AUS sparky here who services and installs public/private hospitals in Queensland (Body protected and cardiac area's on the regular); I find it super interesting the differences in terminology and requirements. Keep it up mate, love the content... P.S should check the logistics to start shipping to AUS - the Boddington, Knipex and Wera range would make a killing over here. Not so easy to get our hands on.
Nice to see a different side of sparky work! I've seen the alarm side work from a patient perspective just before surgery. Alarm went off and a methodical unplugging of gear ensued and a swap over.
Interesting video. You do find unearthed systems on some of the high voltage distribution network and power stations, especially where you have a delta secondary transformer winding to a delta primary transformer winding, so there is no star point to take down to earth. You also find high impedance earthed systems where the transformer winding star point goes through an impedance before connecting to earth to deliberately limit the fault current to a few amps. Otherwise with directly bonded, it would be silly amps time.
Ungrounded systems are a big thing here in USA where requirements are very strict, isolated transformers, XHHW wire with all conductors with more robust insulation to ensure sufficient dielectric insulation, testing is also required to address failures we have line isolation monitors to keep leakage current and monitor potential differences say in operating rooms (OR) at minuscule levels for that a line isolation monitor is used. Specifically this can mean minimizing the length of branch-circuit conductors and using conductor insulations with a dielectric constant less than 3.5 and insulation resistance constant greater than 6100 megohm-meters (20,000 megohm-ft) at 16°C (60°F) which reduces leakage from line to ground. In critical OR rooms power needs to be continuous and not break so GFCIs/RCDs are not permitted and will operate even under fault conditions. Of courses this requires medical equipment to be fully tested for dielectrics and various other leakage tests including patient leakage tests. This requires not just electricians understand ungrounded/isolated systems but it requires medical staff to understand if line isolation monitor picks up leakage current to be too high (remember normal skin resistance os reduced in surgery). If alarms sound then medical staff literally have to unplug medical devices in a specific sequence to isolate the problematic faulting medical device either remove it or leave the OR to go to a working OR with no faults the ungrounded system also ensure the isolated circuit protecting it has dedicated emergency backup power as well. I suspect you will need to cover multiple standards for health facilities never is the case only one standard covers it. Standard wiring regs, emergency power regs, health facilities reg, medical devices reg etc…
@@residualelectrical mate I need to buy some boddingtons gear from load out but living in USA I prepared to pay for the shipping but no option to do that on the website… anyway to get around this?
wy would you say sad i think reading about IT systems was the best thing i have ever done in my life, really opens the avenue to how electronics can wrok
It is worth knowing that most medical equipment is double insulated and meet extra safety regulations in such a way that they have to provide bonding so you can’t get a shot from a metallic thing but most of the metallic things do not have the capacity to become easily energised as well
The grey box (IMD) is the monitoring device you set that to alarm when the insulation resistance value drops below a limit e.g. 100k ohmes also can set the current value based on the KVA rating of the transformer so a 8KVa has a max load of 34a anything over that the IMD will alarm for overcurrent similarly there is an bi metal strip in the transformer that will break at a set temp opening a NC contact setting off an over temp alarm. That device is a joint IMD and EDS the EDS uses a PGH to inject a current down each circuit through an CT to locate which circuit the fault is on. The alarm panel I’m guessing is either an RA-003 or one of there touch panels that they can use to alarm for the IPS and control and alarm other systems in the theatre like UCV and ventilation
Back to my college days - creating a Faraday Cage type scenario guess so there’s minimal potential difference if not any PD. Clever stuff! Makes sense as you say they are skilled or instructed people so regs change or are far more relaxed because of it! Nice work
Definitely interesting location. IT has always been a mystery to me and this vide motivated me to read up about it. Getting some tools from loadout for Christmas.
Brilliant video, IT installations aren't common and unless you're working on NHS/private hospital sites or cleared to work on MOD sites most electricians will never be involved with it. Edit: Only thing I will say is the Isolated Tera system you appear to be running in there is not the same as the Integral Tera we did for the MOD. The system installed for MOD sites is isolated from the incoming supply via transformer, the CPC's were bonded to the neutral at the panel with sense cables to alert to a fault. All accessories, trunking, cable tray, conduit etc was all bonded as well. The idea being that if an attack happened they would not loose power or risk electric shock to soldiers as there is always a path to complete the circuit. Figured I'd clarify although it has been a number of years since I've put an IT system in.
