And Now which Inverter??

adas

Aloha, A lot of questions from me today, so heres the last one...
About inverters.
At inverterstore.com I see 24v Mod Sine wave 5000/10000W going for $419-$469 or so. Are they a good buy even comparing Outback sine wave ones that cost $2000 and up?

What is the difference other than square wave/sine wave differences and a little bit more efficient?


thanks
Frank

System2

Re: And Now which Inverter??

One of the biggest things is what will you be running off the inverter.
Keep in mind that a percentage of electronics will not survive a trip on MSW. And much of what we have today contains electronics, everything from breadmakers to washing machines. Hey, do I smell smoke?
The other thing is electric motors. When I first got into solar, I just didn't want to see what others more experienced users were trying to tell me on this issue, that induction motors (including fridge and freezer compressors) would consume aprox 15 to 20 % more power if run on MSW and convert that extra power to heat. Not only would this extra heat consume more precious energy, but in time cook the motors. Lets just say that in some ways I'm a slow learner. LOL
Many things however will run fine on MSW. CF lights, skilsaws, electric frypans and the like. Other things are trial and error, run it at your own risk kind of thing.
I'm also assuming there was a typo error in your listing of the 5,000 and 10,000 watt MSW inverter. Consider the idle current on such a large inverter if you are just running a couple of CF lights. You might want to consider a small inverter to run the lights when no big loads are on.
There are a lot of other little issues with MSW as well. Little things like buzzing from the CF lights, and even buzzy sounds from switches that operate those CF lights etc, and buzzing on my telephone. All things I could live with, but things that are now gone since I started using a Puresine 300 for all small loads that require power 24/7.
Another thing that I was just not expecting - - peace of mind! I guess I had kind of gotten used to wondering if whatever I was running would survive on MSW. When I shifted to pure sine, it was like a load lifted. That came as a pleasant surprise.
Not telling you what to do, that's for you to decide, just letting you know my own experience.
Cheers
Wayne

adas

Re: And Now which Inverter??

Aloha and thanks Wayne. I have two systems (see my sig)
My residence/office 2500W system has the typical items and hoping to still use the MSW but Pure Sine inverters are not out of the question. I use mostly things not needing Sine wave, Laptops, CF, UPS's. small fridges, pumps, drills, grinders, Intercom, charger for Gem Car, etc. so all has been OK up to now.

I am now putting together my fabrication shop system where 8 employees work. I am starting with the second system in my sig (3360w). There I need to run 3 grinders, one sawsall, Minimal lights, gem car Charger, paint sprayer, mig welder. The mig will run from 2400 watt inverter fine. All these items will be stubbed into my main breaker panel for normal daily operation. If I am using the mig a lot, I have another breaker panel that will run off the 5kw diesel Genny. But also in either system I COULD have a second smaller Sine inverter to run the sensitive things. If using MSW I think the 5000/10000 inverter is sized about right with about 4500 watts needed intermittantly.

BTW I am on an old Military base and cannot get permission from the Navy to use the three phase power just 20 feet from my shop.


I am trying to think these things through with the help of this forum and google and trying to avoid costly mistakes and trying to KISS, keeping it as simple as possible.
Although the both systems are fairly large, I am doing it "on the cheap" (not using rebates) buying used equipment and 'horse" trading.

Frank

System2

Re: And Now which Inverter??

Oh, OK
One thing on the MSW inverters - - in case you aren't already aware -
you mentioned everything connected to your main breaker panel. Many main breaker panels have the neutral bonded to ground, and many, or most, MSW inverters will end their lives with a quick puff of smoke if either of their output terminals is grounded, as they don't have an output transformer which serves to isolate the internal electronics.
Just something to check into and verify before the system is activated.
Cheers
Wayne

adas

Re: And Now which Inverter??

