is a 2 to 3c drop in group temp normal?

[az erik]

While pulling my double shot I realized that the group is almost always heating now. I have a 3 second PI at 35psi currently and 2.0oz shot volume (I cut it manually anyway). There is an odd whooshing noise during the PI and right when the pump kicks in as if a bunch of water is being sent into the group, is there a group level? or is it a solid compressed piece with no leveler? I consistanly see a 2c to 3c drop in the lights on the front of the unit and have set my offset (before setting the offset I didn't see this drop), my offset is 4+.

Ideas and pointers would be great, I think this might explain my early blonding with PI on.

[Endo]

You lost me. What's a group level?

4c temp drop is normal. New cold water fills the boiler when the hot water is pushed out.

[az erik]

That it wasn't like the steam boiler with a water level, it's only full or full in other words, not at x amount of water and some air. I was thinking that the whole group gets 'fresh' cold water when using PI so it has to mix with the heated water, thus dropping the temp of the brew as well as the boiler. I havnt Scaced the pull to see if it falls off or only the boiler drops temp.

[Endo]

You mean does the brew boiler have a water level probe like the steam boiler? No it doesn't. There is no air in the brew boiler.

Cold water is injected near the back of the boiler. The heater, exsiting hot water and thermal mass of the metal parts bring it back up to temp rather quick.

But don't be fooled by the LEDs. At the group head (which is what matters), the water is remarkably consistant (as my Scace tests show):

http://www.youtube.com/watch?v=L2nAP53H8zI

[az erik]

Perfect good to know, glad I'm running the gamut of noob questions :)

[JonF]

By the way, the whoosh is also pretty typical for the rotary unit too . . . mine does too.