@@residualelectrical I enjoyed it, the differences between MOD and NHS even though it's bracketed under the same "IT" system always make for interesting topics. I do miss being involved in that line of work but it's better left to lads younger than myself that don't mind the hours.
The railways use IT systems for signalling power supplies, managing earth faults of cables that run in ducts alongside the railway for miles is a challenge
@@deang5622 I mean you can at that point connect a thick PE and drill in earthing rods and connect it every say... 100 meters. Randomly made that number up. But you then end up with different issues like current flowing on your PE from ground potentials, nearby earthing rods from anything like random consumer units or lightning protection systems dumping fault current into the soil, etc. It's easier not to even bother with an earth at that point and use IT, PELV or SELV or something but then you consider voltage drop and ELV systems are out of question. 110V DC or lower also works but DC in a rough environment like that help corrosion and everything will rust to hell and back if water touches it. To sum it up: IT works, TT is fucky, ELV is not even worth doing, LV DC is maintenance hell, and maaaybe you can get away with a TN system with an earthed live but then you have 2 phases with 400V on them compared to ground.
The additional difficulty railway cables have to contend with is high longditudional and transverse voltages induced in cables from 25 kV traction systems. Grounding systems have to be bonded to the traction return to prevent dangerous voltages but the external ground connections have to be kept outside of apparatus rooms, so cable sheaths have to be gapped before entering buildings.
@@barrieshepherd7694 No such thing as a transverse voltage. Parallel cables induce a voltage because there is capacitance between the cables. Nothing transverse about it. Currents are induced by an inductive effect (by way of a magnetic field). The concept of transverse applies to transverse electromagnetic waves not to voltages. And high induced voltages in signalling cables is easy to contend with by using either differential signalling or optical fibre.
@@deang5622 I beg to differ. Transverse voltages occur in cables across pairs of wires and can cause induced noise levels. Obviously this effects communications cables more than power cables. The inductive field is caused by the 200 odd amps, at 25 kV, 50 Hz, flowing in the overhead contact wire when a train is in section. This causes a significant field around the railway corridor. ITU-T Recommendation K.23 explains it well. While transverse voltages in these circumstances may be low, raising noise levels, longitudinal voltages can be dangerously high.
I got to see an entire Kiddies hospital being fitted out - well over 500 million quid. The amount of wiring for power, hotel, data, comms etc was incredible.
If the equipment is potentially grounded via separate earth connection, drawing extra p-e in parallel to the same outlet the equipment would create The risk of inducting "wandering induction current " (Creating ground loops)
Mate the Penny washers 😂🤦🏻♂️ Sent the apprentice to the van the other week to get the hoover (I fucking know right) anyway. Came back saying he couldn’t find it..went to the van opened the side door and it fell right out on my foot 🤦🏻♂️😂😂😂🙄
I‘m sure they make them, but they are probably way more expensive then regular 3x1.5 or 3x2.5. Similar I usually run 5x1.5 to window shutter motors, even you technically only need 4/5 wires. It‘s just cheaper and on the car anyway.
During the first min or so I thought why’s he wearing a turtle neck on site? Man’s gone all Milk Tray on us 😂 Another cracking video bro, always interesting seeing these types of videos only do light commercial occasionally so enjoy seeing all of these
The i is for isolation and the t is for transformer. This lad has completely missed the point of this. The transformer is a 1:1 traffo basically 230v in and 230v out, but because it is on the secondary side it will not be affected by any spikes on the incoming side(think of it like a filter for the 230volt) also being on the secondary side it means 230v between L1 and L2 (the two browns) but 115v L1 and earth and L2 and earth still not ideal but much safe if there is a fault.same thing with a site traffo, the yellow 110v, that has 55 volts live to earth. He should not cut the earth out, that earth is the dirty earth that should travel with the L1 and L2 from ips panel to IPs sockets, what did they think the two earth bars in the top were for ???? In the back of the IPs socket there is two earth terminals the dirty earth that is connected to the screw lugs and the body of the socket face(class 2 earth or dirty earth) the one that one that the healthy doctors staff come in to contact, and the other only to the earth pin of the plug top(class 1 earth or clean earth) that’s the one on the machine/piece of equipment that the patient who is unhealthy and has a compromised immune system and is more susceptible to injury from an electric shock so this earth goes but to a earth reference bar located in the room that has an much lower resistance. Sorry This is mad long but fuck me he did a really shite job of explaining something very interesting.
