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

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Observations 1

a. If one studies Drawing 1 attached, one can observe that through the 4 pole disconnector (top left) and then the 3 white wires to above the 5 circuit breakers all the 3 white wires top left are joined together by the black busbar. This means these three white wires top left cannot be L1, L2 and N because a short circuit would have occurred rupturing a fuse or tripping a circuit breaker external to this enclosure. If a short circuit has not happened then they more likely to be of the same potential ie: a line or a neutral. The N, L1, L2 and L3 markings on the disconnector are to inform how it should be connected to such a supply if presented to it.

b. Studying further, one can readily see that each of the 2 wire digital power meters are connected across a 20A circuit breaker - this is incorrect. When the circuit breaker is closed the input to the power meter is short circuited and will not read any power consumption. In addition, the power meter requires an L and N at its input where only an L or N (yet to be confirmed) has actually been connected. I note the meters are reading zero.

c. The output side of the power meter connects to the input of a contactor by the blue and white wires and then from the output of each contactor to the floor heating elements ( I assume at this stage). Because only an L or an N (yet to be confirmed) is provided at the input to each contactor then no supply voltage will ever be connected across the elements - therefore they will not heat up. I suspect then that the underfloor heating system does not work at all at the moment.

d. The timer, albeit now redundant, still has two wires to it presumably intended as its supply - blue and white. Since these are derived wrongly from the two circuit breakers on the far right whose inputs are connected together by the black busbar there will be no voltage supply applied to the timer - it will not function.

e. From d), since the wifi switch has been tapped off the input to the timer it too has not voltage supply and will not function.

f. it would be impossible to measure with respect to earth the three voltages 230, 209 and 23V at the input terminals to the disconnector while it was closed because as mentioned when the disconnector is closed all the two sets of 3 white wires are at the same potential because of the black busbar.

It looks to me then that the wiring for the UFH was wrong from the very start or changes have been made which have resulted in a completely incorrect arrangement. Do you know the history of the UFH - did it ever work?

Wow thanks for your detailed reply.
I'll reply to a few of the points and look into it in more detail later and get back to you.

b - The meters are working perfectly. They measure 230v across the input terminals and 230v across the outputs. They turn over and the green light flashes red when current is flowing through. The dining room was turned on last night and used 2000 kwh. Now reading 5.1 kw

c- the outputs of the meters read 230v (across the white and blue terminals) and feed the contactors. These heat up when the timer activates them. All the floor heating works.

d- the original timer on the right also has 230v across the blue and white wires. This has always worked and did switch on the contactors before I switched the timer over to the sonoff.

f- I measured the 3 voltages with respect to earth at the input of the main breaker (3 white wires).

Every contactor's input terminals has 230v across the white and blue wires and also across the output terminals when switched on (and they get hot).

Sorry to throw a spanner in the works.
I'll have a look at the external meter box later and get back to you.

Many thanks
 
That means then that what I see in the photos is inaccurate. Could you draw the wiring for me to study?

Could you confirm (safely) what the black bar along the 5 cbs is and does? Does it connect together all the top terminals?

Does the group of three whites under the disconnector go to above the 3 left side cbs.
 
That means then that what I see in the photos is inaccurate. Could you draw the wiring for me to study?

Could you confirm (safely) what the black bar along the 5 cbs is and does? Does it connect together all the top terminals?

Does the group of three whites under the disconnector go to above the 3 left side cbs.


Your drawing is fine - just the brown and white wires entering the power meters are the other way around. White entering the left terminal and brown entering the right terminal. Everything else matches up.

The black bar along the cbs just appears to join all the cables across which I find odd.
All 3 live power cables?? This will all installed by the authorised national electricity company here, UTE, to their standards.


Yes the group of white wires under the disconnector go above to the 3 cbs in the same sequence also. Left to right.
 

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Only if you feel safe to do so - would you measure and report the voltages at each of the top three terminals ( 1, 3, 5) of the disconnector to earth and then do the same for the corresponding bottom 3 terminals ( 2 , 4 ,6 )? Ac voltage and a scale to read at least 230V.
 
