FERMENTATION CHAMBERs... 10A STC-1000 & 15A Freezers What are the Issues & Fixes?

I am planning to use a chest freezer and an stc 1000 unit for fermentation temp controll...

The stc is rated at 10A,
but all freezers I have looked at, have a 15 A rating.

Frankly I do not know what this all means.

Can you explain it ?

Reading various threads (and warnings from HAIER), I gather there is some risk involved...
on the other hand there is chatter about "protective fuses" and "in-line relays"; "start-up" and "running" loads etc.

What's the bottom line?


What do I need to make the new freezer I want to buy, safe to control with the STC-1000?
(or should I ask, to make the STC-1000 safe to control the new freezer?)



Freezer power: 100V.
Rating: 15A or above.

I'm no expert on freezers, but I'll chime in.
To be safer, put a slow blow 10A fuse inline with the freezer/STC. You may have an inrush current hat is larger than 10A, but that is not a problem. You just don't want to constantly overload the relay.
If I'm not mistaken, I seem to recall the relays in the STC is rated at 10A for 230VAC and 15A for 110VAC.
There are no absolutes, such that you are perfectly safe running 9.9A through the relay but at 10.1A it catches fire. There are tolerances and margins. Those are not to be abused of course, but I don't think you'll have a problem.
Cheers!

Amps is the unit of electrical current.

Don't risk it. Buy a cheap PID controller with Solid State Relay (SSR) off ebay (mine was about $40 for the kit). They can easily handle up to 40A (depending on the SSR).

There are lots of threads about using and setting up these controllers.

What is the power (watts) of the freezer?

Gnomebrewer said:

Amps is the unit of electrical current.

Don't risk it. Buy a cheap PID controller with Solid State Relay (SSR) off ebay (mine was about $40 for the kit). They can easily handle up to 40A (depending on the SSR).

There are lots of threads about using and setting up these controllers.

What is the power (watts) of the freezer?

Click to expand...

if you've already got the STC, you can also just purchase an SSR - rather than purchasing a PID+SSR. (http://www.amazon.com/dp/B008MPJDTE/?tag=skimlinks_replacement-20)

I do not agree with the two replies above.
I think you will be just fine running the freezer straight off the STC. But if you do decide to beef it up, add a relay or contactor with a higher rating instead of an SSR. Relays/contactors are arguably better suited for this application and in the case of a malfunction, relays/contactors typically fail open and SSR's typically fail closed.

Edit: And I looked it up. The relays are rated for 15A@125VAC.

The easiest solution would be to use the STC relay to switch a cheap 20A ice cube relay. The STC relays would only see milliamps of current. No need to get carried away in a situation where a PID is of little to no use.

Must be a huge (or terribly inefficient) freezer. Most consumer models draw only a few amps when the compressor is running.

However, there is a surge of "inrush" current when the compressor starts up. This inrush can be much higher than the continuous current, but typically lasts only a fraction of a second.

I have a couple of 15.5 CuFt Frigidaire that draws 8 amps on startup and 1 amp running

15 amps sounds like a lot

what is the model you are looking at ?


all the best

S_M

I am happy to get your ideas and feedback...
Let me try to answer some questions and ask for clarification of meaning and specialized terminology.

The freezer's I am considering are chest freezers.
Some of the cateloges do not show the power consumption in W; In those cases, yearly power consumption in kWh/yr is given, but for some reason I do not understand, two freezers having the exact same W ratings, may often as not, have different yearly consumption rates in kWh... I don't know what this indicates....
Anyway, in the catelougs where it is given, the power consumption in Watts seems to vary from modle to modle between 60 and 97.

The power supply here is 100 V.
I guess that makes a difference.

The only cateloge I have that explicitly gives wWattage information is from HAIER.
JF-WNC103F (60W) is nice as it already can function in either Fridge or Freezer mode;
it is however, quite narrow and does not really provide enough surface area for my needs.

JF-NC 145F (70W)
JF-NC 205F (78W)
JF-NC 319A (95W)

or something along those dimentions/volumes is more of what I am hoping for.

The paper work for the stc-1000 I made states 100V / 10A (IIRC).
The Operators Manual for the JF-WNC103F (60W) clearly calls for: 100V & 15 or more A.

When alphaomega checked and says
"The relays are rated [at] 15A [for] 125VAC."
does this mean that there is a "safety" or "fudge" factor built in?
(that differs from the paperwork that ships with the units.)

I don't suspect that there is any real difference between the 125VAC and 100VAC designs
but I am just guessing....

Why would Haier say 15 or greater A if 10 are actually going to be sufficient?

What shoud I do?

Blue-Frog said:

Why would Haier say 15 or greater A if 10 are actually going to be sufficient?

Click to expand...

It may be the mfr. stating the minimum circuit ampacity, to accommodate the inrush current spike at compressor startup. This would be to prevent nuisance breaker trips.

Blue-Frog said:

In those cases, yearly power consumption in kWh/yr is given, but for some reason I do not understand, two freezers having the exact same W ratings, may often as not, have different yearly consumption rates in kWh... I don't know what this indicates....

Click to expand...

The insulation R-value of the freezer could make a large difference in the kWh since the compressor run time would change. This value is of no use to you here. Basically "yearly consumption rates in kWh" includes 2 variables: how much time will the compressor run in a year and how many Watts the compressor uses while running.