question about fuse amps

Reply

  #1  
Old 03-07-06, 06:09 AM
John Whorfin's Avatar
Member
Thread Starter
Join Date: May 2005
Location: CT
Posts: 170
questions about breaker/amps/wire guage

Well this relates to our heating system, but it is a fuse question.

We have a heat pump, with the electric auxillary heat when it is too cold. System was installed in the summer and have had the fuse trip on about 7 different days in the winter when it was rather cold.

We had a Tech came out and said the fuse was too low and should be higher.

All of this is fine, but the old fuse was a 40 Amp & he said the system needed a 60 Amp. Now that seems like a big jump to me, and if it really needed a 60 amp would it run 90% of the time problem free with this scenario?

Now the only other factor is that it uses some sort of electrical heating elements for the auxillary heat, and I am pretty sure it has a few of these. So not really sure how many it has and uses, it might only kick in all of them when it is really cold and maybe that is why it only tripped the fuse on those really cold days when it actually needed that much electricity to run it.

Any of this making sense? Does this sound odd to anyone else? I know there are requirements listed on the unit but must confess I am not good at reading electrical requirements for systems like this.

System is up and running so more looking for info and general understanding about a 20 amp difference in fuses.

THanks
 

Last edited by John Whorfin; 03-09-06 at 01:56 PM. Reason: correcting title
Sponsored Links
  #2  
Old 03-07-06, 06:15 AM
John Whorfin's Avatar
Member
Thread Starter
Join Date: May 2005
Location: CT
Posts: 170
seconday question

OK, after reading some more posts in the electrical section I have another question.

The 2 pole breaker. I am assuming this is a breaker that actually looks like 2 breakers connected with a bar?

Our system did have this 2 breaker connected with a bar.

What is the difference between a 2 pole and a regular breaker?
 
  #3  
Old 03-07-06, 07:34 AM
ray2047's Avatar
Group Moderator
Join Date: Mar 2006
Location: USA
Posts: 33,124
Breakers can be either one pole or two pole. I think by regular breaker you mean one pole but a two pole breaker is also a "regular breaker.

On a single phase residential circuit you have two live wires coming in. If it is a 120V circuit one of those wires goes to the load. There must be a breaker on the live wire. Since there is one live wire there is one breaker, a one pole breaker. If it is 240V there is two live wires going to the load it needs two breakers, a two pole breaker. The two breakers can be combined in one case with both breakers connected to the same handle inside the case. Often though the handles are connected outside the case by a bar. The reason for connecting the two handels is so if only one of the two breakers trips that breaker will trip the other. The reason both breakers must be tripped is to disconnect all the live leads for safety. If only one tripped the load might not work and someone might not realize it was hot or the reduced voltage might damage the equipment.

In case the preceding is unclear just a bit of basics. On the usual residential service you have three lines. Two hot that are 240V if you measure between them and a third wire the neutral. Either hot to neutral measures 120V. A 120V circuit has one neutral and one live wire. A 240 V circuit has two live wires. There is more such as ground wires which have 0 voltage to neutral but that is the basics. You never have a switch, breaker or fuse on a neutral wire. On the other hand all live wires must be protected with a disconnect device such as a fuse or breaker.

In your post you say "fuse" but you seem to mean breaker. If it is a fuse check if it is a fast blow or slow blow. In some cases replacing a fast blow with a slow blow may fix the problem but you need to check to see if the equipment manufacturer requires a fast blow fuse.

If it is a breaker you need to check what the manufacturer recommends and if the existing wire size is large enough for a larger breaker or fuse. It sounds like the heating elements which probably draw more current then the compressor are causing the problem but there could be other causes even a failing compressor. Until your sure of the cause I'd be cautious about increasing the size of a breaker or fuse.
 
  #4  
Old 03-07-06, 08:02 AM
John Whorfin's Avatar
Member
Thread Starter
Join Date: May 2005
Location: CT
Posts: 170
Yes I meant Breaker

Sorry about the fuse/breaker thing, blame my parents for that hehe. Growing up whenever the breaker tripped they always said blew a fuse (old school) so it is just something that is kind of stuck in me. And yes by regular I meant single pole.

Anyway, the technician already changed the breaker from the 40amp to the 60 amp. When it comes to the physical wires I no nothing about the gauge and wasnt really asking about that. Was not a failling compressor, just the power draw from the electrial heat on very cold days.

My major concern is that they went from a 2 pole 40 amp to a 2 pole 60 amp. To mean that seemed like an odd jump, but then again I am not an electrician. I was trying to find out if it made sense or if that was really the problem. Also if there is any danger in what they did, I do not think so but again not an electrician.


The old system which we replaced last spring, was the original for the unit so original wiring. When they replaced the unit, the new one obviously needs/draws more power since it has tripped the breaker on many occasions. No wiring was changed when they installed the new system. And as of now the only change was them swapping the breaker.
 
  #5  
Old 03-07-06, 09:02 AM
Member
Join Date: Jan 2006
Posts: 131
what is the fla rating on the nameplate when all stages of aux heat are on. the new system may have a bigger draw, thats why it needs the bigger breaker, bu then the wiring should have been changed as well.
 
  #6  
Old 03-07-06, 09:27 AM
Member
Join Date: Aug 2005
Location: USA
Posts: 995
Originally Posted by John Whorfin
When it comes to the physical wires I no nothing about the gauge and wasnt really asking about that. Was not a failling compressor, just the power draw from the electrial heat on very cold days.

My major concern is that they went from a 2 pole 40 amp to a 2 pole 60 amp. To mean that seemed like an odd jump, but then again I am not an electrician. I was trying to find out if it made sense or if that was really the problem. Also if there is any danger in what they did, I do not think so but again not an electrician.