Only if you feel safe to do so - would you measure and report the voltages at each of the top three terminals ( 1, 3, 5) of the disconnector to earth and then do the same for the corresponding bottom 3 terminals ( 2 , 4 ,6 )? Ac voltage and a scale to read at least 230V.
Will do.
Yes I feel safe to do this. I've worked with valve amps, 500v transformers for power outputs and high amperage power supplies for valve heaters etc, and 400+v caps for years. These caps pack a punch even when disconnected. I know what it's like to get a shock and not pleasant (or safe). A charged disconnected cap can cause a lot of pain.
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Only if you feel safe to do so - would you measure and report the voltages at each of the top three terminals ( 1, 3, 5) of the disconnector to earth and then do the same for the corresponding bottom 3 terminals ( 2 , 4 ,6 )? Ac voltage and a scale to read at least 230V.


1 (top 1st terminal) - 258
3 (top 2nd terminal) - 28
5 (top 3rd terminal) - 240

2 (bottom 1st terminal) - 214
4 (bottom 2nd terminal) - 26
6 (bottom 3rd terminal) - 238

All measured to ground.
 
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Thank you.
If 2, 4 and 6 out of the disconnector were indeed linked together by the black bar above the cbs then the voltage would be the same on each - which is not the case.

So to check further please measure between each of the top terminals of the 5 cbs to earth and then do the same for the bottom terminals to earth.
 
Thank you.
If 2, 4 and 6 out of the disconnector were indeed linked together by the black bar above the cbs then the voltage would be the same on each - which is not the case.

So to check further please measure between each of the top terminals of the 5 cbs to earth and then do the same for the bottom terminals to earth.

This may shed some light on the set up and function of the bus now.

Top CBS
1-202
2-24
3-224
4-202
5-24

Bottom CBS
1-202
2-24
3-224
4-202
5-24
 
Yes that I think has resolved much.

At you convenience could you measure at the disconnector the voltage between:

a. 1 and 2, then between 3 and 4 and lastly 5 and 6 ie: across the poles of the disconnector. Why? Because you measured 258V at 1 and 214V at 3 which indicates to me a problem with this pair of contacts - so we will check them all.

b. 1 and 3 to establish you have a 3 phase supply ( 1 to 3 will be 230V ish) or a split phase supply ( 1 to 3 will be 460V ish) - I am pretty sure it is a three phase supply with one line earthed to produce L1, L2 and N (L3 earthed) all phased 120 degrees apart.

The evidence from the voltage readings suggests to me how the panel is wired which I will now draw out.
 
ah wait think my scribbles of the voltage of 1 was wrong - let me just check.

my apologies - running up and down in between work tasks
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ok that is odd. Not sure why I measured them so differently before. Washing machine is on now. This should have no relevance unless there is an issue somewhere. I'll test again later

Here goes again sorry: (this makes more sense)

1 (top 1st terminal) - 208
3 (top 2nd terminal) - 24
5 (top 3rd terminal) - 230

2 (bottom 1st terminal) - 208
4 (bottom 2nd terminal) - 24
6 (bottom 3rd terminal) - 230

Top CBS
1-208
2-24
3-230
4-208
5-24

Bottom CBS
1-208
2-24
3-230
4-208
5-24
 
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The UFH heating is cleverly connected across L1, L2 and N as shown in the diagram below. The black bar above the 5 cbs confused me; the voltage measurements clarified the situation.

Sometime please tell me L1 to L2 voltage. I am pretty sure you have a 3 phase supply arranged as I have drawn.

Otherwise I would swap the contactors for silent ones. Solid state switches can fail short-circuit which would not be a good thing so don't fit them. They also need substantial heatsinks and ventilation around these because they would get too hot without. If it was me I'd buy silent contactors. The three sets of UFH are each protected by a 20A cb. A 32A contactor is beefy enough to carry up to 20A 'all day long' and be more reliable than one rated close to 20A. Space the power meters and contactors apart so that there is some air movement and one does not warm the other.

Thank you for your patience!

