why on the primary side?

[dmoneyc22]

i work on and install alot of trane and carrier systems and i to have had this same problem however i have been able to locate the problem. i usually find that there is a rubbout in the condensing unit that causes this either the low pressuce control or the rv def sensor all controls check it out

[docholiday]

Jultza,

Me too, you are right. I stand corrected, thanks. VA is volt amps. I think I was heading to make a point about primary and secondary fuses and got sidetracked.

So a 240v-24v transformer with a .32 amp primary would give you a 3.2 amp secondary or about 80VA. and a 115v-24v transformer with the same primary capacity of .32 amps would give you about a 1.67 amp secondary or 40 VA.

[Edited by docholiday on 03-26-2005 at 11:38 AM]

[bodhisatva]

"If you short the secondary, which is the primary's load the primary side will fail as it is the weakest link. A 3 amp fuse on the secondary would be the weakest link if it were present. a .3 amp fuse on the primary would also be weaker than the primary winding. Lesson, learned? A fuse is alot cheaper than the transformer."

Yeah but where can I get a .3A fuse? Something they sell @ Radio Shack? I have enough trouble getting 3A fuses.

[dmoneyc22]

you can go to a gas station and puchase a 5 amp auto fuse and do the same thing
push come to shove you do what ya gotta do lol

[docholiday]

I didnt say it was easy but yes Radio Shack would be one place. My point was that either location would save the transformer. The last post suggested a 5amp fuse. In this case it will be the last thing to fail and pretty much a waste of time, especially if you are dealing with a 40va 115-24v transformer which is only rated at 1.67amps.

[wb]

Those newer style automotive fuses work good with regular slip-on type crimp connectors. Put one of these fuses in series with the secondary.

[majormickey]

I ran into similar problem with a furnace board and a hot surface ignitor burning out for no obvious reasons.I was originally sent to the job site to do a fall service/cleaning.A couple of days passed and then the call-back came,{no heat}.After troubleshooting and finding nothing I checked the off/on switch at the ceiling servicing the furnace.The problem was that they were switching the neautral and not the hot.On my first visit I turned the switch to off thereby causing the 110 volt to back feed through the entire system.{Everything ran fine as long as the off/on switch wasn't used}.The fuse on the board never did get damaged but it burnt out the board and the H.S.I.Anyway after rewiring the off/on,and replacing the parts,everything was OK.

[cem-bsee]

most electronics supply houses have fuses, all elec supply houses can order some -- from 0.01a thru 8a at 120v or more. FYI a standard glass fuse >8a is rated 32 volts! so, use a ceramic fuse = ceramic encased, rather than glass.

HOSFELT electronics is a mail order house. but, they do not have all sizes.

[woowoo]

Originally posted by bodhisatva


Yeah but where can I get a .3A fuse?

http://www.digikey.com
http://www.digikey.com/scripts/DkSea...S&Cat=32113391