Measuring boiler and pump pressure

Equipment doesn't work? Troubleshooting? If you're handy, members can help.

#1: Post by NicoNYC »

Hi all,
I am in the process of fixing up my first real espresso machine; an Expobar Office Pulser in mostly working condition (I needed a project to keep me busy and off the streets). It needs a thorough descaling, the replacement of some leaking fittings and seals, but besides that functions and produces something which approximates espresso. My goal was initially to get the necessary parts replaced and modify it down the line as I got used to using it, but I'm starting to realize that I need to be able to measure brew and boiler pressure in order to get it just serviceable. I don't see it as a particularly precious machine so I don't mind cutting up the case, putting in parts from other brands, etc.

- The previous owner removed the OPV, I can easily get the proper replacement but have no feedback for dialing it in. For about $40-50, I can rig up a temporary gauge on my portafilter, for not much more I could install a gauge that measures the brew pressure. Is there an advantage to either approach? Will real-time brew pressure be useful feedback in dialing in shots or am I best off just setting the OPV once and forgetting about brew pressure?

- The boiler safety valve leaks slightly when the heating element is on. I plan to replace it regardless, but I'm unsure if it's just leaky, or if my pressurestat is failing or incorrectly set (possible scale deposits). I'm assuming the best way to determine this is to hook a gauge up to the boiler. If I do this, I will probably tee it off and leave the gauge inside the machine so I can occasionally check, or is it useful to have a boiler pressure gauge externally visible?

- Does anyone have any recommendations for gauges? If I go with permanently attached, I'll likely get them from a similar prosumer machine so as to have BSPP fittings, something like this: ... duct/15654. I like that this has already has a tube w/ a 1/4" fitting, but premade 1/8-1/8" tubes are available, so I'm open to suggestions on other brands or types of gauges to buy.

- Thread sealing. It seems like Loctite 567 is the way to go, good to 400° and safe for drinking water. Do I apply sealant to every thread that doesn't have some sort of gasket or o-ring to otherwise seal?

I've tried to state my questions as clearly and thoroughly as possible, but thanks in advance for reading this block of text. Also if there's anything else I ought to be doing while I've got it all apart for descaling, I'm all ears.

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#2: Post by randytsuch »

I've used my Office Control for many years now, so here's my opinion

I can't see a reason to add a visible boiler pressure gauge.
Pretty sure I measured boiler pressure via a heavy duty hose through the steam wand early on with my office. I did that to set the pressure lower, in conjunction with adding a thermosyphon restrictor so I could flush less. Before those changes, had to flush a lot to get to temp for a shot.

Built in brew pressure would only be useful if you could make on the fly changes. I'm working on a project to change pump power on the fly, and if I succeed, I'd like to know pressure so I could make adjustments. But if you can't adjust, then I don't see a use for a built in pressure gauge.

I made a portafilter pressure gauge long time ago, with a needle valve, so I could set for a little flow. Set my Office for 9 bar with flow. Checked recently and still at 9 bar.

Instead of measure pressure, I now measure weight of beans in, weight of shot out, and time of shot. I normally stop my shots 25 secs after first drip from bottom. If I hit the shot out target weight, and shot looks good as it comes out, pretty good chance I'll like the shot.

One thing that I added that is really useful is a thermocouple in the group head. Bought an adapter kit from member here, Erics. Your Office needs to have a threaded hole in the group head. So I can flush to a temperature, and adjust temperatures if I think they are off.
I built an arduino based box to read and display the temps. Also has a running timer I use for shot times. I'm sure there are other ways to read and display the temperature, but its harder with an office than with an exposed group machine where you can stick a digital thermometer there.

NicoNYC (original poster)

#3: Post by NicoNYC (original poster) »

Hi Randy,

Thanks for sharing your thoughts, it's especially helpful as you seem to have a similar mindset towards modding/tinkering to add whats useful but not what is superfluous.

I'd actually been planning to add a thermocouple to the grouphead, so it's good to hear that will be helpful. How do you like your arduino solution for displaying the thermocouple temp? I have a spare PID from a sous-vide build that I'll likely repurpose as a temp monitor but might consider going down the arduino path - I bought one many years ago and have been trying to teach myself how to program for it. Do you have any pictures of your setup you could share?


#4: Post by randytsuch »

This was a long time ago, over 10 years, there were fewer options at the time.

I used a TC4 (intended for using for a coffee roaster) to read the thermocouple because I had one. Since I had extra inputs, I put one tc on the outside of the boiler, and one tc on the group head.

Also has running time so I can time my shots

Don't use the buttons now, but will come in handy when I upgrade this later.