Electric HLT Version 2

I use an picnic cooler electric hot liquor tank with PID control because of these factors:

  • Heating element + insulated cooler = efficiency in both heating the water and keeping it hot
  • PID control allows for “set and forget” temp control
  • Convenience of a HLT (even for batch sparging)

It has the following features which are detailed in the below sections.

  • 240V operation
  • Control box
  • PID control with SSR for element
  • Agitator
  • Float switch
  • Sight “glass”

I don’t have a detailed parts list or cost breakdown because I didn’t keep track of that kind of stuff.  Feel free to contact me (or leave a comment) with any questions about the project.

So I built this thing in 2009, and am still using it as of May. 2015!  I’d say having an automated HLT is the #1 timesaver in my brewday.

Construction Overview

I used a rectangular 48qt cooler because that’s what I had on hand.  In the end this format worked very well because the split lid allows for the agitator to remain fixed while allowing access on other side.  Also the shape let me orient the water heater element horizontally which lets it heat a much smaller volume of water than if I had to position it vertically.

Front
Front
Side View
Side View
Inside View
Inside View
Back wall with both float switches
Back wall with both float switches.  The plastic one is only there to fill the hole.

The heating element is a 240V, 4500W copper element from Menard’s.  On the inside it’s secured and sealed with a 1″ stainless locknut and o-ring, both from Bargin Fittings.  I did leave on the element’s stock rubber gasket which provides an extra seal from the back.

The thermocouple is a 6″ K-type probe secured in a 1/8″ compression x 1/8″ MPT fitting.  It’s secured on the inside of the cooler with an o-ring and 1/8″  locknut.

The drain bulkhead is based around a cooler kit Bargain Fittings used to offer, a 1/2″ hex nipple with a washer soldered in the middle.   In the below photo you can see the washer on the outer cooler wall.  A female coupling moves the valve away from the cooler so that the handle freely operates.

Spigot Bulkhead
Spigot Bulkhead

It’s not obvious from the photos but all of the wall “piercings” sandwich the inner cooler wall.  That is, I cut a large hole in the outer wall, scooped out the insulation, drilled the hole, inserted the bulkhead, and then tightened the locknut right against the inner wall.  This gets you a much better seal than trying to tighten a locknut against the outer cooler wall as you don’t have an inch of squishy foam in between.

240V Operation

Using 240V was key to this project because it let me step up to higher power heating elements.  I first installed a 50A GFCI breaker in my panel, and then ran 8 gauge wire out to a 4-prong outlet.  I used four contacts (with the fourth being common, or white) just in case I needed to operate a 120V device off of this same plug.  If I ever do, I’ll be sure to fuse the sub circuit in order to keep the main breaker balanced.

4 prong outlet
4 prong outlet

25′ of 10/3 appliance cord links the outlet to the HLT’s rat tail plug.  I put in this plug right before the HLT so that I can disconnect the bulky power cable and transport it  separately.

Control Box

The heart (and guts) of this whole this is the control box.  The shell is an 8″ x 8″ steel conduit enclosure attached to the cooler with self-tapping sheet metal screws.  This enclosure is not waterproof.

Control Box
Control Box

Three switches are mounted in the front panel.  The main switch is a DPST 20A switch which controls both power leads.  The second switch runs inline with the SSR to provide a manual shutoff for the element.  The third is  a DPST switch used to control the agitator motor.  I tried to keep things tidy by using a terminal bar across the back but it’s still pretty hairy in there.  The main culprit is that I used solid 10 gauge wire instead of stranded so it doesn’t lay down very well.

Inside the Box
Inside the Box

The PID controller and SSR+heatsink I got off of eBay.  In mounting the SSR heatsink I was able to simply sandwich the box wall.  Using some thermal paste on each side, and it pulls off quite a bit of heat.


The thermocouple is a 1/8″ diameter, 6″ long K-type.  Its 1/8″ diameter makes it a perfect fit for mounting with a 1/8″ compression fitting.

