Fire alarm switching on the AC units

[marc5180]

Been called to a faulty today, unit not cooling. Found the leak repaired and then recommissioned. As i was getting ready to leave though the customer told me they were having a problem every wednesday morning when they tested the fire alarms. She said that when the fire alarms were tested all of the AC controllers come on which brings on the indoor units.
Our firm installed these in 2004, the guys who installed them have since left, so i can't ask them if it was ever linked into the fire alarm. I spoke to my boss who doesn't think that it was.

I've heard of the fire alarm switching units off but not bringing them on. I have no idea where to start? Have any of you guys come across this before?

BTW the outdoor is a Mitsi Electrical VRF model PUHYP500YMFC, the indoor models are PEFYP20vMM-A (6 of them) and PKFYP32VGM-A (7 of them)

[catcher22]

I think you will find it is linked to the fire alarm. 1st find the centralised controller and check the wiring.If thats ok its the alarm providers fault.

[chemi-cool]

Fire alarms sould disconnect main supply to the building.

[marc5180]

I think you will find it is linked to the fire alarm. 1st find the centralised controller and check the wiring.If thats ok its the alarm providers fault.

Yes i understand that its linked to the fire alarm but i don't know how? These units dont have a centralized controller (G50) each fan coil has their own seperate controller. Do the alarm providers ever wire into the a/c units or are the installers expected to do it when it is being fitted??

[marc5180]

Yes that's what i thought Chemi, how can it be that it brings them on instead. I would have thought it had been wired in wrong but they have only just started having this problem.
I've asked has anyone been in doing anywork with the fire alarms but i was told that there hadn't been.

[catcher22]

Carnt be sure but is there a forced off /on conection either in the bs box or the o/door unit if .
mark

[catcher22]

Fire alarms send out live feeds to power relays to shut systems down they never cut power to the whole building.
mark

[yinmorrison]

Marc,

Is it my imagination or since you were there today ( Wednesday ) when the alarm was tested and the units were on does that mean the units dont run when the fire alarm goes off or am I missing something?

[marc5180]

They do the fire alarm test at 10am wednesday morning, i got there at 3pm. I asked the customer if there was a way that she could test the fire alarms whilst i was there to see if it cut the units out when they were on and then switch all remotes off and see if it brought them on but the customer didnt have a "special" fire alarm key that they used. The other manager had put it somewhere and nobody knew where so i couldn't test it.

[marc5180]

Carnt be sure but is there a forced off /on conection either in the bs box or the o/door unit if .
mark
Spoke to Mitsi and they say that there is no fire safety interlock on the outdoor units.

[yinmorrison]

Right, so her statement is... ' when the fire alarms were tested all of the AC controllers come on which brings on the indoor units.'... So are the units on when the test is done at 10am and if they are does she mean that they go off momentarily then back on or does she mean something entirely different. ie Is does she mean that the units are not being turned off when the fire alarm is on as they should be.

[catcher22]

Can you get any drawings for the fire alarm system.they should have a copy in their oem.should be easy to find then(i know nothing is that easy)
mark

[marc5180]

Right, so her statement is... ' when the fire alarms were tested all of the AC controllers come on which brings on the indoor units.'... So are the units on when the test is done at 10am and if they are does she mean that they go off momentarily then back on or does she mean something entirely different. ie Is does she mean that the units are not being turned off when the fire alarm is on as they should be.

They dont use the AC that often so it isnt on everyday only when it's hot weather. The units are not on when the fire alarm test is done. They have noticed it happening over the past few weeks and they decided to test it this morning by making sure all controllers were off, then they carried out the test and the controllers and fan coils switched on.

[yinmorrison]

Ah Ha sounds like its breaking a control wire possibly through a mains contactor and when this happens the units will probably reset to on when the power is re-applied. I have seen this happen with a Shopfitter I worked with who fits a Mains Contactor with the coil wired via the Fira Alarm.

[marc5180]

Is this something that the fire alarm company could have put in though and if so should i advise the customer to call them out?

[yinmorrison]

Its difficult to say where the line of responsibility lies as I have found that it is a grey area.Normally AC Contractor or Electrician will run cable from Contactor on HVAC back to the FA Panel and they connect to either no or nc contacts depending on how it operates.Basically you would need to check that this is actually what has been done ( Mains Power via Contactor to HVAC Kit ) Maybe then you could speak to Mitsi if it has been done that way.

