Elk M1G with 2-wire or 4-wire smokes/CO?

benze

Member
I've got an Elk M1G and looking to add a bunch of smokes / CO / LP detectors to the panel.  To be specific, looking for 1 LP, 1 CO and 7-8 smokes for bedrooms, den, basement, and rooms next to the kitchen.  I've used SystemSensor i3 devices in the past, but am not sure what would be best recommended in today's marketplace as smoke detectors, and what is supported by the M1G panel.  For instance, does the M1G support the COPTIR?
 
 
What recommendations are there for the smoke detectors?  Should I use one kind in the bedrooms/upstairs hallways (near bedrooms) and another type closer to the kitchen or in the basement?  Should I have one COSMO in the furnace room and one in the rest of the house?  Or is 1 CO enough for the whole house?
 
Given the number of devices I'm looking to wire up, should I stick with 4-wire and put the CO on one zone, the smokes on another zone and the LP on a 3rd zone?  What would the advantage of 2-wire be over the 4-wire units? 
 
I've looked around for Liquid Propane detectors, and so far the only one I have found which looks interesting is the Marcurco GD-2B.  Are there others on the market that I should be looking at?
 
Thanks,

Eric
 

RAL

Senior Member
There are a couple of decisions you need to make about what type of smoke detectors you want to use.
 
But before we get into that, note that you should use Fire rated cable (FPL or better), and you should daisy chain the wiring,  Don't do home runs.
 
If you use 2-wire smokes connected directly to the M1's zone 16, then you need to use smokes that are listed as being compatible with the M1.  See the chart on page 6 on the M1 manual compatible detectors.   Going that route will limit the number of detectors you can connect to 20 units.  That's usually enough for most homes.  The advantage of the 2-wire smokes is that they are the most straight forward to wire.
 
Another option is to use 4-wire smokes, which can be connected to any zone.  Since power is provide over a separate pair of wires, the number is only limited by what the power supply (or aux supplies) can provide.  The downside of 4-wire smokes is that they require EOL relays, which makes wiring more complex.  Putting the smokes on more than one zone adds yet another layer of complexity, and I'd avoid that if possible.
 
If you choose System Sensor smokes, you can use a COSMODxW module between the smokes and the M1.  The COSMODxW can connect to any zone, as if you were using 4-wire smokes. It doesn't matter to the M1 whether there are 2-wire or 4-wire smokes on the other side of the COSMODxW, since the COSMODxW module shields the M1 from that. And it allows you to use combo COSMO-xW CO/Smole detectors to detect both hazards with one unit.  Using the COSMOD2W provides the advantage (over the 4W) of having a maintenance zone output to notify you of problems, plus makes the wiring easier since it connects to 2-wire smokes and doesn't need an EOL relay.  Both units break out smoke and CO to separate zone inputs on the M1.
 
The Marcurco gas detectors are a good choice.  There may be others out there, but I haven't come across them. 
 
Other advice:
 
Don't put smoke detectors in the furnace room, garage, attic or kitchen.  Instead, use heat detectors in these spots.
 
At a minimum, I'd put a CO detector near any sources of CO, such as rooms with fireplaces, near the furnace, etc. Many building codes now require at least one CO detector on each floor.  It doesn't hurt to have more of them, especially in sleeping areas.
 

benze

Member
Thanks for the suggestions.  I'm trying to understand the advantage of the COSMODxW however with the M1G.  Do I understand correctly that without the COSMODxW I cannot use the combo CO/Smoke units with the M1G since there is no distinct output for Smoke vs CO from the unit itself?
 
From what I read, the COSMODxW are limited to a total of 12 devices.  Which means that if I want more than 12 devices, I need to use 4 different zones on the M1G (2 for the first COSMODxW and 2 for the second one).  But that would imply having  smokes on multiple zones which you discourage.  Can you elaborate why that is not recommended?  Is it too complicated to configure?  How will that impact the Marcurco, which I expect needs to be installed on a zone by itself?
 
If I am going with the COSMODxW, is there a disadvantage of using just COSMO (combo device) everywhere instead of using other detectors, such as the 2251 series?  Or is it just a cost issue?  Additionally, given the COSMODxW, is there a disadvantage of the 4W units (aside from the EOL relay)?  Or phrased differently, are the 2W units that much simpler to install?  I would think that if it is just the EOL relay, that it would not be a big deal; don't some of the SystemSensor units already come with an EOLR built in?
 
Looking at the SystemSensor product lineup, I'm a little lost as to which smokes to consider.  Between the Intelligent and Conventional units, I'm not sure which to select.
 
Thanks for your insights.
 
Eric
 

RAL

Senior Member
You don't want the intelligent smoke detectors. They are mostly meant for commercial applications.
Eric B said:
Eric B, on 10 Mar 2020 - 15:12, said:
Thanks for the suggestions. I'm trying to understand the advantage of the COSMODxW however with the M1G. Do I understand correctly that without the COSMODxW I cannot use the combo CO/Smoke units with the M1G since there is no distinct output for Smoke vs CO from the unit itself?
The COSMO detectors send a notification to the COSMOD interface as to whether it is a smoke or CO event through some type of coding. I'm not sure exactly how they do that. I originally thought that the COSMO could also be connected directly to an alarm panel without the COSMOD (though you'd lose out on the type of event) but I re-read the data sheet and it says that the COSMOD is required.

