Hi,

Some background: I'm making my own espresso machine, I wanted to make a dual boiler, but to be honest, it's just getting too complicated for the steam boiler, so I decided to go thermoblock for steam production, not ideal, but its so much simpler.

I picked up a Jura made thermoblock, 120v 1200watts, mostly because the donor machine was $12 at a thrift store, and it works.

I wanted to know how to control the thermoblock for making steam. I have a pump which periodically I'll activate for a pulse to get some water in there. However, how long do I leave the element on, should I monitor the temperature of it? What should the desired temperature be? Should it be on full blast, or do I need to control it via relay for intervals?

Any advice is appreciated.

Thanks

At a minimum, you want a reliable method of preventing it from overheating (eg, when it runs out of water).

I'd also consider just using a separate pressure cooker like system that sits on the kitchen stove - simple and it produces much more steam.

I'll be doing the same thing for the OSLP machine. You can see it on the lever boards. Right now I'm working with one for brew. Mine is 1000w and stainless internals. It has a factory brew, steam and thermal cutoff thermostats. I wire the TC inline with the heating element, then pulse it with a SSR. The actual temp control is a thermocouple back to a controller, so the TC is just the safety. You can add a thermal fuse to this as well if you'd like.

For steam, temp probably isn't so critical, so you could drive it with the factory thermostat. The only reason I'm using a SSR for steam is that I don't want both elements on at the same time to exceed 15a.

Temp I monitor at factory locations, which is just surface metal temp, but quite close to the heating element I believe.

Thanks for the replies

I guess overheating is a problem, I like the SSR/thermocouple route, especially with 2 heating elements, though coordinating them might be some fun. Since I ripped out all wires, fuses, etc and have no idea what the factory controller was actually doing, I'll start very conservative with respect to power/temperature until I get enough steam that seems dry enough. Does anyone know how long in seconds I can starve a thermoblock from water when it's on full power before overheating? I.e. is it a few seconds or a few minutes?

EspressoForge: A few questions:
- For steaming how many milliseconds do you pulse the pump? And how many milliseconds off between the next pulse? Also when pulsing is it full power or some sort of PWM? If PWM, whats the duty cycle? I'm guessing the standard ULKA style pump.
- How do you plan to interleave the duty cycles between the two elements when you're simultaneously pulling a shot and steaming?

Hi
A steam thermoblock just needs a controller with minimal histeresis, therefore i run my QM Silvano with an old Auber-PID in on/off mode at 160° C. A resettable thermostat will do the job for overheating protection.
Since all coffee thermoblocks are designed for single shots (which means an average flow rate of about 60cc/s) an ULKA NME feeds the thermoblock very well, quiet and without further electronics.

Also important is the steam tip with an adequate hole size..

Regards
BM

Great, thanks BM! 160c it is. How about flow rate for steam? I'll just adjust pulsing until I get a good constant steam. I keep hearing of "wet" steam by thermoblocks, is there any way around this? I.e. what if I go a few degrees higher than 160?

diy_hacker wrote: - For steaming how many milliseconds do you pulse the pump? And how many milliseconds off between the next pulse? Also when pulsing is it full power or some sort of PWM? If PWM, whats the duty cycle? I'm guessing the standard ULKA style pump.

I have no pump, I'm plumbed in at 2 bar line pressure regulated. I also haven't connected the steam side, but my plan is to use a spare needle valve to reduce flow. I'm using one for brew and I like it, but I don't know what flow requirements will be needed for steam. It's possible I may not need anything other than to size the steam tip correctly.

diy_hacker wrote: - How do you plan to interleave the duty cycles between the two elements when you're simultaneously pulling a shot and steaming?

I don't plan to. My machine is a lever, so if I really wanted to I'd start my shot, then flip a switch to steam priority, then steam. I'm really not that coordinated, so even on my BDB (or Strega I used to have) I didn't pull and steam at the same time.

Also, FWIW, I don't use much milk, so my steaming requirements aren't that high. That's why I went for a TB on steam, I don't see the point if I only rarely steam milk for myself, and 90% of milk goes to guests. And of those guests, I'm guessing 90% couldn't tell the difference in steam quality.

The factory thermostats for the Ascaso TB are 98C (brew), 165C (steam), and 190C (thermal cut-off). I don't know if this would apply to your thermoblock...I would look up the specs to be sure, but I'm guessing it can likely handle a fairly wide dead-band. That is how the simple thermostats operate.

IMO modifying any device on an espresso machine, you should really know what you're working with and what the specs are. Thermoblocks aren't that complex and it might not be a big deal, but this is how I prefer to do it with anything electrical or electronic. If I couldn't find info about a part I was using on my build, I would change it out for sure.

diy_hacker wrote:Great, thanks BM! 160c it is. How about flow rate for steam? I'll just adjust pulsing until I get a good constant steam. I keep hearing of "wet" steam by thermoblocks, is there any way around this? I.e. what if I go a few degrees higher than 160?

The maximum flow rate is reached when the temperature does not stabilize and still drops after the heater has kicked in. For the QM Silvano the combination of 1000W heater and ULKA NME is quite fine. The temperature swings between 140° and 180°C and the steam is dry like a fart in the desert

Below 140°C you are losing pressure and below 120°C the steam becomes quite wet. On the QM with the built in thermostat this happens if you steam larger amounts (500ml pitcher) because the heater kicks in too late. (@140°C).

Basically a cheap on/off controller with 5A relais would do the job but mostly they have a slow NTC sensor therefore i use my old Auber PID. That's the main advantage of small steam boilers - they can be controlled fast and reasonable cheap by a pressure stat. And they have a faster ramp up when you start steaming, but that's all.

Regards
BM