Load Shed Without Generator

[Ebixler]

To put all the useless comments like “why don’t you just upgrade the service” to rest I’ll simply say that this is for a elderly family member and the situation is complicated by family living with her etc.
In a nutshell service upgrade is needed. Effectively a 2nd efficiency unit added to dwelling, 100 amp service not cutting it with two ranges, dryers etc.
Being almost 90 a heat pump wants to be added to cool one room. My feeling is that it’s so far over the main will trip with or without regardless so not changing a whole lot over the window unit that it’s going to replace. Cooling is the primary function desired. Obviously if I ever had someone I didn’t care about ask me to work on anything close to this I would RUN. Unfortunately I feel compelled to try to find a solution. Due to non permitted construction a service upgrade is not feasible as it will open a can of worms.
Three questions:
1) Thoughts on how much a heat pump to cool approximately 450 sq ft. room will add to power consumption vs a large window unit during cooling season (Maine where temperatures rarely exceed mid 80’s)
2) Is there any way to use a generator load shed to drop circuits once amperage on a service exceeds a certain threshold?
3) Any other solutions anyone can dial up I certainly welcome
Thanks in advance for your help. I hate to even get involved here but the lady in question is possibly the kindest woman I have encountered and in a bad spot due to other family living with her so if I can find a way to help her be comfortable in her old age without burning her house to the ground I would like to. Limited experience with load shed but seems it needs the generator to operate.

 

[readydave8]

Would minisplit be more efficient than existing AC and thus avoid the issue?

Otherwise I'd look into Generac wireless load shed module, I don't think it communicates w genny but senses frequency and times out independently. But I may be wrong

 

[wwhitney]

Otherwise I'd look into Generac wireless load shed module, I don't think it communicates w genny but senses frequency and times out independently.

That particular module makes the decision to drop out based on AC frequency. And so in that sense it does communicate with the generator; when the generator is overtaxed its output frequency will slip, causing the module to drop out the load. As such, that load shed module will not ever trigger while on grid, since the grid frequency is fixed.

Cheers, Wayne

 

[hillbilly1]

A current relay(s) driving a contactor may be your solution, wire the contacts to lockout another large load if both are called for at the same time, prioritizing one load over another.

 

[hillbilly1]

These are rated a little higher, probably need a time delay relay to prevent short cycling.

 

[Electromatic]

I was thinking some kind of current sensor/relay/contactor setup as well. I wonder if any of the home power monitoring kits have outputs that could trigger contactor(s). They might be more customizable/programmable for deciding when to kill what loads.

 

[winnie]

1) Find a good HVAC person who really understands efficient comfort control in the local area. Some places (Arizona) need cooling. But lots of other places really need dehumidification without much cooling. A 'high efficiency' minisplit that is oversized for a room in a temperate climate will leave it at a perfect temperature with high humidity, or chilly with good humidity.

2) Load shedding is certainly a possibility, but I think you will end up with an expensive system or a 'jerry rigged' system that you will be constantly asked to tweak. I agree with hillbilly1, using current sensing and contactors. You might be able to build something using 'home assistant', an off the shelf energy monitor, and contactors to drop out circuits.

-Jon

 

[synchro]

Are the ranges or dryers electric? If so, is gas available as an alternative?

 

[gadfly56]

I think the mini-split is the go-to solution.

 

[winnie]

In the realm of KISS, I'd suggest improving appliance efficiency and reducing consumption rather than building/buying a fancy load shed system.

I'd particularly suggest replacing the existing window AC with a higher efficiency window AC.

I've been very happy with the 8000 BTU version of this one: https://www.amazon.com/Midea-Inverter-Conditioner-Flexibility-Installation/dp/B0867GMW9X

This is an inverter type window shaker, so at reduced cooling load the compressor dials back to low power, rather than cycling on and off at full power. I found that it dehumidified my room very well without 'over cooling', and it sipped power at low load.

Is the hot water electric? Consider replacing the water heater with a heat pump water heater. This is newish technology so I don't have a good feel for the reliability issues, and heat pump dryers take heat from the surrounding air, and so require makeup heat from something.

Same for the clothes dryer. These can save significant electricity consumption, but I have no feel for the reliability. They apparently require regular lint removal from a heat pump filter.

