Looking for feedback - small additions, service calculations.

[bjp_ne_elec]

I'm interested in hearing from the gang on how they handle jobs involving small additions. Do each of you always run service calculations when working a small addition? I know it is the right thing to do, but when you're estimating a job, you'd have to be sure to include a service upgrade if the addition bumped up the service amperage. I go back and think about when I use to accompany a few different EC's around on estimates, and don't recall them asking pertinent questions to the owner, where they'd have the info to do the calculation. Most of the additions I'm rememering would have just been lighting and receptacles - no heating, etc. involved - so maybe that was why - but maybe he was doing some load calculations that I was unaware of. It's just something that I've been wondering - and I'm very interested in seeing what the feedback is.

Thanks

Brett

 

[jeff43222]

I generally don't bother with doing service calcs for this kind of thing unless we're talking about a kitchen remodel with major changes. In most cases, whether a service upgrade is warranted is often obvious without needing to do the math (e.g., 60A fused service). If someone already has 100A service, they are generally not using it anywhere near capacity. I still look for high-wattage stuff in the panel to get an idea what the load is, though.

 

[bphgravity]

Calculations for additions generally allows the use of the existing dwelling calculation. 99% of the time, an increase of service capacity is not required. In the event the building department wants evidence of this, this is one of the easier calculations.

 

[77401]

For small additions if there is room in the breaker panel I'll just add the circuits.
If the panel is full I can always sell an upgrade by just showing the HO the panel is full.

 

[mtnelectrical]

I think it will on how big your addition if it is only one more room then you would only need 4 or 5 recp and a light fix but if it they have central air otherwise you would probably need another circuit for the window a/c, adding or remodeling a kitchen well defenitive would need a services upgrade of course depending on the service they have. if they only have 60a I would sell them a 150a for future needs and explain then that for 400 or 500 more they would get "the works" a 200 amps service. This you have to tell the GC and owner before anything otherwise if they call you because main breaker is tripping you would be blamed for it

 

[satcom]

Our utility wants a calc sheet, even if there is no load increase, so we do them for all service upgrades.

 

[haskindm]

Most new services are installed with a great deal of additional ampacity. In this area a 200-amp service is about the smallest service installed. If a load calculation was performed, many of these homes would require only a 100 or 150 amp service. It is often possible to just look at the existing panel, and perhaps the heating load and determine if the load that you are adding is in danger of overloading the panel. Most services have more than enough extra capacity to add a circuit or two of lights and receptacles without danger of overload. On an older house with a small service, it may be neccesary to perform a quick calculation. If additional heating or cooling is being added it may be necesary to look at the service more carefully. Each job will be different...
Most of my students are amazed when I teach them service calculations. They have been taught on the job that every house needs at least a 200-amp service. When they do the calculations they are surprised at how low the "minimum requirement" is. Of course I always encourage them to install a service that allows for future expansion.