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Discuss Changing original 32Amp contactors for solid state relays? in the Electric Underfloor Heating Wiring area at ElectriciansForums.net

Yonny24

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Hi Guys,

My underfloor heating has 3 x 32amp contactors. They make a hell of a thump when opening and closing. Bit of a hum also.

I'm looking at the idea of changing them for solid state relays like this one Solid State Relay - 40A (3-32V DC Input) - COM-13015 - SparkFun Electronics - https://www.sparkfun.com/products/13015

Will these work? I'd need to source a 12v switching supply instead of the current 220v. Easily done as I have plenty of 220-12v power supplies handy.
I assume they are much quieter and can be switched endless times without any physical parts wearing out.

Thanks in advance
 

Lucien Nunes

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In theory, yes. You can also get types with 230V AC control input. Depending on the current they are switching, a heatsink may be required as unlike a contactor, there is a small voltage drop across the power device that results in some heat dissipation (although, there's no heat dissipation from the control side as there is in a contactor coil.) Read the data sheet. Depending on the supply voltage, likelihood of voltage spikes and the nature of the load (yours is resistive and therefore should be tame) snubbers and/or transient voltage suppression might be recommended.

My experience with power semiconductor devices is that you get what you pay for. I don't know about the particular product in your link but an industrial SSR of that rating, that I would be happy to rely on, is typically more expensive.
 

marconi

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Yonny24

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You might want to investigate 'silent contactors' to replace your present ones. Here is an example:

View: https://www.amazon.co.uk/Hager-Esc440s-Silent-Contactor-40a-4no-230/dp/B0062X1D2I


These use the usual mains supply voltage to power their coils. Other manufacturers make them too.
Thanks .

That's the one I have for the upstairs floor heating.
Yes it is silent. 40 amp model for all the heating upstairs.

Downstairs we have 3 contactors of 32 amps each but I don't think they consume more than 5000 watts in total. (230v).


5000 watts would be 22 amps in total. hmmm why have 3 x 32 amps? (maybe just what they had and the max amperage is not that important)
Wouldn't one or 2 of these be sufficient in the placement of the 3 noisy contactors?

Also the power prior to the contactors come from 3 x 20amp trip switches.

Thanks for the replies today
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I see the types of heat sinks available now.

View: https://www.amazon.co.uk/SSR-40-3-32V-24-380V-Solid-State/dp/B07JQ2S3Z9/ref=pd_sbs_328_6/259-1440324-8968235?_encoding=UTF8&pd_rd_i=B07JQ2S3Z9&pd_rd_r=2d4cd923-0e7c-478f-b7a4-b92b29eeb364&pd_rd_w=87mxm&pd_rd_wg=XGJ4t&pf_rd_p=2773aa8e-42c5-4dbe-bda8-5cdf226aa078&pf_rd_r=X4E4Y1A3XRD1EP9X00WG&psc=1&refRID=X4E4Y1A3XRD1EP9X00WG


I wonder is 16 amps through a 40amp version will keep cool without a heatsink?
 
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marconi

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A wiring drawing and some pictures would be helpful plus exact numbers for the Ipower of under floor heating pads, cables, tiles. Please include the thermostats. This will help folk advise you.
 

Yonny24

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Here we have the ground floor contactors. 4 thermostats (cheap copies of Honeywell and do not work well at all). Installing a central digital thermostat that will send a signal to the sonoff switch in the fuse box.

Living room
Dining room
Breakfast room and kitchen (2 zones).

Living room about 11-12m2 consumes about 2000 kwh.
Dining room a little less and kitchen/breakfast about 1800 combined.

No more than 6000 kwh. (230v)

Would it be possible to swap out the 3 contactors here for 1 x 4 pole new contactor? How would this be wired? You see we have 2 Lives/ 1 Neutral cable set up coming in.
I see 3 sets of L/N cables going out to each of the 3 zones. I recently added the meters.
 

