Difference between these two fuses!?

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Posted by: from Brantford
2/26/2021 at 1:20:08 PM

Changing fuse in my house just want to know the difference between these two fuses bot are type D and 25 amps but one has a TC mark and the other has a TD mark

Difference between these two fuses!?
Difference between these two fuses!?
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Date/Time2/26/2021 at 2:06:27 PM


TD is indicative of time delay. Hence if you pass the 25 amp mark it will take a few seconds extra before the fuse blows. These style of fuses are normally used for motors. The reason being that motors have in rush current when they start and for a split second they overdraw to get started and then drop to the nominal amperage. so to prevent regular fuses from blowing unnecessarily time delay fuses are what is used.

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Date/Time2/26/2021 at 2:07:19 PM

Hi Jason,

The top one is more of a standard fuse where the TC stands for "Trip Current", it just means that 25amps is the minimum current that will trip that fuse.

The bottom red one is a time delay fuse and is used in situations where motor loads cycle frequently and the start up surge could trip the fuse.

Please not that I am not an electrican and am not providing you electrical wiring advice, however we do see these in older homes with the old fuse boxes.

Hope this helps.

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Jason in Brantford
Date/Time2/26/2021 at 2:10:21 PM

So I could put replace one of them with the other then

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Mohammad from Quality Potlight in North York
Date/Time2/26/2021 at 2:18:36 PM

Dear Jason from Brantford,

They are the same fuse, careful when changing them out as sometimes they can bite, I recommend to wear gloves.


Customer Service


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Lara from The Shock Doctors in Orillia
Date/Time2/26/2021 at 2:41:23 PM

Hi Jason,

It's the difference between how it blows, "time delay" vs. "thermal or heat". 25 Amp fuses should probably be a 15 amp depending on what it is protecting.

I hope that helps.


The Shock Doctors

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Date/Time2/26/2021 at 9:18:43 PM

Td has time delay and tc has dual elements which is function time delay as well

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Date/Time2/27/2021 at 3:47:00 PM

TD= Time delay ,

TC = trip current

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Date/Time2/27/2021 at 4:43:25 PM

To add to what is posted here. Do not replace a TC fuse with a TD and vice versa. You want a fuse to blow as quickly as possible as it may save someone's life. So normally, a TC fuse is what you want.

In the case of motors, they draw a large spike of current when they first start, and then it drops quickly to a much lower level. That also includes condensers in air conditions etc. So for these devices if a fuse blows too fast, you will constantly be changing them. So only use TD fuses when specifically required. If you don't know, get someone that does.

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Date/Time3/3/2021 at 8:54:40 AM

It is funny for such a simple thing, people don't know too much about.

These are called plug fuses and come in different series:

S Series

T Series

W Series

P Series, and

TC Series

The S series has a rejection base or adapter in the panel and will only accept these fuses. This is used to prevent the wrong size fuse from being installed. Generally referred to as tamper-proof.

Also all of the fuses come on the L version which also has a rejection base, so you will see type SL, TL, etc.

The T series is a standard fuse with a dual element that is typically used for general use and small motor applications.

The S and T series range from a fraction of an amp to 30 amps.

The W series are fast acting fuses.

The P series is used for non-time delay (instant trip) for non-inductive loads. Although it is typically single element, it is also made in a dual element version.

The TC series, also has a D rating for CSA approval and is intended for heavy duty (industrial) uses. The trip curve is much higher (more time delay) and are designed specifically for motors. The TC series has an additional spring as part of its tripping circuit.

The P and TC series generally come in 15 to 30 amps sizes.

The designations P and D are for Canadian use, as they meet specific CSA requirements, which are essentially lower melting points. P is used for non-motor loads and the D for heating and cycling loads.

So to answer your question, The green TC fuse is specific fuse for higher current level; the red is a standard T series fuse with a single element which has been marketed as a time-delay fuse.

TLDR; the fuses are different and while they fit in the same spot, they are not intended to be interchangeable.


John Kuehnl-Cadwell, CD, ME

Master Electrician

Datawise Solutions Inc

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