I've tried looking this up and found a few similar questions, but most are debating over transfer switches.
In a normal emergency lighting situation with a backup generator, we would have two transfer switches. One for the optional standby load and one for direct emergency. Then emergency circuit connected fixtures within the building would have a GTD to bypass local switching in the event that normal power was lost. So that there is immediate emergency lighting illuminated throughout all required spaces.
My question though; what is the correct way of connecting/providing emergency lighting if the whole building system is fed from the generator? We would still need the emergency and optional standby transfer switches, but the entire building would be optional standby. The lights would still be connected to an emergency circuit, but the GTD would now see both the 'normal' power and emergency power once the generator switches over. So the GTD would not bypass the local controls and the emergency lights would not come on in an emergency? If the optional standby load was switched off then the system would respond as intended and the GTD would override the local controls. But in an emergency where both sides are fed from an emergency generator, how is this normally handled so that the emergency lighting senses when to override the controls?
In a normal emergency lighting situation with a backup generator, we would have two transfer switches. One for the optional standby load and one for direct emergency. Then emergency circuit connected fixtures within the building would have a GTD to bypass local switching in the event that normal power was lost. So that there is immediate emergency lighting illuminated throughout all required spaces.
My question though; what is the correct way of connecting/providing emergency lighting if the whole building system is fed from the generator? We would still need the emergency and optional standby transfer switches, but the entire building would be optional standby. The lights would still be connected to an emergency circuit, but the GTD would now see both the 'normal' power and emergency power once the generator switches over. So the GTD would not bypass the local controls and the emergency lights would not come on in an emergency? If the optional standby load was switched off then the system would respond as intended and the GTD would override the local controls. But in an emergency where both sides are fed from an emergency generator, how is this normally handled so that the emergency lighting senses when to override the controls?