Bath Pasteurizer Build US

[Chris H]

I'm starting to build a bath pasteurizer with the intention of using the CraftMetrics Pasteurizing computer and looking for advice from anyone who's done it, or maybe a plumber for this project.
So far I have the following BOM:
Tub - Seaplast DX327
Tankless heater - Rinnai CU199iP/11GPM (This unit goes to 185F)
Computer &. Probes - CraftMetrics & Can and Bottle probes
Recirculating Pump - Currently unable to determine size and controller

I'm looking for input on both the current BOM items or anything else I should consider. I've seen recommendations on using a recirculating pump that just pumps continuously regardless of the water temp, but was wondering if it would be better to be controlled in some way so that the tankless isn't making hot water until the water temp is dropping. I'm assuming I'd want to save on fuel, but not sure of how much fuel would be saved or used pasteurizing either way.

Thanks

 

[SanPancho]

The tankless unit isn’t designed to do what you’re asking of it. You’re essentially short cycling it constantly which shortens life considerably. I know because we use these tanks in our hydronic heat installs when it should really be a boiler type system. But you can swap out probably 3-4 tankless units for the cost of one boiler so we do it anyways. It can be done but you’ll be mean to the heater.…

but Yes, you could do exactly what you’re planning.

another option which is a bit more expensive is to add heating setup. use the tankless to fill, and then something like a RIMS tube to maintain heat. You can get the highest wattage elements you can find, link two tubes in line if need be, and have a pretty simple temp control setup with a recirculating pump.

i don’t know what pump specs you’d need but I assume there’s some standards for this, like maybe the pump should exchange the water every 60 seconds. Or 3 minutes. Or 5. Etc. Just make sure you calculate the water volume when it’s full of product, not just the volume of the bin (which would be oversizing the pump). And for best results I’d guess the pump should be constantly moving the water to homogeniz water temps in the bath. But when you do heat calcs you’ll wanna total the glass, the product, and the bath water for btus.

if gas or propane is cheaper/easier then you could essentially do the same thing but instead of a rims tube you add heat by using flame onto something like a kettle over a burner. They sell units that regulate gas flow via solenoid, and even have them that will modulate the gas valves so you can have low-med-high flame settings. You’d essentially put a copper coil in the kettle as the heat exchanger for you bath water and a single pump would recirc the bath water into the hx coil to pick up heat as needed.

sorry if this is redundant for you, just want to point out options that are fairly easy diy.

if this is something that happens once or twice a year then just follow your original plan. If it’s a constant use then I’d consider not stressing the tankless and adding the dedicated heating setup to the rig.