Problem Boiling 4 gallons with a 2000 watt element

[dyqik]

Well just tried it plugged in direct and got the same results getting to 150, but it's still not boiling and its been 35 mins and its only at 204. This sucks.

Those numbers make sense to me. Warning - some (mostly simple) thermodynamics follows:

The heat loss from the walls of your kettle to the air (and your plywood base), as well as by evaporation from the wort surface, is proportional to the temperature difference (everything else being equal). If it's 80F where you are, then the heat losses at 140F are half of what they are at 200F. If you only have only a small amount of power more than you need to reach a boil, then the rate of increase will slow down by a large factor as you get close to boiling. The boil-off rate you eventually achieve is set by the amount of power available after subtracting your heat losses (as stated by other posters). You can measure your heat losses by turning the element off and measuring the rate of cooling of the wort - lid off for walls plus evaporation, lid on for wall losses only. If you have a breeze or other airflow, the heat losses will go up substantially, particularly on humid days.

You will have much higher losses from a large 11 gal uninsulated kettle than Bobby has from his HDPE bucket - SS is a better heat conductor than HDPE, so your kettle walls are hotter. The entire wall of the kettle is probably very close to your wort temperature, while Bobby's bucket will probably only be as hot as the water where the water is in contact with the inside of the bucket wall. This means that you might well effectively have two times the surface area losing heat, so losses that are twice as high as Bobby's bucket.

I can't boil 7 gal of wort in a sensible amount of time in my uncovered uninsulated 8 gal SS kettle using just a 2kW HotRod (drawing ~1.8kW on my wall voltage according to my Kill-A-Watt) without supplemental heat. It seems to stall at around 200-205F in a cool apartment kitchen (I tried this in winter). Your kettle is even larger, and will have higher losses than I do. Note that the volume of the wort doesn't matter very much here, it's mostly the size of the kettle that determines the heat losses. More or less wort doesn't really affect the maximum (equilibrium) temperature, just the rate of increase to that temperature.

Brewing systems like the Grainfather and Braumeister use insulated kettles with lids so that they can get away with 1.6kW and 2KW respectively. Even then, they apparently only get around half a gallon per hour boil off - one gallon an hour needs more heat input.

TL;DR version: Insulate your kettle, and put a lid on it until it boils. Even then, you might want more heat.

 

[Weezy]

Yep
+1
Wrap it with a towel

And put the lid on until you get a boil going.

I get a gentle, rolling boil on 4 gallons with an 1800W induction cooker.

 

[FizzerNoob]

Awesome replies here. It's just underpowered.

 

[Don204]

I have one wrap of reflectix on it now, maybe I will add a second. The lid on until it boils won't be a problem? All the nasties should escape during the boil I imagine. I'm feeling like I may just add a second element anyway to speed things up, I should have less evaporation if I can reach a boil quicker right?

I wonder if there is a foam board I could put under the kettle insulate the bottom.... It would have to handle high temps, any thoughts?

 

[FizzerNoob]

Insulate, lid on until the boil begins... I'd personally add another element. An 11 gallon SS kettle, is worlds apart from an HDPE bucket in terms of thermal properties.

 

[Jwin]

I have one wrap of reflectix on it now, maybe I will add a second. The lid on until it boils won't be a problem? All the nasties should escape during the boil I imagine. I'm feeling like I may just add a second element anyway to speed things up, I should have less evaporation if I can reach a boil quicker right?

I wonder if there is a foam board I could put under the kettle insulate the bottom.... It would have to handle high temps, any thoughts?

Could probably use foil covered foam, though I'm not sure how it would handle the weight

 

[MrVix]

I use a Brewhardware 1500 watt stainless steel 120 volt element. My brewpot is insulated with that foil insulation. It will boil 6 gallons of wort vigorously.

 

[Don204]

So in case anyone is interested I picked another 2000 watt element and hotrod heat stick from Bobby and I got 6 gallons from 150 to boil in 19 mins