Author Topic: How safe is it to use a SSR to control power to a spa? Or use a relay?  (Read 10233 times)

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Offline DougSpindlerTopic starter

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I would like to know how safe and if it would be a good idea to use a SSR to control the power to a spa/hot tub.  We are on a Time of Use rate plan with our power company.  My plan is to use a TPLink smart-plug to provide the timing.  This give me control of a 120 vac circuit.  The TP Link would then be used to control a high current SSR to control power to the spa.  The SSR would be used to control the mains to the spa.  (Placed after the GFCI in the mains power to the SPA.)  I'm wondering if this is a good ideas?  I read SSRs do not interrupt the circuit like a relay would.  The circuit is energized at full voltage be the current is what's being controlled.  I'm wondering if an SSR is a good idea?  Is it safe?  Would it damage and of the electronics or motors?

Or should I just purchase a high current relay?
 

Offline bob91343

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Before you spend too much time on this, realize that there are concerns regarding insurance, and that any installation working from the power line must have a permit covering its safety.

You may design a perfectly working system but if an insurance claim is made, the company will be ready to deny the claim based on not having a permit.
 
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Offline DougSpindlerTopic starter

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What concerns should I have about insurance claims?  Who would be making the insurance claim?
I live in California and a permit is not required for this type of work.
 

Offline DougSpindlerTopic starter

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Oh just did the calculation based on our power company's current rates.  Using the hot tub during peak hours the cost for electricity is $0.54.   Manufacture claims 1,875 kWhr are used per month.  Cost to power the hot tub over a year would be $1,275.

If limited to off peak it would be $225.  Installing an SSR would save me over $1,000 per year. Well worth it.


 

Online Gyro

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It tends to be easier to obtain UL approved high current mechanical relays with decent insulation and contact ratings than SSRs. You'll probably have more choice.

An SSR will have a higher thermal dissipation than a relay too.

EDIT: For something high power like a hot-tub, you're probably looking at a 'contactor' rather than a relay too.
« Last Edit: July 19, 2020, 07:00:55 pm by Gyro »
Best Regards, Chris
 

Offline DougSpindlerTopic starter

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It tends to be easier to obtain UL approved high current mechanical relays with decent insulation and contact ratings than SSRs. You'll probably have more choice.

An SSR will have a higher thermal dissipation than a relay too.

EDIT: For something high power like a hot-tub, you're probably looking at a 'contactor' rather than a relay too.

So just go with a contactor/relay?  Looking on Amazon i'm finding 30a contactor/relay's for $10.

 

Offline bdunham7

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You may design a perfectly working system but if an insurance claim is made, the company will be ready to deny the claim based on not having a permit.

What is your basis for that statement?
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline bdunham7

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So just go with a contactor/relay?  Looking on Amazon i'm finding 30a contactor/relay's for $10.

Either will work fine as long as you are adding them to a complete system and not depending on them in any way for safety.  The contactor is more conventional, easier to work with, probably more reliable and as a bonus, is usually guaranteed to interrupt both hot legs of the circuit. 
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Online Gyro

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It tends to be easier to obtain UL approved high current mechanical relays with decent insulation and contact ratings than SSRs. You'll probably have more choice.

An SSR will have a higher thermal dissipation than a relay too.

EDIT: For something high power like a hot-tub, you're probably looking at a 'contactor' rather than a relay too.

So just go with a contactor/relay?  Looking on Amazon i'm finding 30a contactor/relay's for $10.

Well personally I wouldn't go to Amazon for a guaranteed genuine UL approved contactor these days, I'd use an electrical / electronics distributor, but yes.
Best Regards, Chris
 

Offline DougSpindlerTopic starter

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It tends to be easier to obtain UL approved high current mechanical relays with decent insulation and contact ratings than SSRs. You'll probably have more choice.

An SSR will have a higher thermal dissipation than a relay too.

EDIT: For something high power like a hot-tub, you're probably looking at a 'contactor' rather than a relay too.

So just go with a contactor/relay?  Looking on Amazon i'm finding 30a contactor/relay's for $10.

Well personally I wouldn't go to Amazon for a guaranteed genuine UL approved contactor these days, I'd use an electrical / electronics distributor, but yes.

What difference doest it make where you BUY a product?  Shouldn't you really be concered about the product itself and not who sold it?
 

Offline Benta

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You may design a perfectly working system but if an insurance claim is made, the company will be ready to deny the claim based on not having a permit.

What is your basis for that statement?

Someone gets killed due to DIY electrics in a moist/wet area? A Spa or any safety relevant application is not really the place to use SSRs. You need an installation with 100% safe disconnect, meaning mechanical contacts.
Just the idea makes me shudder.

« Last Edit: July 19, 2020, 08:42:49 pm by Benta »
 

Offline bdunham7

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Someone gets killed due to DIY electrics in a moist/wet area? A Spa or any safety relevant application is not really the place to use SSDs. You need an installation with 100% safe disconnect, meaning mechanical contacts.
Just the idea makes me shudder.

Yes, a two-pole contactor seems a safer to me too.  However, in this case, the SSR would simply be an additional switch to an already (presumably) safe system.  Even if it shorted on, you would be no worse off than before.  The OP isn't counting on it as a disconnect or a normal control switch.  And these spas are fully GFCI protected at the supply.
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline DougSpindlerTopic starter

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You may design a perfectly working system but if an insurance claim is made, the company will be ready to deny the claim based on not having a permit.

