Fuses can be a little con"fusing"...

[Twodose]

How to decide what is the correct type of fuse that should be used in any particular vac motor. I have been using the VAL9414 Lamb motors from KR and the Ferraz Shawmut fuses shown in the picture and they work fine, but would like a little more information on the meaning of the prefix letters for the fuses, I mean old military, new military, old commercial, new commercial, it’s a bit confusing.

 

[MEP001]

I don't know what the letters mean, but that is a fast blow fuse which is filled with a sand material to prevent the metal from atomizing and allowing an arc through to electronic components. It's not the right fuse for a vacuum motor. I use MDL10 slow blow fuses for protecting individual and MDL20 for two motors.

 

[Eric H]

I've always wondered too but you may have just occupied my entire day by looking for the answer.
A quick search comes up with this article. http://www.tpub.com/neets/book3/8e.htm
BTW, I use GLR12 fuse on my JE Adams Vacuums that have Domel motors. The Domel motors that I buy from Windtrax seem to last a lot longer than the Lamb/Amtek or GS motors that K-R used to sell.

 

[Greg Pack]

Well, I hate to say this now that MEP has educated me but in past years I would just use the cheap inline 20 amp fuses and holders I'd get at auto parts stores that were rated for 250V. I can't ever recall it failing to work. I also use the mercury relays which seem to work OK too.

 

[MEP001]

I've always wondered too but you may have just occupied my entire day by looking for the answer.
A quick search comes up with this article. http://www.tpub.com/neets/book3/8e.htm
BTW, I use GLR12 fuse on my JE Adams Vacuums that have Domel motors. The Domel motors that I buy from Windtrax seem to last a lot longer than the Lamb/Amtek or GS motors that K-R used to sell.

I switched to Domel years ago. The brushes last longer than the "value line" KR vac motors they sell now. I change all the brushes every other year and haven't replaced a Domel motor in a decade.

 

[MEP001]

Well, I hate to say this now that MEP has educated me but in past years I would just use the cheap inline 20 amp fuses and holders I'd get at auto parts stores that were rated for 250V. I can't ever recall it failing to work. I also use the mercury relays which seem to work OK too.

I've done that in a pinch, replaced the ABC 20 gray ceramic fuse with a standard AGC 20 automotive fuse in a Doyle unit that had the regular inline fuse holders for each motor. The AGC 20 would still blow if the motor failed, but they would occasionally fail without blowing when the fusible part disconnected from one of the caps. FWIW I don't even use a fuse when I've got a 35 amp mercury relay in it. The breaker takes care of it, then the coin acceptor loses power and no one else will lose their money.

 

[mjwalsh]

When designing component protection sometimes we prefer to have several fuses ... so each tailored correctly amp fuse can save the day from time to time isolating sections of the overall sometime very intricate equipment.

 

[Twodose]

I don't know what the letters mean, but that is a fast blow fuse which is filled with a sand material to prevent the metal from atomizing and allowing an arc through to electronic components. It's not the right fuse for a vacuum motor. I use MDL10 slow blow fuses for protecting individual and MDL20 for two motors.

Do you mean a mdl20 if motors are daisy chained?

 

[MEP001]

If one fuse on one wire powers two motors, yes.

 

[Randy]

We got rid of the fuses about 25 years ago when we installed mercury relays. One of the best things we did. We haven't replaced a timer in years since the only load on the timer is the coil of the relay.

 

[Twodose]

What did you replace with the relays?

 

[Randy]

What did you replace with the relays?

We removed the fuses and installed a 24 volt mercury relay

24 Volt Relay | Mercury Relays Part 35NO-24ATH

The Mercury 35NO-24ATH is a 24VAC, normally open, 1-pole relay for motors or lighting. Hydrogen back-filled.

www.kleen-ritecorp.com

The coil on the relay is controlled by the timer. This way the only load on the timer is the coil. If a motor goes bad it won't damage the timer. We've been using the mercury relays for well over 25 year without one failure. I think the easiest way to describe it would be the relay is a switch and the timer is turning the switch on and off.

 

[2Biz]

Randy is exactly right! I put in the mercury relays 8-10 years ago when he suggested it and haven't had a single timer or mercury relay failure. No fuses, just a 20a breaker for each vac.

 

[Twodose]

What is so different with them than a regular motor contact?

 

[mjwalsh]

What is so different with them than a regular motor contact?

The motor contact is protected by a different part of the circuit than the electronics part that is triggering the coil. No amps or spark on the coil ... BTW a % of us also even have a different voltage going to the possible specific mercury relay's 24VAC coil. The other factor that is the mercury does the switching eliminating the contacts. I have 24VAC on my Vac motor relay control coil so I actually do use a fuse ... mostly in case some freaky wire short develops. Not likely any shorts for us though ... because we tend to use Wago lever locking for terminals.

A mercury relay in this single contact situation is a wise move like Randy & 2 Biz suggested.

 

[MEP001]

What is so different with them than a regular motor contact?

The difference is that the contact is made by a blob of mercury instead of contacts that can arc when they open or close and fuse together or get dirty and heat up/burn out.

 

[mjwalsh]

The discussion about vac motor fuse protection has me thinking a bit. It would be nice if when we walk by a vacuum we could at a glance see if a motor is no longer working. I have had plenty of situations where the breaker did not blow when one of the two motors blew. Hopefully, a customer will tell us immediately about the less suction but sometimes they don't.

It seems like there might be a special pop up breaker for each motor that could be visible? I have Hall's Effect Doughnuts ... like William Pitzer use to advocate ... so I guess I could mess with our logging software to alert us ... but there could be an easier way to get the quick notification. Of course cost could be a factor too for that kind of extra feature

 

[MEP001]

There's a check valve you can put under each motor so if one fails it still works relatively well. You still need to check the vac function regularly.

Coleman equipment uses an indicator that tells when a fuse on a low pressure pump motor is blown. There may be something similar, but it would only indicate while the vac is running.