Oh dear, another one without a clue. Try reading section 710 of BS7671. IT systems are not Earth free at all, they are Earth neutral bonding free, with safety because there is no Earth path from the live conductors. A single contact to a live conductor is therefore not dangerous, the possible shock current being very small. If there is any leakage to Earth the system will alarm, but is still safe. Simple enough!
@@residualelectrical You did a better job than cyclofuka or whatever his name is. IT is Isolation Terra, as you said. The transformer is an isolation transformer so there is no solid reference to ground. Nothing at all to do with power condition / limiting spikes / filtering. It's solely for isolation to ground, hence isolation transformer, not reactor or filter. There may be ancillary equipment to filter, but that's not the job for the isolation transformer. The first alarm is when you get an earth fault on one leg, you them lose the advantages of the floating ground / isolation to earth. Three phase systems in mines, some ships and DC power systems in substations all use the same system, floating ground. This allows for better protection from earth faults, shocks and also allows one leg to connect, or touch ground and not trip the circuit, shock or induce and fault currents. Since basically the first leg to connect now becomes what we all call the bonded neutral. Keeps people and equipment safer and also keeps the run time up. Way more to it, but that's it put simply. You did a good job in your video explaining it.
Nice, IT systems are kinda like the bastard lovechild that is kept in the basement and noone talks about them, you just see a note from them once in a while saying "feed me", hardly ever see mainstream (read; TH-cam sparks and other channels) creators do much, f any, content on them. I'm off to go and drown the childhood memories that I had suppressed for all these years until THIS VIDEO sent me in a spiral. I jest, I spiral anyway 😜🤣
@@residualelectrical If you put "Professional" information on the net IT MUST BE CORRECT! The basis of IT systems in medical locations is that contact with a single live conductor is NOT dangerous, even if you are also firmly touching Earth. All the additional supplementary bonding is to prevent any potential between anything in the room, from static or any other cause. A single fault produces no Danger, and it will cause an alarm from the Earth Monitoring System. Therefore it can be fixed ASAP. Regards David CEng
If you want to learn about IPS you should look at the Health Technical Memorandum 06-01 (HTM 06-01) Electrical services supply and distribution. These are the set of documents that outline the standards for the health environment. Available free on the internet here www.england.nhs.uk/wp-content/uploads/2021/05/Health_tech_memo_0601.pdf I've worked on many of these systems.
In addition to the HTMs (or SHTMs in Scotland), the IET have published a Guidance Note on Medical Locations, it's available on their website but I can't link to it, every time I do my comment gets deleted. If you search for "iet medical locations" it should appear near the top of the search results. It's quite practical and might be informative too.
AUS sparky here who services and installs public/private hospitals in Queensland (Body protected and cardiac area's on the regular); I find it super interesting the differences in terminology and requirements. Keep it up mate, love the content... P.S should check the logistics to start shipping to AUS - the Boddington, Knipex and Wera range would make a killing over here. Not so easy to get our hands on.
Thanks mate, aspiring electrician here. Its neat to get a glimpse into the line of work you're in!
Nice to see a different side of sparky work! I've seen the alarm side work from a patient perspective just before surgery. Alarm went off and a methodical unplugging of gear ensued and a swap over.
It makes a change for it to be methodical unplugging. It's normally a bit frantic and haphazard, particularly if the patient is on the table!
Interesting video. You do find unearthed systems on some of the high voltage distribution network and power stations, especially where you have a delta secondary transformer winding to a delta primary transformer winding, so there is no star point to take down to earth. You also find high impedance earthed systems where the transformer winding star point goes through an impedance before connecting to earth to deliberately limit the fault current to a few amps. Otherwise with directly bonded, it would be silly amps time.