Thermocouple by itself

 

Agitator

The agitator centers around a 240V, 60RPM gear motor I got from Surplus Center.    Note that the motor did not come with a cooling fan, this I yanked from a torn-apart breadmaker.   Without the fan it gets pretty hot so I’d recommend using one.

The mixer is a Lowe’s paint mixer with the head mounted right down next to the heating element so that the water will be mixed regardless of the remaining volume.   Coupling the 3/8″ motor shaft (with flat) to the 5/16″ mixer shaft involved two bushings, one store-bought and one home made.  The store bought one is a 3/8″ bushing which slips onto the motor shaft.  I tapped a #6 hole into one side of the bushing to be able to use a set screw.  To fill the gap between the mixer shaft and bushing I used small a piece of brass sheet.  I forget what the exact gauge is, but it’s about 1/32″ thick.  Two layers of this (one on either side of the shaft) nicely fills out the 1/16″ gap.  First I wrapped it around the shaft using pliers and hammer and then hammered on the motor bushing.

Forming the Bushing
Forming the homemade bushing
Fitting Motor Bushing Onto Mixer Bushing
Fitting Motor Bushing Onto Mixer Bushing
Fitting the Motor
Fitting the Motor

I used a piece of 5/16″ hobby wood as a motor mount.  I would have screwed the motor directly to the lid but its bolt holes were far too tall for any sheet metal screws I had.

Agitator Mount
Agitator Mount
Agitator in Action
Agitator in Action

Float Switch

I mounted a float switch immediately above the heating element in order to prevent accidental burnouts.  It’s  wired inline with the PID controller’s SSR output.  It’s a stainless right-angle switch from “cute-elec”, also on eBay.

Stainless Float Switch
Stainless Float Switch

When I first build the HLT I used cheaper, plastic float switches from eBay.  I went through two of them before switching to the spendier stainless model which have a higher temperature tolerance.  However as you can see from the photo at the top of the page this “stainless” switch  has started to rust in a few spots.. looks like I’ll have to find a better one!

Plastic float switches fail!

Sight “Glass”

My sight glass is a simple piece of 1/4″ tubing.  This is much less breakable and cheaper than a real glass.  A 1/8″ MPT x 1/4″ barb fitting serves as the bulkhead, with an o-ring and 1/8″ locknut holding it together.

Sight Gauge
Sight Gauge

Circuit Diagram

This is how everything logically connects not how the actual physical wiring is done.

Circuit Diagram
Circuit Diagram

9 thoughts on “Electric HLT Version 2

  1. I noticed that the plastic float switches sold on ebay are rated up to 85C, have you had any trouble with yours at boiling temps? There are stainless steel ones rated to 125C for a little more $.

    • Odd that you mentioned this, last month the float switch died on me. I only ever take the HLT up to 172F (78C), but I wouldn’t doubt that the cheap component couldn’t handle even that temp.

      The stainless ones on eBay look pretty slick! And you’re right, they don’t cost that much more.

  2. Nicely done. I see you switch both legs of the 240V. Very smart as a lot of people only switch 1- as though it were 120V. I also like the way you interlock the float.

  3. Looks great…I’m on my third iteration of the sous vide machine now…and yours is the direction I want to head down next. How do you keep the plastic bags from the food away from the immersion element?

      • ah…:) Makes sense.

        Cooking food actually. I’ve got a very similar set up for cooking steak, chicken, turkey…all sealed under vacuum (=french term ‘sous vide’) in a heat resistant plastic bags. Same components – only difference is you put food sealed in plastic bags in the box for long periods at precise temperatures. eg – medium rare steak is 53.5 degrees c for anywhere between 8 and 16 hours…chicken it’s a bit higher 80 degrees c for anywhere between 4 and 8 hours.

        I’ve got a really similar set up to yours, but using top mounted thermocouples and heaters (with a stainless steel surround). I’ve blown a couple of immersion heaters though when there has been slightly too low a water level and it’s been enough for the heater to melt it’s contacts.

        Grateful for your thorough documenting of what you’ve set up though!

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