Sunday, 9 September 2012

Brewery Build #24: New HERMS vessel

The plastic-cooler HERMS vessel worked fine, but didn't like being dropped on the floor.  The plastic was old and brittle and the double-insulated-layer made it difficult to repair.  While I was considering what to do about the HERMS container, Aldi had some stainless 'compost buckets' on special.

My DIY HERMS coil fitted exactly inside the 5L stainless bucket, so it was just a matter of adapting the bucket to fit and adding the heating element.  The trusty TCT hole-saw was used to make the hole in the base of the bucket for the element:

Since the element was a bit larger than the 32mm hole, it needed to be enlarged some:

Enlarging the hole with a hand-file was tedious and boring, so I found a grinding-stone and attached it to the cordless drill, which made the process much quicker:

Our kitchen-kettle was getting a bit old, with the cordless contacts not always working, so I purchased a new kettle for the kitchen and re-used the element from the old kettle for the HERMS.  It looked like this once it was removed from the kettle-housing and the plastic trimmed down a little:

The gasket from the kettle-element was used to measure the hole and hold the element and mount in place:

However, since the wall of the plastic-kettle was much thicker than the stainless bucket, the gasket and screws did not seal adequately.  A new insert-gasket was made by cutting out a silicon baking tray:
I thought it might be amusing to keep the little LED light, but not sure it will serve much purpose and might remove it.

The installed element:

Leak testing:

Checking that it all works when plugged into the PID:

And finally, with a couple of holes drilled into the lid, and lots of fiddling to get the HERMS-coil attached, in use:


  1. Hey, I've just stumbled across your site and I'm really impressed with your brewing rig!!! I've been trying to come up with a good design for a HERMS vessel and I really like what you've come up with.

    Now that you are using the stainless compost bin, do you plan to insulate it to reduce the amount of power you need to pump into the system?

    Since you've become a master at bending stainless tube, is there any chance you'd like to build and sell one of these units?

  2. Adding insulation is very probable, but for the moment I'm just seeing how it goes. Some theory might suggest that leaving it uninsulated helps the PID balance the temperature more easily (if the PID over-shoots it acts as a heat-sink to drop the temps).