Our Valued Sponsor
OpinionsConsumer ReviewsGuides and How TosCoffeeGeek ReviewsResourcesForums
Espresso: Espresso Machines
Overheating HX Machine - The Pressurestat isn't the only reason
Rancilio Silvia - How to
Step by step guide for easy brewing and steaming with the Rancilio Silvia
www.seattlecoffeegear.com
 
Not Logged in: Log In to Postlog in
New Topics updated topics   New Posts new posts   Unanswered Posts new unanswered  
Search Discussion Board search   Discussion Board FAQ faq   Signup sign up  
Discussions > Espresso > Machines > Overheating HX...  
view previous topic | view next topic | view all topics
Author Messages
new_ton
Senior Member


Joined: 11 Apr 2014
Posts: 18
Location: Chincoteague Island, VA
Expertise: I love coffee

Espresso: La Pavoni Pre-Millenium, La...
Grinder: Baratza Virtuoso Preciso,...
Vac Pot: Yama Stovetop (5 Cup)
Drip: Hamilton Beach Carafe
Posted Sun May 11, 2014, 8:19pm
Subject: Overheating HX Machine - The Pressurestat isn't the only reason
 

I've been trying to get my La Spaziale New EK running and it's been consistently overheating. First thought was it had to be the p-stat. I took the p-stat (Sirai) apart and it had a lot of gunk in the diaphragm and the lever action was hard/sticking. After cleaning and lubricating the p-stat it moved much more freely. I reinstalled it and turned the machine back on. No joy, the thing still over heated/pressurized.

Next step was to buy a new p-stat. I found a good deal online and ordered one. It arrived and I installed it in place of the old p-stat. Problem solved right? Yeah, I don't think so Tim. The machine continued to over pressurize/heat.

At this point I'm frustrated and decided to go to my next issue, a leaking hot water valve. By leaking, I mean it was dripping out of the spout whenever it had been on for awhile. I purchased new o-rings for the valve and gave it a nice citric bath prior to the o-ring install. Removed 3 decent and one fossilized o-ring and put the valve back together. The leak had reduced but there was still a trickle. Extremely frustrating.

This got me to thinking the two might be related and I decided to just cap off the hot water valve to see what would happen. Wouldn't you know it, the darn machine started working. The boiler would get up to 15 to 20 psi and the p-stat would kick in and maintain that pressure. Apparently the line that feeds the pressurestat also feeds the hot water valve on my machine. I believe that this is a common design feature as the p-stat requires stable pressure and the hot water valve requires...water, which means both items ideally are fed from the bottom of the boiler (stable temp and guaranteed water).

Now the question is do I source a new (rarely used) valve for my machine or leave it capped off. Alternatively, the spring inside the valve may just be giving up the ghost and needs to be replaced. All I know is that I have two good p-stats now and a machine that puts out a mean espresso.

So if your machine is over pressurizing and you have a leak from your hot water valve, that valve may be your culprit. It may be common sense to some, but it took me a couple of days to figure that one out. Guess I'm slower than most :-P.

Just thought I'd share my little story.
back to top
 View Profile Link to this post
frcn
Senior Member
frcn
Joined: 23 Dec 2001
Posts: 3,427
Location: Northern California
Expertise: Professional

Espresso: Vibiemme Domobar Double
Grinder: Mazzer Kony, Baratza...
Vac Pot: Hario, 2 Cory pots, 1 Cory...
Drip: Behmor Brazen, Bunn A10 mod...
Roaster: computer controlled Hottop,...
Posted Sun May 11, 2014, 9:12pm
Subject: Re: Overheating HX Machine - The Pressurestat isn't the only reason
 

I don't buy that explanation (doesn't necessarily mean I am right), but the pressure in the boiler is the same for the steam as well as the hot water at any given time. Sure, water does not compress, but it can still be under pressure. If the steam reading is 12 pounds of pressure the water pressure will be the same (pound of feathers vs. pound of iron).  And the pressurestat is binary- either on or off. If the boiler reaches "X" pressure and that is the set point, the pressurestat turns the boiler off. if there is a slight leak then the result will be a shorter duration of "off" for the pressurestat. I would pull the plumbing for the pressurestat/hot water valve and be sure that there is no scale, and I would drain or flush the boiler to be sure that there is no floating bits of scale in there that sometimes blocks the flow to the pressurestat. The pressurestat controls the heating element, and the the only way the pressurestat can create a too-hot boiler temperature is to stay on too long (not turn off soon enough) and the only way that can normally happen is either having the pressurestat adjusted too high or the pressurestat not reading the pressure in the boiler correctly and staying on too long.

