Appliances on a UPS?

[Lost_in_the_HTTP]

So, there's the stove/range thread.

The one I picked has more electronics (timers, temps controls, etc.) in it than the one I'm replacing. I get power surges and glitches. I've had power drop out and come back on four or five times in a couple of minutes during storms. I have a large standby generator, but that takes up to a minute to restore power after an outage.

My current gas range uses less than 5 watts normally, but burns about 100 watts all while the oven is on due to some kind of glow coil ignition and safety thing. Not sure if the new one will, but I'll check it with a Kill A Watt.

I have a CyberPower 400 Watt UPS that I'm thinking of using for it to insulate it from those surges and glitches.

That should be fine, but I'm also wondering about plugging the refrigerator into it. Kill A Watt says that only uses 80-90 watts when running, but can go to around 400 for a few minutes while in defrost.

I should be OK as far as wattage, or I can get a slightly bigger UPS. But the main questions I guess are:

>> Will the refrigerator motor and compressor be a problem for the UPS that is normally intended for electronics.

>> Will the simulated sine wave from the UPS damage the refrigerator motor and or compressor?


Side issue is some things I've heard from generator people about the RMS from UPSs causing issues for the generators. Any comments there?

 

[Paperdoc]

For your fridge, one big factor to consider is the surge of start-up current for the motor every time it turns on. It's a modest-sized motor, but it is starting under load, so that surge current can be several times the running load. And you can NOT limit that power. IF the power supply to the fridge at start-up cannot provide what it needs, that is a real strain on the motor every time it tries to start. I suggest you consult a professional electrician about this. For the stove, virtually all its electrical load is for the electronics and a resistive heater coil, so that's not a surge current issue.

A BIG caution about max total load rating versus connected devices. Most UPS units have a spec for both max WATTS load and max VA load. We all know that Watts = Volts x Amps, BUT if you check UPS ratings the VA rating always is a LOT less than the Watts rating. I don't understand that, but I believe it is related to inductive loads like any motor. So your fridge may be a reason to check this detail carefully.

I do not know anything about impact of simulated sine waves on AC motors.

You do not appear to have considered duration of power outage. A UPS commonly is rated for its max Watts output. How long it can maintain that power supply to the connected load is shown often in minutes, sometimes not at all. As you might expect, the minutes it can keep you going depends on the load connected, and on the size of the UPS battery. SOME good UPS makers will even show you the time the unit can continue to supply power for several different connected loads. Just a caution that common UPS units rated for 400 Watts max load of electronics often can sustain that for 5 minutes or so - enough to allow you to shut down your computer cleanly and quickly, but NOT to keep you running though a power failure. So, is your ONLY problem very brief power sags, or do you have failures of 15 minutes to hours?

I'm guessing your query about impact on your generator is because you were considering connecting both devices. I gather the generator is permanently connected in the power lines somewhere and starts itself up when that power line fails. I assume also that it is connected to supply power to most of your house. So if you add a UPS, it would be connected to those common house lines, BUT deliver backup power only to the stove and fridge. So I am not sure what you mean when you say the "RMS" of the UPS can impact the generator.

 

[Lost_in_the_HTTP]

Just a caution that common UPS units rated for 400 Watts max load of electronics often can sustain that for 5 minutes or so - enough to allow you to shut down your computer cleanly and quickly, but NOT to keep you running though a power failure. So, is your ONLY problem very brief power sags, or do you have failures of 15 minutes to hours?

As long as the generator kicks in like it's supposed to, any outage would/should be a minute or less. The generator senses outages of 10-15 seconds before it activates. Then it takes a few seconds to come up to speed before it triggers the transfer switch. It's the potential for multiple outages of 3 or 4 seconds within a few minutes that bothers me with electronics in an $800 appliance and I'd be looking for the UPS to bridge those gaps.

I don't really need it on the refrigerator since there are no electronics in it.

I don't understand the UPS to generator issue either.

 

[Paperdoc]

On that last item, my only SPECULATION (not knowledge) is IF the scheme has the generator DOWNSTREAM from the UPS, so the generator receives UPS output and must detect power failure from that. IF that UPS output is badly simulated sine wave, maybe the failure detection system could have trouble. But I don't anticipate a system organized that way.

 

[bjlockie]

My parents have a Generac.
It is like a whole house UPS that runs off the natural gas line if the electricity fails.

 

[drnickriviera]

I do not know anything about impact of simulated sine waves on AC motors.

I've hear that modified sine wave will make motors use more power, never tested it though. Edit, derp, mind saw modified sine wave, not simulated. Not sure if there would be any impact

I've tried starting a mini fridge on a 300w sine wave inverter, think it was rated 600w surge. Course they could be lying on those numbers. Inverter would spaz out on each startup. If you had money to burn, you could install a soft starter. I use one on my rv ac and it dropped the inrush dramatically.