Ungrounded systems are a big thing here in USA where requirements are very strict, isolated transformers, XHHW wire with all conductors with more robust insulation to ensure sufficient dielectric insulation, testing is also required to address failures we have line isolation monitors to keep leakage current and monitor potential differences say in operating rooms (OR) at minuscule levels for that a line isolation monitor is used. Specifically this can mean minimizing the length of branch-circuit conductors and using conductor insulations with a dielectric constant less than 3.5 and insulation resistance constant greater than 6100 megohm-meters (20,000 megohm-ft) at 16°C (60°F) which reduces leakage from line to ground. In critical OR rooms power needs to be continuous and not break so GFCIs/RCDs are not permitted and will operate even under fault conditions. Of courses this requires medical equipment to be fully tested for dielectrics and various other leakage tests including patient leakage tests. This requires not just electricians understand ungrounded/isolated systems but it requires medical staff to understand if line isolation monitor picks up leakage current to be too high (remember normal skin resistance os reduced in surgery). If alarms sound then medical staff literally have to unplug medical devices in a specific sequence to isolate the problematic faulting medical device either remove it or leave the OR to go to a working OR with no faults the ungrounded system also ensure the isolated circuit protecting it has dedicated emergency backup power as well.
I suspect you will need to cover multiple standards for health facilities never is the case only one standard covers it. Standard wiring regs, emergency power regs, health facilities reg, medical devices reg etc…
@@residualelectrical mate I need to buy some boddingtons gear from load out but living in USA I prepared to pay for the shipping but no option to do that on the website… anyway to get around this?
wy would you say sad i think reading about IT systems was the best thing i have ever done in my life,
really opens the avenue to how electronics can wrok
It is worth knowing that most medical equipment is double insulated and meet extra safety regulations in such a way that they have to provide bonding so you can’t get a shot from a metallic thing but most of the metallic things do not have the capacity to become easily energised as well
The grey box (IMD) is the monitoring device you set that to alarm when the insulation resistance value drops below a limit e.g. 100k ohmes also can set the current value based on the KVA rating of the transformer so a 8KVa has a max load of 34a anything over that the IMD will alarm for overcurrent similarly there is an bi metal strip in the transformer that will break at a set temp opening a NC contact setting off an over temp alarm.
That device is a joint IMD and EDS the EDS uses a PGH to inject a current down each circuit through an CT to locate which circuit the fault is on.
The alarm panel I’m guessing is either an RA-003 or one of there touch panels that they can use to alarm for the IPS and control and alarm other systems in the theatre like UCV and ventilation
Back to my college days - creating a Faraday Cage type scenario guess so there’s minimal potential difference if not any PD. Clever stuff! Makes sense as you say they are skilled or instructed people so regs change or are far more relaxed because of it! Nice work
Definitely interesting location. IT has always been a mystery to me and this vide motivated me to read up about it. Getting some tools from loadout for Christmas.
Very interesting and different Mike. Definitely more content on this if you can. ❤👍👍👍👍👍
Brilliant video, IT installations aren't common and unless you're working on NHS/private hospital sites or cleared to work on MOD sites most electricians will never be involved with it.
Edit: Only thing I will say is the Isolated Tera system you appear to be running in there is not the same as the Integral Tera we did for the MOD.
The system installed for MOD sites is isolated from the incoming supply via transformer, the CPC's were bonded to the neutral at the panel with sense cables to alert to a fault. All accessories, trunking, cable tray, conduit etc was all bonded as well. The idea being that if an attack happened they would not loose power or risk electric shock to soldiers as there is always a path to complete the circuit.
Figured I'd clarify although it has been a number of years since I've put an IT system in.
@@residualelectrical I enjoyed it, the differences between MOD and NHS even though it's bracketed under the same "IT" system always make for interesting topics. I do miss being involved in that line of work but it's better left to lads younger than myself that don't mind the hours.
What is MOD?
@@whatevernamegoeshere3644 Ministery Of Defence
IT system in railway signalling power supply ,
The railways use IT systems for signalling power supplies, managing earth faults of cables that run in ducts alongside the railway for miles is a challenge
You would need extremely thick earth cables.
@@deang5622 I mean you can at that point connect a thick PE and drill in earthing rods and connect it every say... 100 meters. Randomly made that number up. But you then end up with different issues like current flowing on your PE from ground potentials, nearby earthing rods from anything like random consumer units or lightning protection systems dumping fault current into the soil, etc. It's easier not to even bother with an earth at that point and use IT, PELV or SELV or something but then you consider voltage drop and ELV systems are out of question. 110V DC or lower also works but DC in a rough environment like that help corrosion and everything will rust to hell and back if water touches it. To sum it up: IT works, TT is fucky, ELV is not even worth doing, LV DC is maintenance hell, and maaaybe you can get away with a TN system with an earthed live but then you have 2 phases with 400V on them compared to ground.