 
Visit My Website
www.EspressoMyEspresso.com
back to top
 View Profile Visit website Link to this post
new_ton
Senior Member


Joined: 11 Apr 2014
Posts: 18
Location: Chincoteague Island, VA
Expertise: I love coffee

Espresso: La Pavoni Pre-Millenium, La...
Grinder: Baratza Virtuoso Preciso,...
Vac Pot: Yama Stovetop (5 Cup)
Drip: Hamilton Beach Carafe
Posted Mon May 12, 2014, 5:24am
Subject: Re: Overheating HX Machine - The Pressurestat isn't the only reason
 

This is true in a closed (static) system, however it is quite different in a system that has a leak (dynamic) and an additive feature (boiler autofill). With the boiler continually heating, steam continues to be created and the pressure in the upper portion of the boiler continues to rise which in turns "pushes" the water below the steam down as the system tries to reach an equilibrium. In a closed system, this equates to the water and steam being roughly the same pressure. Since I had bleed off thru the hot water valve, the water pressure never reached the required 22 psi (1.5 BAR) needed to open the p-stat. Due to the effenciency of the heating element relative to the small size of the boiler, the steam pressure continued to rise and push down against the water, increasing the steam pressure. The water then dripped out of the hot water valve lowering the pressure enough that the pressurestat could never open and turn off the heating element. The autofill function occurred around 32-36 psi (2.3-2.4 BAR) due to steam escaping from the overpressure valve on top of the boiler. Even at this pressure,which is way too high, the p-stat could not open and the leak from the hot water valve got going at a good pace. The pressurestat recieved pressure from the bottom of the boiler (water) while the Pressure gauge recieved pressure from the top of the boiler (steam) and the difference was very noticable.
back to top
 View Profile Link to this post
frcn
Senior Member
frcn
Joined: 23 Dec 2001
Posts: 3,427
Location: Northern California
Expertise: Professional

Espresso: Vibiemme Domobar Double
Grinder: Mazzer Kony, Baratza...
Vac Pot: Hario, 2 Cory pots, 1 Cory...
Drip: Behmor Brazen, Bunn A10 mod...
Roaster: computer controlled Hottop,...
Posted Mon May 12, 2014, 10:24am
Subject: Re: Overheating HX Machine - The Pressurestat isn't the only reason
 

What you have here is a sealed system. A leak in one specific place in this system affects the entire system with a minor exception that does not (or should not) apply in this case.

B = steam area in boiler
C = Water Area in boiler
G = Auto fill input

Even if there is a leak at "F" the pressure measured at "A" is very nearly the pressure in the entire system. If water is entering the system at "G" and the pressure increases, then the pressure in the entire system is increased virtually equally. The pressure sensed at "E" which is the pressurestat is so close to the rest of the system, it would take some very precise measuring to sense any difference. In a properly operating system the difference would be the friction caused by the water flowing through the pipe D. If F were of sufficient flow (like a full-flow pour), and there was some sort of restriction in the pipe "D" then there would be a lag in pressure drop in the boiler. But the differential you discuss is extreme and could only be possible if the D plumbing were very small diameter OR (and this is a big, important "OR") that there is a restriction or floating debris in the tee and the tube that leads to the pressurestat which causes the pressurestat to lag behind the pressure in the boiler and thus turn off very late. If being a dynamic system caused this sort of radical pressure differential then no such boiler system would work.

There are situations in boilers that do not have a vacuum breaker valve and a false pressure is sensed by the pressurestat upon startup (as in the Oscar and in Salvatore's machines) that causes LOW boiler temperature. But in your case we have something else going on which is most likely extremely HIGH water level in the boiler (like nearly filled), so when the heating element is turned on the "air" (or steam in this case) is virtually non-existant so pressure rises very quickly. Or maybe a clogged pipe not allowing the pressurestat to sense the correct pressure and leaving the heating element on too long. The slow leak from the hot water valve (as I understand it from your description) is a red herring and not the cause of this effect.

So, since you said that there was crud in the pressurestat, we can assume that there is also crud (and likely scale) in the rest of the system. I would pull the water level sensor out and check it for scale. That is the most likely cause of the very high pressure to which the pressurestat cannot respond quickly enough. After that, suspect the water level circuitry.

frcn: system.gif
(Click for larger image)

 
Visit My Website
www.EspressoMyEspresso.com
back to top
 View Profile Visit website Link to this post
jonr
Senior Member


Joined: 25 Jun 2013
Posts: 299
Location: Americas
Expertise: I like coffee
Posted Mon May 12, 2014, 11:46am
Subject: Re: Overheating HX Machine - The Pressurestat isn't the only reason
 

The #1 cause of all pressure-stat problems - the owner hasn't yet installed a temperature sensor + PID controller :-).
back to top
 View Profile Link to this post
calblacksmith
Moderator
calblacksmith
Joined: 25 Nov 2007
Posts: 7,864
Location: Riverside, Ca, U.S.A.
Expertise: I live coffee

Espresso: ECM Vene. A1, La Cimbali M32
Grinder: Azkoyen Capriccio, Major
Vac Pot: 40s era Silex
Drip: Msl. Com. brewers
Roaster: gave it a try, decided no
Posted Mon May 12, 2014, 12:00pm
Subject: Re: Overheating HX Machine - The Pressurestat isn't the only reason
 

While i suppose it is possible that the pstat is plumbed into the water side, i have never seen it done.
Pressure is equal at all points in the system. The water level is set by a probe in the boiler and is not dependent at all on pressure.

