would #6 wire make a difference
alwaysoverbudget
| Posted in Energy, Heating & Insulation on
when wiring the house the central air units were a long ways down the road. we have 2 units a 2t and 5t. i wired for both units with 10gauge wire on 30 amp breakers.i thought 30 amp pretty much was all that was used on residental air. well while installing the 5t i saw it called for a 50amp breaker.well i went ahead and fired it up and it has never popped the 30 amp breaker so i thought i had got by with not having to replace the wire. well now it’s a 104 and the air is having a hard time starting up when it’s hot.will going to #6 have any effect on start up,i’m afraid i know the answer but busting out basement clg isn’t on my wish list.any ideas? larry
hand me the chainsaw, i need to trim the casing just a hair.
Replies
Your first words were:
"when wiring the house the central air units were a long ways down the road"
That alone might be cause for concern. Did you do a line loss calc?
OTOH, what is a "long ways"? You must have run the refrigerant lines the same distance "down the road". This isn't recommended; usually the heat pump sits right next to the house.
Scott.
Always remember those first immortal words that Adam said to Eve, “You’d better stand back, I don’t know how big this thing’s going to get.”
Scott, I read that to mean:
When we were doing the wiring in the house, the thoughts of putting in central air were far in the future.
Maybe he will come back and clarify.jt8
""The early bird gets the worm, but the second mouse gets the cheese." --Dave Barry
i needed agood laugh today! what i meant was it was going to be 10 months before the ac would be set,not that they were down in the next block 800' away.by the way the lines only run about 35'. thanks larryhand me the chainsaw, i need to trim the casing just a hair.
Ahhhh....
*quickly removes literal module, plugs in figurative module....
Thx,
Scott.Always remember those first immortal words that Adam said to Eve, “You’d better stand back, I don’t know how big this thing’s going to get.”
How bout another 240v 10ga 30a may be easier to run to the same spot? Then gang the legs with some majic jack elec.
Undersize causes heat for wire and motors.
"How bout another 240v 10ga 30a may be easier to run to the same spot?"Completely illegal.The problem is to get good load sharing.What you can end up with is most of the power going through one branch until it burns out and then all through the other one.
This is allowed for much larger size wires.
I was thinking each 10-2 as a side of the 240 so more a balanced mix. But I know what your saying.
Do it once do it right,and be done with it.
I did say jacko style. I was thinking each 10-2 carrying one side would give some balance to it.
Do it once, do it right, be done with it.
To the comment below, I'm aware of the MOD. and
Min. Circuit Ampacity( I like to think of this as when all is well)
Maximum Overcurrent Protection Device (MOD) — may use fuses or HACR-type circuit breakers of the same size
Look on the name plate.AC and motor loads don't follow the normal rules of figuring wire size and breaker size.Look on the name plate.It will have something like Min Circuit, that is used to size the wire.And the other is Max HVAC breaker is used to size the breaker.I am guessing that you min circuit is is the range of 30-40 amps and the max breaker is about 50-70 amps.What is the lenght of the run?And have you measured your voltage. A number of places, in general, are experinece low voltage do to demand. And in it is also common in areas where there have been a lot of recent building.
well i looked at the tag,32.6 amps min. ,max breaker 50 amp. so it looks like i really pushing it with 10g wire,about35-40' long run.what do you think go to 8g or just spend a few bucks more for 6g? thanks larryhand me the chainsaw, i need to trim the casing just a hair.
Actually #10 is rated for 35 amps using the 75* column.And the distance is not that far.I would check the supply voltages and have the HVAC techs check the compressor.
when wiring the house the central air units were a long ways down the road
That's an expression of time, not a statement of wire length, right?
well now it's a 104 and the air is having a hard time starting up when it's hot
What does that mean?
Which is having the hard time, the compressor or the fan motor? Sounds like you may have cooked the points on the fan and/or compressor contactor. Could be a simple fix, but you need to run the correct size wire to the unit or you are going to see this problem again.