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marconi

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Could you take a couple more photos? One looking down on the black bar across the top of the 20A circuit breakers and one looking up to the contactors, timer and power meters?

It looks to me that the power meter and the time switch are unused - am I correct?

The wiring looks somewhat quirky so the extra photos will be helpful.

Who wired this up?
 

Yonny24

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Many thanks Marconi. Appreciate your time.

The timer on the right is now unused. Just the L/N being taken from the inputs to power the Sonoff R3 wifi switch on the left that I added this week to control the contactors. Much easier to set times and control virtually.

The 3 slim power meters I added are in use as I'm currently calculating the costs and making notes of daily use. They are wired in between the 20amp breakers and the contactors. (They are upside down as the inputs were on the bottom oddly). Sorry the double cabling (2 x 2mm) was used on the meters as I did not happen to have any 3mm in the house. I'll get around the changing those and making it all neater once the lockdown is over.

The original wiring with the breakers and contactors was all done by the underfloor heating company 'EuroCable' 10 years ago when the house was constructed.

Struggled at first to figure out the L1/L2/N 3 wire cabling config.

Thanks again
 

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marconi

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Sir- could you tell me please what qualifications and experience you have with this type of wiring and electrical accessories?

What I am seeing looks 'confused'. For example the power meters look to be wired across the 20A circuit breakers. The wiring arrangement of the top row of disconnector and 5 circuit breakers is as I said before quirky. And I cannot fathom why you reckon you have an L1, L2 and N power supply. There are other anomalies.
 

Yonny24

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Sir- could you tell me please what qualifications and experience you have with this type of wiring and electrical accessories?

What I am seeing looks 'confused'. For example the power meters look to be wired across the 20A circuit breakers. The wiring arrangement of the top row of disconnector and 5 circuit breakers is as I said before quirky. And I cannot fathom why you reckon you have an L1, L2 and N power supply. There are other anomalies.


No qualifications but many years experience of building valve amps/rebuilding transistor amps, home electrics also over the last 20 odd years.

The output of each 20a circuit breaker is wired to the meter and the output of the meter goes into the contactor.

The original cables (The thick white and brown cables) that were between the 20a breakers and contactors were just swapped over to the power meters inputs - nothing changed there.

230v, 209v, 23v - readings from ground to main cabling entering the main breaker.

Thanks
 

marconi

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What is that black bar along the top of the 5 cbs? It looks like it connects together the top five terminals and is supplied by 3 white wires from under the disconnector connected to its terminals N, L1 and L2.

And a thin Blue (neutral) connects to the underneath terminal of the second from right cb which seems odd to me.

Could you point out to me the main neutral entering and being distributed please?

Are those five cbs double pole types?

Where did you measure those voltages you mentioned in #10?
 

Yonny24

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ok adding some original photos here of the previous original wiring.
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What is that black bar along the top of the 5 cbs? It looks like it connects together the top five terminals and is supplied by 3 white wires from under the disconnector connected to its terminals N, L1 and L2.

And a thin Blue (neutral) connects to the underneath terminal of the second from right cb which seems odd to me.

Could you point out to me the main neutral entering and being distributed please?

Where did you measure those voltages you mentioned in #10?

What is that black bar along the top of the 5 cbs? - Not sure that was original - appears to apply the power across all 5 cbs from all 3 cables as if they are all live. Yes from the 3 white wires from the main breaker.
I have the same upstairs.

That small blue wire suppliers the Live/positive to the timer.
The 3rd white cable coming into the main breaker is the one with 23v to ground. I haven't gotten my head around the 3 cable config yet. You can see they've used the small white wire from the final 20a breaker to supply the neutral for the timer.

I measure those voltages from the ground bus to the 3 main contacts on the 1st main breaker top left.

Original timer on the right was connected from the bottom outlets to each contactor. I removed the outputs as I have the sonoff now on the left.

Hope this helps. If you need more photos/details please ask.
Maybe Uruguayan standards?? I'm an expat from the UK so was odd for me.

Thanks again
 

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