The old system which we replaced last spring, was the original for the unit so original wiring. When they replaced the unit, the new one obviously needs/draws more power since it has tripped the breaker on many occasions. No wiring was changed when they installed the new system. And as of now the only change was them swapping the breaker.
You can't change breakers out to bigger ones without making sure of several things, ESPECIALLY the size of the wiring.

How do you know the compressor isn't failing? While it isn't on my list of probables, you can't rule it out either. It may be drawing more amps than required, which then trips the breaker when the added load of the heat strips kicks in.

If you doubt (in any way) the competence or sincerity or knowledge or non-laziness of the professional who swapped your breaker, you need to verify your wire size.
 
  #7  
Old 03-07-06, 09:27 AM
Member
Join Date: Jan 2004
Location: Oregon
Posts: 1,219
The characteristics of heating systems and circuit breakers mean that it makes perfect sense that a system would work 99% of the time on a 40A breaker, but really require a 60A breaker to be reliable.

However it is extremely important to remember that with electrical installations the fact that 'it works' does not mean 'its safe'.

Circuit breakers are designed to protect systems from overload. Increasing the circuit breaker from 40A to 60A is essentially making the claim that the systems protected by the circuit breaker can _safely_ carry 50% more power.

You need to examine the 'nameplate' of the heating system. It will tell you the circuit breaker rating and conductor ampacity required to supply the unit. You will then need to examine the cable feeding the unit. The cable should be printed with the number and size of the conductors. Provide us with this information and we can probably tell you if things look reasonable.

The biggest danger is if the breaker was increased in size to match the unit, but the wires are too small to carry the additional current. On a cold day, all of the resistance heaters will come on, and the wire will overheat, but the breaker won't trip because it has been increased in size.

-Jon
 
  #8  
Old 03-07-06, 09:41 AM
Member
Join Date: Jan 2006
Posts: 131
the compressor should have a different feed than the aux heat.
 
  #9  
Old 03-07-06, 09:49 AM
John Whorfin's Avatar
Member
Thread Starter
Join Date: May 2005
Location: CT
Posts: 170
Thanks for all the help, I will take a look at the wires themselves when I get home after work and relay that info on.
 
  #10  
Old 03-07-06, 10:51 AM
wgc
wgc is offline
Member
Join Date: Dec 2005
Location: New England
Posts: 362
breaker protects the wiring not the device

Oops, too long of a wait to get in a reply... You guys already did a much better job since I started trying to add something ... deleted.
 
  #11  
Old 03-07-06, 04:17 PM
John Whorfin's Avatar
Member
Thread Starter
Join Date: May 2005
Location: CT
Posts: 170
THe Info

Unfortunately I cannot get any info from wires themselves. There is only about 3 inches of wire that is not in an metal conduit. And the bit of wire that I can see does not list any readable information. The wire itself is pretty think. Right next to it is another wire that is hooked up to 20 amp breaker and it was listed as 12 gauge. The wire for the 60 amp is much thicker, the little bit of exposed wire that I can see before it goes into the breaker is bigger then the entire 12 gauge with insulation. Not sure if this helps anyone with figuring out the gauge of the wire but it is a good size. Anything I do to tell what the actually size is since I cannot read it. To me the entire wire with insulation is about the same size as coax cable. Any help?

OK now for the heating unit itself. I cannot see anything on the "nameplate" that makes sense to me. It listed volts at 208/230 and there was another reading for Phase/Hertz that was 1/60 is this the amps? Excuse my lack of knowledge.

Anyway from the original quote it looks they were supposed to install a 10 KW heat package, no idea how much power that is or would draw, just trying to give some info hear.


Winnie was saying the biggest thing to worry about was if the wire was insufficient it could melt the wire, is there anything else I can check measure to see if the wire is suffiicient to handle the amps?


Thanks again everyone
 
  #12  
Old 03-07-06, 06:14 PM
Member
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
208/230 means that the unit can be run at 208 volts or 230 volts. 1/60 means that the power is single phase, 60 cycles.

You are going to have to find out what size wire you have in place and what is called for.

If you can find nothing on the unit itself, check the owners manual. If you don't have the owners manual, get one. You can probably download one from the Internet or call the manufacturer and have them send you one. You should have one anyway.

As for the wire, if you cannot figure it out from markings on the wire, you will have to examine it. You can do so (carefully) with a wire stripper, or by comparing it against samples of other wire.
 
  #13  
Old 03-09-06, 01:53 PM
John Whorfin's Avatar
Member
Thread Starter
Join Date: May 2005
Location: CT
Posts: 170
Took a while

Ok this took some time, but I did find out the electrical heating elements in our system do indeed need a 60 amp breaker. Now from my searching the internet this then needs a 4 guage wire correct?

Now of course I have to get some sort of measuring tool or some wire to compare it to, since there is no visible wording on the little bit of insulation that is visible on the wire.
 
  #14  
Old 03-09-06, 02:03 PM
Member
Join Date: Jan 2004
Location: Oregon
Posts: 1,219
Generally, 6ga copper wire or 4ga aluminium wire is sufficient for a 60A circuit.

Remember to make any measurements with the power off!

-Jon
 
  #15  
Old 03-09-06, 06:22 PM
ray2047's Avatar
Group Moderator
Join Date: Mar 2006
Location: USA
Posts: 33,124
Now of course I have to get some sort of measuring tool or some wire to compare it to, since there is no visible wording on the little bit of insulation that is visible on the wire.
Home depot will sell one foot of wire. You could get two or three different sizes and compare. Just be sure it is the uninsulated wire you compare. The insulated diameter may vary depending on wire type.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes