I just got my order on some tomzn products on e-bay has anyone used these products before? And whats your experience with it. I bought the 63A change over contactor for my Non-critical loads (Tv’s, dish washer, geyser element, normal plugs etc.) and a small 25A change over for my Critical loads (wifi, alarm, cctv, gate motor, electric fence, lights).

I also got the tomzn DC surge protection for my PV panels protection. These items were dirt cheap compared to local stuff.

I currently have ACDC change over fitted but had to do repairs on the plastic casing  when installed 3 months back, as it was cracked when I originally took it out the box. I never returned it and decided to just order  the tomzn online as spare backups for when the ACDC pacs up.

The tomzn looks a bit more solid than the ACDC and I think I will swap these items as soon as I have time.

@Gerrie what was the price that you payed for them. I spotted some of there stuff in photos of installers overseas and local.  On ACDC stuff, there stuff is made in house local and not really good product, well some of them, and there service and after service don't really good to. 

3 hours ago, Gerlach said:

 what was the price that you payed for them.

The 63A contactor was R206, the 25A contactor was R177 and surge protection was R133, I had to pay extra R60 to collect from the post office.

Total still under R600 for lot. I paid about R500 for the one 63A acdc contactor that was cracked. 

Not bad at all. 

The one thing I noticed with these specific items is that its not commonly known to most of our local sales guys a couple of them actually told me you don't get these type of contactors and wanted to sell me the standard contactors that would not work for me. So I guess its actually easier to order online as you can also read the specs on items before you order.   

Jip, and some of them don't even know the specs of the stuff. I had 2 week long straggle with ACDC where i was looking for info of a 6kw inverter that they where selling. 3 sales guys, 2 tech guys, 3 solar guys, warehouse guy and the manager and still no info till date and no call back or specs of the unit. Called there head office and the guy told me his not going go look for the unit because his not lis for it.   I founded the info my self later by finding a old online book of ACDC of the specs of the unit. 

I actually have imported some electrical stuff to and where happy with it. 

I've used TOMZN 63A adjustable under/over voltage protection relays with digital voltmeter/ammeter readouts with great success. Very good build quality (including the internal PCB and electronic components), works as expected and zero failures going back the last 3 years. 

Regarding their AC MCBs, interlocking MCB type manual transfer switch and RCBOs, the low ultimate short-circuit breaking capacity (4kA instead of 6-10kA for 63A rated MCB) could be an issue in certain applications especially in industrial installations.

Lastly, polarised TOMZN DC MCBs could be the best in the Chinese market. I found arc quenching permanent magnets to be much stronger in TOMZN MCBs compared to CEMIG and CENOE brand DC MCBs.  Last year, a double pole TOMZN 125A 500VDC MCB employed as a DC disconnect device for an Axpert MKS 3kVA-24VDC inverter worked as expected and interrupted the battery circuit when the inverter developed an internal problem thus saving us from a spectacular fireworks display. A YouTube review of a single pole TOMZN 125A DC breaker by Bigclivedotcom can be found here

Just an update on my Tomzn change over contactors. They switch on and off every day controlled by a timer sonoff switch.

Its been about two months now since I installed it and am happy with it. These units are quite decent and the terminal screws looks quite solid. On the weekend I used a welding machine and there were a bit of heat on the 63A contractor but it looks like it will survive. I will definitely suggest these as a cheaper option.

Hi Gerrie

New to the solar world. What does a change over contactor do exactly? 

Does it switch to mains when a load reaches a specific amp draw?

10 hours ago, Donwil said:

What does a change over contactor do exactly? 

The change over contactor basically is the same as a change over switch that most people fit in their DB’s. But the change over switch has to be switched manually, which is a schlep especially if there is no one at home to do so. The change over contactor is used more if you want a automated system. (Can than be wired to other devices like sonoff switches, linked to a smartphone)

This is where the c/o contactor makes life much easier and you can conveniently switch between grid and solar from anywhere. This than works as a fully automatic system where you don’t really have to switch anything anymore, you just set the timers on your phone and keep an eye on it every now and than to monitor it.

I have set up timers on my phone for when my system must switch to solar in the mornings and to grid in evenings, and I now basically forget I have solar as it operates even when I am not at home or when I forget about it.

10 hours ago, Donwil said:

Does it switch to mains when a load reaches a specific amp draw?

Yes, My system switched to grid only if overload occurs or if battery falls below set point. (Amp cannot be set on my system but I could add load-shed relays that will do that if needed but I had no need for that) I actually have two different change over switches in my DB. The critical loads and non-essential loads. Each with their own timer settings. Non-essential comes on later to allow batteries to first charge up after evening use.

