Heating Element - Questions on SSR and Voltage

[Brokenjeep]

Hey everyone, I picked up a 50l milk can the other day and had a few parts for an electric element thrown in with it!

He threw in:
2 x SSR – Fotek SSR-25 VA 25A/250V
1 x Element - Camco 02613 6000W 240V Screw in Water Heater Element Foldback
1x RV4NAYSD504A - Rotary Potentiometer

I found Still Dragons econobox build instructions with 1 SSR and will have no problems following the schematics to wire it as demonstrated but I have some questions.

I had intended on running it on 20A 120V but since the Fotek and Element are listed at 220v will I need 220 or will it just under perform on 120?

I should also add that I have a healthy fear of electricity and have done lots of work and had it inspected by ESA before, just haven’t worked with elements and SSR’s.

I searched the forums but sadly didn't see any questions/answers so basic... and this is my second post here so hopefully I didn't break any rules. Thanks in advance!

[sw_reijnders]

why do you want to use 2 SSR's?

[hpby98]

Hey everyone, I picked up a 50l milk can the other day and had a few parts for an electric element thrown in with it!

He threw in:
2 x SSR – Fotek SSR-25 VA 25A/250V
1 x Element - Camco 02613 6000W 240V Screw in Water Heater Element Foldback
1x RV4NAYSD504A - Rotary Potentiometer

I found Still Dragons econobox build instructions with 1 SSR and will have no problems following the schematics to wire it as demonstrated but I have some questions.

I had intended on running it on 20A 120V but since the Fotek and Element are listed at 220v will I need 220 or will it just under perform on 120?

I should also add that I have a healthy fear of electricity and have done lots of work and had it inspected by ESA before, just haven’t worked with elements and SSR’s.

I searched the forums but sadly didn't see any questions/answers so basic... and this is my second post here so hopefully I didn't break any rules. Thanks in advance!

The way it works using a 220v element at 110, is its 1/4 of the power rating

So your 6000 watt at 220v becomes 1500 Watts at 110v

[Brokenjeep]

why do you want to use 2 SSR's?

That was actually one of my questions.. Didn’t recall him saying it was a spare but at the time I figured I would Google University it. If its spare that’s cool.. but wasn’t sure if it was to be used for 220v in some schematic I haven’t seen yet.

[Brokenjeep]

Hey everyone, I picked up a 50l milk can the other day and had a few parts for an electric element thrown in with it!

He threw in:
2 x SSR – Fotek SSR-25 VA 25A/250V
1 x Element - Camco 02613 6000W 240V Screw in Water Heater Element Foldback
1x RV4NAYSD504A - Rotary Potentiometer

I found Still Dragons econobox build instructions with 1 SSR and will have no problems following the schematics to wire it as demonstrated but I have some questions.

I had intended on running it on 20A 120V but since the Fotek and Element are listed at 220v will I need 220 or will it just under perform on 120?

I should also add that I have a healthy fear of electricity and have done lots of work and had it inspected by ESA before, just haven’t worked with elements and SSR’s.

I searched the forums but sadly didn't see any questions/answers so basic... and this is my second post here so hopefully I didn't break any rules. Thanks in advance!

The way it works using a 220v element at 110, is its 1/4 of the power rating

So your 6000 watt at 220v becomes 1500 Watts at 110v

Ok great thanks.. that answers one of my questions. Any confirmation on the Fotek SSR? Is 220 just its max rating and it can run just fine at 120 as well?
Thanks agian!

[sw_reijnders]

why do you want to use 2 SSR's?

That was actually one of my questions.. Didn’t recall him saying it was a spare but at the time I figured I would Google University it. If its spare that’s cool.. but wasn’t sure if it was to be used for 220v in some schematic I haven’t seen yet.

you only need 1 ssr
also on 220v.
if you use 2 ssr's they will work against eachother

[durty_dunderpants]

does the SSR not suggest something like 24-380V? either way it'll be fine on 120V. and i'd go as far as to say you don't wanna be running it on 240V with that element. you're pushing the max current as is (25A) even before you take into account that those cheap SSVRs are not always up to their rated value..

[sw_reijnders]

does the SSR not suggest something like 24-380V? either way it'll be fine on 120V. and i'd go as far as to say you don't wanna be running it on 240V with that element. you're pushing the max current as is (25A) even before you take into account that those cheap SSVRs are not always up to their rated value..

true

@Brokenjeep
for 110v the 25A SSVR will do (13,5A), but for 220v 6000w you should use a 40A SSVR.

[Brokenjeep]

SSR

does the SSR not suggest something like 24-380V? either way it'll be fine on 120V. and i'd go as far as to say you don't wanna be running it on 240V with that element. you're pushing the max current as is (25A) even before you take into account that those cheap SSVRs are not always up to their rated value..

Awesome info thanks again. I will build it exactly as the still dragon build shows and run it on 120v. It does show the range between the two poles but then below it re-stated 250 so I didn't want to take chances! Well, actually.. maybe I will take it over to my buddies house to try!

https://www.stilldragon.org/uploads/Fil ... e48c77.pdf" onclick="window.open(this.href);return false;" rel="nofollow

[StillerBoy]

2 x SSR – Fotek SSR-25 VA 25A/250V

The Fotek SSR are good units.. Your SSR-25 will work ok on 120 volt, but will not work well on 240 volt..

If you upgrade to 240 volt, you will need the SSR-40 or 40 amp of the same manufacture..

Also, you don't mention a heat sink.. you will require a heat sink or else it will overheat and reduce the life of the unit.. and also put some thermal compound between the heat sink and the SSR..

Mars

[zapata]

What kind of still are you running? At max of 1500 watts do you even need a controller? I'd think a steady 1500w would be fine for most small pot stills or even reflux stills.
I almost always ran without a controller when I was on 120v.
I might save the trouble until you have a bigger 40A unit and 240v available. Just a thought.

[cede]

My 2 cents:
Those SSR have an integrated power control. They are not regular SSRs sont it's better not to try to put them in parallel.
You have 6000W/240V heater that is 25 Amps. Well, your SSR would do, but would heat a lot (There's a security factor but it might be close to 1 ). I'd rather use a 30A or more.
Btw, you need a cooling heatsink on your SSR or it might end in smoking piece of melted silicium

That said, why would you derate your heater and use it on 120V ?
You could use the full power on 240V to heat up the charge faster and then reduce the power during distillation.
Electric dryers are normally on a 30A circuit, you could plug there.

[fizzix]

To repeat: Never parallel TRIACs and SSRs to a common load. One will eventually overtake the other, defeat the operation, and likely burn up.

[Yummyrum]

That said, why would you derate your heater and use it on 120V ?
.

Its commonly done . The 240V 5500w elements have a large surface area . By running them at 120 V it reduces scorching ....But you are right , It could always be run off 240V but turned down real low .

Brokenjeep . As I don't have 120V here I can't say for sure but I believe that sometimes the Pot value needs to be changed when running on 120 V ...it will still work but there is a dead section then all the action happens in the other section .

IE you turn it up half way an nothing happens but the keep turning and then the power starts to be applied . No biggy .

[cede]

Yummyrum yes you're right about scorching, I thought it was the ULWD waved element, not the simple foldback one that has less surface.
Reducing voltage or using a regulator on 240V, I think it will behave the same, it's just a matter of power after all

[Brokenjeep]

Fantastic guys, really.. really appreciate all the feedback! I have picked up the 12 gauge waterproof wires, 6x6 box, 20amp plug, gromits.. yadayada. Still need to pick up some thermal paste but I feel the heatsync I got is a little small... will look for a larger one. I will drill a bunch of holes in the box and hope for the best.

I have been busy making up my first sugar wash! I initially was going to to do the Birwatcher but was told by the guy at my local not to use regular yeast so I grabbed some Still Spirits Vodka yeast and am now waiting for my double batch to cool down to 30c. Went all out and bought spring water.. corn sugar and am following everything to the letter.

My still is a North Stills 50l 4 plate flute.. if this doesn't produce my wife is going to kill me!

I will post some pics of the SSR/Element setup!

Thanks again.

[acfixer69]

I guess some just got to learn by doing. That's the lead dog in the hook um of turbo yeast. Next it'll be carbon filtering. Break out the billfold there coming for it. If reading the basics here didn't teach about and why it sucks you ain't listening. If your wife can drink turbo you got an easy piesy. Off topic but a good time to tell ya.

