All-Electric RIMS, Element Design

[KJB5200]

Hi All,

I'm working on a major overhaul of my brewing platform - I'm switching to an all-electric 5gal RIMS system that is loosely based upon theelectricbrewery.com's rig. Originally I had planned on a three element design with two 1500W/120V elements: one heating my strike/sparge water and another heating the RIMS tube. A third 4500W/240V element would handle the boil after the mash had finished. Now my dilemma:

I've read about underpowered elements being a poor choice for a RIMS tube, especially for step-mashing because of the inability ramp up temps quickly. So, in the design I mentioned above, would a single 1500W/120V element in a 5gal system be effective?

The alternative I've considered is putting 4500W/240V ULD element in the RIMS tube and wiring a 120/240 switch so I can ramp up the temps quickly in 240V mode for steps but bring the wattage back down for maintaining temp (and heating my sparge water as necessary). I've read that voltage output can be controlled through the BCS-462 I just purchased too, so I'm not sure if a physical switch is necessary but I've read comments that this type of design will be problematic for the controller (i.e. - every voltage switch will require changing specs in the BCS software?).

This may all seem a bit disjointed and lacking direction, but this project has gone on for months with little progress and I need to get back to brewing. Any suggestions?

 

[thargrav]

Just for reference - It takes 8.34 BTU to raise one gallon of water 1 degree F.

A 4500 Watt element will dump 15355 BTU / hour, or 256 BTU / minute into your RIMS tube.

Just for nice round calculations, assuming 75% of the energy goes into your wurt (water) and you have a total of 10 gallons a 4500 Watt element should be able to raise your temperature by about 2.5 degrees / minute.

[256 btu min]*.75 = 199
199/10 gallons = 19.9
19.9/8.34 = 2.4 degrees / minute

 

[PJoyce85]

This is my tube set up.

I have a 2500 LWD element running on 220V in my RIMS tube. It took just under 10 minutes for the liquid to go from 152 to 168 on the sensor. It then took just over 2 minutes for the mash to catch-up (16 degree difference).

That's between 1.3 and 1.6 degrees/min.

So, assuming you are doing a protein, beta, alpha and mash out, there should not be a change of over approximately 20 degrees between the steps (unless you do low protein and high beta) and it is recommended to ramp the temp no more than 1.5 - 2 degrees/minute.

So that would be approximately 8-13 minute ramp time between rest temps giving you approximately 24-39 minutes of ramping time (on the sensor).

This is based on my system and I'm horrible at math, so everyone go easy if you see something wrong

 

[KJB5200]

Thanks for breaking it down in terms of energy and degrees/min thargrav! It sounds like in a 4500W/220V element would be more than enough for quick/efficient step-mashing in a 5gal system, but a 1500W/120V element would still be underpowered.

It sounds like my best bet might be to have a 120/220V switch on my RIMS element - that way I could kick up the power for step-mashing, then switch it to 120V to give over the other 120V leg to the HLT element and get my sparge water heated. Anyone have any experience with 120/220V manual switches integrated with a BCS-462 unit? I read in another post that changing the voltage manually would require a change in the programming specs of the BCS but I'm not sure how involved that process is.

 

[Handsaw]

As you wort gets hotter and hotter, you lose more and more heat out the sides (and top and bottom) of the kettle so the temperature rise per minute will get slower and slower.
Because I'm basically lazy, how many BTUs/min does a 5500 watt element produce?

 

[thargrav]

A 5500 watt electric element puts out 18,577 BTUs / hr or 313 BTUs / min.

 

[Handsaw]

Thanks.

You specualted that 75% of the power went into the wort. Since the element is immersed in the wort, why wouldn't 100% go into the wort? There is no where else for it to go is there?

 

[thargrav]

Thanks.

You speculated that 75% of the power went into the wort. Since the element is immersed in the wort, why wouldn't 100% go into the wort? There is no where else for it to go is there?

The 75% is an overall assumption that factors in losses through the bottom, sides & top and electric efficiency is probably better. And since everyone's system is different there is only one way to tell - turn on the element and measure temperature rise over time. You can calculate your actual efficiency from the results. I need to do this with my system & post the results here.

 

[ChuckO]

The 75% is an overall assumption that factors in losses through the bottom, sides & top and electric efficiency is probably better. And since everyone's system is different there is only one way to tell - turn on the element and measure temperature rise over time. You can calculate your actual efficiency from the results. I need to do this with my system & post the results here.

That's probably a good assumption, as heat is lost through the walls of the RIMS unit, the tubing and the pump. Also, the grain has a different specific heat than water, so that changes the result.

My 5500 watt RIMS unit will raise the temperature about 1.6 deg. per minute when I am doing a 5 gal. batch using 12 lbs. of grain with 3.75 gal. of mash water.