I use a 5KVA clone Axpert inverter that has  the very basic functions, but this suits my home application as mine was a DIY install at a very low cost, I did not have the budget to install the fancy inverters with the pylon batteries and all the bells and whistles that comes with it.

 

@Gerrie, will you please share how you use the sonoff switch to control this Tomzn unit please. And a wiring diagram if possible, i am looking at something similar. I am going to integrate this with my current home assistant implementation. 

Edited November 6, 20204 yr by rengro46
Added additional detail

7 hours ago, rengro46 said:

I am going to integrate this with my current home assistant implementation. 

@rengro46 please excuse the hand drawing, there are many different ways to control the tomzn contactor if you already have some sort of home automation control you could possibly just control the tomzn straight from your current system without a sonoff switch. But if you decide on a sonoff switch you need space to fit it, I fitted mine inside my DB board and my wifi is close to the DB so I never have issues with bad signal. 

The Eskom supply is wired thru the normally close contacts of the tomzn so that when the inverter is switched off or trips than Eskom will automatically feed the DB again. Only if the inverter output is on it will supply power to the Sonoff and than the tomzn contactor can be switched On or Off via the sonoff switch.

I believe some inverters has this function built in but I have no experience with them. I have a cheap clone but fortunately it does the trick. The drawing just show one tomzn contactor to make it simple but I actually have two tomzn’s fitted, the one for essential loads and the other for non-essential loads and they can be switched individually. My essential loads switch to solar at 7h00 and non-essential on at 8h00 than in evening my non-essential switch back to eskom at 18h00 and essentials later at 20h00. That leaves me with about 80% battery for load-shedding. If there is lot of bad weather I just switch between solar or Eskom with my phone. It works great for my needs.

Thank you very much Gerrie, very interesting. 

Hi @Gerrie, i found your post quite interesting. I was looking at these Tomzn contactors. I have a 3 phase home installation but a 1 phase inverter which i plan to install so it will be grid tied but in case power goes which happens very rare it would be nice to switch to inverter btw. inverter has a AC OUT which i could connect the contactor to and switch things so i have power while the power is lost BUT the problem is, all my appliances run on a 3phase system however i don't have any appliances REQUIRING 3 phase e.g using the 3 phases at the same time so i was thinking to get 4P Tomzn contactor and take all the phases and connect them to the same output from the inverter thru the contactor. What do you think ? I can't see why that would not work.

6 hours ago, donnib said:

Tomzn contactor and take all the phases and connect them to the same output from the inverter thru the contactor. What do you think ? I can't see why that would not work.

Hi @donnib, I’m sure you could feed the single phase from the inverter to all three phases in your DB, however it will not be a very simple task due to your grid tie requirement. If you had a off-grid system it would be much easier because once the tomzn switch your loads over to inverter power it also isolates the Eskom side completely and you don't have to worry about the three phases on Eskom side shorting and causing a big bang. A grid tie inverter will need more contactors with safety interlocks to ensure no shorting on Eskom side is possible.

7 hours ago, donnib said:

the problem is, all my appliances run on a 3phase system

If you have a three phase appliance like a three phase oven or a three phase motor those will need to be isolated completely before you short circuit the phases because the oven or similar three phase equipment will cause overloading when switched on and possibly also cause other problems on the inverter. 

7 hours ago, donnib said:

One factor to keep in mind when converting from three phase to single phase the neutral conductor that might feed three phase Sub-DB’s down steam will now be under sized for the single phase application because of the three phases that are 120 degrees out of phase, normally the neutral diameter in cables are the same size as the phase conductors but single phase will require the neutral conductor to be the same size as the three phase conductors together, which mean some changes to the neutral is required. (This would be quite important for bigger installations with long cable runs to eliminate voltage drops, but small installations might not have any significant impact)

3 hours ago, Gerrie said:

A grid tie inverter will need more contactors with safety interlocks to ensure no shorting on Eskom side is possible.

I wasn't aware that a contactor wasn't a 100% guarantee that it was a isolation between the two. Is it because there is a risk when it switches that it can connect both at the same time ?

3 hours ago, Gerrie said:

f you have a three phase appliance

What i meant is that my appliances are on different phases so they are balanced so i don't consume over just one phase but there is no appliances that ACTUALLY takes use of the 3 phases but now that i think of it all this transfer of all 3 phases is not a good idea since if i sell the house and people then install 3 phases things then there will problems in case they run on the inverter since they may require 400V which they won't get so that would be a no go solution.

