This is Turtle.
Yes the fuse link type fuses are still made but nobody buys them anymore. The links cost $.80 and the replacement fuse cost $1.09. It's not really worth it.
Yes we are in the Throw away Economy Generation !
TURTLE
This is Turtle.
Matt you don't need to get your draws in a knot for you stated you was not a electrician and your answer would be taken as a consumer answers for your reply would be a view of a consumer and not the so called professional. Get Off the Soap box and just be one of the people here.
TURTLE
This is Turtle.
Ha , The Fused disconnect cost about $15.00 and breaker & can will cost about $40.00+ and you ask him why he uses the fused disconnect box. Now if everybody here was Million aires your reply would ok.
TURTLE
You'd have to ask the original installer. I was too busy making sure lots of other stuff got done OK while the place was being built and didn't stop to question why it was fused then. I'd already agreed to the overall price of the HVAC system, so questioning why it needed fuses wouldn't have made any price difference anyway.
Fuses there never made much engineering sense to me though.
But, a couple of others on this thread have raised questions about whether the equipment manufacturer may have particular requirements about the line feeding it being protected by fuses rather than just a breaker. I can't think of any technical reason for that requirement for a piece of equipment which is principally just a 1/4 hp fan motor with occassionally a 35.5 amp resistive heater load added to it.
I kinda thought that "simple is better" that's why yesterday I bought what looks like a simple and robust 60 amp Square-D "plug disconnect" which I'll probably swap in this weekend.
Jeff
Well now, I'll check the specs and if that's the case it sure makes sense now! And too bad the original installer didn't see it that way too, it would have saved me a lot of nuisance fixups.
Thanks, and I hope the 60 amp Aquare-D non-fused plug type disconnect switch I just bough yesterday isnn's similarly rated.
Jeff
This is Turtle.
No that Square - D breaker looking disconnect is rated above the 40 amps but usely in about 2 to 4 years the breaker will burn inside the breaker and go out and then you can replace it with a real breaker square- D and keep going. A lot of HVAC people don't like them for that call back coming in 2 to 4 years. Now if you replace it now with a real breaker to apply to the application you will not see it down the road.
TURTLE
Do they make a 100A disconnect that just has a pull-out block with 2 cartridge fuses in it? That's what I think I would use if they are available that big. Put in whatever size fuses you actually need to protect the heater, (45A?) or just put 100A fuses in it and let the breaker back in the main panel provide the protection.
Bob
This is Turtle.
Yes they do but your looking at about $68.00 + Tax . It will come with a lever on the out side and spaded type fuses and the fuses are about $8.00 each even being 60 amps to 100 amps sizes. The 60 amp disconnect is the breaking point between commercial and residentiual equipment and the price reflects it. Now this type fuse box / fused type disconnect will run at 90 amps till the cows come home but the 60 amp cheap o will run till the sun goes down. .
The standard 60 amp fuse / disconnect $15.00 verses the 100 amp fuse box / fused disconnect at $78.44 is a far cry between them in quality and in price. At about
5 times the cost the public will not go for 5 times the price when Home Depot sells them for $15.00 and the home owner can replace them pretty easy.TURTLE
Jeff Wisnia wrote: ...
Note that NEC requires no more than 80% of rated amperage for virtually all boxes, irrespective of manufacturer. It's a good rule of thumb that many don't adhere to.
Another thing during this thread (that hadn't popped to the fore in my mind until last night for some reason) is that in the attic you may not have adequate (or any to speak of) air flow around the box so that the ambient temperature ratings may not be valid since they're based on "normal" air circulation. If the box is in an area where there isn't a convection path over/around it, it may well have an internal temperature rise well above that you observed w/ the brief open box test you did.
I think the upgrade to a 100 A box would solve the issue plus, perhaps, if there is a restriction around where it is presently mounted, moving it to a more open area couldn't hurt (and just solve the problem w/o the other box).
No, the one I bought is the "pull-out" kind. I looked at the one with the "breaker looking" switch in it and decided not to take the risk of its switch contacts fouling up by themselves. The plug-in contacts look pretty robust and feel tighter than a virgin's cooze. I'll swap it in and report back in a year or two.
I'm still scratching my head in amazement that a closed switch with what appears to be adequate ratings located in a benign environment will slowly develop increased contact resistance, but I've seen it and believe it, so it must be so.
Again, my apologies for wasting all the bandwith on this simple little problem. It's my engineer's mind dammit, I have an overwhelming desire to learn why things like that happen, I guess it's one of my my retirement hobbies, thoroughly non-cost effective, but fun, like many other hobbies.
Jeff
Thanks, but I don't think it's likely to be a temperature problem as our attic is quite well vented by continuous louvered vents along the entire length of the soffits at the roof edge overhangs in front and back, and a ridge vent all along the top. Even in the summer when I've been up there it never feels like it's over 100F, and in the winter, like last night It felt like it was down in the 40s.
The disconnect is located on a piece of plywood nailed to a couple of vertical 2 by 4s tacked between a ceiling joist and a roof joist and is "in the clear" about 2 feet off the "floor", so convection definitely should do its thing, as long as we don't run low on gravity.
I'd agree with a 100 amp box, but I'm gonna try the 60 amp Square-D pullout disconnect first. The contacts in it for the plug blades squeeze them from both sides, unlike the switch contacts in the problematic GE fused disconnect I'm wasting so much bandwidth discussing.
Jeff
...
Well, was just a possibility as noted...
May well work as well...and what are usenet groups for, anyhow??? :)
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