Question about fuses for element controller

Ordering everything to control a heating element. I've got the pid, ssr + heatsink, water tight k thermocoupler, outlets and a watertight box. May get indicator lights too.
I'm wondering about what type of fuse holders people prefer, what the amp rating of the fuse should be and where do I need them to be to properly protect everthing?

It's a 110 volt system, 2000 watt element, 25amp ssr
here's the pid http://www.auberins.com/index.php?main_page=product_info&cPath=1&products_id=3

Hey there... if you are only going to be pushing 110V, You could plug directly into an outlet that has absolutely nothing chained to it, and it should be GFCI protected as well as have a breaker in the main panel at the correct fuse rating for it.

Sooo P=IR

2000W= (AMPS)(110V)

18.18Amps drawn at 110 v

You need a 20amp GFCI Fuse for the outlet and nothing else should be plugged into it

Been running heat element without controller with 20 amp gfci. No need for a fuse besides that? Fuse between PID and 12volt source?

Bowtiebrewery said:

Sooo P=IR

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Not to be a bit-picker, but it's V=IR and P=IV - but the math is correct.



I would suggest a circuit breaker on the heating element power supply and fuse to protect the PID if you wanted.

That PID is AC powered, so to protect it you'd fuse between the 110V and the PID. It's rated at <5 watts, so you'd need a ~50mA fuse. I'd get a fast blow.

A fuse on the 12V line would protect the SSR output of the PID in the event the SSR failed to a short somehow. It's rated for 30mA out, so I'd get a 30mA fast blow.

Forgot the "What kind" question.

It's up to you. I'd base that decision on two things -

1. What kind of fuse holder can you find
2. Are the fuses easy to find for replacement

I'd go with either 3AG (also know as AGC) or with blade type like in most cars now days. Either of those will be very easy to get at the parts house/wal-mart. It would be easier to find the 3AG in the amp ratings that you are going to need. Those are the glass tubes used in old cars.

^^^ sorry internally I was thinking "Power" lol

I don't know if I can explain this correctly without juggling with my words but here's a shot at it.

You need to fuse the line that is going to the outlet with a 20amp fuse...

i have an attachement that P-J sent to me that would be extremely helpful if you wanted me to send it to you.

The fuse/breaker size is determined by the wire size you use.
The wire size you use is decided by the load it will bare.

this is to protect the wire from getting too hot and causing a fire.
Considering this is coming from a 20A 110V circuit the breaker in the panel or gfci is already protecting a service cable and any thing branching off of it up to 12awg. Say you tap off the 12awg wire with a piece of 14awg wire you need to put a 15A fuse between the two. iirc, in the first post of the primer there is a list of proper fuse/breaker sizes for the wire size.

Edit: yeah, its under Circuit Ratings and Circuit Protection. Also a section called Suggested fuse sizes.

CodeRage said:

The fuse/breaker size is determined by the wire size you use.
The wire size you use is decided by the load it will bare.

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Typically, yes. But there is nothing wrong with sizing a fuse to protect a device so long as the wire is sufficient size (big enough) to handle the rated current of the device/fuse.

I like using supplementary breakers instead of fusing. They never need replaced. There are several sizes of breakers for $8 at Automationdirect.com. I'd use a 5 amp or less for your PID. The heating element will be fine if its being fed from a 20a GFI.

Huff360 said:

Typically, yes. But there is nothing wrong with sizing a fuse to protect a device so long as the wire is sufficient size (big enough) to handle the rated current of the device/fuse.

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agreed, at the end of the post I mentioned it addresses that. The important thing is to protect the wire, didnt want to add more complexity to the answer in this thread with device protection.

CodeRage said:

agreed, at the end of the post I mentioned it addresses that. The important thing is to protect the wire, didnt want to add more complexity to the answer in this thread with device protection.

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Agreed. Hard to tell exactly what is meant sometimes.

Thanks for all the answers. I'm putting y fuses before pid (50ma) and before 12volt on ssr (30ma). I'll have my fuses between power supply and component, but I've see drawings with fuses put after components. What's the advantage/disadvantage of both ways.

Budzu said:

I like using supplementary breakers instead of fusing. They never need replaced. There are several sizes of breakers for $8 at Automationdirect.com. I'd use a 5 amp or less for your PID. The heating element will be fine if its being fed from a 20a GFI.

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That's more or less what I do. Everything is protected by a 30A GFI and a 30A panel breaker. The low current 120VAC devices (lights/meters/PIDs/timer/pumps/etc) are on a 7A fast blow fuse fuse. 5A would probably be fine too. I think with all my of my low current stuff running (including pumps) I'm only pulling 2-3A. Wire use for these is rated to 15A, so the fuse that protects the wire is 7A.

The point here (as others have said) is that you're protecting the thinner wire rated at 15A. You need this fuse since the breaker will only pop if you pull more than 30A. That means that if it's the thin 15A wire trying to pull more than 30A, it'll melt/fry if you don't have a 15A or lower fuse to protect it.

Some people go even further then and put separate really low current fuses for each of the devices (PIDs, timers, etc). I don't bother with that. IMHO, I think it's overkill.

Kal

I wondering how often that fuse or breakers trip? I would think that if the system was done right, you're not going to blow fuses often. I'm just trying to justify using the fuse holder that I already have

kal said:

Some people go even further then and put separate really low current fuses for each of the devices (PIDs, timers, etc). I don't bother with that. IMHO, I think it's overkill.

Kal

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Guilty!

Bugaboo said:

I wondering how often that fuse or breakers trip? I would think that if the system was done right, you're not going to blow fuses often.

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If designed right it should never blow. It's insurance. Like an airbag in a car.

If there's any way you can make the fuse blow through normal use then the system's not designed right. If the fuse blows it's because something else failed and needs to be fixed/replaced.

Kal

I get what fuses do and I'm not questioning the need for the security. I guess I'm asking if blows outs are common? If you don't blow a fuse more than once in a great while, I don't understand the need for a circuit breaker instead of a normal glass fuss.

I decided to go with breakers just because they can be reset. I would hate to get halfway through a brewday, blow a fuse, then have to run to Radioshack or the autoparts store to get a replacement. You could keep spares on hand, but I'm really good at losing critical things like that when it really matters.

That being said, if a breaker does trip in a properly designed rig, it seems to me like you've got bigger problems than missing fuses. Probably better find the cause before powering back up.