Eric B said:
Eric B, on 10 Mar 2020 - 15:12, said:
From what I read, the COSMODxW are limited to a total of 12 devices. Which means that if I want more than 12 devices, I need to use 4 different zones on the M1G (2 for the first COSMODxW and 2 for the second one). But that would imply having smokes on multiple zones which you discourage. Can you elaborate why that is not recommended? Is it too complicated to configure? How will that impact the Marcurco, which I expect needs to be installed on a zone by itself?
If you decide to go with the COSMOD/COSMO route, and you need more than 12 detectors, then you need to decide whether you want to go with the 2-wire or 4-wire smokes. I believe it's only the 2-wire smokes that are limited to 12.

[Edit]: I checked with the techs at System Sensor, and they say the limit of 12 also applies to the COSMOD4W. Sigh.

There are two or three places where things get complicated with the smokes. One is that you'd like all the detectors to sound when any one of them triggers an alarm. Each COSMOD does tandem ring for the detectors connected to it, so if one detector triggers, the COSMOD will reverse polarity to all the detectors in the chain, which will cause them all to sound. But if you have two or more COSMODs, then the other COSMODs don't know that they should be sounding, too. To make that happen, you need to connect up the CO and Smoke trigger inputs to voltage outputs on the M1. And then write some rules so that when any smoke/CO input triggers, the M1's trigger output turns on. Plus another set of rules to turn the output off when you do a smoke reset.

Another thing you need to consider is the amount of power the smoke detectors and COSMODs require. Each COSMO-2W has a max power requirement of 50mA. And the COSMOD2W requires another 181 mA.

You'd like to power all the smokes and COSMOD2Ws from the M1's SAUX power outputs, since that is a resettable power output. Being resettable means that when a Smoke Reset command is issued from the keypad, the SAUX power drops for a few seconds, causing the smoke detectors to initiate a reset when the power is restored.

The M1 is limited to a combined total of 1A across all its power outputs, including the Data bus, SAUX and VAUX. So you need to look at your overall current draw for all the other devices you have that are powered by the M1 and see if you can handle all the smokes. Elk has a nice current draw spread sheet to help you do this.

Say you have 16 smokes, and two COSMOD2Ws. That's 1.16 A to power them, and you're over the max the M1 can provide without even considering any other loads. So you'll need an aux power supply. If you put the smokes on the aux supply, then you'll need a relay to switch the aux power supply output to the smokes to make it resettable via a Smoke Reset operation. The relay would be powered from SAUX. When SAUX drops, the relay drops out, cutting off the aux supply output; basically, it just mirrors what SAUX is doing.

One last complication with having smoke detectors on multiple zones is handling the reset itself. Initially, one detector triggers an alarm condition on one of say 2 fire zones. When you eventually cancel the alarm, the Smoke Reset will drop power to all the smoke detector zones (or COSMOD2Ws). But only one zone was in alarm condition. When power drops on the other zone, that will create a new alarm condition on that zone due to the power monitoring (EOL) relay. And now you have to do a second reset for that condition. But that will trigger a new alarm condition on the other zone. Ultimately, you may have to power off the entire panel and just restart it.

I'm not sure how the COSMODxW behaves when you issue a smoke trigger to it. I don't think it will turn around and create a trigger on the zone input, since that would be a false indication to the panel. But if it did, it would make the reset process much easier since both zones would then be in alarm condition, and a single reset would clear them both together.

A way around the reset problems would be to have individual reset relays controlling power to the zones, and then using rules and M1 outputs to reset the zones independent of each other. It's just all added complexity.

Eric B said:
Eric B, on 10 Mar 2020 - 15:12, said:
If I am going with the COSMODxW, is there a disadvantage of using just COSMO (combo device) everywhere instead of using other detectors, such as the 2251 series? Or is it just a cost issue? Additionally, given the COSMODxW, is there a disadvantage of the 4W units (aside from the EOL relay)? Or phrased differently, are the 2W units that much simpler to install? I would think that if it is just the EOL relay, that it would not be a big deal; don't some of the SystemSensor units already come with an EOLR built in?
The 2251 is part of their intelligent detector series, and is meant primarily for commercial installations.

There's nothing wrong with using COSMO detectors everywhere (except where you should have heat detectors and not smokes).

The 2-wire smokes aren't much different from the 4-wire models. It's just mostly how they are powered. The extra wires create more connection points where something can go wrong due to a poor connection. That's why the EOL relay is there to keep tabs on things.

One advantage of the 4-wire COSMOD4W is that you can also connect heat detectors to the daisy chain, and they don't count against the limit of 12.

[Edit: the following deleted after SS says the limit of 12 applies to the COSMOD4W as well]

If you really need more than 12 smoke detectors and want to avoid having them on more than one zone (I'd recommend that), then going with the 4-wire units us probably the better way to go. Your current draw calculation will tell you whether you'll still need an aux supply and a power control relay to mirror SAUX power.
 
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