Unstable grid power - Need help please

pjudepjude Registered Users Posts: 9
Hi,

I'm currently in Haiti. Our environment consist of a magnum inverter, batteries, outback charge controller and generator. We would like to connect to the grid. But the grid power is very unstable (the power is always up/down). We afraid if we could not find a way to stabilize the power our equipments will be damaged. What equipments do we need to buy to place in front of the main panel to address this problem? The main breaker in the panel is 100 watts.

Thanks,
Jude

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Unstable grid power - Need help please

    A few questions:

    Can you run everything you want from the existing inverter set-up?
    Or is the desire to add grid power due to an increased load demand?
    In other words, are you looking to the grid for supplemental charging of the batteries when the solar doesn't perform or do you need more power than the existing system can supply?

    The grid instability: is it just a problem with it going off frequently, or is the power often low/high Voltage or out of frequency?

    If you could provide details as to the models of the existing equipment that would be helpful too.

    It would not be difficult to utilize the grid, even if unstable, by feeding it to the inverter's AC in (if so equipped). Whenever the grid was available, the loads would be shifted to that and the batteries would be charged as well. When the grid goes down, the batteries would take over. This is providing the inverter can handle all the loads you need to run and the only grid problem is the on/off one.

    If the grid power is "out of spec" you could use it to run a stand-alone battery charger to feed the batteries and continue to operate the loads from the inverter. That way the grid becomes supplemental charging power whenever available. It may not be the best charging power, especially if the grid Voltage is habitually low or high. This also won't help if you need more power for additional loads.

    Stabilizing an undependable grid is not something the end user can do. You can only make use of the power when available, storing it up in battery capacity for when it is not.
  • RCinFLARCinFLA Solar Expert Posts: 1,280 ✭✭✭
    Re: Unstable grid power - Need help please

    If the grid is so unstable that the inverter continually disconnects and reconnects you might be better off getting a large current switching power supply battery charger that can accommodate the grid fluxuations and run the inverter from batteries all the time.
  • pjudepjude Registered Users Posts: 9
    Re: Unstable grid power - Need help please

    Hi,

    Thanks for the prompt response. I have a Magnum MS-4024 inverter installed with a MNE-240 E-panel. I'm thinking the environment would look like so:

    Grid---->Meter---->Stabilizer---->Mainpanel (100 watt breaker)

    I would like to use the use the Grid to charge the batteries only. It I could use the grid to power few lights that would be great. But my main priority is to charge the batteries.

    The power coming from the grid sometimes low and other times high. But it seems to be high more often.

    My system is currently as followed:

    Main panel ---> (40 AMP double breaker connects) --->Sub panel ---> epanel ---> Inverter ---> Batteries

    In the sub panel I have the breakers that power the house appliances.


    now since grid power is "out of spec" and I'm using a 24volt environment (12 batteries), What type/model of stand-alone battery charger would you recommend that I purchased?

    Thanks,
    --Jude
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Unstable grid power - Need help please

    This is not a good situation.
    There really isn't any easy, inexpensive way to stabilize fluctuating grid Voltage. The "it seems to be high more often" part is the worst. As you suspect, that's what fries equipment. When the Voltage goes low you can often just ignore it; whatever won't work on it will shut down. Again it depends on the actual device and the amount of Voltage fluctuation. Some inverters, like the Outback series, can be programmed to drop AC IN if it is too low or too high. Magnum does not have that feature (from what I can see).

    So, do you have any Voltage range on this wavering grid power? Most AC devices will stand +/- 10% from their nominal rating (as in something meant to run on 120 VAC will work from 108 VAC to 132 VAC, although possibly with a shortened lifespan).

    RCinFLA's idea of a switching power supply to charge batteries (thus "filtering" the irregular Voltage through the inverter set-up) is a good one, although even that would have to be protected against too high a Voltage spike.

    There are variable transformers available which can take Voltage up or down, but they do not automatically adjust.
  • BB.BB. Super Moderators, Administrators Posts: 29,518 admin
    Re: Unstable grid power - Need help please

    There are ferroresonant transformers and even UPS's that have variable tap transformers to stabilize the output voltage... In theory, they are probably more efficient (90% or better?) than the simple AC->DC->AC converter/inverter setups (80% efficient or so, down towards 50% if you have a power outage and need to discharge/recharge batteries).

    Usually, you look at your critical equipment and only run a UPS/Inverter system to those pieces of equipment (power glitch that can lose data or cause process problems).

    You would not stabilize the (old fashion TV, Stereo, your kitchen mixer, etc.)... It could cost you 10-40% more in electrical costs to "stabilize" your power--so you need to pick the few devices that need it.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Unstable grid power - Need help please

    Yes, there are whole-house surge protectors like these:

    SquareD: http://www.homedepot.ca/product/surgebreaker-plus-whole-house-surge-protector/901424
    Leviton: http://www.smarthome.com/4860/Leviton-51120-1-Whole-House-Surge-Suppressor-Surge-Protector/p.aspx

    No, they will not do anything for habitually high Voltage; just sudden spikes.

    How effective are they? Better than nothing, but not a 100% certain solution either. I get a bit miffed about TV shows promoting these things with the hosts claiming it will protect your whole house against lightning strikes, et cetera. Can't be done. It may mitigate the worst effects in some instances, but nothing can cover every potential circumstance with absolute guaranteed prevention of damage.
  • pjudepjude Registered Users Posts: 9
    Re: Unstable grid power - Need help please

    Hi,

    I have another question on the same subject. Can I put a surge protector/suppressor in front of the main panel? I know that would not stabilize the voltage. At least it would provide me with a level protection to ground the voltage surge. Please educate me what brand/model of surge protector/suppressor would you recommend that I purchase?

    I see two different models:

    - TE/1C40 surge protector
    - Surge Guard 30A Hardwire - Model 34520

    Thanks,
    --Pjude
  • pjudepjude Registered Users Posts: 9
    Re: Unstable grid power - Need help please

    Hi,

    I'm sorry I didn't mean to ask the same question again. I see these models:

    - TE/1C40 surge protector
    - Surge Guard 30/50A Hardwire - Model 34520 / 34560
    ======================================
    Automatic reset on power restoration.
    Automatically shuts off the power when the following is present:
    -- Open neutral
    -- Low (<102V) and High (>132V) Voltage
    Caution indicator light indicates:
    Miswired pedestal
    -- Reverse polarity
    -- Elevated ground voltage
    -- 2 minute 15 second reset delay protects A/C compressor.
    -- 1050 Joules of power surge protection.

    Thanks,
    --Pjude
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Unstable grid power - Need help please

    That sounds like something much more suitable to protect your system than a mere surge suppressor. The high and low disconnect function is similar to what can be programmed into an Outback inverter. But I have no experience with such a device so can't say if it is good/worth the investment. Perhaps someone else here has used one?
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