Changing original 32Amp contactors for solid state relays?

[Yonny24]

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)

 

[marconi]

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 ;-)

 

[Yonny24]

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

 

[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

 

[Yonny24]

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

 

[marconi]

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.

 

[Yonny24]

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.

 

[marconi]

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

 

[Yonny24]

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.

 

[Yonny24]

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?

 

[marconi]

ABB ESB40-40-230AC/DC - https://new.abb.com/products/GHE3491102R0006/esb40-40-230ac-dc-installation-contactor

The ABB contactor is a good make and well suited. It is a silent or hum-free design and the 40A AC1 (resistive and low inductance or PF nearly 1) rating for the contacts is excellent for your application.

I don't know what the Uruguay electrical regulations stipulate for switching to countenance single pole switching. At the moment all your contactors are used for double pole switching; this is certainly necessary for those UFH elements wired across L1 and L2 but for those across L1-N and L2-N single pole may be allowed - I just don't know. However, double pole is to be preferred because it maintains uniformity of wiring scheme for the UFH system and there is some advantage in splitting the arc across two pairs of contacts when they open to prolong life. I would not opt for single pole switching.

The aforesaid means that to continue with double pole switching you would need to obtain a 6 pole contactor if you wanted one to switch three sets of heating elements in the way a showed in my last diagram. Such a contactor I is rarer than 4 pole and thus I expect pricier. I don't know if you can obtain a silent 6 pole contactor.

Using one contactor to switch 2 or more UFH zones has two drawbacks; if it fails you have lost all heating and when it closes or opens the large current change will cause a noticeable and perhaps troublesome voltage transient in your home and maybe to your neighbours. Far better to sub-divide the load switching over 3 contactors to reduce the magnitude of each transient step. Already I notice that you have quite a variation in supply voltage as loads in your home are powered on and off which indicates a higher supply impedance than is typical in the UK. Switching the UFH zones as one will be noticeable and annoying.

Which leads on to the idea of switching each zone directly using a wifi 'contactor'. In theory this is possible but great care is needed to ensure the power contacts have an adequate AC1 rating and can cope with frequent switching during the day. I'd have to see the specification to comment further. Would it be silent? Would I do it in 'one step'? - no, because I like my functionality appropriately realised in the best possible way. I speak from an industrial background so in the domestic setting one might be more inclined to economy of components.

Sorry about the rather long-winded reply - I have nothing else to do.

 

[Yonny24]

ABB ESB40-40-230AC/DC - https://new.abb.com/products/GHE3491102R0006/esb40-40-230ac-dc-installation-contactor

The ABB contactor is a good make and well suited. It is a silent or hum-free design and the 40A AC1 (resistive and low inductance or PF nearly 1) rating for the contacts is excellent for your application.

I don't know what the Uruguay electrical regulations stipulate for switching to countenance single pole switching. At the moment all your contactors are used for double pole switching; this is certainly necessary for those UFH elements wired across L1 and L2 but for those across L1-N and L2-N single pole may be allowed - I just don't know. However, double pole is to be preferred because it maintains uniformity of wiring scheme for the UFH system and there is some advantage in splitting the arc across two pairs of contacts when they open to prolong life. I would not opt for single pole switching.

The aforesaid means that to continue with double pole switching you would need to obtain a 6 pole contactor if you wanted one to switch three sets of heating elements in the way a showed in my last diagram. Such a contactor I is rarer than 4 pole and thus I expect pricier. I don't know if you can obtain a silent 6 pole contactor.

Using one contactor to switch 2 or more UFH zones has two drawbacks; if it fails you have lost all heating and when it closes or opens the large current change will cause a noticeable and perhaps troublesome voltage transient in your home and maybe to your neighbours. Far better to sub-divide the load switching over 3 contactors to reduce the magnitude of each transient step. Already I notice that you have quite a variation in supply voltage as loads in your home are powered on and off which indicates a higher supply impedance than is typical in the UK. Switching the UFH zones as one will be noticeable and annoying.

Which leads on to the idea of switching each zone directly using a wifi 'contactor'. In theory this is possible but great care is needed to ensure the power contacts have an adequate AC1 rating and can cope with frequent switching during the day. I'd have to see the specification to comment further. Would it be silent? Would I do it in 'one step'? - no, because I like my functionality appropriately realised in the best possible way. I speak from an industrial background so in the domestic setting one might be more inclined to economy of components.

Sorry about the rather long-winded reply - I have nothing else to do.

Many thanks for the full write up.
I'll look for 3 abb contactors following your advice.
Now the upstairs box is a right mess and I want to tidy it up.
Looks like we have 1 contactor for 4 zones. 4 live cables going out but one neutral for each 2 live cables. Live cables on terminals 2 and 3(2 coming out of each). I'll need to draw this out as looking at the mess it's impossible to see. I traced which wires go to which ufh last night as I want to control my office ufh independently.

 

[marconi]

As you are the father, spouse and breadwinner please take heed of this: If you are going to be putting your fingers in among the wiring you must invest in an approved voltage indicator in order to prove dead once you have de-energised and isolated. A digital voltmeter or a neon screwdriver are not reliable. You do not need to spend much. I have a DILOG because they are good value for money and I rarely do any work these days preferring to employ an electrician for anything major.

ISOPK2 | Di-LOG - https://www.dilog.co.uk/product/isopk2/

Time spent discovering how things have been wired is well spent - do not assume anything.

 

[Yonny24]

As you are the father, spouse and breadwinner please take heed of this: If you are going to be putting your fingers in among the wiring you must invest in an approved voltage indicator in order to prove dead once you have de-energised and isolated. A digital voltmeter or a neon screwdriver are not reliable. You do not need to spend much. I have a DILOG because they are good value for money and I rarely do any work these days preferring to employ an electrician for anything major.

ISOPK2 | Di-LOG - https://www.dilog.co.uk/product/isopk2/

Time spent discovering how things have been wired is well spent - do not assume anything.

Thanks for the link of suggested equipment Marconi. Sound advice.

I've done a sketch of how I believe 2 of the rooms are wired up upstairs. From one of the 4 pole outlets they have 2 live wires going to each room. Just one blue neutral though on series. I would like to have these 2 controlled rooms controlled independently. Not sure how that would be achieved without installing a new digital thermostat on the wall. Would like to have them cabled independently like I do downstairs with the double pole contactors or something similar. They only draw about 1000w each.

 

[Yonny24]

I'm thinking I'd probably need to feed an individual neutral cable to one of the rooms so they are separate circuits.

I'll wait for advice.

Thanks