The additional difficulty railway cables have to contend with is high longditudional and transverse voltages induced in cables from 25 kV traction systems. Grounding systems have to be bonded to the traction return to prevent dangerous voltages but the external ground connections have to be kept outside of apparatus rooms, so cable sheaths have to be gapped before entering buildings.
@@barrieshepherd7694 No such thing as a transverse voltage.
Parallel cables induce a voltage because there is capacitance between the cables. Nothing transverse about it. Currents are induced by an inductive effect (by way of a magnetic field).
The concept of transverse applies to transverse electromagnetic waves not to voltages.
And high induced voltages in signalling cables is easy to contend with by using either differential signalling or optical fibre.
@@deang5622 I beg to differ.
Transverse voltages occur in cables across pairs of wires and can cause induced noise levels. Obviously this effects communications cables more than power cables.
The inductive field is caused by the 200 odd amps, at 25 kV, 50 Hz, flowing in the overhead contact wire when a train is in section. This causes a significant field around the railway corridor.
ITU-T Recommendation K.23 explains it well.
While transverse voltages in these circumstances may be low, raising noise levels, longitudinal voltages can be dangerously high.
“Where’s that German attitude? Just fcukin blitz it” had me in stitches 😂
@@residualelectrical Nearly fell off my beanbag laughing when I heard that! Brilliant vid on IT system 👍
This is brill mate. Keep it up !
Great video, the intro and outro are amazing, I like your content very much.
Hager domestic boards seem a odd choice for that particular job. Nice work 👍
13:20 Here in the US those are called impedence grounded systems. A must for all hospitals
A testing video for this system would be cool
I got to see an entire Kiddies hospital being fitted out - well over 500 million quid. The amount of wiring for power, hotel, data, comms etc was incredible.
Nice work! Is that transformer tapped to limit the voltage that can arise on the earth under fault conditions?
Marine systems run a similar set up for their ups systems. I'm often swiping out worn out bender units (Earth leakage detector).
I remember when I was in hospital seeing earthing bars behind a glass panel it was in the cardiac unit
Good to see a prooper and specialist Electrician
If the equipment is potentially grounded via separate earth connection, drawing extra p-e in parallel to the same outlet the equipment would create
The risk of inducting "wandering induction current "
(Creating ground loops)
2:34 nice: that moment where something you've cut just slides into place!
In simple terms the Patient in the Operating Theatre is insulated from even a 30ma fault current
Nice job. Very interesting
Mate the Penny washers 😂🤦🏻♂️ Sent the apprentice to the van the other week to get the hoover (I fucking know right) anyway. Came back saying he couldn’t find it..went to the van opened the side door and it fell right out on my foot 🤦🏻♂️😂😂😂🙄
Great video Mike! What do you have around your neck at the end?
Interesting how they don't make a double brown with no earth cable specially for this.
I‘m sure they make them, but they are probably way more expensive then regular 3x1.5 or 3x2.5.
Similar I usually run 5x1.5 to window shutter motors, even you technically only need 4/5 wires. It‘s just cheaper and on the car anyway.
Used a dewalt stapler first time for the other week straight through a cable less than 10 clips in 😢
It earthing arrangements are great until there is an accidental reference made to earth
More please, very interesting
Thankyou sir ,noted
I like this song. What is it and who made it?
I see burgess electrical services vans everywhere these days 😂
Interesting stuff thanks.
All the gear u got and working in the dark crazy get a light feller
👌
What helmet are you wearing?
During the first min or so I thought why’s he wearing a turtle neck on site? Man’s gone all Milk Tray on us 😂
Another cracking video bro, always interesting seeing these types of videos only do light commercial occasionally so enjoy seeing all of these
@@residualelectrical Yeah it looks proper I need to get some new gear so will be hitting them up for sure 👌🏻
That was one of the most interesting electrical video I’ve seen 👍🏼 maybe show us a real example of a fault actually happening on the system 🫣
Funniest ever film Stepbrothers🤣
what happens if the nuetral breaks somehow on the equipment, or is there two blues aswell?
