Spark V3 Parts Prep - PowerSwitchTail II vs. PowerSSR Tail


#1

Cheers to Elco and the BrewPi Community -

Looking to dive in once V3 is released and I'm putting together a parts list based on the latest Spark posts and gleaning what I can from the significant history of the BrewPi ecosystem.

After reviewing the "Fridge Hacking" guide, I'll be opting for an external "Switched Power Cord" to control the Fridge compressor and heating elements directly. (I realize that this will leave the existing thermostat in line and could result in conflicts at lower temps, but the True GDM-07 Commercial unit I have is able to approach freezing before toggling naturally when at "max cool" setting - I don't expect controller fights at ferm temps)

I'm also opting for this choice so the result is "portable" between fridges easily, pending fridge upgrades.

Regarding "Switched Power Cord" options -

I've seen back and forth on multiple forums regarding Mechanical vs. Solid State relays for this portion - Heat, switching speeds etc. Many on the "plug-and-play" mechanical side opted for the PowerSwitchTail II, but I noticed they also offer an SSR base option, the PowerSSR Tail.

(Given I'm expecting to purchase a V3) It seems like the SSR option is cheaper, meets spec, and is more robust than the mechanical route. Any issue going this way?

EDIT: I suppose Mech vs. SS relays may operate differently to the "control" signal sent - Looks like the Mechanical one fails open...What would the SS version do?


#2

SSR is the better choice.

They switch on an AC zero crossing, which will cause less interference.

For your heater, you should definitely pick an SSR, because it uses PWM with a period of 4 seconds. Switching a mechanical relay every 4 seconds is not recommended.

A downside of SSRs is indeed that they fail closed, but it is unlikely if you have a good SSR.

The powerswitch tail is indeed a good option.


#3

Fantastic - Thank you for your die-hard support of your product!

PS - The talk you gave years ago (On YouTube) about early versions of BrewPi is what got me stoked try this - when a guy really geeks out about something he loves, its infectious and people want to get on board. Cheers!


#4

I suppose if you were concerned enough about the SSR failing closed you could have a safety relay in-line. It would open when the temp got above a certain point that would signify the SSR failed closed. For example, if you've got your ale set to 68F, you could set the safety relay to trip at 70F. Then your beer would cycle between 68-70F in the event of an SSR failure.

Having two SSRs would be pretty safe against a dual failure but if you made the safety relay a mechanical then you'd have the added safety of it failing open.


#5

@Gonzo A fantastic idea - Do these units you describe function analog or digitally for setting?

Poking around trying to find one that fits the bill, if you have any advice there -


#6

I use these from Fotek.

I am thinking if I have any issues of switching to these

They cost more but may be worth it. They are made in America instead of overseas. Sometimes the Fotek's are knock offs and cannot handle their rated amps. If you stay under the 25 amp - most fridges are 15 amps or less you should be fine. If you are going to use something that is close the rated amps, I would get a better SSR.

Hope this helps.


#7

I have not had good experience with fotek and heard several others that would not recommend them.

I think the ones we have in the store are a much better alternative, but shipping costs might be prohibitive if you only need SSR. PQLYT is also a very good brand, I sold those before.


#8

You could just use the same ones you would use for the rest of the BrewPi system and set it up through BrewPi.


#9

Ah, to clarify, I was looking for recommendations for these specifically:

I'm interested in how these are set, or if there are recommendations for these.

(For the "traditional" SSR portion, I'll be sticking with the PowerSSR Tail - My fridge's compressor can be accessed directly with a standard plug)