Re: 240v vs 120v Silvias
You get no arguments there. Without a PID, small boiler non-hx machines such as the Silvia, Gaggia, are like a playground swing in the dark, going from one side to the other. When it finaly settles down, someone (the thermostat) gives it an almighty push once again and off it goes.
--Robusto
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Re: 240v vs 120v Silvias
Well according to PID kits site - a Watlow SD3C on a Silvia takes 120 seconds to recover to steady state .... so without the SSR it would recover all of 1 second faster!!!! (That would require the use of an unreliable mechanical relay) or without the PID altogether recovery time is about 90 seconds - with massive overshoot - taking an additional 100 seconds or so to coast back to ideal temperature.Originally posted by robusto link=1171793225/15#17 date=1172725765
Yes, the SSR does sap a little power, but I wont be standing impatiently next to the Silvia cursing that its taken an extra 1/500th of a second to reach steady state!
--Robusto
I know what Id prefer
.
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Re: 240v vs 120v Silvias
Yes, the SSR does sap a little power, but I wont be standing impatiently next to the Silvia cursing that its taken an extra 1/500th of a second to reach steady state!Originally posted by JavaB link=1171793225/15#16 date=1172722828The effect of that voltage drop is compounded as 1% less voltage causes 1% less current to flow in the appliance- so the power becomes 0.99 X 0.99 or 98% of what it should be - in Australia it is 99% of what it should be..... and longer cables make this even worse in both cases! (like extension cords on heat guns)
This is also significant with PIDs where the solid state switch drops about a volt (often a bit less)..... this also reduces heater output far more in America than in Australia......
Thus endeth the "Circuit theory 101 lecture"

--Robusto
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Re: 240v vs 120v Silvias
One other thing to remember when talking about American appliances...
Because the voltage is half and the current must therefore be double for the same power output (very approximate for ease of explanation):
The voltage at any appliance is lower than the supply because current flowing through the power cables causes voltage to drop due to the "resistance" to current flow - so American power cables are thicker to (hopefully) reduce this drop.... but a 1 volt drop in America is 1% where in Australia it is only 0.5% of the voltage.
The effect of that voltage drop is compounded as 1% less voltage causes 1% less current to flow in the appliance- so the power becomes 0.99 X 0.99 or 98% of what it should be - in Australia it is 99% of what it should be..... and longer cables make this even worse in both cases! (like extension cords on heat guns)
This is also significant with PIDs where the solid state switch drops about a volt (often a bit less)..... this also reduces heater output far more in America than in Australia......
Thus endeth the "Circuit theory 101 lecture"
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Re: 240v vs 120v Silvias
When looking for how much "grunt" an appliance has, you have to look at watts. Thats irrespective of whether youre in the USA, Melbourne or in your 12-volt car.
The current in the USA is approx twice that of Australia, but when working out what power the appliance has, you look at Watts.
watts = amps x volts
A 4 amp appliance in the US would produce 440 Watts (w= 4 amps x 110 volts)
But a 4 amp appliance in Australia would produce 960 watts ( 4 amps x 240 volts).
A 50 watt TV which can run on 12 volts takes a hefty 4 amps of current, (which can cause heating along the power circuit).
The same 50 watt tv on 240 v draws a trifling --and safer-- 0.2 amps.
These are approximations only, as mains power is probably closer to 230 V and 12v power can range from about 13.8 volts down to 11 for a flat battery.
--Robusto
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Re: 240v vs 120v Silvias
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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Re: 240v vs 120v Silvias
Not unless the current is higher than what were running in Australia!
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Re: 240v vs 120v Silvias
Just visited a US website selling the Silvia, and for that market a newer model has a 960 watt boiler, while the standard model is 800 Watts.
In any case, both are less powerful than the Australian and Eurpean models at 1100 W.
So the overseas modles would take longer to heat the same volume of water -- 300 ml.
--Robusto
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Re: 240v vs 120v Silvias
Hey CJHFIELD
55 sec is about inline with my Silvia too, unless the weather has been extrene [2 weeks of 30+ in Melbourne recently]
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Re: 240v vs 120v Silvias
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.
Matt
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Re: 240v vs 120v Silvias
240v should have a lower current draw than the 120v machine if that is the case....
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Re: 240v vs 120v Silvias
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.
Chris
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Re: 240v vs 120v Silvias
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.
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Re: 240v vs 120v Silvias
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,
--Robusto
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Re: 240v vs 120v Silvias
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.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?
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).
As for warming the puck, try it and see....
Cheers,
Mark.
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