Hello from me and my Conti Empress - Page 4

A haven dedicated to manual espresso machine aficionados.
Sansibar99
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#31: Post by Sansibar99 »

Hi Matt,
I think, you'll get along with a cheap multimeter...
Regarding physics class: I learned some bits then & there, but forgot most of it over the years ;-)

What really astounds me when I think of it:
Boy, the things I learned from restoring espresso machines... ! :mrgreen:

@kaldi61: I found a fine tutorial on an old OE-site, for the cases of element resistance going infinite. This could happen, if you had water entering from the top. Doug removed the isolaters and carefully baked the element dry in his kitchen oven. Then he re-isolated it - and could continue using it.
LMWDP #422

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drgary
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#32: Post by drgary »

I tried awhile back to learn the basics of circuit testing with a multimeter and put together this guide in a restoration thread.

How To Think Like An Electrician

Orphan Espresso's explanation of shorted heating element testing and repair is here.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

Mattsaxon (original poster)
Posts: 32
Joined: 9 years ago

#33: Post by Mattsaxon (original poster) »

Hi all

Still not a lot of progress on the resto, I have work deadlines whistling past my ears thick and fast and sadly the old people dramas show no sign of abaiting.

Any way I have ordered hopefully all the fastenings etc required for the rebuild when it eventually begins, in the meantime I tried quickly testing the elements with a meter, I didn't have much luck getting a resistance reading, so just to make sure I wasn't flogging a dead horse I took Nelson's tip and wired them up individually and did a quick test - they get very hot very fast, so that's a relief. I still want to find out how to test things like this properly.

I will probably have to as I have just picked up a 50s Fiorenzato grinder, the motor hums but it doesn't want to spin, the top bearing has literally eaten itself, so when I have replaced the bearings hopefully it will work if not I will have some trouble shooting to do!

My next job will be to have the frame and heat shield stripped and zinc plated I was going to nitromors it and spray but I think the zinc plate will be a longer lasting solution.

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kaldi61
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#34: Post by kaldi61 »

Hey Matt - tell me what kind of meter you have, and what happened when you tried to measure resistance. One of the things I always do when I am measuring resistance is I touch the two test leads together, making a circuit, and the resistance on the meter should fall to zero. Then you can say it's working, although it's no proof of accuracy. Resistance measurements are in general the 'right' way to check them, and I believe when they do fail their resistance usually goes up. If you get a short, i.e. no resistance, some part of the element is touching something it shouldn't.
-Nelson

LMWDP #506 "It's not just for breakfast anymore."

Mattsaxon (original poster)
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#35: Post by Mattsaxon (original poster) »

Hi Nelson

Annoyingly I think the multimeter I bought might not be working. When I set it to measure resistance it always shows 1 on the display which the manual states either means to set it to a higher setting which makes no difference or that the circuit is open or there is no input, when I touch the probes together it stays at 1 it also has a continuity setting with a buzzer, again when I put this across say a fuse or touch the probes together - nothing.

Equally this could be user error but the continuity tester should be pretty foolproof.
Frustratingly because I am so electrically illiterate I have no way of knowing for sure. :roll:
I would be happy to leave it that the elements heat up so all good, but they were originally wired in parallel so I don,t know how it is important it is to check the resistance.

The elements are stamped as 800w 220v.

On a separate note I have aquired an old Fiorenzato grinder from the 50s I have replaced the bearings and while doing this I noticed that it has 220v / 50hz stamped on the stator plates there is no further info on the machine in the form of a plate. Initially I assumed that the machine was single phase and didn't spin because of a seized top bearing, however I am beginning to think it is more likely to be a 3 phase motor as it has no capacitor or centrifugal switch for a split phase/starting winding which I think explains why it hums but only turns a fraction of a rotation. It simply has 3 wires -red,black and white going directly into the windings which seems from my research to be common for lower voltage 3 phase motors but again I have no way of testing continuity across the wires which apparently is one way to confirm this. It's a lovely grinder and I am happy to invest in a single to 3 phase inverter to run it, but would like to be sure that it is 3 phase before shelling out for the inverter.
Maybe time to find a local electrical engineer who works with motors - not that easy in the UK.

