IMO Shuretest VD is weak


Lets get it on the table. How long should a ckt be put under load before a voltage drop is computed

Me thinks that the suretest window is too short

Any one have some knowledge in this area??

If we can test as HI in a professional manner we can serve our clients better


If it where me (and it’s not) I would be concerned about damaging circuits that where already marginal to begin with.

Yes of course it would be nice to find all problems for your client but lets say Joe Handyman ran 16/2 zip cord to the receptacle using only tape for the splices.

As bad as it is it is functioning.

Now I come along plug in a Sure test with a 20 amp 30 second test and promptly burn the bad connection open.

Now what?

Me; It was bad to start with.

Them: It was working fine before you plugged that thing into it.

IMO VD can be determined in a very quick test, a longer duration will only serve to heat things up if they are marginal.

Are you also ready to replace fuses and reset tripped breakers?

Keep in mind I am not a big fan of checking VD on residential circuits in the first place. Few residential circuits are loaded even close to the sure tests load and VD is not in itself a safety issue assuming a properly wired circuit.

JMO, Bob

Some more info. :slight_smile:

Here is an ecerpt from one of the links.


Good point about the smoke test and I understand about the engineering problem in larger homes

Just for something to throw around – If VD is tested for a short time that would not allow for some heating of a poor connection are we saying that a ckt is good when in reality it is bad?

My thoughts are – go for the smoke test esp. if I am on some one else’s insurance.

We turn on AC units electric stoves etc and let them run awhile. Too bad it is hard to check for VD on those units.

I am very mixed about this testing esp with a short time load. Result is if I do not like something and don’t have a good feeling for the results I don’t want to do it.

Right now I do not do VD test unless ask by the client. Its that big GRAY line the Paul talks about.

And thanks for the links. Good points made by the authors


Thanks for posting these two links. I have been looking for an article that I had read some years ago regarding the VD and in particular in using the SureTest analyzer. This one is almost exactly the same information. From the original article I am referring to it indicated the VD found in most newly constructed home it was not uncommon to find VD in excess of 5% but less than 10% and many of the controlling authority types were beginning to rethink the 5% limitation. It is also my understanding the SureTest does not in fact introduce a 20 amp load but rather the test is determined from data that is extrapolated from the 15 amp load circuitry. I wish I could find this elusive article as this question on VD has come up several times. Thanks again.

I would not be surprised to find out the Suretest is only testing for one cycle, firing a triac. As Bob pointed out, it has to be short duration or you would be opening overcurrent devices.

Found this just looking around. Thought some might find it useful. Don’t just look at the voltage drop calculator. Down below that is a bizillion different kinds of calculators from soup to nutz

I understand your view and I agree depending on how you write the report.

If you go with something like this:

“Using a suretest xxx the circuits did not exhibit significant voltage drop”

This is not the same as saying the circuits are in fact reliable or safe.

Short of ripping the place apart no one can certify that the circuits are safe.

However it is certainly up to each HI to decide how far they go.

I am conservative, I would not want to do testing that may become destructive.

As I said I do not take VD in dwelling units to be a significant issue. I also do not believe it is fair to apply 5% VD limits on a electrical system after the job has been wired.

If you know for certain that the contract documents with the EC required less than 5% drop than IMO you should indeed look for it.

If it was a code minimum installation per contract upping the requirements after the job is done is not fair to the EC.

Maybe I would feel differently if the HIs report stated something like this.

“The electrical system appears to comply with local codes and is safe but some circuits exhibit excessive voltage drop”

Often the jobs I work on do indeed have VD limits per contract and as long as I know that going in I have no problem complying with them.:slight_smile:

We have done jobs so large that 20 amp receptacle circuits required 4 AWG copper to stay under the 5% drop.:eek:

Yes, I saw that when I read the links I found.

As you can guess I do not own a Suretest, maybe it’s time to get one.

I test for VD on new construction and warranty inspections only. Typically, I won’t even mention anything under 10%, as this is where our AHJ “draws the line.”

I use the reading at 15 amps as this (I believe) is the most accurate based on the operation of the SureTest.

