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Mark Rosenbaum
01-11-2011, 02:02 PM
I came in this morning to a furnace heading South on the pyrometer.
I found out that the fuse in the Watlow controller burned out.
These are specialty fuses and can not be found locally. They are about $100 each. Watlow would not send me one because I do not have an account with them. They are a Bussmann fuse (mine is 250A) and can be ordered through a Bussmann distributor. I am urging anyone with a Stadelman furnace to find out what fuse is in your controller and have a spare on hand. A day or two of down time can greatly effect if you blow for a week or if you have to wait a week for the crucible to heat up to temp again.

Dennis Hetland
01-11-2011, 02:32 PM
What type of fuse is it? Type R, type L? What's the part number? Are you sure it's a 250 amp? Could it be a 250 volt?

Victor Chiarizia
01-11-2011, 03:03 PM
don't think i'm wired that way. all my fuses are standard sizes and amps. where is this fuse located and what does it protect? vic

Brian Wong Shui
01-11-2011, 03:37 PM
The fuse is a Semiconductor Fuse located in the Watlow Power Series Controller (behind the sliding door). Bussman Part Number 170M1321 for the 250A version. Expect to pay $50-80 plus shipping. You can check with http://www.fusecoinc.com They might have it in stock in Dallas (Atlanta is iced in right now). It protects the input to the SCR.

The question is why did it blow a fuse? Is there a short somewhere (like the transformer) or was there a lightning strike?

Dennis Hetland
01-11-2011, 04:24 PM
$49.80 from Bussman through Eoff electric supply in Salem, Oregon. If you order within the next 45 minutes they can ship it today. Call 503 587 5002 ask for Brian and tell him Dennis told you to call.

Pete VanderLaan
01-11-2011, 04:57 PM
it's sort of solved. great price though.

Mark Rosenbaum
01-11-2011, 05:44 PM
Thanks for the replies...yes, I ordered from someone locally because my google search could not come up with anyone else.
Brian, that is the part. Today was spent trying to find the part. Tomorrow will be spent trying to find out why it happened when we get a new one installed.
Vic, check your SCR it's right where Brian said ...
Dennis, thanks for the info, I'll keep that on file.

$50 for piece of mind.....I'd do it if I were you ;)

Doug Sweet
01-11-2011, 07:00 PM
I'm confused about the location of the fuse. Mark can you post pictures when you do the replacement?

Josh Bernbaum
01-11-2011, 09:18 PM
Ditto what Doug Sweet said, is this fuse attached to the Watlow controller or the Watlow SCR? I agree with Brian that it's real important to find out why the fuse blew.

Steve Stadelman
01-11-2011, 09:26 PM
This is the fuse located inside the S.C.R. usually only wild power spikes kill it because the algorithms within the scr shut it down.

Mark Rosenbaum
01-11-2011, 11:24 PM
I'm confused about the location of the fuse. Mark can you post pictures when you do the replacement?

Doug:
It is in the SCR behind the panel door. Slide the cover on the SCR and it is the small white box about the size of 1/2 a pack of gum inside near the top of the unit. I'll take pics when I'm in the studio tomorrow.
Steve:
What is an example of a wild power spike? It wasn't a lightning strike. It happened after we turned the furnace up 50 degrees to blowing temp. So when we examine the electrical power train tomorrow, there's a chance that we won't find anything?

Jordan Kube
01-11-2011, 11:58 PM
Check your connections. Always have spare fuses. Even the ones that are expensive and don't blow very often.

Check your connections. Always have spare fuses.

Steve Stadelman
01-12-2011, 10:31 AM
Mark, there is every chance you will find nothing. Of course, feel free to call.

Mark Rosenbaum
01-12-2011, 10:51 AM
Mark, there is every chance you will find nothing. Of course, feel free to call.

Thanks Steve!

Robert Gary Parkes
01-12-2011, 10:59 AM
Again thanks to Brent, Had the same event happen, only while we were having a party in the Studio, having consumed the better part of a bottle of fabulous Scottish single malt, I opened up the control box.. and low and behold!! There was a spare fuse waiting....ordered two more, as I am out in the sticks and subject to all kinds of weird power fun...

Mark Rosenbaum
01-12-2011, 11:06 AM
Again thanks to Brent, Had the same event happen, only while we were having a party in the Studio, having consumed the better part of a bottle of fabulous Scottish single malt, I opened up the control box.. and low and behold!! There was a spare fuse waiting....ordered two more, as I am out in the sticks and subject to all kinds of weird power fun...

Well Robert, Brent promised me a lot too, and I never got what he promised. He did a total rebuild here a year ago and charged me an arm and a leg. I gave him a lot of advice on his new business. I did not get any instruction manuals, any spare fuses, no meter, nothing.
I'm very grateful to Steve and his help whenever I can't solve something here.

So, any info on why your fuse blew???

Mark Rosenbaum
01-12-2011, 01:17 PM
Well, we couldn't find anything wrong...all wires looked good, all connections were tight. Sometimes, things just happen.
Here is a picture of the culprit....it is the small white box underneath the #2 wire.

David Russell
01-12-2011, 02:14 PM
do all watlow scr's have this internal fuse? and if so i assume it's a different fuse for different size/capacity scr's?

i can tell right off that the scr in mark's pic is different than one i have access to.

Steve Stadelman
01-12-2011, 02:41 PM
If you have a 200 or smaller furnace it uses a din-a-mite scr that is externally fused, the fuse holder is to the left of the scr and yours uses that 100amp round semiconductor fuse. The power series scr's are internally fused.

