Since installing a PID on my Linea, I realize how much incoming cold water affects the brew temps and am now on a mission to preheat the brew water. I've tried wrapping the steam boiler with copper piping and running the cold water through that pipe prior to entering the brew boiler but there isn't enough heat transfer to keep the water hot. I was thinking that I could add a water line that goes in to the steam boiler and then back out to the brew boiler. Would this work? If it could, is there a mathmatical formula to calculate the length of piping required to heat the flowing water about 100f when travelling through the steam boiler's tank? I was thinking I could use the flange on the heating element to gain access to the boiler but if I have to, I could just drill two holes in the boiler tank and install the pipe fittings.

mitch236 wrote:I realize how much incoming cold water affects the brew temps and am now on a mission to preheat the brew water.

Move.
Presently, the cold water tap at my house is producing water that is no lower than 87 degrees Farenheit. If I get to it early in the morning.
Nothing worse than getting all hot and dirty and sweaty doing yardwork, jumping into the shower, and turning the cold tap on full only to be doused with water in excess of body temp.
I guess my point is that you could get a two or three gallon holding tank that would stabilize at room temp. cold water running into that would change the temperature little, and water from your reservoir would be less cold.
Or, you could get your incoming water from the hot side of the house circuits instead of the cold?

mitch236 wrote:I was thinking that I could add a water line that goes in to the steam boiler and then back out to the brew boiler. Would this work?

This is exactly how some DB machines work, like the Izzo Alex Duetto II (as well as the Brewtus III, not sure for this one).

See the Bella Barista Closer Look (3.5MB PDF): http://www.bellabarista.co.uk/pdf/IzzoAlexDuettoIIcloserlookv4.pdf,
schematic on page 3 and multiple pictures where you can see the steam boiler HX outlet to the brew boiler.

There are issues with doing this. In contrast with a regular HX machine, you cannot flush the HX over-heated water... it always ends up in the brew boiler. The HX needs to be appropriatly configured such that it:
- avoids bringing too much over-boiling water (which sat for too long in the HX) into the brew boiler
- and at the same time still preheat cold water enough to be useful.

Izzo indicates that they found a custom and undisclosed way to address this... (see page 8 of the same PDF).

Also, if you intend to add the flexibility of turning off the steam boiler (for economy/heat production reasons), this will also affect the water temperature coming to the brew boiler.

--
Louis

Does it affect brewing temp or brew boiler temp?
I have a hard time believing the heat transfer happens so fast from the inlet to the group on a 1.8L boiler. It's just 0.05L water.

mitch236 wrote:Since installing a PID on my Linea, I realize how much incoming cold water affects the brew temps and am now on a mission to preheat the brew water. I've tried wrapping the steam boiler with copper piping and running the cold water through that pipe prior to entering the brew boiler but there isn't enough heat transfer to keep the water hot. I was thinking that I could add a water line that goes in to the steam boiler and then back out to the brew boiler. Would this work? If it could, is there a mathmatical formula to calculate the length of piping required to heat the flowing water about 100f when travelling through the steam boiler's tank? I was thinking I could use the flange on the heating element to gain access to the boiler but if I have to, I could just drill two holes in the boiler tank and install the pipe fittings.

Three approaches -

1) Play with PID tuning so that you get a system that reacts quickly and aggressively to cold water coming into the boiler. The neck of the boiler has a convection loop within it, but the surrounding metal damps out some temperature variation, and lets you get away with aggressive PID tuning while still providing repeatable brew temps. This works pretty well on multi-group Lineas. Dunno if the boiler on a single group is too small for this trick to work.

2) Install a small point of use hot water heater between the pump and the boilers. I believe that this was David Schomer's trick, and according to Bill Crossland it works pretty well.

3) As I recall, Paul Pratt built some feedwater preheat pipes that could be retrofitted into Linea steam boilers. You might contact him for details.

-Greg

sweaner wrote:Mitch, how much is it really affecting your brew temperatures?

Probably not much but I can see by the PID readout that the boiler temp drops by almost 10f pulling one shot. I have to do some pre-shot ritual which includes getting the PID into overheat mode right before pulling the shot so the heater element is on when I start. With my current proceedure I can keep the measured pf temp within a half of degree. It is more of an exercise in control rather than better coffee!