How do I install thermal protection on a Conti Prestina?

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negrocorto
Posts: 133
Joined: 17 years ago

#1: Post by negrocorto »

I am about to finish rebuilding/restoring my Conti Prestina, now that I have replaced the element that burned out due to a slow drip/steam, which caused the water level to drop, thus the fried element. Can anyone show me how to adapt some sort of thermal protection device, or send me to a site with a tutorial or explanation? I really want the best protection I can manage in order to prevent this mishap again.

Is this what I should be looking for, a thermal link cut-off? https://www.espressoparts.com/128-thermal-link-cut-off

I would prefer a resettable device, but if this is easy enough to install and get to, this thermal link will do.

Thanks for your help!

HoldTheOnions
Posts: 764
Joined: 9 years ago

#2: Post by HoldTheOnions »

There are two types of thermal protection.

First is if the thermostat fails, you have a second fuse (which you linked to) or safety thermostat that will kick in and kill the power. This is a necessity to prevent fire / water damage / exploding boiler.

Second is a water level probe that keeps enough water in the boiler so the element doesn't burn out. A thermal fuse or safety thermostat won't sense the element is overheating if there is not enough water in the boiler. The second is nice to have, but not a necessity. It could cost more than heating element to add this to your machine, if not already a feature. Have to do more research unless someone else can speak to it here.

OldNuc
Posts: 2973
Joined: 10 years ago

#3: Post by OldNuc »

The slow leak that does not cause a boiler pressure loss without an automatic level maintenance system is near impossible to protect against unless there is a sight glass and then a simple optical level sensor can be rigged up to kill power to the element on low level. This type of system is going to cost between $50.00 and 250. 00 depending your level of electronics expertise and mechanical ability. There is nothing that is going to come out of a box and be designed to fit with directions in good English.

negrocorto (original poster)
Posts: 133
Joined: 17 years ago

#4: Post by negrocorto (original poster) »

I was afraid of that, and was hoping someone could explain how to protect my machine, because frankly I had a hard time envisioning it. Unless someone can explain something I'm not aware of, I'll let it go and just be more vigilant at keeping an eye on the water level through the sight glass.

Thanks for your input.

OldNuc
Posts: 2973
Joined: 10 years ago

#5: Post by OldNuc »

I looked up the parts and made a rough hookup drawing for a La Pavoni but as it has to fit around the sight glass it looks weird all out in the open. Some units where the glass is viewed through a rectangular opening in the case it would be out of direct user view. After giving all of this some thought I decided it was simpler to just make sure that there was water in the machine and it did not have a valve open when at pressure. Also do not turn it on and walk off, watch it heat up to pressure so if there is a leak you can shut it down.

If you hold a pencil behind the sight glass when it is full of water and rotate the pencil so its axis is at a 45 degree angle to the sight glass angle you will see that you have rotated the view of the pencil seen through the sight glass about 25 degrees off the pencil axis. This is how the sensor functions the light source and receiver can not see each other if there is water in the glass due to this refraction. Lots of surplus sensors out there for about $40.00 ea. Then you have to build out the remainder of the circuit as the sensor will not switch 10A-20A heater power.

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drgary
Team HB
Posts: 14348
Joined: 14 years ago

#6: Post by drgary »

Another possibility is to install a PID and set an alarm condition that shuts down the machine if temperature exceeds a pre-set level.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!