-Jon

 

[LarryFine]

I just saw a This Old House episode that included installation of a stand-alone heat pump for existing water heaters.

 

[BarryO]

Coincidentally, I recently had a mini-split installed in my garage, which is about the same square footage as listed here (it both heats and cools). I got a 15,000 BTU unit because it gets hotter here in the summer than the mid-80's, and even though the garage door is r-17.5, it's still a garage door. You could probably get away with a 12,000 BTU (maybe even a 9K). These things don't use that much power; a 12K 23 SEER unit has a FLA of about 6-7 amps.

 

[James L]

You could probably get away with a 12,000 BTU (maybe even a 9K). These things don't use that much power; a 12K 23 SEER unit has a FLA of about 6-7 amps.

Most assuredly could get it done with 12k
Probably could get away with 9k

I would install a DC inverter unit.
They use phase-shift speed control

The good thing there is it doesn't cycle on and off, it slows down. Saves compressor and uses less power

 

[Ebixler]

Wow
Just circled back to this and haven’t begun reading but I felt overwhelmed by the amount of response and everyone’s willingness to do so. With a pessimist view on people as a whole (decade ownership of a company with double digit amount of techs doing service work/small jobs coming from the internet will have this effect) it is nice to see a example that contradicts. I’ll circle the wagons tonight and moving forward will make a effort to reciprocate. My sincere gratitude to all who took the time to help.

 

[Ebixler]

Would minisplit be more efficient than existing AC and thus avoid the issue?

Otherwise I'd look into Generac wireless load shed module, I don't think it communicates w genny but senses frequency and times out independently. But I may be wrong

My intuition without any research to substantiate is that the difference can’t be such that it makes a significant difference given one ignores the fact that the service is overloaded anyway. I will say that I can’t remember ever seeing a scenario where someone was routinely popping their main breaker. I am not ignoring the fact that it’s possible but in this case it’s 3 adults total in the house. One of them is 90 and does one load of laundry per week which eliminates laundry at the same time for all intensive purposes. Any meals requiring a oven are eaten together which checks that box. They are family and are the ones who have made the decision to not upgrade, I’m inclined to warn on the danger and tell them to communicate whenever using the oven or dryer and wash my hands…….. I haven’t gotten to the options suggested and look forward to learning about some things that I’m ignorant about but curious on thoughts about the above? The NEC should probably adopt it for load calcs next code change

 

[Hv&Lv]

Something like a generator load shed module won’t be an option without a generator.
They sense frequency to operate and you won’t pull the grid frequency down by loading.

 

[hillbilly1]

My intuition without any research to substantiate is that the difference can’t be such that it makes a significant difference given one ignores the fact that the service is overloaded anyway. I will say that I can’t remember ever seeing a scenario where someone was routinely popping their main breaker. I am not ignoring the fact that it’s possible but in this case it’s 3 adults total in the house. One of them is 90 and does one load of laundry per week which eliminates laundry at the same time for all intensive purposes. Any meals requiring a oven are eaten together which checks that box. They are family and are the ones who have made the decision to not upgrade, I’m inclined to warn on the danger and tell them to communicate whenever using the oven or dryer and wash my hands…….. I haven’t gotten to the options suggested and look forward to learning about some things that I’m ignorant about but curious on thoughts about the above? The NEC should probably adopt it for load calcs next code change

I did a service change many years ago where they only had a 100 amp service that served a farm house and a mechanic’s shop. His elderly mother would holler out the door “Jerell, don’t be welding, I’m starting supper” LOL!

 

[kwired]

Something like a generator load shed module won’t be an option without a generator.
They sense frequency to operate and you won’t pull the grid frequency down by loading.

I agree, unless you maybe have many megawatt service and the load to go with it, (but that kind of makes you a large industrial customer and not a SFD customer class) you are not going to pull down the grid frequency to make typical load shed modules function.

 

[Barbqranch]

If an electric water heater, they may be able to run with it switched to 120 volts (if their usage pattern permits). I did that to ours when I had to temporarily move it for a month. Never ran out of hot water, even though it took 4 times as long to heat.

 

[readydave8]

Yes I was mistaken about Generac module since it senses frequency

I don't remember exactly how Kohler module works but remember running wires thru CT, if I senses current to shed loads maybe could be adapted?

I don't want to research since it's hard, and a subsequent poster already knows the answer