AC

[Brokenjeep]

I guess some just got to learn by doing. That's the lead dog in the hook um of turbo yeast. Next it'll be carbon filtering. Break out the billfold there coming for it. If reading the basics here didn't teach about and why it sucks you ain't listening. If your wife can drink turbo you got an easy piesy. Off topic but a good time to tell ya.

AC

Wise words! Next time I will go back to the classics as I intended to do in the first place! I went in saying I don't want anything turbo but got talked into it.. classic newb! I had a bag of DADY yeast in my hand and he talked me into putting it back and getting the other one. Any opinions on that one?

[Brokenjeep]

That said, why would you derate your heater and use it on 120V ?
.

Its commonly done . The 240V 5500w elements have a large surface area . By running them at 120 V it reduces scorching ....But you are right , It could always be run off 240V but turned down real low .

Brokenjeep . As I don't have 120V here I can't say for sure but I believe that sometimes the Pot value needs to be changed when running on 120 V ...it will still work but there is a dead section then all the action happens in the other section .

IE you turn it up half way an nothing happens but the keep turning and then the power starts to be applied . No biggy .

I will watch out for that and confirm in testing.

Yeah, going back to 110 is a handicap.. I bought all the wires that will handle 220, just going to get a couple tests runs over low and slow!

[zapata]

You've got a $3,000+ still, powered by 120V@1500 watts and running turbo?
I'm not going to say a word about it. But hopefully it won't be long before you know all to well what I'm not saying here

Don't forget your cleaning and sacrificial runs.

[Brokenjeep]

You've got a $3,000+ still, powered by 120V@1500 watts and running turbo?
I'm not going to say a word about it. But hopefully it won't be long before you know all to well what I'm not saying here

Don't forget your cleaning and sacrificial runs.

Zapata, I completely hear what you are saying! (and hear everyone's tsk tsk!) I mentioned in my welcome intro that this beast fell into my lap and I wanted something I could grow on. As for the 110 I decided to run it for the first batch, I don't care how long it takes so long as its a low controlled boil and I think this will achieve that.. (AND did I mention that the power was thrown in for free?) You know how it is, on the first run all I care about is that I don't blow myself up!

As a testimate to the Forums I have learned (among other things):
1. Don't touch turbo, even if it comes with the best sales pitch in the world.
2. Wire up for 220 with a good controller (I have to produce before I can get signoff on more funds from the treasury)
3. All about sanitation vs cleaning

[Yummyrum]

Brokenjeep .
I nust realized a glearing issue here .
1500 w will not be enough to run a 4 plate still ..... certainly not a perforated plate one . There just won't be enough power ( vapour available ) to load and hold the plates . You might get away with it on a plate with bubble caps but you are still running it almost 50% less power than is tipically required so even if you do get bubble action , your take off rate would need to be rediculously low and certainly nit what the still was designed to do.

You need another element . Perhaps one on full and the other adjustable .

If 240 is a avilable you should use it .

[zapata]

Jeep, the power thing is part of where I was going, but maybe I should be more helpful. Maybe we can get you running 240 cheaper easier than you think?
I'm assuming you are in US/Canada with 120/240 split phase power?
If so, do you have a drier outlet you can use? Or a stove outlet?
Your 25 A ssr is a little small for your element, but the right sized one can be had in the $10-15 range. Surely you can sneak that past the CFO?
The only thing you'll probably have to spend money on is GFCI protection, which I would insist on myself but to be honest many people don't have. At least as a proof of concept if you are careful you could put that off until you can get approval for another $70-100 for what is life saving safety gear after all.
What's holding you back from 240v? We can get you there.
Check your panel box, you may well find unused 240v circuits, when I moved into my house I had unused 30, 40, and 50 amp circuits just sitting there waiting to be used. Including heavy gauge wiring under the house and outlets in the wall easily moved to where I wanted them without buying anything.

[jonnys_spirit]

I'm considering adding a sub panel with a couple distillery circuits because I only have one breaker position open in my main basement panel and am currently using the dryer with an extension I made up. I could make that one open breaker a 60 or 90 amp breaker that feeds a sub panel which I can then break out to dedicated 240V outlets for controllers / on-off elements.

There's probably a couple ways to make it work in most cases. I find that I also want to do laundry when I'm hangin in the basement on stillin' days..

