Conti Prestina Espresso Machine Restoration 101 (Completed and Indexed) - Page 58

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
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RayJohns

#571: Post by RayJohns »

depending on the thickness of the sheet metal (and what type of metal you have), you might be able to use what's called a nibbler. I have a nice hand one here. They also make air powered ones (and I'm sure electric ones as well), although I have never had enough of a need to purchase one.

The little hand one I have can probably handle up to to maybe 1/32 thickness, not sure. I bought it originally to cut the square hole in the base of the La Pavoni - but yeah, no. Those Italians didn't skimp on their sheet metal back in the 70's. I had to break out the die grinder and a bunch of files.

Ray

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drgary
Team HB

#572: Post by drgary »

Drip Tray Grate Overlay Template

Today I literally went back to the drawing board and created a well-fitted template. It will be cut out of one sheet of stainless steel, will have a back lip created out of rubber or metal molding, and will be tacked using TIG welding to the grate underneath by a pro.

Here's the template in place. Where you see the edge slightly protruding on the left I would grind it so it's flush.

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Here's what it looks like against a dark background:

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The right side is slightly larger to cover the hole pattern evenly. The measurements are:

12 1/4" wide
5 5/8" deep
back crossbar is 1" wide
left arm is 1 5/8" wide
right arm is 1 3/4" wide (Added after hand fitting, 1 13/16")

Next I'll need to source stainless steel plate. I'll see if I can find a professional to make clean cuts to close tolerances as well.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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drgary
Team HB

#573: Post by drgary »

Wiring and Plumbing Lessons from Bill Jackson

As I rebuild I'm referencing old threads and this one from 2006 by Bill Jackson gives me ideas for doing a very nice job of wiring and PSTAT placement. I'm posting these photos of his rebuild here as a reference for readers.

Here's Bill's thread first:

Conti Rebuild

I really like his approach to wiring. Here are photos of that. I like his use of a terminal strip and a 10 amp fuse. If the fuse works as well as my thermofuse I'll use his solution instead. The thermofuse is a bit clumsy to work with and the ability to replace a fuse in a receptacle is a more elegant solution. For those more knowledgeable than me, does it accomplish the same protection in case the machine starts to overheat, or do these fuses accomplish separate things?

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I like his use of double wiring throughout. This must create an efficient transfer of energy. I also like his use of cable ties.

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My lights will be placed differently but it's helping to see his.

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His placement of the Sirai PSTAT is high and horizontal. I've planned mine vertical and lower down so the adjustment screw can be reached through a hole in the front plate after removing a cover there. It's been so long since I disassembled my machine I don't remember whether the cup tray lifts off. His installation implies that it does, giving easy access to the PSTAT. If that's the case I'll like use his placement because this will avoid prematurely clogging it with scale.

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He also insulates the boiler, something I plan to do. I would like insulation that does not expose fiberglass externally like that, so if anyone can recommend better material that's also cost effective I'm interested.

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Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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berkinet

#574: Post by berkinet »

drgary wrote:...For those more knowledgeable than me, does it accomplish the same protection in case the machine starts to overheat, or do these fuses accomplish separate things? ...
Different animals. The thermofuse cuts the current if it gets too hot, like if the boiler is empty and the heating element is on. The electrical fuse (10amps in this case) blows (or trips, if you use a circuit breaker) when the current flow exceeds the rated capacity. So, if your heating element is roaring away at 5amps in an empty boiler, the electrical fuse will not blow.
drgary also wrote:... I would like insulation that does not expose fiberglass externally like that, so if anyone can recommend better material that's also cost effective I'm interested. ...
Try McMaster-Carr. I used the 93315K71

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RayJohns

#575: Post by RayJohns »

drgary wrote:I really like his approach to wiring. Here are photos of that. I like his use of a terminal strip and a 10 amp fuse. If the fuse works as well as my thermofuse I'll use his solution instead. The thermofuse is a bit clumsy to work with and the ability to replace a fuse in a receptacle is a more elegant solution. For those more knowledgeable than me, does it accomplish the same protection in case the machine starts to overheat, or do these fuses accomplish separate things?
A thermal fuse trips when the surface (that it's in contact with) increases to a certain temperature. A normal fuse (such as a 10 amp fuse) blows when the electrical current draw exceeds 10 amps (such as a short to ground). The two do not have anything to do with each other. If your boiler goes dry, you can burn the heating elements out by drawing 8 amps. The electrical fuse won't have any idea the boiler is overheating or your PSTAT is stuck, etc.
drgary wrote: I like his use of double wiring throughout. This must create an efficient transfer of energy. I also like his use of cable ties.
As Ferrari says, "Form follows function". Running two wires to everything is a bit OCD for my taste. Is there a point to it? You can run two pipes to the hot water side of your shower also, but there's no real point to it. If the draw to the load is 10 amps, just use a single wire rated at 20 amps or something. Running two wires all over the place just because your terminals have two blades instead of one is aesthetically interesting, but it doesn't really serve any real purpose (unless you are expecting one of the two wires to be kidnapped and held for ransom or something).
drgary wrote: He also insulates the boiler, something I plan to do. I would like insulation that does not expose fiberglass externally like that, so if anyone can recommend better material that's also cost effective I'm interested.
Silica fabric; same stuff I used to insulate the boiler from the electronics in my PID La Pavoni. Probably 1/4 or 1/8 inch thick would be best. You should be able to purchase it on McMaster or perhaps ebay.

I would not suggest using fiberglass around food.

Also ditch the whole double wiring stuff, unless there is some legit reason to employ it (or unless you just have spare wire around and think it looks neat, etc.).

Let me know if I'm understanding the fuse subject correctly. Not 100% sure what you are getting at there.

Ray

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RayJohns

#576: Post by RayJohns »

berkinet wrote:Try McMaster-Carr. I used the 93315K71
+1 on the Ceramic insulation. Silica or Ceramic would both be excellent choices.

Ray

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drgary
Team HB

#577: Post by drgary »

I understand you both. Great help. Thanks. It looks like adding a 10 amp fuse is a good safeguard for its own reasons. Thanks, Ray for taking my mind off the distraction of double wiring. I don't expect it to be kidnapped or anything! :lol:

Does 10 amps seem right for the fuse? My circuits are generally 15 to 20 amps. They are GFCI but I understand that those can fail over time.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

jedovaty

#578: Post by jedovaty »

drgary wrote:Does 10 amps seem right for the fuse? My circuits are generally 15 to 20 amps. They are GFCI but I understand that those can fail over time.
Depends on the draw of your machine.. what's the wattage of your heating element? Work the math backwards to get current drawn, and then add a couple amps to that number to get a fuse power.

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drgary
Team HB

#579: Post by drgary »

1000W. How do I calculate that?

Let's see. Following the formula for Ohm's Law: V/R = I

120 volts/15 ohm resistance = 8 amps. That suggests a 10 amp fuse is correct. Is that right?
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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yakster
Supporter ♡

#580: Post by yakster »

You also have P = IE or I = P/E so for a Wattage of 1000 / voltage of 120 you have a current of 8.33 A.

There is one reason to avoid running two conductors of a lower rating as opposed to just one conductor. If you are counting on both conductors sharing the current load, you could have a different resistance in one of the wires causing the other to take more of the current and overrate the capacity of the wire. You normally want to run just one wire. I suppose you could even theoretically run into trouble if you lifted just one of the wires and all the current flowed through the remaining wire.

That wiring does look clean and I like the placement of the terminal blocks.
-Chris

LMWDP # 272