:)

Marconi
 

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The UFH heating is cleverly connected across L1, L2 and N as shown in the diagram below. The black bar above the 5 cbs confused me; the voltage measurements clarified the situation.

Sometime please tell me L1 to L2 voltage. I am pretty sure you have a 3 phase supply arranged as I have drawn.

Otherwise I would swap the contactors for silent ones. Solid state switches can fail short-circuit which would not be a good thing so don't fit them. They also need substantial heatsinks and ventilation around these because they would get too hot without. If it was me I'd buy silent contactors. The three sets of UFH are each protected by a 20A cb. A 32A contactor is beefy enough to carry up to 20A 'all day long' and be more reliable than one rated close to 20A. Space the power meters and contactors apart so that there is some air movement and one does not warm the other.

Thank you for your patience!

:)

Marconi

I'll get back to you soon - just had an incident where my wife's car battery died completely when she needed to go out most- looks like a dead cell. 3v when disconnected!!

Not a happy wife at the moment. (apparently my fault for buying a GM car)
 
My last missive for today - Lucien Nunes is the chap if you want to discuss valve amplifiers.

Corrigendum: the disconnector also includes a 40A cb in each pole which I did not make clear - before my colleagues correct me ;-)
 
Any chance of a picture of your meter(s)?

Sorry haven't got around to that yet. Home schooling after work till 10pm then bed due to early zoom meetings.

Just now I measured the voltages across the terminals of the main disconnector breaker.
225/226v across each one. 1-2, 1-3, 2-3.

So we have a 3 phase supply by the looks of it.

Now what kind of new contactor would I need for the 3 zones and how to wire this up properly?

Many thanks
 
It is not easy for me to research the brands available in Uruguay. What I suggest you do is google or go to an electrical supplier and look for:

1. Silent contactor - the ac mains applied to A1 and A2 is rectified inside the contactor and then used to energise the coil.
2. Double Pole
3. At least 32A ac resistive load rating ie: low inductance like the UFH load.
4. 220-240V ac supply for coil (but see 1 above).
5. DIN rail fitting.
6. Study the number of switching operations figure - to handle a large number of open/close contact actions at rated current is a sign of 'goodness' so a high value to be preferred to a contactor with a low/lower figure.

Once you have found some options I will check them before you purchase should you wish.

The digital power meters are wired before the contactor as now. You will though ditch the doubled up 2mm2 for a single suitable 4mm2 wire.

With regards to wiring them in to the control logic - are you using your phone/wifi and SONOS switch to replace the timeswitch? And this then provides the live feed to the zone thermostats? The switched live from the zone thermostats then provides the A1 input to the corresponding zone contactor with a Neutral being provided to the A2.

Or are you going to have wifi thermostats too some of which incorporate a time/day programmer?

Or are you going to go the whole hog and introduce smart home technology to control the UFH? If so you would be better off starting a new thread and exploring options with EF colleagues who install this for a living. Once you have contactors you can apply a switched live to them via wifi switches which you can interface with smart home technology. My neighbour has British Gas HIVE but there are other suppliers.

Regards

Marconi
 
It is not easy for me to research the brands available in Uruguay. What I suggest you do is google or go to an electrical supplier and look for:

1. Silent contactor - the ac mains applied to A1 and A2 is rectified inside the contactor and then used to energise the coil.
2. Double Pole
3. At least 32A ac resistive load rating ie: low inductance like the UFH load.
4. 220-240V ac supply for coil (but see 1 above).
5. DIN rail fitting.
6. Study the number of switching operations figure - to handle a large number of open/close contact actions at rated current is a sign of 'goodness' so a high value to be preferred to a contactor with a low/lower figure.

Once you have found some options I will check them before you purchase should you wish.

The digital power meters are wired before the contactor as now. You will though ditch the doubled up 2mm2 for a single suitable 4mm2 wire.

With regards to wiring them in to the control logic - are you using your phone/wifi and SONOS switch to replace the timeswitch? And this then provides the live feed to the zone thermostats? The switched live from the zone thermostats then provides the A1 input to the corresponding zone contactor with a Neutral being provided to the A2.