Cheers!
-j

[zapata]

(Lol, I thought I was responding to OP, just realized Im not. Oh well, Johnny and brokenjeep, maybe it's useful to you anyway)

That's a butt load of power unless you need it for other things. A good smaller "sub panel" is a spa panel, mostly because it's often the cheapest way to get 240 GFCI protection. 50A is the most common size, 60A is common too. I use one I picked up for about $60 and have variously plugged it into the drier outlet, a stove outlet, and hardwired it onto the previous stove circuit.

I didnt look around too much, but here's an eBay find, it looks like a 125A panel, with a 50A GFCI breaker in it and room for more. Might make a perfect sub panel for you, but the main expense would probably be running the wires to it. You could use that 50A GFCI breaker for your stilling needs, and add another for your drier, or some 20A120v GFCI breakers for pumps fans or whatever.

Spa Disconnect Panel. Model # UG412RMW25OP | eBay http://r.ebay.com/E02Fxc" onclick="window.open(this.href);return false;" rel="nofollow

At that point it's a matter of how much you want to spend wiring it, and how much you trust yourself to do it vs. Hiring a sparky which will definitely add to the cost.

Simply wiring it with a drier plug for supply and inline with your controller will give you 240v GFCI immediately, and you can upgrade later so you don't have to choose still or drier. $58 for the panel + $10 for a drier plug + $15 for a 40A SSR = $83 to sneak past the missus. $73 if you pull a drier cord off one at the dump. $68 total is you also shop hard for the SSR.

I've been interrupted a few times while typing this, hope it isn't too rambly.

[Brokenjeep]

Yummyrum – you are probably right that I am way underpowered for bubble plates or perforated plates (oh and thanks a lot for launching me into another couple hours of reading material on the performance of perforated vs bubble plates BTW!) Does anyone else find the more they get into this art/hobby the less they can share with their buddies? I have never seen a bubble plate in action and I went through about 20 youtube vids today and was surprised by the rolling boil in the pot and plates.. making me wonder if this will cut it.. I thought it was a slow steam!

Zapata, sw_reijnders, durty_dunderpants (and everyone else!)– The only thing that is keeping me away from 220 is a reasonable entry point and pure fear of 220(before my first batch). I am ashamed to say, I did a huge reno on the house, pulled electrical permits pulled my own 200 feed to the house, swapped pannels.. even ran a 220/40amp up to the garage because I thought I might pick up a welder so I am ok there... although it’s not GFI, I don’t even know if they make 220GFI’s..by the conversation I am sure they do!

I see the DealMux SSR (DealMux a12050400ux0780 Amps Single Phase SSR Solid State Relay, 24-480V AC, 60 Amp) cheap as chips on amazon I can get tomorrow... (CFO will not even notice!) so that leaves my element (I gather I am pushing it with 220/40) and Potentiometer (do I need a heavier resistance or will this one work?) Wire – I picked up 12gauge waterproof for everything, am I stepping up to 10 or 8 gauge now?

Stuff in the pic:
1 x Element - Camco 02613 6000W 240V Screw in Water Heater Element Foldback
1x RV4NAYSD504A - Rotary Potentiometer.

So that brings me to my current conundrum. I have this turbo batch just kickingoff like nuts downstairs... I have done a bit of work towards my 120 setup, I am thinking I should just get through it with supplemental heat.. my buddies country cooker or maybe pull a couple of bubbling plates and run it twice... going to sleep on it.

Thanks again for all the feedback! For the people down under in the sun I have included an off-topic pic of my jeep in the snow dump this evening.

[zapata]

I think if you've got 220/240 available in the garage it only makes sense to use it. Go out in the garage, fire up a space heater and have fun. Your still will also be a bit of a space heater too. Nothing wrong with a healthy respect for 240v, but a 4" column is a big boy toy, and needs a good bit of power. It's really 240 or gas, and I do not think gas is safer, and it sure won't be fun out in that snow! Especially since electrical work is not brand new to you.

I see a couple options.
1. Get a smaller element to match your current SSR. I don't think I've used anything other than a 40 amp SSR, but theoretically your 25 amp should work fine with say a 4000 watt element. $12 Amazon prime in the US, but maybe more in canada? If you aren't using a special stainless steel element from a brew supplier you can probably just pick this up at a hardware store and run as soon as tomorrow. 4000 watts will power your still, it just won't heat up quite as fast as 6kw (duh), but a lot of people prefer a slightly slower heat up for flavored spirits anyway.