LRA (locked rotor amperage ) is close to the start up current draw and may be as much as 3.5 times the FLRA (full load running amps). You plate rating and the time delay in a breaker allow for the high start up current normally, then the running amperage is well below the full low amperage. Without knowing what those numbers are for your unit it is hard to guess at what is happening.
Bottom line is you used undersized wire for the equipment. While it has worked under normal conditions, this extreme weather may be adding to the equipment load, and wire load.
Give us more information.
BTW, IMO you should go ahead and upgrade the wire to the correct size for your family's safety. Maybe find and alternate route, so you don't have the damage your finished ceilings.
Dave
whenever it gets up to about a 100 degrees outside air temp the compressor does not want to start,sometime actually kicking it's internal circut breaker and then rests itself about 3-4 mins. later. while this happing the condensor fan and inside blower unit are running with no problem.the fan/compressor relay points look pretty good,not burned or anything.thanks larryhand me the chainsaw, i need to trim the casing just a hair.
As I said earlier you need to get a voltmeter on it.And the label information.You could have low voltage due to the POCO. You could have low voltage do to inadequate wiring. You could have an AC problem.And BTW, this is not an uncommon problem with AC units. They do have hard start kits for them.Don't have any idea why or when they are used.
Having wire sized too small can cause lots of bad things to happen- and not all of them show up right away. Wear on contactors, loss of hp at start-up, motors running hot, etc.
Rule #1: Read the nameplate!
Rule #2: MINIMUM is just that- going larger, especially for a long run of wire, is a good idea.
Doubling up pairs of small wires, rather than using a big wire, is a method fraught with hidden problems. While there are situations where it can be done, it is way too easy to err, and have some code violations. Leave it to the pros at the Power Company.
Don't be so hasty with "quick fixes", until you KNOW the cause of your problem. If the problem is low voltage, through the entire neighborhood, due to heavy summer use... then there is little you can do (except shut of your stuff to protect it!).
Finally, there are few areas where improvements have happened as they have in HVAC, in the past few years. The new, higher efficiency units just might work fine for you. Twice, recently, I've pulled #8 wires, where #10 would have complied with the nameplate.
> Doubling up pairs of small wires, rather than using a big wire, is a method fraught with hidden problems.
For little stuff, like #6 - #10, I can see it not being cost effective. And code requires that all the conductors be in the same conduits and boxes. The splices have to be well done so you don't get unequal current distribution. What other problems are there?
But it's been common practice here for over 80 years to run multiple 4/0 x 50' -- even up to dozens per phase -- for lighting. They get lugged to solid bars in each spider box.
-- J.S.
Not to get to buried in the details, but the paired wires have to be as electrically identical as possible. Same wire type, same form, same length, same impedance, etc. The less "identical" they are, the more heat will be generated by the differences; and heat -even a few watts worth- will cause problems.
If the two wires are not exactly the same, the "voltage drop" will differ. The effect of this will be current flowing even when the appliance is off, with the heat being concentrated where the wires connect. One wire will feed the other, and heat will be made. They also need to terminate in a proper manner- and not with two wires under one lug. The need to be in the same raceway- not one wire run next to the existing romex. Making the "hot" wires larger, you also need to up-size the ground and neutral as well. Your boxes and raceway may become over-filled. During future maintenance, it is quite easy to get wires mixed up, especially if you don't already know that you have "parallel feeders." Sure, you "see it all the time"... as done by the pros at the power company. This is a method best left to them.
Absolutely I agree that for small stuff, paralleling multiple feeders is a bad idea. You can make it work if you have to, but it's still a bad idea.
Today the Best Boys go around with clip-around ammeters to check that none of the 4/0's are running hot. In the old days, they'd just feel the insulation.
-- J.S.
As Bill mentioned, there are "hard start kits" available. They consist of a capacitor that , when discharged, gives a "jump start" of voltage to the compressor to help it start.