Pulsing coffee maker.

Our coffee maker at work, it’s one of those large basket filter types that brew into a thermal carafe, pulses the heated water onto the grounds. Somebody noticed this and wondered why, so I told her it was to control the amount of water (wetting) on the grounds. Mr. Smarty Pants interrupted and said no, it’s so the water can heat back up.
I know a little about coffee. Both water temp and time are important. For one thng, the thing has a large tank which pre-heats the water before the brew will start. For another, the basket is way too small to handle all the water at once.
If you pull the basket out enough to watch you can see the water level being controlled on the grounds by the timing of the pulses.
Anyone have intimate knowledge of how these things work?
BTW; I use an electric tea kettle and a Chemex pour over filter brewer at home. No machine.

Many coffee makers have a little thermal cutoff switch that trips when some part or other reaches say 95°C. This cheaply imparts an oscillation to the heating mechanism which prevents the water from overflowing the grounds basket.

I think your explanation is the correct one. The water is added in pulses so it can seep evenly into the grounds. If you just added it in non-stop it would pool to one side or the other.

Does the coffee brewer have a seperate hot water spigot on it? If so, wait until there is no coffee being brewed, and fill one of the carafes from the spigot. If the water at the end is still hot, then you know that the machines doesn’t have to stop to reheat water. If the water at the end is colder, then Mr Smartpants might have a point.

More than you would ever want to know about pulse-brew, courtesy of the Bunn-O-Matic corp. (PDF): BUNN - Bunn-O-Matic Corporation

You’re generally right, or at least closer to being right. It’s mostly so you can have a huge honkin’ commercial brewer with a huge brew basket and a huge spray head, but still be able to make small batches without completely swamping the grounds.

That would be “Mr. Smarty Pants”. If you get it wrong he’ll get all huffy. :wink:
But, maybe I’ll try that.

If it isn’t one of those and it’s just your “Mr.Coffee” type coffee maker it’s even simpler.
A water reservoir, some plastic and metal tubing, gravity, a one-way valve, a heating element, and what happens with water when you run bubbles through narrow tubes.

All here.

CMC fnord!

I actually found one.
It’s plumbed, through a filter, to tap water. Ours has the options listed on page two. It won’t let you start brewing until the water is hot. That pretty much discounts Mr. Smarty Pants theory. Nyah nyah!
I should print that PDF and leave it on his desk. Actually, we all have work benches, but choose to call them desks.