Boiler size, and availability of groups for home built lever

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jontyc
Posts: 124
Joined: 11 years ago

#1: Post by jontyc »

  1. I'm planning on using a 1.5L boiler from an spare BZ99 I have, but I see such large boilers in domestic levers such as Achille (4.5L), Leva (5L) and Profitec 800 (3.5L). What's the reason for this? I find plenty of steam and ample recovery from my 1.5L/1300W boiler and thought the extra time inherent in back to back shots on levers would allow even smaller boilers.
  2. I haven't decided on a group yet, but where are people buying LSM, CMA or other feasible groups from? Cost will also be a consideration.
Also a thanks to Andre and the others here inspiring me to go ahead and build one as the lure of the lever has had me for a while, but have just never seen an off-the-shelf one that ticks all the boxes.

aaronmaestri
Posts: 240
Joined: 17 years ago

#2: Post by aaronmaestri »

Im no expert and I'm not sure about the specific machines you mention, but many levers don't use a HX system, they use a dipper system, taking water directly from the boiler to brew the coffee. I would say you would need a larger volume of water for a dipper, just to keep everything stable.
I have a Carimali lever and a FAEMA Urania, both have dipper style groups and both have large 5l boilers.
Im sure others on here will have more informed insights than me

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rpavlis
Posts: 1799
Joined: 12 years ago

#3: Post by rpavlis »

The obvious disadvantage of a large boiler is that it takes forever to get it warmed up!!!!

For steaming you can get by with a tiny boiler IFF the steam tip be properly designed. You need to know the heating element power and determine how much water it can vaporise per second. You need to know the pressure you want. There are engineering formulae that can be used then to determine the diameter of hole(s) in the steam tip that will be correct to keep the boiler pressure up without fluctuating. You can probably find an online calculator to do this. I think I have the formulae some place.

realdoctor
Posts: 192
Joined: 16 years ago

#4: Post by realdoctor »

5 l is about the minimum size for a machine designed for commercial use. It was the defacto standard for commercial single group machines for years. I would guess this has a lot to do with recovery time when pulling shots fast.

I suspect that the answer for home machines is as suggested - a dipper with less than 3 l might have trouble with group temperature. It also would take forever for a commercial group to heat properly. If you are going to use a commercial group on a 1.5 l boiler, you probably want some form of group heating. The Strega uses electric group heating; some machines manage it with a thermosyphon.

jontyc (original poster)
Posts: 124
Joined: 11 years ago

#5: Post by jontyc (original poster) »

I'm thinking that the smaller the boiler however, the quicker a group could get up to temp, as (for a given heater element), there's less water and boiler metal to heat. And with the classic dipper group head trying to dissipate excess heat after a shot, a smaller boiler would help in that it would have cooled more from replacement water than a bigger boiler. Seems like there's an optimal boiler size for a specific arrangement where the boiler reaches it temp at the same time the group head drops to an ideal temp. Wrong?

Managed to find a local supplier of a LSM group head (which I'm getting the best vibes from as well), not too badly priced either.