UPS EPO  - Page 1
Forum section: electronics / beginners

author: margo
author_rank: Newbie
timestamp: November 22, 2021, 10:03:07 pm
content: Is it safe to UPS itself use epo signal ? ex. full, half load.

author: Benta
author_rank: Super Contributor
timestamp: November 22, 2021, 10:12:17 pm
content: I've no idea what you mean. Please use complete words and sentences.

author: margo
author_rank: Newbie
timestamp: November 22, 2021, 10:21:04 pm
content: Uninterruptible power supply devices have EPO function [emergency UPS Power Off]. Is it safe to UPS to power off the load immediately?

author: Manul
author_rank: Super Contributor
timestamp: November 22, 2021, 10:23:22 pm
content: Well, if UPS has such capability designed in, then it should be safe, no matter the loading. Afterall it is called "emergency off", and not "self destruct". Though it should not be used as a casual way to turn it off, only emergency and should be very rare event.

author: fordem
author_rank: Regular Contributor
timestamp: November 23, 2021, 12:39:37 am
content: I've seen UPSs that had a "known propensity" for self destruction when the EPO was pushed, and I know at least one customer who routinely pushed the EPO on one of those models with no ill effect.When doing a "narrated start-up" (a requirement of the commissioning process), we would point out the EPO button to the customer and instruct them to use it only in case of an emergency, and define an emergency for them, a fire or a case of electric shock - the customer who routinely pushed the EPO was not a unit that I had commissioned, it was sold by one of our competitors and we ended up supporting it.The real reason to have the EPO function is to kill the power to the load as rapidly as possible, and this is done with no regard for possible damage to the UPS - if you consider the consequences of not shutting the power off RIGHT NOW to be a "life or death" situation, then damage to the UPS becomes a matter of little significance.Most larger UPSs have a specific shut down sequence which can take anywhere from a few seconds to several minutes if the unit is part of a parallel redundant system (several UPSs in parallel), and many of them do not power the load off when they are shutdown, they transfer to bypass and a separate procedure must then be followed to remove the bypass power from the load, the EPO bypasses this sequence and de-energizes the output contactors immediately."EPOing" a larger UPS at "full load" can be a scary thing to witness, but, it was also the final step in what was called a "witness test" where the customer would be flown to the factory to witness their unit go through final testing - the unit would be run up to 100% load and then the customer asked to push the EPO button, there would be a tremendous bang, almost like an explosion, and you would literally see the UPS cabinet shudder.

author: margo
author_rank: Newbie
timestamp: November 23, 2021, 01:01:28 am
content: I rather was thinking about negative consequences by shutting down UPS (EPO) with 5-10% of its full load.

author: Rick Law
author_rank: Super Contributor
timestamp: November 23, 2021, 02:55:45 am
content: You should also consider: safe for the UPS itself doesn't mean it is safe for the load.Some machines such as disk arrays and servers doesn't like sudden power down. Depending on your set up, some UPS will inform the server to do a power-outage shut down if AC power is lost, and maintain power as long as it can so the server can shut down properly. The emergency power off likely doesn't do that but instead just cut the power out-right. Sudden power lost may not be liked by your load, so check and make sure.

author: fordem
author_rank: Regular Contributor
timestamp: November 23, 2021, 01:51:59 pm
content: Quote from: margo on November 23, 2021, 01:01:28 am5~10% as in this post, is a far cry from the full, half load specified in the original post - what I will tell you, having spent the past twenty-five years commissioning & maintaining UPS products, is only use the EPO if it's an emergency situation, and emergency situations, as mentioned before are life & death, imminent danger of fire, etc. - sometimes you'll get away with it, sometimes you'll trash the UPS.

author: margo
author_rank: Newbie
timestamp: November 23, 2021, 10:05:29 pm
content: Is there an information about e.p.o. in terms and conditions ups warranty by manufacturer. Is it will be replaced if ups will fail after e.p.o. during warranty period?

author: tkamiya
author_rank: Super Contributor
timestamp: November 23, 2021, 11:17:17 pm
content: Most UPS beyond consumer level ones, has this feature, Emergency Power Off. Here's a picture of back of my 1.5KVA UPS made by APC. All of my rack mount UPS have this connector. I personally do not use it. They are designed to be hooked up to either a normally ON or normally OFF button on a wall, and you can quickly shutdown the ups itself, and its output. APC sells unreasonably expensive button for this.To OP:You should typically not use UPS at its full capacity. It will last so short time that servers won't have time to shutdown properly. Using them at 50% or lower is more common. This is a button to use for cases there are no other method to use. Yes, it will abruptly shutdown the power to whatever is connected. I'll save long explanations as to why, but it can potentially damage some power supplies. But, remember, you pressed it because not doing so will result in more damage?This is similar to using fire extinguisher.... Using one will almost certainly damage some articles, but not using one will burn down your house. So you use it.As far as I know, I have never seen any statement as to warranty, etc, for using EPO. What may happen will largely depend on what's connected, which is beyond the control of UPS manufacturer. Let me say this though. What will happen is NO WORSE than suddenly unplugging your server.Guys? Let's remember not everyone on this forum use English as their native language? Some struggle to write in languages that is foreign? Let's give OP some room here....

author: fordem
author_rank: Regular Contributor
timestamp: November 24, 2021, 12:51:02 am
content: Quote from: margo on November 23, 2021, 10:05:29 pmI've never seen anything in a warranty statement specifically addressing damage caused by use of the EPO feature, you might want to consult the manufacturer ofyourUPS.Warranty typically covers defects in materials & workmanship (this wording is taken directly from a statement of warranty), damage resulting from customer actions are generally not covered, that said, I have repaired units that were damaged by use of the EPO during the warranty period, at no cost to the end user.Quote from: tkamiya on November 23, 2021, 11:17:17 pmAs far as I can tell, the OP's question is specific to damage to the UPS itself as a result of triggering the EPO, and not damage to the downstream load.

author: tkamiya
author_rank: Super Contributor
timestamp: November 24, 2021, 12:59:38 am
content: I think, as long as OP doesn't hear "self-destruct sequence initiated....", with red lamp and blaring syren, OP should be alright...