Build yourself a cheap digital boiler power regulator

[Nicks90]

@The-Engineer-That-Brews , thanks for the explanation. It's really helpful. My background is in mechanical, so I normally steer clear of any electronics but in this case I'm not sure what would be a safe alternative.
I have a 3kW tea urn which boils way too vigorously. An SSR with the appropriate heat sink will probably do the job but it needs a rather complex (for my skill set) control circuit. I guess a could use an SSR with resistance control but I couldn't source one. What else can I use?
@Bill_g, appreciate your point, a good airflow is a must.

@GeorgieV
Before going to all that bother of electronics, take the plastic /metal cover off the bottom and take a look at your elements.
I have a 2.5kw urn and when I bypassed the faulty over temp cut off I noticed it has two bonded elements to the base. A 1kw and a 1.5kw element wired in series.
My plan is to simple wire in a rocker/cam switch that means I can use it full power or flick the switch one way and isolate the 1kw element to achieve a more sensible boil.
20amp 4kw cam switches can be had for a tenner like this one.

 

[Nicks90]

Ps. This will replace the existing on/off switch.
Alternatively you could just add a 2 way rocker switch to enable disable one of the elements and leave the existing on off switch in place.

 

[GeorgieV]

@GeorgieV
Before going to all that bother of electronics, take the plastic /metal cover off the bottom and take a look at your elements.
I have a 2.5kw urn and when I bypassed the faulty over temp cut off I noticed it has two bonded elements to the base. A 1kw and a 1.5kw element wired in series.
My plan is to simple wire in a rocker/cam switch that means I can use it full power or flick the switch one way and isolate the 1kw element to achieve a more sensible boil.
20amp 4kw cam switches can be had for a tenner like this one.

Thanks @Nicks90 , it's a good idea. Mine has 2 elements in parallel. I assume they have equal power rating. I suppose a cam switch should work, though it won't be a smooth power transition.

 

[bobukbrewer]

I have used a triac with an aluminium sheet 15 inches by 12 inches by 1/8 inches as a heat sink for over 15 years. I used proper heat sink paste between the triac and the aluminium. It is mounted on my garage wall, 3 inches from the plate to the wall, to allow good airflow. It is plugged in to a normal 13 amp socket for both safety and legality.