Or are you going to have wifi thermostats too some of which incorporate a time/day programmer?

Or are you going to go the whole hog and introduce smart home technology to control the UFH? If so you would be better off starting a new thread and exploring options with EF colleagues who install this for a living. Once you have contactors you can apply a switched live to them via wifi switches which you can interface with smart home technology. My neighbour has British Gas HIVE but there are other suppliers.

Regards

Marconi

Hi Marconi.


No not easy for any of us to research items here. Nothing like screwfix etc.

Can I use one 40A contactor to replace all 3? Using the 3 poles of a 4 pole contactor?

This year currently got one sonoff temperature probe (TH10) in the living which will have a schedule and temperature range (from the app/amazon/IFTTT) and in turn activate the other sonoff R3 inside the fusebox to energize A1/A2. I imagine 95% of the time it will be switched on for the few hours it will be on a day.

Maybe in the future if we continue using the floor heating I'll look at more advanced systems to control each zone.

Many thanks
 
Nearly on the outside of a bottle of wine now so to be safe I will answer tomorrow morning.

Until then it'd be useful to know what you want to achieve in terms of functionality for each zone now.
 
Nearly on the outside of a bottle of wine now so to be safe I will answer tomorrow morning.

Until then it'd be useful to know what you want to achieve in terms of functionality for each zone now.

almost 6pm in the UK so ok for me to crack open a bottle now? Probably not yet as I'm preparing SQL scripts for a major live deployment on Monday! (Database developer)

Salud!
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We're also going to evaluate the cost of running the UFH this winter. We had plans to install another heating system (plus double glazing) but the global crisis put a stop to that.

I love the UFH but been calculating the costs and will be about 1 GBP per hour. That soon adds up. 9-10 kwh for both floors. We'll be testing a different number of zones to see how much we need on to heat the house sufficiently.
 
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How much is a kWh day and night? We buy our gas and leccie from EDF (Electricite de France) and have Economy 7 so cheap 7 hours overnight 0000-0700 GMT at:

Electricity day unit rate: 15.67p per kWh
Electricity night unit rate: 9.73p per kWh
Daily standing charge: 23.86p per day

Gas unit rate: 2.870p per kWh
Daily standing charge: 20.48p per day
 
How much is a kWh day and night? We buy our gas and leccie from EDF (Electricite de France) and have Economy 7 so cheap 7 hours overnight 0000-0700 GMT at:

Electricity day unit rate: 15.67p per kWh
Electricity night unit rate: 9.73p per kWh
Daily standing charge: 23.86p per day

Gas unit rate: 2.870p per kWh
Daily standing charge: 20.48p per day

We have the double tariff plan. (single, double and triple available) If you have triple 00:00-07:00 is even cheaper but then 7am-5pm is a bit more expensive. We have a pool with pump/filter running 7-8 hours until 5pm so the triple tariff is not worth it for us.

Also just had a 10% increase in prices this year. Normal developing world inflation!!


11pm - 5pm: 4.6 pesos kWh (8.64 pence)
5pm - 11pm: 11.59 pesos kWh (21.77 pence)
monthly fixed charges: £35 more or less


Our fixed charges are quite high as we have 15kW available. You can have a smaller kW available with less fixed charges but obviously that won't work with UFH. Also we have A/C for the summer. Years ago in a small flat we had A/C and kept tripping the main breaker due to the small kW available.

Dinner time gets expensive with the oven and hob at 22 pence per kWh! Unless you are very organized and cook before 5pm!

I was with ovo in Lichfield, UK. Was impressed with them and worked out fairly cheap on the dual tariff.
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Btw this is the contactor used for the 1st floor. 3 bedrooms, landing and 2 bathrooms. All through this one 4 pole. Split into 2 zones (2 cbs). Super silent 40a.
 

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I was thinking. Upstairs the small zones don't pull much current.
There is a contactor for 4 zones.
The small landing for example only pulls about 800-1000w?
Surely I can safely wire this directly from the 16amp CBS to a wifi switch of 10-16amps instead of the contactor?
 

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