Another XW Question

sub3marathonman

I am slowly learning about the XW inverter, and now I've got another question.

To supply power to the subpanel, I can either supply it from "Grid Passthrough" on the XW6048, where it then goes from the grid to the inverter, then back to the main panel, and then to the subpanel, OR supply it from "AC1 out" where it goes from the inverter out on "AC1 out" to the subpanel.

Is there is a difference in efficiency between these two options? Is the "Grid Passthrough" strictly using the grid power, without any losses, while the "AC1 out" is using battery power to power the inverter which then powers the subpanel? Is the electricity from the inverter "cleaner" than the regular grid power?

RCinFLA

Re: Another XW Question

Don't understand your comment about "from "Grid Passthrough" on the XW6048, where it then goes from the grid to the inverter, then back to the main panel,"

The sub-panel should be fed from 'AC out'. There is no AC1 out.

I think the part that is a little hard for some folks to understand is the inverter output is running in parallel with the grid. It's not an 'either or' situation. There is a relay that disconnects the AC out from AC1 grid input when grid goes down. The inverter just picks up the AC out load when AC1 relay opens. The inverter will shut down and AC1 (or AC2) grid relay opens if excessive AC out load is detected.

I did a search on "Grid Passthough" on the user and installation manual and turned up nothing. Guess you refer to 'Bypass mode' which I believe is just inverter inactive. You will save the 25 watts, or so, that the inverter consumes when active, but you lose the 'UPS' function if the grid goes down. If inverter is inactive it also means there will be no battery charging. There is 'passthru' on page 36 of op manual which refers to bypass mode which is inactive inverter.

There is a 'Bypass breaker' shown on the distribution panel. Having this bypass breaker is a good idea if the inverter ever needs to be serviced. It allows the XW6048 to be taken out of the power path to auxilary panel.

There is no separate charger. The inverter should be called inverter/charger. The difference between outputtng and inputting is just a small variation in the PWM cycling on the primary side of inverter/charger transformer. If its output node is slightly below grid voltage it will push power to battery. If its output is slightly above grid voltage it will push power to grid.

This parallel function has some neat capabilities.

For solar or wind supplimenting, there is a charge controller to the batteries. This charge controller is set so its voltage is slightly above the charge voltage set by XW6048. As the battery node is raised above the XW6048 charge set point the XW6048 will suck off excess trying to maintain its set point and push the excess power to AC out node which either goes to your loads or back out to grid if your loads are less then the pushed power.

Second, if you are running on a generator on AC2 input and you have a surge load like a motor startup that exceeds the generator capability the XW6048 can suppliment the generator to supply the surge load. It all depends on what you set the maximum AC2 input current to. If you set it to 15 amps max. then current above this will be supplimented by inverter (up to max output capability of inverter). You can also supply loads that exceed either the generator or inverter with the combination contribution of the generator and the inverter added together. This supplimenting is also related to the 'load shaving' capabillity.

To your question about 'cleanliness' of AC out. Generally the answer is yes. There is some filtering on AC output path. The inverter/charger will try to match the sinewave from the grid to a point where the grid falls outside the set parameters on the XW6048 (low AC1 voltage, high AC1 voltage). Now if a lightning strike hits the grid and there is a high voltage spike on AC1 input, the inverter will momentarily open AC1 grid relay because the grid went outside the set parameters. It does take a finite amount of time for the XW6048 to detect the abnormality so some of the lightning spike can make it through the filtering to AC out. It can also potentially damage the XW6048. I recommend putting a high current capable surge suppressor in the main A.C. distribution panel to help protect the XW6048.

sub3marathonman

Re: Another XW Question

It says "Grid Bypass" and "Inverter 1 Out (AC Loads)" and "Both Off to Disconnect AC Output" under the two 60 amp breakers on the Power Distribution Panel. These two breakers are connected like a manual transfer switch so that both cannot be on at the same time.

When the "Grid Bypass" is chosen as ON, it is my understanding that the XW inverter is then not involved in the flow of electricity at all.