I suspect that the issues are related to clogged lines and scale buildup.  The water drip should have no affect other than the need to refill the boiler often.  I have had leaking valves and they have never caused an over pressure condition.

 
In real life, my name is
Wayne P.
Anything I post is personal opinion and is only worth as much as anyone else's personal opinion. YMMV!

Feed the newbs, starve the trolls and above all enjoy what you drink!
back to top
 View Profile Visit website Link to this post
new_ton
Senior Member


Joined: 11 Apr 2014
Posts: 18
Location: Chincoteague Island, VA
Expertise: I love coffee

Espresso: La Pavoni Pre-Millenium, La...
Grinder: Baratza Virtuoso Preciso,...
Vac Pot: Yama Stovetop (5 Cup)
Drip: Hamilton Beach Carafe
Posted Tue May 13, 2014, 9:43am
Subject: Re: Overheating HX Machine - The Pressurestat isn't the only reason
 

All I know is that once I capped the hot water valve both p-stats started working (I put the original back in). Whenever I removed the p-stat, the water was free flowing out of the 1/4 pipe to the point of soaking thru the hand towel I wrapped the pipe in while I fiddled with the p-stat (10-15 minutes). We are moving at the end of the month (new job) so I do not want to dismantle the machine to check for scale. SWMBO would kill me, as I have a lot of other projects to wrap up. I will post an update sometime next month with my findings. Thank you all for your input!
back to top
 View Profile Link to this post
frcn
Senior Member
frcn
Joined: 23 Dec 2001
Posts: 3,427
Location: Northern California
Expertise: Professional

Espresso: Vibiemme Domobar Double
Grinder: Mazzer Kony, Baratza...
Vac Pot: Hario, 2 Cory pots, 1 Cory...
Drip: Behmor Brazen, Bunn A10 mod...
Roaster: computer controlled Hottop,...
Posted Tue May 13, 2014, 10:39am
Subject: Re: Overheating HX Machine - The Pressurestat isn't the only reason
 

We are approaching deer whistle and aluminum hat territory..   ;-)

 
Visit My Website
www.EspressoMyEspresso.com
back to top
 View Profile Visit website Link to this post
view previous topic | view next topic | view all topics
Discussions > Espresso > Machines > Overheating HX...  
New Topics updated topics   New Posts new posts   Unanswered Posts new unanswered     Search Discussion Board search   Discussion Board FAQ faq   Signup sign up  
Not Logged in: Log In to Postlog in
Discussions Quick Jump:
Symbols: New Posts= New Posts since your last visit      No New Posts= No New Posts since last visit     Go to most recent post= Newest post
Forum Rules:
No profanity, illegal acts or personal attacks will be tolerated in these discussion boards.
No commercial posting of any nature will be tolerated; only private sales by private individuals, in the "Buy and Sell" forum.
No SEO style postings will be tolerated. SEO related posts will result in immediate ban from CoffeeGeek.
No cross posting allowed - do not post your topic to more than one forum, nor repost a topic to the same forum.
Who Can Read The Forum? Anyone can read posts in these discussion boards.
Who Can Post New Topics? Any registered CoffeeGeek member can post new topics.
Who Can Post Replies? Any registered CoffeeGeek member can post replies.
Can Photos be posted? Anyone can post photos in their new topics or replies.
Who can change or delete posts? Any CoffeeGeek member can edit their own posts. Only moderators can delete posts.
Probationary Period: If you are a new signup for CoffeeGeek, you cannot promote, endorse, criticise or otherwise post an unsolicited endorsement for any company, product or service in your first five postings.
Home Espresso Machines
Watch videos with Gail & Kat, Rocket, Jura Capresso, Saeco, Rancilio, Quick Mill, Nespresso
www.seattlecoffeegear.com
Home | Opinions | Consumer Reviews | Guides & How Tos | CoffeeGeek Reviews | Resources | Forums | Contact Us
CoffeeGeek.com, CoffeeGeek, and Coffee Geek, along with all associated content & images are copyright ©2000-2014 by Mark Prince, all rights reserved, unless otherwise indicated. Content, code, and images may not be reused without permission. Usage of this website signifies agreement with our Terms and Conditions. (0.322829008102)
Privacy Policy | Copyright Info | Terms and Conditions | CoffeeGeek Advertisers | RSS | Find us on Google+