Any HVAC / Refrigeration guys? Milk tank and condenser unit questions.

[Mercedesrover]

I picked up another milk tank for my maple syrup operation. According to the tag it wants 23k btus of cooling. It came with an ancient but working dual-fan condensing unit that draws 30 amps. Probably 3hp or maybe a little bigger. The trouble is I only have 30 amps to the building and this thing though working for now, is pretty shitty looking. I don't need to cool 100 degree milk on a 100 degree day. I only need to cool 45 degree sap down to 32 degrees on a 55 degree day. Can I get away with a smaller condenser unit? Say 1.5hp? Will the expansion valve or anything else need to be messed with?

Second question; It looks like the condenser runs independent of the milk tank? There wasn't a switch on the condenser unit and it seems to just runs until it detects the tank has reached temperature and shuts off? I'm really not sure how that works. The condenser was wired straight into the breaker and that was it.

Any help or instruction is appreciated.

 

[posford]

Can't answer in regards to condenser sizing, but our milk tank has what I believe is just an aquastat that kicks on the compressor at a high temp, and shuts it off at low temp. Sort of like a thermostat for a furnace, you don't wire the furnace thru the thermostat.

Someone I knew doing syrup didn't bother to refrigerate the sap, a milk tank is insulated enough it should keep for a few days, just boil more often

 

[gunracer1]

that's not much of a load you are asking of it. but I'm to stupid to remember how to calculate it. but I'm still thinking you will be money ahead to just use a refrigerator.

 

[Mercedesrover]

Someone I knew doing syrup didn't bother to refrigerate the sap, a milk tank is insulated enough it should keep for a few days, just boil more often

Using this particular tank for concentrate. Its a higher sugar content and as such spoils more quickly.

 

[posford]

Using this particular tank for concentrate. Its a higher sugar content and as such spoils more quickly.

Gotcha, never messed with R/O. I'd be looking for another cooling unit, although one as small as you'd ideally need is probably going to be a niche thing, therefore $$$. Shitty old cooling units will run about forever, as long as you can stomach the inefficiency. Might be cheaper to get more power in the building?

 

[Mercedesrover]

how big is the tank? Ill do a quick calc for you

635 gallons.
Thanks.

 

[Mercedesrover]

Based on your spec given, assuming a full tank, it will take an hour and a half to cool 635 gallons utilizing all 23k btu/hrs.

It would be safe to say that sap is thicker and denser than syrup, so those numbers are conservative. Might be more like 2 hours.

So i would not suggest going to a smaller condenser.

Thanks. I'm concentration to about 8% sugar so its much closer to the density of water than the density of maple syrup. Sitting in a glass it looks just like water.

The time it takes to cool it down isn't as important as maintaining it. If it takes 4 hours to cool it 15 degrees that would be just fine.

 

[[486]]

Can I get away with a smaller condenser unit? Say 1.5hp? Will the expansion valve or anything else need to be messed with?

you can run a smaller condensing unit on too large an evaporator, just be sure that the oil is draining back to the condensing unit, as it will not be carried as well by a smaller volume of gas through the evaporator

expansion valve might need fucking with, but you can probably get by without changing it out if you're looking for the same evaporator temperature and using the same refrigerant
TXV or CPEV is a question that'll come up (just post a picture of the expansion valve)

 

[Mercedesrover]

;n296598]expansion valve might need fucking with, but you can probably get by without changing it out if you're looking for the same evaporator temperature and using the same refrigerant
TXV or CPEV is a question that'll come up (just post a picture of the expansion valve)

Was R12 but I'll fill it with R134. (I do still have a tank of R12 at the shop but I'm saving that....)

 

[[486]]

Was R12 but I'll fill it with R134. (I do still have a tank of R12 at the shop but I'm saving that....)

it does take different oil (either pag or poe instead of the mineral oil used with r12) but that's not a huge deal, just the 134 doesn't carry the mineral oil through the loop
you can mix the oils and it'll work out, so don't worry too much about getting the old evaporator surgical-clean

the expansion valve will likely be totally fine with the change in refrigerant, even if it is a TXV

if you are using an older condensing unit that's full of mineral oil you can mix in some butane or propane which will carry the mineral oil around the loop real well but that'll fuck with the expansion valve setting a lot more than switching from 12 to 134 will

 

[[486]]

oh and R12 is pretty quickly becoming worthless as all the big commercial equipment that uses it has pretty much been replaced by now
Got some laying around too, and keep ending up with more but never use it on anything. Thinking about finding a market to sell it off into.