What is your basis for that statement?

Someone gets killed due to DIY electrics in a moist/wet area? A Spa or any safety relevant application is not really the place to use SSDs. You need an installation with 100% safe disconnect, meaning mechanical contacts.
Just the idea makes me shudder.

Did you read and understand my post?  Did you see there is a GFCI in the circuit.  In the US, a GFCI is considered a safe disconnect.   Not sure how much safer it could be.
 

Online Gyro

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What difference doest it make where you BUY a product?  Shouldn't you really be concered about the product itself and not who sold it?

Yes, absolutely, that's why I stick to places where I'm sure I'm not getting cheap knock-off copies, especially when safety critical. However, if it's a genuine brand from a legitimate looking seller...
Best Regards, Chris
 

Online langwadt

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It tends to be easier to obtain UL approved high current mechanical relays with decent insulation and contact ratings than SSRs. You'll probably have more choice.

An SSR will have a higher thermal dissipation than a relay too.

EDIT: For something high power like a hot-tub, you're probably looking at a 'contactor' rather than a relay too.

So just go with a contactor/relay?  Looking on Amazon i'm finding 30a contactor/relay's for $10.

Well personally I wouldn't go to Amazon for a guaranteed genuine UL approved contactor these days, I'd use an electrical / electronics distributor, but yes.

What difference doest it make where you BUY a product?  Shouldn't you really be concered about the product itself and not who sold it?

the chances of actually getting an UL approved contactor that meets specification at electrical/electronics distributor is vastly higher
 

Offline DougSpindlerTopic starter

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It tends to be easier to obtain UL approved high current mechanical relays with decent insulation and contact ratings than SSRs. You'll probably have more choice.

An SSR will have a higher thermal dissipation than a relay too.

EDIT: For something high power like a hot-tub, you're probably looking at a 'contactor' rather than a relay too.

So just go with a contactor/relay?  Looking on Amazon i'm finding 30a contactor/relay's for $10.

Well personally I wouldn't go to Amazon for a guaranteed genuine UL approved contactor these days, I'd use an electrical / electronics distributor, but yes.

What difference doest it make where you BUY a product?  Shouldn't you really be concered about the product itself and not who sold it?

the chances of actually getting an UL approved contactor that meets specification at electrical/electronics distributor is vastly higher

Are you sure?  Look at all of the "fake" immolation Chinese products that are out there where expert's can't even tell the difference.  An electronics distributor is just going to resell what they were sent.  Who knows for sure if the item meets specs or not?   

 

Online Gyro

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Because they have a fully documented suppy trail from the manufacturer. Amazon is just like all the other 'international marketplaces' these days, with the same cautions.

I wouldn't expect to get a genuine semiconductor from Amazon any more than a China seller on ebay for instance. The same applies to other [Edit: much more easily faked] parts.
« Last Edit: July 19, 2020, 08:24:16 pm by Gyro »
Best Regards, Chris
 

Offline bdunham7

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Are you sure?  Look at all of the "fake" immolation Chinese products that are out there where expert's can't even tell the difference.  An electronics distributor is just going to resell what they were sent.  Who knows for sure if the item meets specs or not?

That's not really true.  Experts usually CAN tell the difference and reputable distributors use appropriate supply chain practices to avoid counterfeits.  It still can happen, but getting a fake brand-name contactor from Grainger or even Home Depot is a lot less likely than getting a fake from Lonely Baby Garden Store on AliExpress.  And a NOS unit in a worn box from some eBay seller is also very unlikely to be fake.
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline DougSpindlerTopic starter

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Because they have a documented suppy trail from the manufacturer. Amazon is just like all the other 'international marketplaces' these days, with the same cautions.

I wouldn't expect to get a genuine semiconductor from Amazon any more than a China seller on ebay for instance. The same applies to other parts.

Take a look at the fake Cisco products that are on the market.  Or the fake chips.  Not sure a suppler could even spot the difference. 
 

Online Gyro

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You're in the US - Just buy it from Digikey or Mouser, it's not difficult!  ::)
Best Regards, Chris
 

Offline bdunham7

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Take a look at the fake Cisco products that are on the market.  Or the fake chips.  Not sure a suppler could even spot the difference.

Let's say they can't.  Does it matter?  Do you think Cisco is selling the fake Cisco products??
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline DougSpindlerTopic starter

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You're in the US - Just buy it from Digikey or Mouser, it's not difficult!  ::)

I could, but from Amazon I get it on Tuesday.
 

Online Gyro

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Sigh, don't they offer next day? I'm sure you need to buy other stuff anyway.
Best Regards, Chris
 

Offline DougSpindlerTopic starter

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Take a look at the fake Cisco products that are on the market.  Or the fake chips.  Not sure a suppler could even spot the difference.

Let's say they can't.  Does it matter?  Do you think Cisco is selling the fake Cisco products??

How are fake Cisco products getting into the supply chain?  These are not just isolated incidents either.   
 

Offline DougSpindlerTopic starter

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Sigh, don't they offer next day?

They do, but 2 day shipping is free.  I wonder what Digikey and Mouser would charge.  Don't they have a minimum order size?  I think they would charge more than $10 just for the shipping.
 


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