Need help configuring new reef - 180-280g

[bcoons]

Originally posted by Dudester
Would 2 20W circuits be enough for a system like this?

I hope you mean 20 AMP circuits!

A twenty amp circuit gives 20A X 120V = 2400 watts. When you add up all your lights and pumps and stuff you probably won't hit 2400 watts. But, I'd have some overcapacity and redundancy anyway, and it's not much more to run two circuits as one, so I'd go with the two.

Having two circuits would allow some redundancy by splitting critical pumps and systems between the two, so if one tripped a breaker, the other would still be up. This is complicated somewhat by the use of the ReefKeeper, as it is (usually) providing power from a single source. What you really want to do is set up an "essential bus" and "non-essential bus" like we do in military systems. Then you can put your UPS setup on the mission critical bus.

Anyway, that's my typical long winded answer to your question. Two circuits.

[Dudester]

Thanks, Bruce, that's as clear an answer as I've ever seen regarding the provision of electricity, a subject of which I truly have little knowledge. I agree with the essential vs. non-essential bus setup, and you're right that the ReefKeeper will complicate this. I'm not sure yet how I'll configure the electrical components, but I agree that I'd rather have too much power than not enough. Running an extension cord through the office will not be an option!

[melev]

Keep in mind that you are only allowed (by code) to use 80% of the power on each circuit. So with a 20amp circuit, you are only allowed 16 amps for safety reasons. So you don't have 2400 watts to your disposal as indicated above.

[bcoons]

Originally posted by melev
Keep in mind that you are only allowed (by code) to use 80% of the power on each circuit. So with a 20amp circuit, you are only allowed 16 amps for safety reasons. So you don't have 2400 watts to your disposal as indicated above.

melev - I certainly don't mean to question your knowledge and experience in this hobby, but I would pick a nit with you on this one. I'm pretty familiar with the NEC from one of my other interests, which is photovoltaic and other alternative home energy installations. I am aware of no such requirement in the Code. Now, having said that, the Code is updated every year and I may have missed something in the last revision, and if you can cite a section number I'll stand corrected.

It is true that almost all design and capacity guidance in the National Electrical Code (NEC) uses the 80% rule. Voltage ratings, temp ratings, conductor and conduit sizes, circuit protection devices (fuses and breakers), etc. are all derated with a safety margin of 80% of capacity. So in designing the installation the electrician oversizes almost all componenets.

In the case of circuits such as we are talking, the code will require that the ampacity of the conductors, i.e. the wire guage, of the circuit is sized to handle 120% of the expected load. So, in Mike's 20 Amp circuit the wire gauge will be sized to handle the overload, as are the breakers, so he can use the full 20 Amps. (Typically 12 ga.)

This pretty much has to be the case for the practical reason that 99% of consumers have no clue as to the ampacity of the circuit nor what they are drawing. Unless you have a clamp on ammeter it is very difficult to measure actual amps drawn by our aquariums. (Although at least in our hobby we generally have published figures for the watts drawn by pumps, PHs, lights, etc.) Most consumers will load up a circuit until it trips the breaker and then back off a notch (an old engineering trick! ) So the idea of the consumer being able to determine that he is only drawing 16Amps on a 20 Amp circuit probably won't work.

Again, please don't take this wrong. I have learned so much here, and especially from you, in the 8 months or so that I have been studying this hobby. (And it's been fun to actually hear your voice on ReefTalk!) But I thought I should throw in my .02 on a subject where I do have some limited expertise.

Regards,
Bruce

[melev]

Bruce, feel free to correct me when you see the need. I've had a couple of electricians out here, as well as discussing electrical with the guys in hardware stores, and of course here on RC as well as DFWMAS, and power is a topic that comes up often.

The electrician told me categorically not to pull more than 80% on a breaker, and he had me turn on everything on the circuit, and measured it with the clamp-on meter to see what was being pulled. He then reported the numbers to me, giving me the green light.

As you pointed out, wiring is important. If you have 14/2 wiring in your walls, then a 15 amp breaker is fine. However, (and I might have my numbers mixed up as it's been months since I was doing this) I don't believe you can put a 20 amp breaker on that same wiring because it would possibly overheat. If the wiring is 12/2, switching breakers is fine.

In the case of this thread, having three circuits built in advance would be easier then adding a third one after the fact, and by providing 3 circuits the owner can divide the power consumption easily.

This is similar to having a tank with one drain vs three drains. Three drains will do the job more quietly, as they aren't being taxed as hard as a single drain would.

With my own set up, I have one 20 amp regular circuit, and two 20 amp GFCI breakers. I want the breaker to trip quickly if I fall into the tank pulling the light rack in with me, or if I lean into the sump, fall in and shatter the heaters. I don't want the circuit to trip and kill my return pump, so it is on the regular breaker.

[bcoons]

I think we are in violent agreement! It's always better to be conservative when rating circuits. Yes, 14 ga wire is the norm in 15 amp residential circuits, and 12 ga for 20 A circuits. And you're right, when building in a custom installation it is not much more expensive to have the electrician put in a couple more circuits. I think I would like at least two, if not three 20A circuits for a setup like Mike is contemplating.

What I'm working on now are a couple of methods to provide backup, un-interruptible power to just a couple of systems (like circ pumps and maybe heaters) that are normally powered from the ReefKeeper II. I want to have a battery/inverter setup that will automatically cut over when AC mains fail, but I don't want to power the whole RK II and all it's loads. So I'm designing a seperate relay box assembly that will take two or three items from the RK II and use relays to automatically cut over to inverter power that could hold the system up for a few hours.

I have the relay design worked out. Current issue is whether most aquarium related pumps and devices will work with a modified square wave inverter output, or whether I will have to go with a more expensive true sine wave output inverter. I know that my little filters and stuff on my FW aquariums will work on my cheap modified sine/sqare wave inverter, but I have no experience yet with the larger Mag, Dart, Sequence, etc. pumps used in the bigger SW systems. If you have any experience or comments on that I'd love to hear it.

Heh, heh, let's see how much we can keep this thread alive while Mike is off playing in the snow!

[melev]

I think you could ask in the Advanced Lighting & Filtration forum about using an inverter to power a pump. My first thought is will the inverter even have the power to do so in the first place, and not burn up or shut down.

Did you look at the thread by David Playfair that I linked in the Show Notes?

[Dudester]

Wow, I never got an email update after my 2/24 post. Glad to see that you guys continued to discuss. I just rechecked this thread because tomorrow morning I'm meeting the owner of a company that potentially will service this tank that I'm planning. I wanted to get a list together of my current plans. Come to think of it, I'll just send him a link to this thread. I'll keep y'all informed about what we discuss.

[martinphillip03]

looking for e-mail updates

Marty

[Dudester]

Thanks for your interest, Marty. This system has ballooned substantially. We're well on our way to a nice office reef. Check out this thread

[martinphillip03]

I am on page 14 of your step by step account of my first reef. It is great. It may take a month before I get here.

Marty
No reef tank yet

[Dudester]

Glad you're enjoying that thread Marty. You only have about 35 pages to go, as it has split once. You're doing the right thing by reading a lot before diving in; it will pay dividends in the end. Let us know if we can help.