[Daikin=Overated]

Ah Ha sounds like its breaking a control wire possibly through a mains contactor and when this happens the units will probably reset to on when the power is re-applied. I have seen this happen with a Shopfitter I worked with who fits a Mains Contactor with the coil wired via the Fire Alarm.

Sure thing!

Check the distribuition board in the cupboard or where ever. They'll most likely be a 240v fire alarm shutdown relay. This is actually the incorrect way of going about things as in turn this typically disconnects the radial supply circuit to the indoor units only which instantly screws the comms between indoor/outdoor in most cases, and worse still surges which have on my sites blown the indoor PCB's (fan coil/BS box).

Forced stoppage is the recommended way! However not all manufacturers provide this contact in their CCU's. Forced stopage often requires a non-volt contact to the outdoor unit.

I'd say that your going to need to book a return visit to see if the fan coils are shutting down or not. Depending on what circuit the fire alarm control signals isolating-you may be getting a low volt comms signal from the CCU irrespective of shutdown relay isolating power to indoor units hence controllers appearing to be operational.

I'd say the responsibility lies with the consultant,however like so many aspects of this industry, to the best of my knowledge it is not compulsory to incorporate fire-alarm shutdown within the design.

Hope that helps. Have a good weekend all!

[Greengrocer]

We have just done a Mitsi Elec job with a fire alarm interlock as an after thought (building control wanted this installed on a shop!!). Equipment was 1 x 20kW Std Inv outdoor serving 2 x 10kW Ducted indoors & 1 x 10Kw Std Inv Outdoor serving 2 x 5kW Ducted indoors (ground & basement systems).

Solution for this set up was a 24vDC signal (upon alarm) from the fire panel to 2 off Relays - one on each of the master indoor units. The relays switch NV contacts & are connected to a 3 wire adaptor (Mitsi PAC-SA89TA-E £4 accessory) that plugs into the indoor PCB. Relay was put in an adaptable box with appropriate terminal blocks and cable glands and fixed to chassis of indoor unit).
Once alarmed the remote controllers (PAR 21MAA) are overridden, on/off buttons go dead and each system stops. Any other means of interlock will probably put the system into a fault condition e.g. comms, power failure etc.
This setup is also listed for City Multi systems.
If the alarm company have done the work I doubt whether they have used Mitsi approved accessories or interface techniques. Probably cutting the indoor unit power or comms wiring. Suggest you get the customer to get the fire panel company to call you to discuss.
We had to "interface" with ADT on our job which went OK once we had figured out what was actually feasible on site & what type of signal the fire panel could provide us with.
I have some basic schematics and Mitsi wiring info if anyone is interested. There's also some info on the Mitsi Elec 2008 Tech DVD (under controls) if you have access to one..... Hope this helps.

[Thermatech]

If you find that the fire alarm relay cuts the 240v power to the indoor units then you might find that the indoor units have been set for power failure auto restart on the indoor unit circuit board dips.
So after the fire alarm relay connects the 240v power to the indoor units after the test then all the indoor units auto restart even though they were off before the fire alarm test.

There is no problem with turning off Mitsubishi City Multi units by turning off the 240v power supply. This is because the outdoor unit has the control transformer & sends 30v d/c communication voltage to all indoor units. So they can all communicate with remote controllers & outdoor units even if 240v at indoor unit is switched off. The indoor units just cannot run fan without 240v. If you try to switch on at the remote controller with 240v off at the indoor units then the controller just goes blank display again after a few seconds provided you have 30v d/c type remote controllers.
Ofcourse with most vrv/vrf system that run with 5v or 12v d/c comms if you switch off 240v power at any indoor unit you get comms error & system shut down.
This is because they need the 240v for the circuit board & to shut down the LEV valve to prevent refrigerant bypass through the unit.
But on City Multi the indoor unit can also use the 30v d/c comms to shut down the LEV & stop refrigerant bypass.
So with City Multi you can turn 240v power off to any indoor unit at any time & the rest of the system will continue to operate normally. because the indoor unit has used the 30v d/c to close the LEV valve & prevent any refrigerant bypass through the unit while its is switched off.

As there is no central control then the indoor units might have 3 wire addaptor & minature 12v relay connected to the indoor circuit boards & daisy chain back to fire alarm panel for forced stop.