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drgary
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#36: Post by drgary »

Hi Matt,

Here's a link to a site that tells you how to use a multimeter. This may help.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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Paul_Pratt
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#37: Post by Paul_Pratt »

Matt it would seem to be a 3 phase motor.

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kaldi61
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#38: Post by kaldi61 »

I believe Paul is right. You are right about three-phase motors not normally having capacitors either for starting or running. Three phase motors take 3 hot lines. Based on the incomplete plate information, you cannot tell. 220 v could have been single phase, two hot lines (black and red) and a white neutral. But with the lack of capacitor, and the fact that it's just not working, I think you have your answer. A 60-70 year old 3 phase motor may have plenty of life in it, but investigate carefully if you want to go with a phase-changer versus replacing it with a 220v single-phase motor. Or get the house wired for 3 phase - which is a goal of mine so at some point I can outfit my shop with a ridiculously large lathe and vertical mill, way bigger than a human would ever need. Or a 3-phase Robur! :D
-Nelson

LMWDP #506 "It's not just for breakfast anymore."

Mattsaxon (original poster)
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Joined: 9 years ago

#39: Post by Mattsaxon (original poster) »

Hi guys

Thanks for the link Gary, it was helpful to check my basic understanding against the clear steps on there, anyway long story short the probes on the meter are defective, I took them out and ran a length of wire between the ports on the continuity test setting and got a result so I will take the unit back and exchange it, at least it wasn't user error this time :P

Paul and Nelson I agree all the signs point to three phase and I guess as a lower voltage rating with only 3 wires it's also likely though not definitely delta wired which will enable me to hopefully use a simple starter / drive unit like this one. I might even be able to wire in a DC rated switch in place of the existing to operate the remote input circuit of the drive unit.

https://www.motorcontrolwarehouse.co.uk ... 1kb12.html

I think because the motor is such an intrinsic part of the grinder construction swapping it out for a single phases unit would probably not be possible, the idea of having a 3 phase supply is of course the most desirable for exactly the reasons you outlined there are so many fantastic second hand 3 phase tools out there :twisted: unfortunately I don't think the budget will stretch to that one :(

Thanks again for all the help, I have the frame for the Conti stripped and painted and am tentatively starting a dry run on the reassembly as time allows. I'm still trying to decide where / how is the best place to add a vacuum breaker for timer switched start up, I quite like the idea of taking it off a T at the top of the pipe that runs to the pressure gauge and the pressurestat if that would work, I don't really want to put it in boiler top plate as there are already a lot of holes in there and I don't want to do a drill and tap and damage the plate if I stuff it up.

Mattsaxon (original poster)
Posts: 32
Joined: 9 years ago

#40: Post by Mattsaxon (original poster) »

Sorry 2 posts in one day, so necessity being the mother of invention and today being Good Friday and the shops are shut I put my bush mechanic fix on the multimeter to use. Firstly on the elements for the Conti using a length of 240v lighting flex (resistance showing as 0.01 ohms on the meter) as my "probes" I got readings of 69 and 65 ohms for the 2 elements respectively. Using an online calculator against my own basic understanding I think this equates to approximately 3 to 3.6 amps per element?

Also using the same leads I did a simple continuity test across the 3 wires on the grinder motor which showed continuity A-B, A-C, B-C with resistance of 26.4 ohms across each pair of wires. Using the same calculator this gives me figures of 1830 watts and 8.3 amps.
edit: after further reading from what I can understand the resistance across a pair of wires equates to 2/3 of the total resistance for the motor so the actual resistance is more like 40 ohms giving a wattage of 1210 and and amperage of 5.5.

I will do some research on what sort of ranges I should be expecting for the elements and motor, any feedback definitely welcomed :P