When "Inverter 1 Out (AC Loads) is chosen as ON, then I think, but I'm not sure if the electricity is coming from the grid, into the batteries through the XW charger, then from the batteries to the AC Load. RC's comment, "I think the part that is a little hard for some folks to understand is the inverter output is running in parallel with the grid. It's not an 'either or' situation" helped clarify things too. But, if the electricity is going into the batteries and then to the AC Load, doesn't this mean there is a loss of efficiency, as opposed to bypassing the inverter, and if so, approximately what percentage would this loss be? Also, I'm wondering if the output is then limited to 6kw continuous by the inverter, or if both the inverter and the grid can "work together" (as RC said) to supply more than 6kw continuous when the grid is on. (I do understand that if the grid is down, the inverter will output 6kw continuous as a maximum.)

RCinFLA

Re: Another XW Question

Electricity is not going from the mains to battery to load output. It goes from AC1 directly to AC out through a hard connection through AC1 relay.

The inverter is running in parallel, similar to a regular power plant generator running on the area grid. If the power company's generator pushes torque into the generator it will push power into the grid. The harder it pushes the more power that generator is contributing to the grid.

In the case of the XW the inverter is syncronized to the grid, just like a power plant generator must be syncronized to the grid phase to be 'on line'.

The phase and voltage of the grid is matched before the AC1 (or AC2 in case of generator) relay is engaged to parallel the inverter to the grid.

When the inverter has been syncronized, the AC1 relay closes and connects the AC1 input directly to AC out port. Straight wire connection thru relay. The inverter just happens to also be connected to AC out port.

The inverter is bi-directional, it can either pull from the grid to charge battery or push to grid from the batteries in the case of sell mode. The difference is only a slight modification on the running inverter MOSFET switching PWM duty cycling. It does this on the fly so it can immediately go from charging battery to supplying AC out load if AC1 goes down. If just maintaining a float charge voltage on fully charged batteries there is just a little bit of current sucked from the grid and pushed to the batteries to maintain float voltage.

If grid (AC1) goes down, there is actually a momentary overload on the inverter which it quickly detects and opens AC1 input relay. The inverter now takes over the AC out load previously being supplied by AC1 connection (thru AC1 relay).

There are separate A.C. current and voltage sense measurements on AC1, AC2, and AC out points. These are constantly monitored by the controller. In the case of grid AC1 going down, the excessive current going out through AC1 port, as the inverter tries to power the grid, is detected within a cycle and controller opens AC1 relay. It keeps inverter running to take over AC out loads. If current and voltage detectors on AC out port detects excess load on AC out it will shut down the inverter. AC1 has priority selection over AC2 so if you run generator with grid AC1 available it will select AC1 to connect to, not the AC2 generator port.

In bypass mode AC1 relay is closed but inverter switching is shut down. The large output transformer is still connected to AC out. In this condition the transformer just becomes a large unloaded 'wall wart' on the AC out port.

It takes about 26 to 28 watts to run the inverter. In bypass mode there is a few watts lost having the output transformer still connected and to continue to run the controller and display. Similar to search mode power (<8 watt spec). Search mode is used when off grid. The object is to save the 28 watts taken to run inverter if there is no output load required. The inverter wakes up periodically (I think it is once per second) to allow for output port current measurement. If it detects a load greater then search current set point the inverter stays running. There is another power saving mode you might be interested in. It is called 2-stage charging (no-float). When the battery completes the bulk charge it does not go to float charge. This is a new function over the old SW series. I think it shuts down the inverter and waits for battery to drop below 'recharge' set point where the inverter wakes up and refreshes the charge on batteries. Again, I think, during the idle period the inverter is off but acts like the passthru or search mode function from an AC loading point of view. In this case if AC1 goes down when inverter is idle, the AC1 relay opens and the inverter immediately is activated to supply AC out loads.

I attached a simplified functional diagram. Refer to terminal diagram Fig. 2-15 on page 2-17 of Installation manual.