Mark Rosenbaum
01-12-2011, 03:09 PM
If you have a 200 or smaller furnace it uses a din-a-mite scr that is externally fused, the fuse holder is to the left of the scr and yours uses that 100amp round semiconductor fuse. The power series scr's are internally fused.

Mine is a 400lb-er, so it is different.....but get extra fuses for whatever your unit uses! ;)

David Russell
01-12-2011, 03:15 PM
steve you did recommend that i switch that fuse from an 80 amp to a 100 amp since my scr is run at about 70 amps out of 75 max. i have a couple of questions the switch

is this because the 70 amps that i use is just to close to the 80 amp limit of the fuse?

i ask this because as i understand it the scr has a 75 amp max capacity, now if that is protected by a 100 amp fuse, it seems that the scr would be "overpowered" long before the fuse has blown....

i am sure i am unclear on something here......

Steve Stadelman
01-12-2011, 04:28 PM
Yes, go with 100 amp fuses.

David Russell
01-12-2011, 04:39 PM
recently done......

but please help me understand.......
if the aforementioned fuse limits the passing amps thru the scr to 100amps, when a errant spike of power that is over 75 amps but under 100 amps occurs how does that not incapacitate the s.c.r. ?

Steve Stadelman
01-12-2011, 05:30 PM
At this point all I have to say is 100 amp is best for that furnace, as to in-depth discussion of semiconductor fuses and how they work (it is different from standard fuses). I need to refer you to Larry crane at Watlow. 507-454-5300.

David Russell
01-12-2011, 06:05 PM
gotcha and understood.

once again thank you steve........

Doug Sweet
01-13-2011, 06:10 PM
My 100 pounder has a 80 amp round semiconductor fuse. Should it be upgraded to 100 amp round semiconductor fuse? The spare is also 80 amp.

Doug Sweet
01-13-2011, 06:13 PM
My 100 pounder has a 80 amp round semiconductor fuse. Should it be upgraded to 100 amp round semiconductor fuse? The spare is also 80 amp.
:)

Steve Stadelman
01-14-2011, 09:32 AM
Doug, your furnace should only be drawing about 45 amp at the max. Only switch to the 100 amp fuse if you are having bad dreams.

Keith Weiskamp
02-07-2011, 09:57 PM
Speaking of blowing fuses ...

I have a 300 lb. moly that keeps blowing a fuse about once every few months. My shop has a 600 amp panel and the furnace is wired from the panel with a 200 amp breaker. Inside the shop I have a breaker box that is wired to the panel and has two 100 amp fuses. This breaker box is wired to the furnace. All pretty basic stuff.

The breaker box contains the fuses that are blowing out every now and then. The timing of when one of them blows out seems kind of random to me but it always seems that a fuse will blow at a really critical time during the work cycle! The fuses are Bussmann dual-element 100 amp time-delay fuses, rated at 250 V. I'm not sure why they keep blowing. Only one of them blows out at a time. I haven't had any power outages or storms, etc.

All of my connections have been tightened on a regular basis. The fuses never blow out when I'm ramping up the furnace to 2320 to charge or during the time when I'm charging. They only blow out when we're working at 2100, or when I'm increasing the temp from idle (1900) to 2100.

I was wondering if anyone else has encountered a problem like this or if anyone has a suggestion for fixing the mystery fuse problem. I've had a few electricians over to take a look at the situation and still haven't found a solution other than keep replacing fuses.

-Keith

Bill Worcester
02-07-2011, 10:57 PM
aloha, i had a similar years ago - it was a bad fuse box- replaced it- no problems since . aloha, mr bill

Jeff Thompson
02-08-2011, 12:32 AM
I was having a problem kind of like this. I dialed down the max amperage on the scr to below 90% and that fixed it(maybe down to 87%). I used the current limit adjustment pot, its one of three tiny pots that are actuated by a small flat-headed screwdriver.... don't know what your scr is like, tho. Use an amp-clamp voltmeter to measure the amps going to the transformer.

Steve Stadelman
02-08-2011, 12:56 PM
Keith, do check the amperage going to the transformer, should be 80 or less. Call me if you want help.

Keith Weiskamp
02-08-2011, 04:51 PM
Hi Steve,

Thanks for the response. I did measure the amperage going to the transformer and I don't get any reading close to 80 amps whenever the high contactor or the low contactor is switched on.

I spoke with Watlow and I'm going to send Larry a set of previously blown fuses so that he can x-ray them to determine a possible cause of the failure.

If he comes up with something interesting that I might need help with I'll try to contact you.

Thanks again,

-Keith

Paul Hayworth
08-14-2013, 06:29 AM
http://www.slideshare.net/jaydeedee/effective-heat-installation-guidehttp://www.slideshare.net/jaydeedee/effective-heat-installation-guide

Toby McGee
08-28-2013, 01:31 PM
Thanks for posting that manual. That's the first I've seen of it.

Dennis Hetland
08-29-2013, 10:31 AM
Here's the Kanthol Super Handbook.
That other manual tells you to lay the cables on the top of the furnace which I think is a really bad idea. Notice figure 45 in the Kanthol Super Handbook for an example of a busbar set up.

http://www.mtixtl.com/machineflyer/Handbook.pdf

Pete VanderLaan
08-29-2013, 12:28 PM
The furnaces Steve built didn't have the cables laying on the furnace top, they were in conduit clamps and held elevated above the crown and then in turn they attached to the straps. The cooling tubes did lie on the crown sometimes.

I do agree that the buss bar is a better way of distributing power. Have a lot of paper ready if you're downloading the kanthal handbook.