Break over current for an ssr is minimal and the heat comes from the amperes of the load traveling through the ssr.
2 Likes
The issue with oversizing SSRs is that the leaking voltage can actually run your heater. IMO if youāre not planning on cycling the element at greater than 1hz, an SSR is a mistake and you should just get a guided contact relay. Even then, for most heater applications, a delay after break timer will get you where you want for reliability with a minimal impact on precision. Basically, fuck SSRs
Also, if you care about heater precision, an SCR is the right tool anyways
4 Likes
Iād be curious what @SidViscous experience is with leakage current running your heater, Iāve certainly seen SSRs fail āOnā and run the heater even with no voltage applied to the control pins, but this is hardly a normal condition.
Because of this when using an SSR in heater applications I really like to see a dual control scheme where you have a PID that controls an SSR in addition to an overtemp & flow switch that controls a relay or contactor upstream of the SSR that can break the circuit if it sees a problem.
I will disagree with Sid on at least somewhat oversizing SSRs if for no other reason than that most of the SSRs on common marketplaces (esp eBay and Amazon) are clones or knock-offs of the real deal and not rated for the continuous load of the products that they (poorly) attempt to emulate. I happen to like Crydom and have had few failures with the real deal but would much rather run something at 50% of its rated capacity than 90%, from experience very few commercial products are rated for the kinds of abuse and duty cycles I subject them to.
3 Likes
Dammit!
So of course I get BOTH 
5 Likes
Before I get into regaling you with stories of crydom SSRs failing out if the box, Iāll make the point that 50% of rated load is fine, running at .05% is a problem. Most SSRs leak up to .1% of their rated current, some well over 1%. Their advantage is they donāt really have a cycle life. Thatās about where the advantage ends.
I do agree that having a main power contactor that is latching in case of overtemp or E stop is a good plan for any control panel
5 Likes
Since Iām gonna use it for sterilizing bulk substrate is a PID even necessary?
The goal is to turn the water into steam as fast as possible and the coil is submerged in water so Iād have to keep the PID set at a high temperature anyways to heat the water up quick like I want.
Would it be a better idea to just put a pressure sensor on it to tell the coil when to shut off?
Ideally a PID works best
You can control your heat, this is my unprofessional opinion
Do my exact setup imo as it works perfectly but it would require purchasing exactly what I purchased
You could probably use a simple thermostat and a contactor if all you are doing is boiling off water. Youāll want some way of shutting it down when the water gets below a certain level or exceeds a certain temp so you donāt burn out your heating element.
Chromalox makes some nice electric steam boilers with all the pressure and safety equipment already equipped, though thatās probably going to cost a chunk of money compared to outfitting what you already have.
3 Likes
The other benefit of using a simple boiler aquastat is that they inherently have slow response, so you donāt have to worry about over-cycling contactors
3 Likes
Lol itās just what the supply houses call a thermostat that reads water temp instead of air temp
https://www.supplyhouse.com/Aquastats-Wells-350000
If youāre wondering why theyāre surprisingly expensive for a thermostat, itās because itās a big problem when your forced hot water boiler doesnāt turn off lol
2 Likes
Franklin: wrf is that ?
is it a sterilizer? what is make and mdl?
what is it that you are trying to do?
if that is a steam sterilizer the feed back is based on pressure not temp.
sterilizing ābulk substrateāā¦
how big is bulk?
I do not understand sterilizing anything bulk with 115V input?
are you even sure that electrical box was the original controller?
post a photo of the entire unit, plus make and model
thanksā¦perhaps I can help
1 Like
Bulk substrate being a general term for shit Iām gonna grow mushrooms on which is what Iām gonna load it with, not referring to the volumeā¦? If thatās what your trying to ask.
I bought this at an auction for $20, thereās no stated model this thing is probably pretty old. It said Boekel on it but the plate fell off.
I didnāt build this thing, what are u getting at. It still heats just slow as hell. Iām not starting a commercial operation
I think itās just an old pressure cooker. @moronnabis
@SidViscous would an aquastat be useful in this situation since thereās no pump to move the water?
Thereās no reason why it wouldnāt work, they just have a thermostatic bulb that reads the temperature
Boekel ASTM 25515016 Cement Menzel Autoclave 350PSI 115V
The Cement Autoclave consists of a welded ASME certified steel cylinder with a bolted cover mounted on a sturdy supporting frame and enclosed in a heat insulated metal housing. The unit is designed to handle pressure in the 60-350 psi (0.4 -2.4 MPa) range and consists of steam vessel, pressure regulator, pressure gauge (0-600psi), air vent valve, power switches, and a safety pop valve set at 350 psi. All components are pressure tested and designed to meet the highest safety standards.
1 Like
Impressive!
Image search?
these come in two modelsā¦(??) 115V and 220 Vā¦
what does the original plug look like, picture please?
Q1: with the top off and water covering the heating element , plug in to 115V outlet if
the plug is a normal usa type 115V plug turn small dial clockwise all the way up.
How long does it take to boil the waterā¦
if the water doesnt boilā¦your heating element is shot.
- put that modern controller awayā¦ deep sixā¦you never want to see it again.
- I am glad to see the cover (top)ā¦you will notice it has controls not unlike a pressure
cooker, with a blow-off safety valve (which may or may not work) and a controllable
leak valve (black handle turn valve)ā¦
due to the design for tempering cement, the blow off valve is wrong for sterilization
of growth mediaā¦and the regulator may be designed to work best in a different range.
You want 15 psiā¦(235F) for 1/2 hr. or so.
You may have to call Boekel for a new sealā¦to fit itā¦
You might put it on a shelf, and just buy a canning autoclave at good will or Habitat restoreā¦
or look on Craigās list.
If it does not boil the water in 15 minutes or lessā¦the heater element is no good (or)
the unit is 220 Vā¦which you might try as well.
You could easily replace the heating element, and the contol system on topā¦with
items stripped from a canning pressure cookerā¦if for some reason you like the
size of chamberā¦looks interesting , should have an ASTM stampā¦you need to hydrostatically check it for cracksā¦or bring it up to steam pressureā¦see if it appears to leakā¦
Changing that heating element may be problematic due to designā¦
get a large pressure cooker from Craigs listā¦time and money you will be a lot better off.
1 Like
yes, I did 35 years of reselling high TEK scientific equip.
1 Like