Boiler Electric to Propane Conversion

Need help with equipment usage or want to share your latest discovery?

#1: Post by alittlemohr »

Hi, New to this site. Just converted my Mr. Espresso to propane. Wanted to post just in case anyone is looking to do the same and wants to save themselves some of the hassle I went through. : ) If anyone has any questions let me know. I am almost done making my commercial coffee maker run on propane as well. I will try to take more pictures tonight. I wanted to use a variable pressurestat but ended up using the existing p-stat relay in the machine. I chose to make it just propane even thought it would be easy with this model to switch from propane to electric or both with a simple switch. This machine has an extra lead in the relay that can be used for the thermostat line of the propane system. I used propane systems from RV heaters. If I do it again I will use the fully automatic (no pilot) system from Suburban. You can get the individual parts online for about 125 dollars.

My project is for a full coffee shop on a rickshaw. Check it out if you like: Should launch in about a month.

Chad C.

#2: Post by Chad C. »

My god man... Welcome, for starters!

How are you going to run the pump and solenoids for what looks like a solenoid group machine? Your work on your flame tube & Venturi set-up demonstrates understanding and ability, but I'm not sure that you'll get the tunable and efficient results that the CMA/Astoria gas kit provides, especially in an outdoor setting.

I can't orient myself in regards to the propane delivery system, is it a diaphragmatic design? More info (lots of pics, and ideally a video) about the relationship between boiler pressure and the application of fuel would be of interest.

I have a two group lever machine that runs on propane most of the time, and I love it.

alittlemohr (original poster)

#3: Post by alittlemohr (original poster) »

Still working on pictures. I will have more in about a week when everything gets mounted to the cart. The flame is set to one setting and then kicks in when the electricity would normally do so. My cart requires 220,110, 24v dc and 12v dc so there is a lot going on. The espresso machine has 220 going to it for the controls ad 12vdc for the propane valve. I installed a computer fan behind the ventri to make the flame a little hotter and cleaner. It starts just fine but once the system warms it does not burn quite as clean without the extra air. The cool thing will be the commercial coffee maker. The espresso machine took 25 minutes to reach temperature from ambient temp. I have made some adjustments and expect it to take about 20.

I wish I had a lever machine but this was a great deal at $650 with a grinder. I will have to keep my eyes open for a lever back up!

Chad C.

#4: Post by Chad C. »

Damn, that's quite a contraption! So it sounds like its pressurestat is wired to 12v, and sends or interrupts the 12v current needed by the propane device to deliver and ignite the fuel? If I'm even close, I've never heard of such a thing. Innovative!

One of the things I like about the propane system on my machine is that its fuel delivery and subsequent flame size are incremental, meaning that the flame size isn't all or none. This keeps the boiler and the groups at a very constant temperature. The system instantly delivers the correct amount of propane to create a flame size that keeps the boiler at its set pressure. Immediately as the steam valve is opened, the flame size increases. The standard machine's electrical pressurestat cycles between an average of about two tenths or two atmospheres on the gauge, which equals a difference of 8-10 degrees for the water at the grouphead. With the electrical pressurestat, the boiler will have to reach its low point in the cycle before it sends electricity to the heat source.

My rig is entirely free-range, meaning that it can go anywhere. Its water is supplied by the Flo-Jet BW3000A 12v DC. I power it with a riding lawnmower battery, and it lasts forever. It sends pressurized water to the water inlet of my machine, so when I actuate the manual water fill lever, it actuates the Flow-Jet and fills the machine. The system, and the response of the propane regulator to the steam valve is shown below:

I look forward to seeing what you've been up to. Keep posting, your design ability is impressive!

alittlemohr (original poster)

#5: Post by alittlemohr (original poster) »

The Velspresso Cart has been inspected by the health department! If you are ever in Milwaukee check us out! If you have any questions on a propane conversion of an espresso machine or a coffee maker let us know.

User avatar
Team HB

#6: Post by TomC »


This is all very cool and it's a great thing that you're sharing what you've done and learned, but please avoid posting the same topic in multiple sections of the forum. It will be easier to follow if it's left in one thread.

Join us and support Artisan Roasting Software=


#7: Post by pocojoe »

Great Job!

I see how you turn off the main burner with the pstat; but what are you using for a pilot assembly, for when the pstat kicks the propane back on, and how do you shut down the main flow of propane should wind blow out the flame?

It looks like there is a valve that has a small line running from it- is that for a pilot light? Is there a thermocouple in the system?

can you tell us what control you used - a Johnson control from Suburban?

Agree that diaphragm control is more trouble than it is worth!

Thanks for posting!

Safety Third- First Roast, then Grind


#8: Post by PeppercornEspresso »

Hey everyone this is my first post here so don't hold back.

I read this thread about converting an espresso machine to propane and was so glad to have found it. I am setting up a coffee cart to use in versatile settings and I would love it to be self sufficient. Batteries plus lpg(what we use instead of propane in Australia) seems like my only option*. My machine is a 2group Cimbali m21 and it actually had a factory option of using gas and has the space available and a hole for a knob. I don't expect to be able to find the factory parts (or particularly want to pay the kind of premium I would expect).

Anyway has anyone else done what Alittlemohr did? Or does anyone know him personally so I could get in contact with him. He mentioned would be happy to explain what he did in more detail. I have a pretty good understanding of what to do I just don't want to have to reinvent the wheel if he's already made the mistakes and learnt from them.

thanks in advance!
*it would be my preference no to have to use a generator if I don't have to (a quiet (still loud) generator rated at the wattage I need would cost a lot as well as being inelegant)


#9: Post by sfellars »

This is relavent to my interests!