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I know temp surfing has been done to death but I cant seem to answer this question - is there a difference temp surfing an Australian 240v Silvia to a US model?
It would come down to the difference between the power output of the heating elements of each machine. If the element outputs are the same, then there should be no difference...
I may be wrong, but the 110V Silvias made for the USA market have a lower wattage element.
But when surfing the web for surfing the Silvia info, be aware to read the date on the posts. Much of the material was written when the Silvia had a 110º thermostat. Since then its been dropped to 100º.
Also in line with Mal & Robusta is that, your GPO [240V] has a tolerence of +/- 10% and this will also effect the power output of the heating element and hence the timing of a temperature surf.
Reverse TIME/temp surfing [where you wait for the heater to turn off and then commence timing] is probably more reliable, as it relies only on convection cooling of the boiler, therefore voltages/powers etc have no effect and only ambient temperature becomes a factor.
see http://www.coffeegeek.com/forums/espresso/machines/18247
I would be very interested to play around with different thermostat values in an attempt to narrow the temperature deadband closer too the sweetspot..................has anybody tried/heard anything on this?
Also, worth considering is whether to leave the dosed PF in place for some time, so the grind will have warmed up to the group head temperature, and/or whether a pre-infusion burst prior to brewing would have any effects..............any comments?
Originally posted by reubster link=1171793225/0#3 date=1171840438
I would be very interested to play around with different thermostat values in an attempt to narrow the temperature deadband closer too the sweetspot..................has anybody tried/heard anything on this?
Also, worth considering is whether to leave the dosed PF in place for some time, so the grind will have warmed up to the group head temperature, and/or whether a pre-infusion burst prior to brewing would have any effects..............any comments?
Taking your last point first --preinfusion. This has been covered in previous posts, but....Silvia does not have a group which lends itself to preinfusion. The moment you press the brew switch, assuming the boiler is full, the puck is hit with pressurised water.
Since preinfusion is about swelling the puck with gently-delivered water ahead of the main blast to prevent channelling, momentrily hitting the brew switch and then waiting for a few seconds before continuing, I would think, is not going to achieve that result.
The deadband. Its there for the durability of the thermostat. The more it cycles on/off the shorter its lifespan. I do believe that the deadband on Silvia is ridiculously wide, though.
Originally posted by reubster link=1171793225/0#3 date=1171840438
I would be very interested to play around with different thermostat values in an attempt to narrow the temperature deadband closer too the sweetspot..................has anybody tried/heard anything on this?
Also, worth considering is whether to leave the dosed PF in place for some time, so the grind will have warmed up to the group head temperature, and/or whether a pre-infusion burst prior to brewing would have any effects..............any comments?
You can achieve zero dead band on/off control with most PID controllers. However, this wont remove the dead band as there is a response delay due to the distance between the heating element and the sensor. This can amount to temperature swings of 5 degC or more. PID control is really the optimum for stabilizing the boiler temperature in this machine.
Start/stop preinfusion in the Silvia will not give you what you want, as turning the pump off will also open the 3-way valve and depressureize the puck, probably damaging it in the process. To get a reasonable pre-infusion youd best install an extra switch that just turns off the pump but doesnt operate the 3-way valve. However, to get less hit and miss, it would be better to add a timer to time both the on pulse and the off dwell time before turning the pump back on. Otherwise another idea would be to use a variable rising pump rate by driving a pulse width modulator with a rising voltage with a tunable rate (for the more electronics minded person only).
Warming the dosed portafilter. Yes, as Sparky alludes, not a good idea. Nothing like strong heat to destroy coffee flavour. A lot of effort goes into designing good grinders that wont heat the beans -- and thats at a relatively low temperature, too. Imaging what a hot group will do to the grinds.
The portafilter and empty basket should sit in the group right through the pre-heat cycle so that very little heat loss occurs during brewing,
Enjoyin the discussion guys, I raised the voltage tolerance issue and to an extent the preinfusion/pre warming issues in a devils advocate kind of way as I think some of the "mystique" behind this time surfing needs some myth busting: ie the ideal wait time will vary for all machines/roasts/grinds/ambient temperature etc.
Having said that I love how the pursuit of the perfect shot mixes scientific and emotional arguments. .........just like my other hobbies: diy audiophile and valve guitar amps.
I think I can answer my own question. My Silvia takes about 55 sec to get the boiler back up to temp when I have flushed enough water through to get the light on. This seems to be in line with our US cousins so I guess the heating element has the same output.
There is a way of doing preinfusion on Silvia, but it has an obvious drawback. Simply open the steam valve as you activate the pump, and the pressure and water flow through the group is drastically reduced. Slowly close the valve and the pour will slowly start. Obviously, this will draw cold water into the boiler; the effect will depend on the starting temperature, and might not be a bad thing. I have not systematically compared shots using this technique, but would be interested to know if others have.
Correct, since Electrical power P = [V] Voltage x [I] current.
More current [2.18 X ] in the US [110V] can produce the same power in Australia [240V]
but current or voltage values are not required in the comparison Robusto is making because it is a comparison of powers.
Power is measured in watts [eg 960Watts vs 1100wats]
Heating energy is measured in Joules.
1 watt = 1 Joule of energy dissipated in 1 second
1 joule = the ammount of energy required to heat 1gram of dry air by 1 deg C.
So power will have a direct effect on the heating time.
You could estimate that an Aussie silvia will heat 1.14 times faster [1100/960] but There are really too many variables [eg ambient temp] to make accurate comparisons.
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