2. Upgrade your SSR. I think 60 amps is overkill for the 6kw element. I really don't know if there is a drawback to using it vs a 40 amp unit. Looks like amazon.ca does have a 40 amp unit though. I think your potentiometer will work with any of the SSR options, but maybe someone else will comment to be sure?

Either of those options will work fine. I'd go with option 2.
Either way you need a 240v plug to match your welder outlet.

Wiring:
You say you have 12 gauge wiring. If that is SJ type, it's probably fine for either option. You might want to hear some other opinions about usung it for a 240V 6000 watt load, but my understanding is that as this basically an appliance plug, it is rated at full amperage (25a) and is not subject to the 80% rule. However appliance cords at full amperage are not expected to be run continuously (more than 3 hours) and if codes matter there may ne some temperature things to consider (I'm NOT an electrician, but have read them argue about this very thing in brew forums). So it's kinda up to you, personally I would be fine with it because you won't be running on high for 3+ hours, you will be turning down below 20 amps after you start boiling. I use 12 gauge SJ cord at 23.5 amps all the time and it does not get hot. I would be comfortable at 25 amps, but maybe just make sure it doesn't get warm on full blast heatup.

Some might argue to apply the 80% rule here anyway and upgrade to 10 gauge, and I wouldn't say they are wrong. Personally I'd downgrade the element to 4500 w before I bought and fought 10 gauge wire.

This leaves GFCI. I just read on a brew forum, and it seems the GFCI options we have stateside are much more expensive up north. Bummer. I will say that at least some here probably don't have GFCI protection. I have run without it, but would not do so now other than for maybe a run or two where I felt compelled to for some reason and took extra precautions. Like checking the still with a volt meter before touching it. Every time. Yes, that is extreme, but like you I have an extreme respect for 240. Once or twice till you prove the concept and get wifey to sign off on it? Ok, maybe. Most failures I've seen and read where GFCI could have saved the day came up over time. Wires corroded, insulation charged through, elements wore out etc. They weren't day one accidents, where you are already being extra careful with brand new gear (and if like me are testing for voltage as soon as you power on). For a limited test without GFCI I would be extra careful that no liquids can possibly get into any electrical. Self fusing silicone tape to wrap everything, a shield or even a wall corner between any Plumbing and the controller box, a shield over the outlet etc. Imagine a plumbing fitting slips off and starts squirting water everywhere, how far can it spray to element connections, wiring, outlet etc?

But GFCI options that I know of.
1. GFCI breaker in the panel, yes they make them. Easiest and cleanest option though often pricey. Just swap it out for the existing one. Since your panel is new, maybe affordable, but maybe not for Canada. I have an old panel so a 240v GFCI breaker for me was $200 USED!
2. Spa panel. In US, $60 new. I've heard $150+ for Canada. These are usually fed with SJ cord to a wall outlet so they aren't legally sub panels, they are just part of your homebrew appliance. And in case you are wondering, it is perfectly fine to plug a 50 amp GFCI spa panel into an outlet protected by a 30-40 amp breaker in the panel. The smaller panel breaker protects everything for load, the spa panel simply provides GFCI for anything downstream of it. Spa panels take up more space in the still room, but you can use them as an on/off switch, which your controller currently doesn't have.
3. GFCI inline plug adapters. Something like this:
http://a.co/8SbSrTM" onclick="window.open(this.href);return false;" rel="nofollow
Ouch! Hate to tell ya, but that $600 CDN doohicky is more like $150 in the US!

A few other things.
1. You really need a heatsink. I think it was mentioned before, but get one.
2. I don't think its been mentioned how you boiler takes elements. Is it a female thread port, a triclamp adapter or what? If its from northstills, looks like they use triclamos, do you have a triclamp adaptor for your element? Or do you habe some way of covering the element connections?
3. Whatever it is MAKE SURE YOUR BOILER IS GROUNDED. This may not be obvious as apparently some manufacturers don't provide an easy way to do it. Screw a ground wire right onto the base of the still if you have to.
3. It wasn't clear if this still is new, or just new to you. If it's new, search for the thread on proper cleaning, it involves a soapy scrub, a vinegar run as well as a sacrificial throw away alcohol run (that turbo would be perfect here:) if it's just new to you use your own judgement for how much cleaning it needs, but a full regimen would not be excessive.