I guess what i could do is like you, just add few contactors that i can control either manually or from an app that so if i want in case of power loss i can move things over to the inverter. Do you see problems in that? Sorry if i am taking over your post, maybe i should move my discussion in a separate post ?

7 hours ago, donnib said:

I wasn't aware that a contactor wasn't a 100% guarantee that it was a isolation between the two. Is it because there is a risk when it switches that it can connect both at the same time ?

When it comes to three phase it would be better to have two contractors that is mechanically interlocked like used in generator auto-change over panels. That ensures that the two different supplies do not mix. That is seen as 100% isolation between the two supplies. But this now goes against grid tie systems as grid tie is connected to your Eskom supply. Thats why a single phase off-grid inverter would be easier to feed three phases as it would isolate anyway under normal working conditions. Then you just jump over to whatever phase you want to feed.

 

7 hours ago, donnib said:

I guess what i could do is like you, just add few contactors that i can control either manually or from an app that so if i want in case of power loss i can move things over to the inverter.

I would also rather go this route, you could also split your DB board to have all essential equipment on one phase and then you supply only that phase from inverter. 

3 hours ago, Gerrie said:

I would also rather go this route, you could also split your DB board to have all essential equipment on one phase and then you supply only that phase from inverter.

True, problem is that i would violate the rule to balance my loads on the 3 phases not that they probably check that. Another question, this interlock feature. Does the contactor for example this https://www.aliexpress.com/item/32788838320.html?spm=a2g0o.productlist.0.0.781862eduKwEq3&algo_pvid=5f7eb79b-2000-4cec-82fe-11930755fe0a&algo_expid=5f7eb79b-2000-4cec-82fe-11930755fe0a-8&btsid=0bb0623116052573552506214ee90b&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_ fullfill the interlock i mean is this 100% secure to use so both AC and and PV out are not mixed or is there something else required beyond this ? If you have link to what you think is required that would be nice to see. thx

I found this video so this may be what you are saying ? 

 

So i need to connect two contactors control signals to each other ? This is electrical interlock but is there a requirement of a mechanical interlock ?

1 hour ago, donnib said:

Does the contactor for example this https://www.aliexpress.com/item/32788838320.html?spm=a2g0o.productlist.0.0.781862eduKwEq3&algo_pvid=5f7eb79b-2000-4cec-82fe-11930755fe0a&algo_expid=5f7eb79b-2000-4cec-82fe-11930755fe0a-8&btsid=0bb0623116052573552506214ee90b&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_ fullfill the interlock i mean is this 100% secure to use so both AC and and PV out are not mixed or is there something else required beyond this ?

The above Tomzn contactor would not be safe as it has no way of mechanical interlocking. I don’t think Tomzn makes the 3phase version of change over contractor. (Just to clarify I used a change-over contactor and not a normal contactor like the above Aliexpress one). For three phase you might be limited as to use industrial contactors with built in mechanical interlocks this also becomes pricey. Mechanical interlock to my knowledge is a requirement for preventing both contactors energizing at the same time. Mechanical interlocking is basically a locking pin between two contactors preventing one of being pushed in while the other is already in.

When purchasing contactors you should specify for mechanical interlock as most don’t have that function. To stay on the legal side of things the design and material should be agreed with the electrician that is going to do the C.O.C.

Thank you @Gerrie, Can you recommend a change-over contactor with both electrical and manual interlock for just one phase ?

6 hours ago, donnib said:

Thank you @Gerrie, Can you recommend a change-over contactor with both electrical and manual interlock for just one phase ?

For electrical and mechanical interlock the best would be something like the Schneider LC1D50 as per attached picture, as they offer both interlock features and it can be used three phase or single phase just select your correct current rating. 

@Gerrie thank you very much for your help, i will have to dig into Schneider products and see if i can find the the preassembled one in parts since i can't find it here online for example the LC1D50, i even tried some of the smaller ones since for one phase i only need 16A @ 230V

8 hours ago, donnib said:

i will have to dig into Schneider products and see if i can find the the preassembled one in parts since i can't find it here online for example the LC1D50

Hi donnib if you only need 16A the closest size to that is 18A as per the catalog and the part number would be LC2D18P7 (18 meaning it is rated up to 18A also the P7 meaning 230Volt control coil if you are using 230V.)

My previous post i made a mistake with part number typing LC1 instead of LC2 hope this makes it easier to find.