La Pavoni pressurestat adjustment

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hankbates
Posts: 446
Joined: 13 years ago

#1: Post by hankbates »

My 1999 vintage LP romantica pro came with what I think is a Signal-Lux M3 pstat, which works well, repeats and has low dead band. Except that I can't seem to be able to get its set point below about 0.7 bar. Measurement is taken on the LP gauge which repeats well and zeroes out.

I have played around with the toothed plastic wheel (I haven't broken it yet) but the adjustment seems to bottom at the above point, and I don't want to push it.
I would like to get the set point down to about 0.4 bar, as I find that I can consecutively make good shots with the boiler at this level, with no group cooling other than the heatsink which makes it look like a renaissance painting.

Has anyone else been able to modify one of these pstats to go significantly lower? Are there others in common use which will allow setpoints this low?

I found the following on McMaster Carr, and think that it may be what I am looking for:
Compact Pressure Switches

Use with air, water, hydraulic oil, and diesel fuel
Pipe Connection: Brass NPT male
Amp Rating: 10 amps @ 125/250 volts AC

Activate controls from process lines in tight spaces. Switches are single pole, double throw (SPDT)-they switch one circuit. Accuracy is ±1 psi or ±5%, whichever value is greater. Housing is brass and seal is Buna-N. Temperature range is 0° to 225° F. Switches have spade terminals and are UL recognized.
Actuation
Range, psi Deactuation
Range, psi Max.
psi Pipe
Size Each

2-10 0.3-1.5 250 1/8 3460K21 $28.14

Product Detail
Compact Pressure Switch, 2 to 10 PSI Actuation Range, 1/8 NPT
Each
In stock
6-30 0.9-4.5 250 1/8 3460K41 28.14



Perhaps I would not be the first to try one of these. Any comments?
They also make a version of this switch for adjustments from 6 to 30 psi which would also be good for me, but also good for those who prefer 1 bar for better steaming.
Some people rescue dogs and cats, I like to rescue Livias…

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AZRich
Posts: 207
Joined: 11 years ago

#2: Post by AZRich »

I replaced my original defective one 2 years ago with this easily adjustable one from Stefano's:

http://www.espressocare.com/products/it ... -la-pavoni

I just tried adjusting it down on my 2009 LP Pro and it bottomed out at .4 - .45 max so should be what you need.
(guess I might as well try a shot there :D )

Rich

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hankbates (original poster)
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Joined: 13 years ago

#3: Post by hankbates (original poster) »

With the Millenium (post 1999) machines, you probably would find that the machine will be too slow to heat up.
The steam heating function in the pre-m group is very helpful for quick startup, but is too much of a good thing for second and later shots.

I am having a little trouble finding the actual thread size on the pstat, the 1/8" pipe connection available on the mcMaster unit may not match up to the pipe....
Some people rescue dogs and cats, I like to rescue Livias…

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homeburrero
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#4: Post by homeburrero »

hankbates wrote:I am having a little trouble finding the actual thread size on the pstat, the 1/8" pipe connection available on the mcMaster unit may not match up to the pipe....
The pStat end of the pipe has a compression cap fitting with a 1/4" BSPP nut. To get the right fit with that 1/8" NPT you'd need an adapter.

1/8" BSP is 28 tpi, NPT is 27 tpi, and BSP is slightly smaller. Because of the NPT taper, a male 1/8" NPT will thread into a female BSPP, but not very far before it binds, so probably would not fit properly.

Here's a nice BSP/NPT discussion: http://viewmold.com/Products/Technical% ... ndard.html

On your pStat, you normally seal where the end of the pStat orifice meets the compression cap, not on the threads.

Note: The element end of the pStat pipe has a 1/8" BSPT male fitting (normally requires use of a sealant), and the PStat end has a compression cap fitting with a 1/4" BSPP female nut.
Pat
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hankbates (original poster)
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Joined: 13 years ago

#5: Post by hankbates (original poster) »

Thanks to both of you, that is just what I needed.
Some people rescue dogs and cats, I like to rescue Livias…