You have a SWEET still, worth more than several of my cars. Invest just a few more bucks in it and it will be more fun than a motorcycle, and safer than a volvo.

[durty_dunderpants]

i'm not based over by yous so i'll leave electrical code things to zapata and others..

just thought i'd say his idea of putting a plug and some sockets on a spa panel is a good one (i've done similar many a time myself) - essentially a diy inline gfci adapter. especially if you do want to upgrade anyways and would hardwire it on the wall later. i don't know if it would be more/less economical for you but another option is to just buy the GFCI breaker by itself and wire that direct into your controller box until you're ready to upgrade the garage.

maybe post up what wire you have. like zapata says, SJ 12 awg is rated for 25A, and that should incorporate a safety margin. obviously bigger is often better but not essential.

60A would be my choice of SSVR if going with a cheap one - pick your required amperage and double it. (similarly, if your fotek SSVR is not genuine - most on ebay/amazon are counterfeit - then i wouldn't put more than 10-12A through it.)
be careful with buying the SSVR though; when i copy/pasted the model number in your last post there it looks like voltage triggered SSR rather than resistance (SSVR). you want the resistance controlled one to use that set up. maybe post a link before pulling the trigger?
your pot is standard for the application. you'll have to trial it to see how fine the control is though. that can vary pot to pot.

[Brokenjeep]

i'm not based over by yous so i'll leave electrical code things to zapata and others..

just thought i'd say his idea of putting a plug and some sockets on a spa panel is a good one (i've done similar many a time myself) - essentially a diy inline gfci adapter. especially if you do want to upgrade anyways and would hardwire it on the wall later. i don't know if it would be more/less economical for you but another option is to just buy the GFCI breaker by itself and wire that direct into your controller box until you're ready to upgrade the garage.

maybe post up what wire you have. like zapata says, SJ 12 awg is rated for 25A, and that should incorporate a safety margin. obviously bigger is often better but not essential.

60A would be my choice of SSVR if going with a cheap one - pick your required amperage and double it. (similarly, if your fotek SSVR is not genuine - most on ebay/amazon are counterfeit - then i wouldn't put more than 10-12A through it.)
be careful with buying the SSVR though; when i copy/pasted the model number in your last post there it looks like voltage triggered SSR rather than resistance (SSVR). you want the resistance controlled one to use that set up. maybe post a link before pulling the trigger?
your pot is standard for the application. you'll have to trial it to see how fine the control is though. that can vary pot to pot.

Ok, I am going to try to process all this info and answer in reverse order while researching!

Looked at Spa Panel vs Breaker and it looks like they are the same price.. (A hell of a lot!) but probably worth it based on my experience getting shocked with 120 a couple times.

I think I am going to replace my current one below with that GFI and here is a pick of the outlet I put in as well for the welder I am going to use:

The wire I have picked up is "Chord 3/C 12 AWG SOOW E46194 600V -40C TO 90C FT2 Water Resistant". Honestly I don't think I could get any larger chord in my pot housing!

I am going to save the controller conversation for the next reply! Thanks again!

[Brokenjeep]

First off thanks for all the input, I have re-read this post more then a few times and have continued research on others.

I am going to pull the trigger on this one.. I couldn't see where it said resistance controlled but I think it is. I have a small heatsync and put holes in the box for airflow, just need thermal paste. Just combing the fourms for the wiring.. I don't get that 220 is the same setup as the 120? We have 2 hots so shouldn't it change? I will keep looking.

Lerway 40A SSR Solid State Relay for PID Temperature Controller

Input : DC 3-32V
Output : AC 24-380V
Current: 40A
Type : SSR-40DA
It's good for heater, oven, or other appliance up to 3500Watt power consumption. Ideal for PID temperature controller.
Specifications for this item
Brand Name Inkbird
EAN 0714485002663
Part Number SSR-40
UPC 714485002663

https://www.amazon.ca/Lerway-Solid-Stat ... rds=SSR-40" onclick="window.open(this.href);return false;" rel="nofollow

I am going to re-use my 12 Gauge wire 6000 element and Potentiometer

1 x Element - Camco 02613 6000W 240V Screw in Water Heater Element Foldback

1x RV4NAYSD504A - Rotary Potentiometer