Wayne from NS Cana wrote: »

Oh, OK
One thing on the MSW inverters - - in case you aren't already aware -
you mentioned everything connected to your main breaker panel. Many main breaker panels have the neutral bonded to ground, and many, or most, MSW inverters will end their lives with a quick puff of smoke if either of their output terminals is grounded, as they don't have an output transformer which serves to isolate the internal electronics.
Just something to check into and verify before the system is activated.
Cheers
Wayne

Aloha, Wayne. Is not the Neg in a PV system just the ground? As the neutral in the a/c grid system is also the ground? My limited understanding is that the difference in neutral and ground in a grid system is the Potential Difference that the Electric company has in Their ground and the Consumers ground, thus that is why things need to be grounded in the Grid system at the consumer.
Other than grounding the chassis of the inverter, I do not understand the difference in Neg and ground in a PV system.
Hmmm the difference in Neg at the DC side and Neutral at the inverted output side?

frank

System2

Re: And Now which Inverter??

Normally in AC electrical systems in North America, one of the power supply wires is connected to ground. This grounded AC power wire is referred to as "neutral", which can be thought of as a current carrying ground. The actual Ground wire does not normally carry current. It's just there in case of a ground fault. Yes the NEGATIVE from the battery is usually grounded. Thus the problem with grounding one of the AC outputs from the MSW inverter, it would connect the battery NEG to the output of the inverter and without an isolation transformer, current would loop in through the inverters input and output in such a way as to destroy the internal electronics. Same as many modern car stereos. The real old ones used ground for one of the speaker terminals, but now they have what's often referred to as floating ground, so if you actually do ground one of the wires going to a speaker - - POOF!
So be sure to check the instruction manual with the MSW inverter to see if the one you get warns against grounding one of the AC outputs. If it does, you must make sure there is no connection of any kind anywhere between ground and either one of the AC power supply wires, at the inverter, the breaker panel, or anything supplied by the panel. The neutral bar in most North American panels is directly connected to actual ground inside the panel.
Hopefully I've explained this in a way that can be understood.
Cheers and good luck.
Wayne

mike95490

Re: And Now which Inverter??

Wayne from NS Cana wrote: »

So be sure to check the instruction manual with the MSW inverter to see if the one you get warns against grounding one of the AC outputs. If it does, you must make sure there is no connection of any kind anywhere between ground and either one of the AC power supply wires, at the inverter, the breaker panel, or anything supplied by the panel.

Make SURE none of your appliances has "cheated" it's ground to neutral !

Trip the main breaker to OFF. Switch all items plugged in ON, and measure Hot & Neutral to Ground. (measure first for any stray voltage, then switch meter to Ohms.)

adas

Re: And Now which Inverter??

Aloha, and thanks to alerting me to to the ground problem. I really do have a concern now as my office is made out of a steel shipping container, which has the a/c elec. panel which is attached to another steel container that has the disconnect, combiner, etc which is connected to the next steel container (battery room) which has batteries, disconnects, steel shelving and inverter.
so I have a lot to check out, but luckily it has been working great up to now.....


frank

adas

Re: And Now which Inverter??

Aloha, no sooner did Wayne give his ground/neg/neutral advise, did I discover it for myself, but did not fry the inverter!
So is it best to completely isolate the 24v Neg from ground and then to Ground the Neutral in the 110v side?
Or do not even ground the neutral in the 110v side?

thanks
frank

System2

Re: And Now which Inverter??

That is one question I cannot answer. Thinking of lightening surges and induced spikes, either way you're living on the edge. In my case, when using MSW inverters, I decided to make sure the PV.s controller and batt neg were all well grounded, but let the AC float ungrounded. BUT - - -whenever there was the slightest hint of lightening, I would run through the rain to the shed and pull all the connectors on the inverters. The one time I was away and didn't do it, the inverter was destroyed.
With the pure sines I now have, the AC can be grounded to the battery Neg and to proper ground rods etc with no harm to the inverter. So, most lightening spikes occurring on the AC lines, can zip right through to the ground rods, no harm done.
I'm sure others can add to this question.
All the best.
Wayne