My write up is simple;


They are kind of pricey. Hopefully they have corrected the problem on the connecter plug on the Model that replaced the 61-155. After any significant use the plug on the top of the tester developes hairline cracks internally and you had to twist the tester and/or cord to make a good connection. It is a strange dance that would often confuse the client. Im sure the fact that it had a break in the internal connector may have had some effect on the readings. Everyone I know that has one has had to send it back for repair or replacement at least once, myself included. This particular model has a lifetime warranty so it is mostly an inconvenience as the turn around time is quick and the lady at the trouble desk is very helpful and responsive. The LCD screen is difficult to read at times but the newer model has LED and appears to be much nicer. If mine ever breaks again I was told I would most likely just get the new model. I do not think it has the lifetime warranty. Thanks for your reply.

P.S. I went to the small booklet/manual that came with the 61-155 it states in there the voltage drop measurements are taken under the12 amp load (not the 15 amp as I stated earlier) and extrapolated for the 15 and 20 amp measurements). This allows the user to test a 15 amp rated circuit at full capacity or 80% capacity and test a 20 amp rated circuit under full capacity. Thought I better clear up my obvious mistake.

Is the % voltage drop the issue, or is voltage less than 108 vac with a high % drop?

I don’t discuss % unless the voltage gets below 108 vac.


I agree. The real problem is how low the voltage goes not the %

In my mind what is the no load voltage at the disconnect point and then turn on all loads in the home and get them to draw current - HVAC, electric stove, lights, etc. Then start measuring voltage.

To me this is too much work for what is a normal HI fee. I would have no problem adding this type of inspection as an extra service.

Sometimes I think people don’t give a —

The real problem to me is that a short load test will not show up a problem

I do like some of the “report words of wit” that have been posted - Think I will use them

Wonder what the % of homes old and new have a VD problem - may it is not worth testing because they for the most part pass



I would imagine if you mention the words “voltage drop” to someone you will probably lose about 99% of the general public and their eyes will glaze over. They may shake their heads in agreement but nothing will register in the old gray matter. I almost never do VD checks unless I see other things, conditions in the home’s system that would lead me to suspect they may be some power problems and I may do the check just for me rather than trying to impress the client. Takes a couple of seconds, looks impressive to the casual observer but is mainly just gathering some data for the inspector so he will sleep a little better or may prompt me to dig a little deeper for the CYA factor. Chances are very good that by this time I have already made the determination to call for the specialists.

The drop is the issue. As I stated, excessive VD is an indication of high resistance in the circuit. Resistance translates into heat (that’s the reason for the short load duration).

If nothing else, it’s an “efficiency” issue.


Do you thing VD is a problem?

If it is I can see Shuretest stock going up

I might even buy one

Right now it is my heat gun an the Fluke if as you say you feel you need to check for a VD.

I am also thinking of an additional test for true load testing since the EC in my area do not do it. I have done this type of testing in the Telecom and USN so it is not a problem but would have to buy some equipment and contact my insurance co to see if I could afford the general liability inc

Happy Easter



Your thoughts

When a device (HVAC etc.) is feed low voltage it will draw more current like a drunken sailor. This will build up more heat in the device and will shorten its live.

I do agree that the two are tied together. And IMO the voltage is the issue not the %. I will give you points for your side – the NEC keeps talking about % so you must be right.

Is there anyone out there that thinks that the NEC cares about voltage under load??

I know that in my past it was voltage and current the % was not the problem

Sometimes I know I am dating my knowledge but the laws of Physics and basic electricity should not change

Do I sound like I know what I am saying? If I do DO NOT CALL ME son of JOE

Trust me I will change my name an log into NACHI as someone else


Smoke test

Here is what I have in my brain as a problem

We test the ckt and it looks OK

Load it down and the weak point starts to heat up. Resistance and VD starts to go up real fast. The device (Stove - HVAC) starts to draw even more current causing the problem to get even worse.

Can not the industry come up with a testing MOP and equipment that will show the problems (small $$) or am I looking for a problem that is only in my house.

I think suretest is leading us down a path that if something goes wrong the HI gets it in the court case when the house burns down and the kid is dead but suretest does not

We and suretest says it is OK

Yes, I have too much time to kill (TV is bad and all projects for today are done)

Just looking for thoughts

Maybe Suretest could check in