[gav]

240V 5.5kW 15G 3-vessel system. I have refined this process for mashing/step-mashing, after about 1 year of use:

1. Measure water into MT and fill HLT just below top of HERMS coil, set heat-controller to dough-in temp, heater ON.
(controller sensor is located at output of HX. Temps are also monitored at MT and HLT, both probes 5" from base)
2. Water pump ON (HLT recirc), wort pump ON (MT-HERMS recirc)
3. When MT gets to dough-in temp, set controller to mash temp, wort pump OFF, dough-in.
4. Dump enough cold water into HLT to bring temp down to mash temp.
5. Wort pump ON, recirculate mash with valves wide open (1/2 ID hose/fittings, 1/2 OD HERMS)
6. When time for mashout (or next step in step mash), set controller to 100% output.
7. Immerse 1.5kW stick heater into HLT, plug it into separate circuit.
8. Empty boiling water from electric kettle into HLT. Refill electric kettle from HLT, bring to boil.
9. Repeat previous step until HLT temp approaches target, unplug then remove stick heater, set controller to mashout temp or next step mash temp.
(Repeat steps 6-9 for step mashing)
10. Turn heater OFF after mashout, all pumps OFF, all valves CLOSED before transferring hoses for sparging.

I've found this process to be the fastest way to ramp up mash temps. I start with a smaller volume in my HLT - a gallon or two of cold water brings the temp down to mash temp instantly. I keep a 2L electric kettle on hand for boiling water.
I use a DSPR-120 Mash/Boil controller and dual-temp meter, with RTD PT100 probes, all from Auber.
HLT and HX sensor outputs are calibrated to reflect the 2 deg delta between MT and HLT temps.

[BrewBama]

To each his own. If that’s the way you like to brew then by all means have at it.

BLUF: Having to go thru all that each time I raise temp during a mash sounds like the hassle factor would be a little too high for me to make a step increase.

I had no idea using HERMS was so interactive. Using RIMS sounds so much easier: increase temp on controller, wait for rise time (plan for a 1.3*F/min rise.), start timer for temp rest.

I generally mash in, use four temp rests, and mash out.  Having to use steps 6-9 each time to move to another temp rest would make me want to use a single temp (~152*F) with that system.

[Edit:  I do not mean to sound discouraging. It sounds like you have found a process that works. I simply mean to say that your process would be a little too much interaction for me to have to go thru each brewday. ...but if it works for you then good to go!]

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[Kevin]

I've only just started using a HERMS system this spring but I fill the HLT and heat to strike temp. I then pump that water over to the MT and dough in. After that the pump is started and recirculation begins.

[ynotbrusum]

I've only just started using a HERMS system this spring but I fill the HLT and heat to strike temp. I then pump that water over to the MT and dough in. After that the pump is started and recirculation begins.

But if you have pumped out the water from the HLT to the mash, wouldn’t you need to refill and reheat the water in the HLT? Or is the vessel large enough to hold both the strike volume and the sparge/HERMS water?

I can only heat one vessel at a time, so I get the strike water to temp plus a few degrees in the boil kettle and pump it into the mash tun by underletting the grain, then start heating the HLT water to the second step temp.  When it hits the temp of the mash, I start to recirc, raising the mash to the second step.  After reaching the second step I hold for the time of the second and then go to mash out by heating up the HLT over the course of a few minutes.

[Kevin]

Mine is a 15 gallon, three vessel system like yours. I typically fill the HLT with way more water than I will need for the day... as much as 12 gallons. I'm not concerned with exact volumes at that point.

When the strike water is at the set point I pump the required volume to the MT and dough-in. As an example lets say there is 12 lbs of grain at 1.5qt/lb which will require 4.5 gallons.

There is now 7.5 gallons remaining in the HLT. Plenty enough to keep the HERMS coil immersed. (I will turn the heat up in the HLT to about 170 at this point) Recirculate and mash for an hour.

The example above may require between 5 and 6 gallons for sparging. This is probably going to leave the boil coil exposed near the end but before it gets to that point I will have turned off the heat to the HLT and swapped the plug over to the boil kettle.

There's some hose swapping, control panel buttons to push and pumps to turn on and off in between but that's pretty much it.