the good news is the pressure transducer is easy enough to install if you have the very early LR model without the relay, and even easier if you have the current LR with the relay (which the pressure transducer eliminates)

so i am comfortable that users will find it straight forward to upgrade their LR

we have some fine tuning to do; the programming needs to be altered to hold the pressure set by the user (it currently defaults to 3.0 bar every time the machine is turned off) and we need to put a delay on how often the pump cuts in restore the pre-infusion pressure to the set pressure

for example, if the pre-infusion pressure was set by the user to 3.0 bar, as the water soaks down into the puck the volume of the pre-infusion circuit in effect increases and so the pressure drops

the pressure transducer obviously detects the smallest drop in pressure and so the pump is coming on for a fraction of a second to lift the pressure by a fraction of a bar back up to the target pressure of 3.0 bar

with the pump cycling on and off many times in a second to maintain the pre-infusion pressure at 3.0 bar it results in a noise that will cause the nervous owner to ask if anything is amiss and the last thing i want is a flood of emails arising from a cosmetic issue of this nature.  so we need to add a delay in, perhaps the pump will not turn on until the pre-infusion pressure has dropped 0.2 or 0.3 below the target pressure, for example.  this should make it sound less erratic, and reassure owners that their machine continues to function normally

other than those two issues it worked exceptionally well 'out of the box'

i will update you again when we place the production order, and after that it is simply a waiting game for the producer to deliver them to us, probably in September or October i imagine

it is clear that i have not done a great job of explaining how our machines differ, and which one is best for your needs

it is probably easist to start with the L3 and work down

for whatever reason i sense there is a perception that lever espresso machines somehow work by magic internally and nothing could be further from the truth; they are very simple and easy to understand

secondly there seems to be a sense that the LR is somehow different from the L1/2/3 commercial range and again this is a misunderstanding

so, starting with the L3.  it is a 20 litre boiler lying east-west in the machine, with a 7.5KW immersion element in it

running north-south through the boiler are three inclined heat exchangers; they start low at the back where the cold water feeds are connected and are inclined at about 45 degrees and exit near the top 'front side' of the boiler immediately behind the groups

when the cold water enters the bottom of the heat exchangers the hot water of the surrounding boiler heats the cold water in the heat exchanger, causing the hot water to rise towards the top of the heat exchanger

at the top of the heat exchanger one thermosiphon pipe connects the top of the heat exchanger to the back of the lever group; the return pipe for the thermosiphon is connected from the back of the lever group down to the bottom of the heat exchanger where the cold water enters

the pressure switch for the immersion element has been set to turn the element off at 1.0 bar and this should never be altered; on all our current models the brew temperature is not regulated by altering the boiler pressure.  please do not adjust it or you are likely to experience an erratic performance from the machine

instead you match the L3 to the roast you are using by adjusting the pre-infusion pressure, which in turn adjusts the preinfusion temperature (and by extension the brew temperature) and when the pre-infusion pressure is altered the brew volume also moves

a central concept to keep in mind when using a lever machine is the idea of equilibirum.  so if we raise the pre-infusion pressure the shot volume increases and the pre infusion temperature is raised significantly.  happily all these three variables are moving in the direction that we want them to if we want to make an espresso using a lighter roast, i.e. none of the movements are working against us in our desire to extract a light roast correctly.

the same is true if we wish to extract a dark roast optimally; we reduce the pre-infusion pressure and the shot volume reduces and so does the pre-infusion temperature

how do we change the pre-infusion pressure on the L3?  with a high quality pressure reducing valve and gauge which is fitted to the cold water line, external to the machine, as shown in the attached image

it is exactly the same method of regulation for the L2 and the L1; an external pressure reducing valve (regulator in North America), and a gauge attached so you can tell what pressure you have exiting the valve

here is the next important message in this post: in prinicple the LR is regulated in exactly the same way as the L3/2/1 and delivers an espresso of equal taste and quality

what is special about the LR is we have worked hard to make it a plug and play unit so everything is 'in the box' and it takes up less room in a domestic kitchen

with the LR there is no need to go off and source an external pressure reducing valve and gauge, no need to connect the machine to a cold water connection, no need to plumb the machine to a waste water connection

for the LR our latest effort to offer an upgrade to customers from the standard Mater pressure switch (which regulates the pre-infusion pressure by turning the pump on and off) is merely a refinement so users can change the pre infusion pressure quickly and precisely, but the manner in which the LR works is not changing

the LR is a commercial machine in the sense that it makes coffee to the same high standard as the L1/2/3, but it is not a commercial machine in the sense that by definition it has a lot more 'gear'  inside and that will always get beaten in the reliability stakes in the long run if it is set against the L1 which has almost nothing inside the casing that can fail with high 24/7 usage in a tough commercial environment with mutltiple operators of the machine, perhaps none of them caring to any extent about the well being of the machine

in the LR with the optional pressure transducer and electronic adjustment that owners can purchase to replace the Mater, this allows you to change the pre-infusion pressure and know exactly how much you have moved the pre-infusion pressure by.  once you know what pre-infusion pressure you consider optimal for any given roast it means any adjustment you make to the pre infusion pressure you will get 'right first time', without the need to recourse to physical pressure gauges to measure the pressure at the puck

one thing is for sure; if you want to run light roasts on a lever espresso machine pre-infusion at boiler pressure is hopeless.  you need a machine that allows you to pre-infuse at a pressure greater than boiler pressure, becuase the dose is larger and the the grind is finer, and also becuase you want a higher brew temperature to eliminate any sour notes that a light roast will put in your cup if you pre-infuse at boiler pressure.  with a modern nordic style roast it is highly likely that pre-infusion will not complete in a reasonable time (less than 30 seconds) if you are pre-infusing at boiler pressure

with the variable pre infusion pressure offered on our londinium lever machines you can run it like a dipper (1.5 bar pre infusion, or even less if you wish) or take the pre-infusion up as high as 6 bar if that is your desire.  in practice we have never found a need to take the pre infusion pressure above 4.0 bar, but the opportunity is there if you wish

Finally we have our prototype electronic pre-infusion control to test and sign off into production

This unit will be made available as a post purchase bolt on for all the existing LONDINIUM R owners