school bell system

[fender62]

we use a danfoss 841 school bell timer system, lately we have noticed all the bells are not rinnging loud enough and seem a few seconds shorter than they used to be when ringing, what could be the fault of all of them sounding dull and ringing for a shorter time, than they used to, we had some major
renovation done within the school recently, i cannot see how any of that would effect everybell though, could it be the danfoss 841 unit itself, or its powersupply

 

[sparkymarka]

Check power supply at a guess

 

[fender62]

the psu was recently replaced with a new one

 

[bernardgreen]

The 841 is a simple 7 day timer and not a complete school bell system.

http://heating.danfoss.co.uk/xxTypex/287574_MNU17532478_SIT313.html

If the bells are ringing for a shorter time then check that the duration setting in the 841 has not been changed.

If the bells are not ringing as loud as before it might be the voltage supplied to them is lower. Either the power supply is defective or is being over loaded and not supplying the expected voltage. The shorter duration of ringing might be the power supply is shutting down due to over load.

Are the bells 230 volt or ELV ( 12 or 24 volt ).

If the cabling for the bell system was changed during renovation then check the cables are large enough to carry the current with out excessive volt drop ( especially for ELV and the high currents )

 

[fender62]

elv

 

[bernardgreen]

How many bells ?

Photos or details of the PSU would help.

Does the 841 switch the mains to the PSU or is the PSU permanently ON and its output switched ?

Was the new PSU the same power and voltage as the original ?

Sometimes it is necessary to set the PSU to be a few volts higher than the operating voltage of the bells to deal with voltage drops.

Can you measure the voltage on the PSU output when the bells are ringing ?

 

[OwainDIYer]

possibly a partial short circuit somewhere, or a bell intended for a lower voltage system has been wired in,

either would lead to power supply overload as suggested

 

[fender62]

ill take some pics and count the bells, thanks