Breaker question

[MrSaLTy]

I am in the process of building a eHERMS system mostly based on Kal's work. You can see what I have done so far in my build thread here...

https://www.homebrewtalk.com/f51/my-eherms-mostly-kal-clone-home-brewery-421059/

My question relates to having breakers in the control box itself. It will be a 30A panel with 5500w elements (one at a time). I want to add breakers inside the panel like many of PJ's diagrams. I plan on having a double pole breaker for the 240v 'bus'. If the element is 5500w and I have 240v supply that's 22.9A. Can I use a 25A breaker or do I need a 30A? Would like some opinions on this. I have a 25A breaker but would need to buy a 30A if I need it so would rather not have to buy one if I can help it.

Thanks!

 

[DaleHair]

My question is, if the panel is on a 30a breaker why add another breaker inside except for control voltage.

 

[The10mmKid]

I'd go with the 30A, as it is recommended to only load a C.B. at 80%
You can get a fast acting one to possibly save the SSR when the element shorts out, but that usually only works in theory.

'da Kid

 

[BadNewsBrewery]

The question stands - why have an internal breaker? If you are running a 30a breaker in your main panel, and appropriately sized wiring for 30a to the panel and to your 30a loads, why have a breaker at all? A few small fuses for your PIDs / Pump would make sense, but putting another 30a (or 25a) breaker in line wouldn't gain you anything that I can tell.

 

[The10mmKid]

Bad News, the only benefit from this additional breaker is from keeping the entire system from shutting down due to the breaker tripping in the main panel.
One would need to size/spec a breaker for the specific load . . . the heating element in this case(well, the SSR too as they can short to their case/ground).

Just depends on what situation you desire if something goes wrong.

My preference would be that I see I'm not heating even though my heat indicator light is on - vs - heah, why is my entire unit dead.

I've not been looking at the eHERMs diagrams much as I'm no where near that level of brewing yet. I'm taking baby brew steps.

'da Kid

 

[jeffmeh]

Bad News, the only benefit from this additional breaker is from keeping the entire system from shutting down due to the breaker tripping in the main panel.
One would need to size/spec a breaker for the specific load . . . the heating element in this case(well, the SSR too as they can short to their case/ground).

Just depends on what situation you desire if something goes wrong.

My preference would be that I see I'm not heating even though my heat indicator light is on - vs - heah, why is my entire unit dead.

I've not been looking at the eHERMs diagrams much as I'm no where near that level of brewing yet. I'm taking baby brew steps.

'da Kid

I'm still not clear regarding the benefit of the additional breaker, other than that you have (unnecessary) redundancy in case one of the breakers fails to trip. What benefit do you think you will be getting?

 

[The10mmKid]

I'm with you Jeff as it pertains to a main 30A breaker in the control box . . . not needed . . . . however in theory(code), if your only breaker is the 30A feed from the main panel . . . . ALL wiring inside the control box needs to be #10AWG . . . . no fun there.

I would also have a 5A or smaller single pole breaker if I'm stealing one side of the 240V for the controls. (Easier to run 18ga wire for the switches/lamps/etc)

I would be inclined to have a C.B. sized for each heater circuit so that if it has a short, the entire system is not dead. As in, I now have to run into the house, across the basement/garage only to find out I still do not know what tripped the main/first 30A breaker.

Fuses would work too. Especially the Fast Acting type.

If one does not understand how a breaker reacts to overcurrent, it is interesting reading. They react differently to shorts and/or extended periods of elevated current.

 

[jeffmeh]

I absolutely agree regarding using some lower rated fuses or breakers to downsize the wiring inside the panel, Kal uses one 7a inline fuse, but there are plenty of other ways to do it.

As for separate breakers for each element to aid in troubleshooting, I would hope that the panel wiring is sound enough such that shorts and troubleshooting would be rare enough to make that a moot point. If not, something is very wrong.

 

[The10mmKid]

I also think that the low hour use of these eHERM setups would limit the need for extra protection.

That being said, in my +25 years of heating plastic, fluids and dryer/oven air; I have seen numerous elements failing to the media (in our case water) and SSR's failing (shorting closed and to their mounting base).

Add to that, we use quality components such as Watlow and CRYDOM; not the lowest cost stuff available on the web.

Just adding what I know and experienced to the big picture.

'da Kid

 

[MrSaLTy]

You guys are right... there is no strict need for another breaker in my case and it would basically be redundant. It would be more appropriate in cases where the panel is being supplied with 40A or greater. That being said... I have an extra 25A breaker and using it would prevent me from having to go to the main breaker panel and check it in case of the breaker tripping. Not a big deal by any means. But since I have it I guess I wanted to know if I could use it or am I cutting it too close so to speak. I am however going to use a lower amp rated breaker for all the 120v things split off in the panel. If everyone thinks it's a dumb idea to use the 25A break I certainly don't need to use it. Mostly just looking for opinions.

 

[ajdelange]

The breakers in a panel are there to protect the wiring between the panel and the load. Breakers in equipment are there to protect the equipment and to serve as disconnects.

 

[The10mmKid]

MrSaLTy,
Perform an amp draw reading after it is built and at full load.
You may be surprised at the amperage, it will probably be less than the math shows. Then maybe your 25A breaker will be the ticket.

The heater rating of 5500w(actual or promised wattage?) is only effective at 240V . . . . . I'd be surprised if you have that much of either. I'm betting 228V for the house.

Measuring the heaters' resistance while it's off will get you closer, but that value will change slightly when the element heats up.

Here is a nice calculator if you want to play with the values. I'd start with the actual resistance and your house voltage.
http://www.csgnetwork.com/ohmslaw2.html

'da Kid