device.
    Just do not use it this way. It is against code and for good reason.

    I have looked at doing this but I have plans to isolate the genny with a containment that draws combustion air from the outside and exhausts the same way. Vents for cooling the equipment would be required as well.

    This can be done pretty easily. Just do not tap into the appliance vents. Nothing good will come from that.
     

    churchmouse

    I still care....Really
    Emeritus
    Rating - 100%
    187   0   0
    Dec 7, 2011
    191,809
    152
    Speedway area
    Ok, If i wanted to cut through the outer brick wall, I would vent it right outside, but the the exhaust stack already in there, I think it would be easy enough just to tap into that.

    Nope. Bad idea. Just a bad idea.

    I have been in the HVAC trades most all of my life. Seen a lot of things in that time. This is a 1st for this but again, Bad.
     

    ghitch75

    livin' in the sticks
    Site Supporter
    Rating - 100%
    117   0   0
    Dec 21, 2009
    13,501
    83
    Greene County
    if you do put it in the garage make sure you bring in the intake air from the outside.....you will suck all the oxygen out of the garage......then if it is a air cooled unit you will have to get it fresh air to cool......

    i wouldn't put it in there as to the exhaust could leak and leach into your house.........you would be better off building you a small in closer outside to put it in.....as far as kw go for no more than you will be running a 5500 to 6500watt would do you fine....
     

    Cameramonkey

    www.thechosen.tv
    Staff member
    Moderator
    Site Supporter
    Rating - 100%
    35   0   0
    May 12, 2013
    31,682
    77
    Camby area
    if you do put it in the garage make sure you bring in the intake air from the outside.....you will suck all the oxygen out of the garage......then if it is a air cooled unit you will have to get it fresh air to cool......

    i wouldn't put it in there as to the exhaust could leak and leach into your house.........you would be better off building you a small in closer outside to put it in.....as far as kw go for no more than you will be running a 5500 to 6500watt would do you fine....


    This is is a good idea. And 6" of blue foam board insulation does wonders to muffle the sound. Not exactly the same, but we used to have a compressor room at my office that was right next to a classroom. When the industrial compressor will turn on you could barely hear it inside the classroom. Instead of sounding like a large industrial air compressor it sounded like a furnace.

    And don't worry about totally killing the sound for secrecy. When your house is the only house on the block still with lights on during an outage, whether they can hear a generator or not, it will be obvious you have one.
     

    churchmouse

    I still care....Really
    Emeritus
    Rating - 100%
    187   0   0
    Dec 7, 2011
    191,809
    152
    Speedway area
    And don't worry about totally killing the sound for secrecy. When your house is the only house on the block still with lights on during an outage, whether they can hear a generator or not, it will be obvious you have one.


    We have a black out policy. For obvious reasons.
    Cover the windows and go full grey.
     

    Leo

    Grandmaster
    Rating - 100%
    30   0   0
    Mar 3, 2011
    9,733
    113
    Lafayette, IN
    Church mouse made a good point about cooling air. I was at an outdoor wedding reception and the band was using a generator to run the PA. Because of the noise, they built a little shed around it with hay bales, it worked ok for a while. Shortly into the first set let's just say the band went from smokin' hot to flamin'.
     

    IndyDave1776

    Grandmaster
    Emeritus
    Rating - 100%
    12   0   0
    Jan 12, 2012
    27,286
    113
    Church mouse made a good point about cooling air. I was at an outdoor wedding reception and the band was using a generator to run the PA. Because of the noise, they built a little shed around it with hay bales, it worked ok for a while. Shortly into the first set let's just say the band went from smokin' hot to flamin'.

    All true, but a garage is a long way from stacking hay adjacent to the genset. More space, less flammable construction, and presumably some air circulation all go a long way.
     

    SSGSAD

    Grandmaster
    Rating - 100%
    14   0   0
    Dec 22, 2009
    12,404
    48
    Town of 900 miles
    I don't think you want to use your chimney. I would not vent it anywhere that fumes can mitigate back into the house. Chimneys work best when there is plenty of heat and volume to keep the fumes rising. Whatever size you think you need, buy the next size bigger. A big block engine at 50% load is better than a small engine at 100% load.


    I may be talking apples, and oranges, but here goes .....


    I was taught in the Mil., that a generator work best, at 70-80% output .....

    I don't know if that is true of the "civilian" ones .....

    Ex., 7000 watt, should be running about 4900-5600 watts .....
     

    churchmouse

    I still care....Really
    Emeritus
    Rating - 100%
    187   0   0
    Dec 7, 2011
    191,809
    152
    Speedway area
    I may be talking apples, and oranges, but here goes .....


    I was taught in the Mil., that a generator work best, at 70-80% output .....

    I don't know if that is true of the "civilian" ones .....

    Ex., 7000 watt, should be running about 4900-5600 watts .....

    70 to 75% of max load rating. If you push past that it will not end well for the genny. Just like a breaker they are rated at max inrush or start up load. A 12A sweeper might spike at 15/17 Amps momentarily until the stater gets up to speed and off the start winding. Then it settles in at its rated amp draw which a 20 A circuit will carry easily.
    Just because it says 5K watts on the side does not mean (and it won't) it will pull 5K full bore.
     

    Cameramonkey

    www.thechosen.tv
    Staff member
    Moderator
    Site Supporter
    Rating - 100%
    35   0   0
    May 12, 2013
    31,682
    77
    Camby area
    I may be talking apples, and oranges, but here goes .....


    I was taught in the Mil., that a generator work best, at 70-80% output .....

    I don't know if that is true of the "civilian" ones .....

    Ex., 7000 watt, should be running about 4900-5600 watts .....

    Not sure if you are correct, but I know power inverters act that way; You will get more efficient the more load you put on the circuit. The lower the load, the higher % of DC electricity is expelled as waste heat instead of AC current. (I learned way too much about this trying one of those "you cant get there from here" projects.)

    Efficiency example:

    Country Selection Page
     

    Tactically Fat

    Grandmaster
    Site Supporter
    Rating - 100%
    22   0   0
    Oct 8, 2014
    8,270
    113
    Indiana
    In all honesty, a 12-15 kw Generac isn't "that expensive"... Like $3500k or so.

    Then there's installation and the associated parts.

    15kw is plenty for a ~1500 sq ft home.

    My brother-in-law's 20kw Generac retails for like $4500. It's plenty big for his huge house.
     

    Kaneda13

    Adeptus Mechanicus
    Rating - 100%
    13   0   0
    Aug 13, 2013
    311
    18
    Indianapolis
    OK, lots of great info here guys, thanks! So, I'm looking at moving it out behind my barn (just want it out of sight, that's one of the reasons I was thinking of putting in the garage). Now, my next question would be, does anyone know how deep you have to put electrical lines in Indiana? I've got a septic field out there, so I'm concerned about how deep I would have to put the conduit and line. Also, I'm not sure how the tie in to the electrical box works (12V in a car I'm good with, anything other than ceiling fans and light fixtures I leave to the professional), could it be wired in so that the A/C Heat pump isn't on the generator? I'm just thinking that if I can get a smaller unit, then I won't have to have as large of an engine and maybe get a longer running time on a tank of fuel.
     
    Top Bottom