I know this is an old thread. But I happened to be discussing this very topic with a coworker and remembered this thread. I didn't think to ask the electrician or dig into whether the backup generator I had installed was suitable by itself for electronics. After doing some reading, I'm relieved to find out the generator I have is indeed suitable. The generator I have is a Generac 20kW unit. Generac doesn't provide exact THD numbers of their generators. They use 5% as a cut off line between suitable and not suitable. The generators which they say are suitable for electronics have a less than 5% THD rating. The ones they state are not suitable have a THD greater than 5%.

With your spec of 5 to 12% THD, I would definitely look into getting a line conditioner. Depending on how many electronics and the amount of draw, you may want to look at just getting a UPS with line conditioning capabilities.

 

Thanks for replying, this is a topic that many don't seem to know just what to do with; so let me ask you this. When you say line conditioner, just exactly are you referring to, a surge protector, a UPS, or an inverter. I hope it is not an inverter because one that will handle the power of my generator would cost 3 to almost 4 times what my generator cost. I have a brand new Smarter Tools 9500w, and it started off running out of the box at 130 volts @ 68.7hertz. After running it for 3 hours it scaled down to 122 volts at 62.2 hertz. I am assuming this is because the alternator on this unit is a brush driven unit and the brushes and armature needed time to properly seat in. I am assuming that after running it at load, with I intend to do for a couple more hours will seat things in properly. I intend on installing either an Intermatic # IG2240-IMS or an Eaton CHSPT2ULTRA whole house surge protector. These are MOV units, but have really good warranty's, and we do get some power line surging from time to time, so I thought that would help. But are Computers really all that touchy about THD, since their own power supplies are supposed to help take care of some of these problems....aren't they? I asked this question on another site called City-Data, and got this lecture about artistic earth grounding, which was touted as being all the protection I should need, sounded like fringe science to me, and it won't stand up to local codes.

I assume that after break in, this generator should stay on the low end of the hertz range somewhere around 60-62, but am wondering just exactly how much say a 12% THD bumps me up to. I suppose if a UPS is important, then would I need it for my new fancy Nancy furnace and all it's computer controls? Any advise would be most appreciated. Thanks

 

How are you measuring your Total Harmonic Distortion? And, have you measured the THD of your primary power supply? Saying, your backup generator may be "cleaner" than your primary incoming power.

As for surge suppression, I would recommend getting quotes from electricians and having them install on your main power. They can drive a ground rod (subject to local Code Requirements), install a surge breaker, and protect everything on your house.

It doesn't sound like much, but everything has electronics in it. A decent surge can wipe our your kitchen appliances.

 

Actually my new generator has an hour meter, and volt meter and a Hertz meter, so I can watch what it does from that standpoint. According to our power company (Avista, formally Washington Water Power) our power range is regulated at levels no less than 112 volts, and no more than 140volts. Our home usually comes in between 119.5volts to 122volts. Hertz output is suppose to be between 60 and 62 cycles. I am not an electronics tech or engineer, so I don't have an oscilloscope, but I have a good multi meter that does measure Hertz output but haven't done that yet....I probably should. Only it expresses it in decimals and not percentages of Total Harmonic Distortion; and I haven't the brains to extrapolate the exact formula for making the conversion. I just wonder what is acceptable, for example if incoming hertz starts off at 60 to 62 cycles, and then jumps up to say 68 cycles.....is that bad enough to harm electronics? Dirty power has become an issue since me have 2 very large windfarms not far from us, and when they cycle in, you can see a difference in the lights, but it is brief. But I guess they are notorious for THD pollution. I live in Spokane Washington, and we had major outages last November from a wind storm that knocked most of the city out for days. Our power was out for 7 days...., and the weather people said that we should expect a lot more wind from now on.

While the power company says that "we don't surge" many homes around us had surge related damage in their homes, burned out control boards on furnaces, microwaves, TVs etc. all from that storm and their attempting to restore power, I shut my mains off, and waited until the power had been on for at least 20 minutes. So I am trying to plan ahead and protect my stuff. We don't get much in the way of electrical storms around here, so I don't need an L.P.S, and I am well grounded with 2 10 foot rods just on the other side of my homes foundation connected with a 4 foot strap and well bound, as well as a strap running to our copper city water pipes, all according to code, so I am good there.

