Wiring La Pavoni Pro to indicate pressurestat status

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skyboltone
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#1: Post by skyboltone »

THIS IS FOR 120V US GROUNDED NEUTRAL WIRING SYSTEMS ONLY!! If you want P-stat "on" status for 220V systems, wire a separate lamp in parallel with the element.

Some time ago Homeburrero posted a wiring diagram for the LP pro. He notes on the drawing that you can hook up the line wires either way around on the switch. This is not strictly true. If you put the line wires across the lamp side of the switch, the lamp will be illuminated any time the cord is plugged into the wall. In his diagram, the line cord should be wired to the side of the switch with the wipers. His diagram looked like this:


If you wire it this other way though, the lamp in the switch will only be lighted when there is voltage to the element. This way you can get an accurate idea of when your P-stat opens. On the other hand, the machine could be energized but the light will be dark if the P-stat is open. I suppose this could possibly lead to leaving the machine on and leaving it. Use your head on this mod. The other way to do it is to add a neon lamp in parallel with the element. I may do that.

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homeburrero
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#2: Post by homeburrero »

Dan,

I like your alternative wiring so that you have the switch lamp indicating whether or not the element is powered. Good point about not doing that on 220V - clearly would be a problem on a "split phase" US 220V system.
skyboltone wrote: He notes on the drawing that you can hook up the line wires either way around on the switch. This is not strictly true. If you put the line wires across the lamp side of the switch, the lamp will be illuminated any time the cord is plugged into the wall. In his diagram, the line cord should be wired to the side of the switch with the wipers
Thanks for the note about swapping wires. When I said the wires can be swapped, I meant that the two cord wires on the right side could be swapped, and that also the two pStat/thermofuse wires on the left side could be swapped. I thought I had it covered by saying that both cord wires need to be on the terminals closest to the switch body edge (which are not lamp side terminals) but perhaps I needed to be more clear about that. Maybe I should edit the existing pic to make that more clear in the image? (Not even sure if I can do that, but if it can be done while keeping the same image URL I'll go for it.)
Pat
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skyboltone (original poster)
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#3: Post by skyboltone (original poster) »

The switch will go into the cutout either way; with the power turned on by pressing the back half of the switch, or turned around by pressing in at the front half. I assembled mine earlier today and the light went on regardless of switch position. I had the line wires installed across the light. I've run one boiler full of water through it to flush out the grease and verify everything is working as it should. But that's a story for my restoration thread.

I wasn't quite sure how the light worked inside the switch but your diagram cleared that up for me.

Thanks
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homeburrero
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#4: Post by homeburrero »

skyboltone wrote:The switch will go into the cutout either way; with the power turned on by pressing the back half of the switch, or turned around by pressing in at the front half.
My old Pro and my newer G106 both power on by pressing the front (away from the boiler) half, but I was aware from looking at Francesco Ceccarelli pictures that is not always the case. In fact most of his pics have it in there the other way around.

As long as you know that the outgoing terminals that power the lamp and the element are near the middle of the switch, and that the incoming terminals where the cord wires go are always near the edge of the switch body you should always get the wires to the correct side of the switch.
Pat
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skyboltone (original poster)
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#5: Post by skyboltone (original poster) »

Ahh. Ok, now I follow. I failed to understand your instruction from the diagram.

Thanks
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Almico
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#6: Post by Almico »

I have an LP Pro and never felt the urge to know if the p-stat was engaged or not. As long as the correct pressure is maintained, what does this knowledge do for you?

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hankbates
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#7: Post by hankbates »

Why not just replace the switch with one from a late model europiccola? You will need to add an extra wire or so, but the diagrams are readily available.

I have this setup on my 1999 Pro, and I think it is useful to know when there is power to the element. Because there is some time lag (virtually nothing in these machines happens instantaneously) before the heated water next to the element diffuses through the boiler, you will be feeding somewhat hotter water to the group when the element is on, as opposed to when it is off. The gauge (particularly one with some crud in its tube, or other hysteresis) will lag slightly behind.
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homeburrero
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#8: Post by homeburrero »

I can tell when mine kicks on just by listening and looking at the gauge, but I suppose a light might help. For maximum steam power there's a technique where you open the wand and watch for the light to go on, then close it and count 6 Mississippi (or whatever is right for your machine) before re-opening the wand - that way you have the element energized and hot, and the pressure near max when you start your steaming.
Pat
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skyboltone (original poster)
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#9: Post by skyboltone (original poster) »

Well gentlemen; I have no idea wether it will help or not. It's certainly optional. I just knew from my reading that it is a feature of some of the LP machines. In any case I sure wanted to know when I first turned on this wreck I've been rebuilding. I didn't know what to expect as the pressure rose. I was eyeballing it from around the corner through a pair of safety glasses. As it turned out the needle on the gauge just turned clockwise steadily until it reached exactly 1 bar and then stopped rising. The pressure stat was working correctly.
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skyboltone (original poster)
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#10: Post by skyboltone (original poster) »

hankbates wrote:Why not just replace the switch with one from a late model europiccola? You will need to add an extra wire or so, but the diagrams are readily available.

I have this setup on my 1999 Pro, and I think it is useful to know when there is power to the element. Because there is some time lag (virtually nothing in these machines happens instantaneously) before the heated water next to the element diffuses through the boiler, you will be feeding somewhat hotter water to the group when the element is on, as opposed to when it is off. The gauge (particularly one with some crud in its tube, or other hysteresis) will lag slightly behind.
Thanks for the tip Hank. I wasn't sure if all of the switches are the same size but then of course they are because the replacement bases from Espressocare fit all the models. Good call.
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