TPN / L.V central switch panel.

[kme]

THOUGHT that`d whet your appetites........Guiness Drink

Called to a hotel the other day - They`ve got individual 2KW heaters in each guest room, fed via a contactor in the adjoining dist cupboard / dry riser.

Behind reception, they`ve got 119 illuminated toggle switches in a grid. 1 switch per room.

should be straightforward this; each switch fires the associated contactor, operating the heating, yes?

NEARLY!

Ten rooms ( together) weren`t operating. The maintenance guy`d had a look in this panel, and found a relay which, when partially withdrawn, caused the rooms to work again........... ? :|

I get there - (no diagrams, info or contractor details) - and find 15 relays on a top hat rail, along the top of this board. Each relay is a 5V coil, 4 pole 2 way unit; with only one pole connected. The "faulty" relay is the only one energised; and the wiring is N/C.

Does anyone on here have the foggiest idea what these relays might be doing there? I can`t understand why we`ve got 5V relays firing banks of rooms (which are on different phases, mind you), configured to break the circuit when 5V is delivered to a relay. WHY, FCOL? What purpose do they serve? What is their mission? Who is their leader? Are they just trying to send me demented?????????

H E L P ! (please)

KME

 

[green-hornet]

My guess would be that on first fix this would have been the main control operated by the reception to ensure the rooms were only heated when booked etc etc.

Then half way through the build they changed their minds and decided that if each room was to have its own cu or control panel then they would put some contactors there.

When they did the second fix they forgot what was installed and wired everything up, it worked so they left it. Waiting for you to come along and try to suss out what on earth did they do.

As for their leader? well he has long gone and would not now admit to knowing anything about them.

This is one of the major problems with especially larger installations were no records or diagrams are kept.

 

[Evans Electric]

Sounds as if it is over complicated to me KME , a right nightmare !! What are these 5v relays switching , the 2 KW loads or are they switching the contactor coils. ? Your confused ! So am I !

And who uses 5 volt relays anyway ? The usual is 12v----24-----50----110 --240 methinks

Deke

 

[bob]

you can get any rating and voltage at rs

 

[Andy™]

At a guess, id say they are wired so if the contactor coil fails, the heating stays on, and guests can then turn heater off as necessary. but then it could take a while for staff to notice heater is permanently wired

No idea why 5V, but since they are 5V, could the problem be caused by volt drop to the coil?

What do you mean by 'and found a relay which, when partially withdrawn, caused the rooms to work again'?

 

[SPARKY TIM]

Interesting? :|

Is it possible the 5 volt relays are some sort of remote control such as a thermostat or maybe a fire shut down ?

 

[sparkyrj]

fire alarms seems a good bet , to shut off heaters in the event of the alarms activating, but the 5V seems odd.

 

[Andy™]

Interesting? :| Is it possible the 5 volt relays are some sort of remote control such as a thermostat or maybe a fire shut down ?

would it not be easier to have one large contactor for the fire shut down, rather than many individual ocntactors per room

thermostat may be a good point though, but it would probably be easier to connect stat directly to heater rather back to a central point

 

[Oracle]

Were they wired into a BMS?

5V is normally used for control circuits from a PLC or controller.

So basically each relay controls approx 10 rooms. When removed (or de-energised) allows the rooms to be heated?

O.

 

[kme]

Tim, Andy, Oracle - you`re on the right track here guys. Sorry to Deke & the stinger; I probably didn`t explain too well.

Reception have control of the supply to the contactor; which in turn fires the heating. When a guest checks in, that room`s switch is operated. The relays (indirectly) appear to affect approx. 10 rooms ( on different phases).

Andy - the bit about partially withdrawing the relay was that if the switching contacts are still in circuit; but the coil is not, the relay reverts to n/c status, thereby returning power to the affected rooms.

I considered thermostat, but there aren`t any. Fire panels are not reporting an issue, so they haven`t triggered an output.

Mystery!!!!!

 

[spinlondon]

Won't be fire if they have to be energised to switch on.

Are they connected to a time switch, or are they part of some kind of phase control to adjust loads?

 

[Andy™]

Looks like it may be tracing cables to see where they go and where the break is....

Have fun!

 

[kme]

Won't be fire if they have to be energised to switch on.Are they connected to a time switch, or are they part of some kind of phase control to adjust loads?

They don`t mate. They have to energise to switch OFF!

No time switch; other than a 45A DP 2pole switch, with a printed sheet of on/off times alongside.

They can`t adjust the load; they just break a (low current) circuit - they`re only little 5A resistive relays......(Bless `em)

Looks like it may be tracing cables to see where they go and where the break is....Have fun!

Nah mate - they won`t go for anything like that. Make it work - quickest & easiest.....

 

[Andy™]

Nah mate - they won`t go for anything like that. Make it work - quickest & easiest.....

so bypassing faulty parts then?!

 

[bob]

personly i would have it computer controled eg. PLC, DMX (could poss work)

bob

 

[spinlondon]

Sorry, I meant off.

Does the 45A double pole switch do all of the relays, or just the 10 that are playing up.

Do you think the list of on off times is there for manual switching?

Could it be that someone has changed a faulty time switch for the double pole switch?

Could someone have removed a time switch?