I am just wondering what is acceptable as I am not really sure. I was trained as a millwright, so I am a fair to good electrician, and installing a surge protector is no problem for me. We had huge ones in the plant I used to work at, but they were capacitive/inductive discharge and were choked by the largest diodes I ever saw, and it was set up to dump surge power on the neutral as well as the ground line. The place I worked had a full floating incoming energy system, that is to say, neutral and ground were not mixed like they are in homes. I have no real experience with whole house surge protection systems for homes, as I never really considered that I should have one...., but since last November, I have since changed my thinking about that. There has been a lot said on the web about MOV surge protection, and most of the whole house units use those as well. I have found a couple that do not, and are set up similar to what the mill used to have..., but they are spendy.

I understand that none of the whole house units protect from THD, so I was wondering what 6 to say 12% extra from the baseline 5% THD off of 60Hertz looks like..., or what figure that would be, for example if 60 to 61.5 or 62 hertz represents the 5%..., which I do not know if it does or not...., what are the higher numbers? And How much extra voltage (a decent surge) can home equipment actually handle until something goes T.U from too much power?

This old inquiring mind would really like to know......Thanks for any and all advice.

Rick

 

You ask some really good questions, Rick. To be honest.... I don't know.
I guess for grins I could hook up a frequency meter at my house and see what it does.

It sounds like you have two issues going: 1) ongoing power generation, and 2) the potential for a power spike.

1) In general, devices have become pretty rugged in the voltage it will accept. At the same time, power generation has become a bit better over the years. So, I don't see a lot of issues with appliances/ devices being ruined by poor power. Unless you know of neighbors and/or report from your power generation company of problems, I wouldn't look to investing too much money in this. It may not be needed.

Also, you can look at the specifications of the devices in your home and see what it calls for. You can call the mfg. of some of the devices and see if they have tested their products across a range (voltage/ hertz/ THD). Recall... in general mfg. make products to ship globally. Some areas have very good power quality, and some have pretty rough power grids. So they make their equipment to accept a pretty broad range.

2) Most people I would strongly recommend not even attempting a home surge suppressor. Even though you mention you're pretty strong in this area, and judging by your work experience you could handle the work, I would still recommend getting an electrician. Reason being.... if you have to pull the meter (to kill the main power going into the panel) the utility company will not be happy about that. Having a licensed electrician (with a permit on file) can help remedy that.

Also, you may be able to find a suitable home surge suppressor that can... clean up the incoming voltage a bit.

 

The power generator issue is really only for when we have another long outage, and for that I should have a surge protector of some kind, even the highly rated Honda's, do not put out as clean of a voltage and THD rating as advertised....all the time. I have a couple of friends with one, and his runs about like mine. As for power company spikes, facts are they do happen, I know since our last outage of several who have had troubles.

I think your right though...., mlst electronic equipment does seem pretty rugged. I have 4 computers, and never have had a power issue, frankly....ever since our first one in the late 90s, we have never had an electronic issue....., now virus issues.....oh ya.

I am probably going to put the Eaton CHSPT2ULTRA in, it has really good specs, and a decent price and good guaranty.....for what it is worth anyway. As for installing the thing, it shouldn't be a problem, but I will have to check with the city if I need a permit, then of course an inspection. They are fairly lenient where do-it-yourselfers are concerned, so long as it is permitted and inspected, only on a few issues is it a no no, like trying to hook up your outside power lines , or changing around gas lines....that kind of thing. They also don't want most people installing lightening protection systems on their own.....but then we don't get much lightening up here as in other parts of the country.

As for THD...., I am curious about it, as I have some computer tech friends that consider it a serious problem, one thinks he can build a whole house inverter on the cheap......something tells me he is full of beans. I just am not sure how many hertz over the standard of 60 cycles is really bad, so if anyone knows the answer to that question, I'd love to know. By the way....thanks for your help There Drabdr.

Rick

 

Hey... honestly, I probably gained more by your posts than anything I contributed. You're a very good technical writer, and you have some good things to think about in your posts.

I hope you do update here if you find out more about the THD and such.

 

Aw shucks...t'wern't nuthin......Seriously though, I would like to understand more about THD, I know where it comes from and why, I just don't know how much is to much, or exactly what the percentages me in real numbers. If I knew that, then I would have a better idea of what to look for from my generator, and incoming power company power. I know that there are some pretty stringent regulations they have to hold to, at least in the state of Washington. And I understand from a couple of electrical engineers I know, that the new windfarms have made it tougher. So, with that all said, I will pass on anything I learn about this when I can find an expert that has time to talk.....everyone is so busy now days.