Thread: Car fuse is furnace?

Can anybody a good reason why there is a car fuse in this COLEMAN electric furnace?

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did you call Coleman?

.........pretty common in these (and Miller-Nordyne) units - this fuse was 3amp? In a manufactured home?........Greg

In my opinion you are beyond the normal home inspection and if anything looks out of the ordinary you should recommend further evaluation by HVAC contractor. The fuse connection does not look factory installed but should not be a problem as long as the value is correct.

With that being said, I think the buyer would be more interested in why the second heat strip in the picture is not connected!

that type of car fuse was very common in older furnaces 1980's, 1990's, and some sooner
The 3 amp used to blow a lot very easily, especially in older houses with less than upgraded electrical. We used to replace them with 5 amp and then no more problem.

Originally Posted by Gregory Booth

.........pretty common in these (and Miller-Nordyne) units - this fuse was 3amp? In a manufactured home?........Greg

Its a stick built home from the late 90's.

dfg.jpg What do you think of the wire covering used in the furnace.

These types of fuses are commonly found in furnaces. They are used in cars and many other products.

Yes, it s a car fuse, they are used on the low-voltage side of air handlers to protect the LV-transformer from being burned up when you miss-wire or short out the thermostat wiring. They are usually 3 or 5 amp fuses. They are Still used in brand new air handlers.

Just for clarification.
That is not a "Car Fuse", it is a "Blade Fuse".
You will often see them is cars, but they are also used in other things.

As a former A/C tech these fuses are very common in furnaces. If it did not have one we would in install a fuse to protect the transformer against burn-out. A cheap solution to saving a transformer.

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As a former A/C tech these fuses are very common in furnaces. If it did not have one we would in install a fuse to protect the transformer against burn-out. A cheap solution to saving a transformer.

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As a former A/C tech these fuses are very common in furnaces. If it did not have one we would in install a fuse to protect the transformer against burn-out. A cheap solution to saving a transformer.

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My recollection is that those fuses, like other fuses, have a rating for their tested and approved use.

Many of the tubular glass fuses have a 250v rating along with their amp rating, while others have a 12v rating along with their amp rating.

The plastic fuses, as I recall, have a 12v rating along with their amp rating.

The voltage for transformers used in a/c systems are 16v or 24v, as I recall (I could be wrong on this as my recollection is from back in the 1970s and 1980s). Unless 12v transformers are used, and if those fuses have a 12v rating, those fuses would not be rated for that use. Too many unknowns to make a definite statement as to whether or not they are OK.

Originally Posted by Jerry Peck

My recollection is that those fuses, like other fuses, have a rating for their tested and approved use.

Many of the tubular glass fuses have a 250v rating along with their amp rating, while others have a 12v rating along with their amp rating.

The plastic fuses, as I recall, have a 12v rating along with their amp rating.

The voltage for transformers used in a/c systems are 16v or 24v, as I recall (I could be wrong on this as my recollection is from back in the 1970s and 1980s). Unless 12v transformers are used, and if those fuses have a 12v rating, those fuses would not be rated for that use. Too many unknowns to make a definite statement as to whether or not they are OK.

The lowest voltage rating I am aware of is 32v.

Originally Posted by Vern Heiler

The lowest voltage rating I am aware of is 32v.

Guess I will need to look at some fuses I have in the garage and see what their rating is.

http://www.littelfuse.com/~/media/au..._datasheet.pdf

Most were 32v some were up to 58v

Originally Posted by Rick Cantrell

http://www.littelfuse.com/~/media/au..._datasheet.pdf

Most were 32v some were up to 58v

This entire conversation about proper fuse, use of fuse, rating of fuse is way off mark. The fact you identified a "fuse" in use was a good catch - the REAL culprit here is the fuse was simply used as a convenient BY PASS of a thermal high limit (see the ceramic limit terminals on the heater bank). Some hack has deleted the safety limit in this furnace - SHUT it down until repairs are completed by someone with a lic.

They both serve the same function, but will likely have different ratings. Auto fuses are premised on having on or around 12 Vdc, whereas household appliances, if they have a fuse, will be based on 110 Vac (or 220 Vac, in Europe).


What kind of fuse does a furnace use?
Most new furnaces have a 3-5 amp fuse on the low voltage side to protect the circuit board and transformer from a possible short or overload. If someone were to put too many accessories on the existing transformer the fuse should protect it.