HERMS Coil Size/Placement - 55 Gallon System

[brewinginct]

I'm putting together a 55 gallon electric brew system using Blichmann Boilermakers. I'm going to use a HERMS system to control the mash temperature, and I'm trying to figure out the coil size and placement for the HLT.

What size should the coil be (length/diameter)
Where is the best spot on the kettle to install it? Is there any issue with having the coil higher/lower?

Thanks!

 

[benchill]

Have the same setup. The issue with locating HERMS coil is the fact you need two huge elements in there. Instead of the very large Ultra Low Watt Density elements that we originally had, we switched to Low Watt Density (you can't scorch water). This opened up room in the bottom of the kettle. We wanted to place the coil at the bottom of the HLT because our coil mounted higher would be out of the water if we had a good amount of grain in the mash tun. To keep that from happening, we began heating strike water in the boil kettle and keep our HLT with more water in it.

Instead of a large diameter coil, we changed up and went with a 10" diameter coil (25' - 1/2" ID) that would fit between the elements and sit at the very bottom of the HLT.

Also, please know that HERMS will keep your mash temp perfectly but will be very very slow to raise the tun to mash out temps.

I know that sounds like a lot of ramble and a picture would be much better, but I don't have any handy.

 

[brewinginct]

benchill, thanks for the detailed reply! Heating water in the kettle would definitely solve the problem of having the coil exposed. I'll have to look into those Low Watt Density elements, too.

Do you have any tips for speeding up the mash out time?

 

[stevehaun]

You got some great advice from Benchill. I brew 30 gallon batches in a 55 gallon BK. I heat all my water in the BK and then pump into MT and HLT when I mash in.
He made some important points that I want to re-emphasize.
Temp control is function of flow thru the mash, wattage of your HLT elements and the thermal mass of the mash itself. As long as you have at least 9000 watts in your HLT, flow will be your rate limiting feature. I originally had a 25 foot HERMS coil with 1/2" OD (about 3/8" ID) copper tubing. Flow was limited by the resistance of the HERMS coil. I then switched to a 25 foot HERMS coil with a 5/8" OD copper tubing and my flow was limited by my mash (mostly your crush). If you use a 50 foot HERMS coil with 1/2" OD you will likely have poor temperature control and a very limited ability to raise your mash temperature.