So are the sockets individually cabled or are they part of a ring/radial
Yeah the makes more sense now, Cheers👍🏻
The i is for isolation and the t is for transformer. This lad has completely missed the point of this. The transformer is a 1:1 traffo basically 230v in and 230v out, but because it is on the secondary side it will not be affected by any spikes on the incoming side(think of it like a filter for the 230volt) also being on the secondary side it means 230v between L1 and L2 (the two browns) but 115v L1 and earth and L2 and earth still not ideal but much safe if there is a fault.same thing with a site traffo, the yellow 110v, that has 55 volts live to earth.
He should not cut the earth out, that earth is the dirty earth that should travel with the L1 and L2 from ips panel to IPs sockets, what did they think the two earth bars in the top were for ????
In the back of the IPs socket there is two earth terminals the dirty earth that is connected to the screw lugs and the body of the socket face(class 2 earth or dirty earth) the one that one that the healthy doctors staff come in to contact, and the other only to the earth pin of the plug top(class 1 earth or clean earth) that’s the one on the machine/piece of equipment that the patient who is unhealthy and has a compromised immune system and is more susceptible to injury from an electric shock so this earth goes but to a earth reference bar located in the room that has an much lower resistance.
Sorry This is mad long but fuck me he did a really shite job of explaining something very interesting.
@cylou
Gibberish on stilts.
Oh dear, another one without a clue. Try reading section 710 of BS7671. IT systems are not Earth free at all, they are Earth neutral bonding free, with safety because there is no Earth path from the live conductors. A single contact to a live conductor is therefore not dangerous, the possible shock current being very small. If there is any leakage to Earth the system will alarm, but is still safe. Simple enough!
@@residualelectrical You did a better job than cyclofuka or whatever his name is. IT is Isolation Terra, as you said. The transformer is an isolation transformer so there is no solid reference to ground. Nothing at all to do with power condition / limiting spikes / filtering. It's solely for isolation to ground, hence isolation transformer, not reactor or filter. There may be ancillary equipment to filter, but that's not the job for the isolation transformer.
The first alarm is when you get an earth fault on one leg, you them lose the advantages of the floating ground / isolation to earth. Three phase systems in mines, some ships and DC power systems in substations all use the same system, floating ground. This allows for better protection from earth faults, shocks and also allows one leg to connect, or touch ground and not trip the circuit, shock or induce and fault currents. Since basically the first leg to connect now becomes what we all call the bonded neutral. Keeps people and equipment safer and also keeps the run time up. Way more to it, but that's it put simply. You did a good job in your video explaining it.
👍🏼👍🏼👍🏼
Can you tell me how much you earn, a rough figure, for reference.
I would think, cards in, somewhere in the £20-30/hr region. Self employed near London would be nearer £100/hr.
Nice, IT systems are kinda like the bastard lovechild that is kept in the basement and noone talks about them, you just see a note from them once in a while saying "feed me", hardly ever see mainstream (read; TH-cam sparks and other channels) creators do much, f any, content on them. I'm off to go and drown the childhood memories that I had suppressed for all these years until THIS VIDEO sent me in a spiral.
I jest, I spiral anyway 😜🤣
Électricien Installateur....
See Section 710 in BS7671. The explanations here are not correct and very poor.
@@residualelectrical If you put "Professional" information on the net IT MUST BE CORRECT! The basis of IT systems in medical locations is that contact with a single live conductor is NOT dangerous, even if you are also firmly touching Earth. All the additional supplementary bonding is to prevent any potential between anything in the room, from static or any other cause. A single fault produces no Danger, and it will cause an alarm from the Earth Monitoring System. Therefore it can be fixed ASAP. Regards David CEng
@@residualelectrical in fairness David may well have written 710 so might have a bit at stake chap. 🤣👍
If you want to learn about IPS you should look at the Health Technical Memorandum 06-01 (HTM 06-01) Electrical services supply and distribution. These are the set of documents that outline the standards for the health environment.
Available free on the internet here www.england.nhs.uk/wp-content/uploads/2021/05/Health_tech_memo_0601.pdf
I've worked on many of these systems.
In addition to the HTMs (or SHTMs in Scotland), the IET have published a Guidance Note on Medical Locations, it's available on their website but I can't link to it, every time I do my comment gets deleted. If you search for "iet medical locations" it should appear near the top of the search results. It's quite practical and might be informative too.