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Light Bender
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Discussion Starter · #1 ·
Had a discussion the other day about tee tapping on an addressable system. I say no, it can’t be done unless it is a DCL wired as a style “B”. Others disagree.

Is it allowed or not (in Canada) and if so, what are the conditions that allow it?
 

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eddy..good morning to your sir from "south of your border location"
I don't usually involve myself in comment, involving Canadian practices. But little curious so here comes a question.

When you are referring to "Style B" under Canadian standards.
Below your border, we having the denoted Class A & Class B systems.

Posing the silly "Yankey Type" mentality question..
Are Style B and Class B
.. Would they be "one in the same" animal ? :unsure:
 

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Light Bender
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Discussion Starter · #3 ·
eddy..good morning to your sir from "south of your border location"
I don't usually involve myself in comment, involving Canadian practices. But little curious so here comes a question.

When you are referring to "Style B" under Canadian standards.
Below your border, we having the denoted Class A & Class B systems.

Posing the silly "Yankey Type" mentality question..
Are Style B and Class B
.. Would they be "one in the same" animal ? :unsure:
Here are the terms we use as per our CAN/ULC standards.

Class B circuit and Class A Circuit are used for conventional wiring.

For addressable systems we use the term Data Communication Link. (DCL)
Data Communication Link style A (DCLA)
Data Communication Link style B (DCLB)
Data Communication Link style C (DCLC)

(DCLC is an “A” loop that includes isolators)
 

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The manufacturer's instructions will say whether or not T-tapping is allowed and if it effected by wiring configuration.
 

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Depends on what the data and equipment use, When I was working with Siemens our BAS and fire could T-tap our older systems and the comm's would still work with whatever addresses we used. It wasn't good, you would get some signal degradation or intermittent comm between devices but overall..you saved some labor.

That being said, Anything made from pretty much 2000 on (I think modbus, bacnet) did not like T-tapping at all, and you could bring the whole trunk down.

Code wise, I imagine fire alarm systems have something to say about it, but we never got told for anything else not too and I don't recall reading not too. But I think I would need more information about what you are T-tapping to say more
 

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Light Bender
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Discussion Starter · #6 · (Edited)
Depends on what the data and equipment use, When I was working with Siemens our BAS and fire could T-tap our older systems and the comm's would still work with whatever addresses we used. It wasn't good, you would get some signal degradation or intermittent comm between devices but overall..you saved some labor.

That being said, Anything made from pretty much 2000 on (I think modbus, bacnet) did not like T-tapping at all, and you could bring the whole trunk down.

Code wise, I imagine fire alarm systems have something to say about it, but we never got told for anything else not too and I don't recall reading not too. But I think I would need more information about what you are T-tapping to say more
For sure some panels will not work properly with a tee-tapped circuit. Like Edwards EST with their “mapping” thing, it doesn’t like tee-tapped devices.

But even if the panel is ok with it, As per the CAN/ULC we can not tee-tap on a DCL except for a DCLB.

(DCLB as in an addressable circuit wired like a class B, no return wiring)
 

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From way down south, near the Mexican border.

Addressable says to me a Class A system with 4 wires and a com wire for the addressable issue. I have never T'd a FA system, just in and out and back to the panel.
A T indicates to me a dead end and that would only work on a Class B two wire system with end of line resistors.
 

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I am in quebec. From how I understand things, when the manufacturer states that the system must be installed as a class A or class B system, it refers to the definition that is found in ULC 524. In that case if you have any T taps in the system then it is not according to the manufacturer's instructions and does not conform to the the ULC 524 requirement that it must also follow the manufacturer's instructions.
The systems I have worked on have always specified how they must be installed. I am currently doing additions to existing Siemens MXL systems which work just fine with T taps and no return as is stated in the documentation. If there is more than one zone of course the isolators must be wired in class A as per 524 but the zone created by the isolator can have any number of t taps.
From what I have heard the Simplex mapping function doesn't like t taps. When I was working with mircom systems we always did class A with the zones between isolators like in figure A18-9(page 143 ULC 524) but i would have to ask around why exactly we did it like that.

So as a general answer to your question is that yes it is permitted by the CEC and the relevant ULC codes as long as the system conforms to the manufacturer's specifications. I have also seen buildings where the city has more strict requirements than the codes so the AHJ may require that the loops be wired as class A or B even if the manufacturer doesn't require it.
In my experience if I ever have any questions I call up the tech of the company and they are very happy to answer any questions.
 

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Light Bender
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Discussion Starter · #9 · (Edited)
@aidonius I was also taught like you explained that tee tapping within the zone on addressable is ok for some manufacturers……but it is not. It does not meet ULC 524 standards.

On a DCLC (addressable loop with isolators) ULC 524 table 1 states that in a DCLC everything must still work. If you tee tapped a device and the wiring to it opened, it would not work so you would not meet the requirements of table 1.
157836
 

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I see what you are saying. The systems that I have seen T taps on are systems where all of the isolators are together in a 24x24 box beside the panel. The isolators are wired together in a DCLA and the output of each isolator goes to the zone as well as to the next isolator. This way, each zone is considered a DCLB and a T tap will not affect the ability of the zone to meet the requirements of Table 1. They are not DCLC circuits like you see in figure A18-9.
However, these are new sections(additions) to buildings and systems that are 25-30 years old and in buildings owned by the STM(montreal transit) which are not required to follow any of the ULC standards for fire alarm(524,536,537) for whatever reason. So I do not know whether this would be permissible in a completely new building. I have certainly never seen it anywhere else. All of the other places I have done have had true DCLC but those have been completely new constructions or retrofits(complete replacement of the existing alarm system).
 

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For sure some panels will not work properly with a tee-tapped circuit. Like Edwards EST with their “mapping” thing, it doesn’t like tee-tapped devices.

But even if the panel is ok with it, As per the CAN/ULC we can not tee-tap on a DCL except for a DCLB.

(DCLB as in an addressable circuit wired like a class B, no return wiring)
I'll be honest, I didn't realize I replied to the fire alarm systems when I hit reply and most of this terminology escapes me. Too many things fall under googles DCL systems as well (data class language keeps showing up) I should have edited my comment as I am out of my realm here. At best I have tied into fire alarm relays for monitoring and safety system shut off.

To follow up, knowing the tech's I worked with and the sites in question there is every chance that what they did would not pass an inspection either.
 

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Having thought about it, I can't think of any other situation than a DCLB like mentioned in the first post. It's the only time when you can meet the requirements as set out in ULC 524.
I should see a siemens tech tomorrow and I will ask and see if they have anything to say about it.
 

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Light Bender
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Discussion Starter · #13 ·
Having thought about it, I can't think of any other situation than a DCLB like mentioned in the first post. It's the only time when you can meet the requirements as set out in ULC 524.
I should see a siemens tech tomorrow and I will ask and see if they have anything to say about it.
I bet the tech will say it’s allowed. Every tech I have ever spoken with does not understand what table 1 in ULC524 is saying.
Unless someone took training other than CFAA, you won’t be taught this because CFAA teaches that tee-tapping is ok on addressable circuits with no mention of Table 1.
 

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The way I phrased it was more about whether there were any other situations(other than a DCLB) in which you are permitted to have t taps and the answer was no. So unless somebody else chimes in with an answer i think that should be it
 
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