3/4 inch drain solenoids - how fast does yours drain? - The Planted Tank Forum
 
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post #1 of 10 (permalink) Old 01-12-2008, 03:34 AM Thread Starter
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3/4 inch drain solenoids - how fast does yours drain?

I'm working on an autofill/drain system and my 3/4 drain solenoid is providing very slow drain rates, I'd estimate 50-60 gallons/hr compared to about three times that without the solenoid inline.

The drain is running to my basement from the upstairs, tank water level is 4 ft above the floor and the the drain is on the floor so I'd estimate the pressure at 15 ft * 0.433 psi/ft = 6.5 psi. The solenoid is rate to 1 psi to function so I'm gathering that its running fully open.

When complete the drain solenloid will be taking a portion of whatever the outlet pressure of a Fluval FX5 is, I'm guessing 5 to 8 psi based on things I've seen on this and other boards.

I know others have run booster pumps for such duty, I'm not pumped to do so, and my drain rate isn't absolutely unlivable but I'm trying to get a good sense of other people's experience.
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post #2 of 10 (permalink) Old 01-12-2008, 04:54 PM Thread Starter
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Well, now that I've purchased a Dema valve I've decided to research solenoids, I'm not sure if I'll go this route, but it may be useful to others doing autochange systems so...here are some options. Type D and Type G solenoids (from my searching) seem to be what we're after and nearly all of the ones listed below are Type G. I've been looking for a 3/4 valve because I'm draining a fairly large tank, you may want to go smaller.

Valin has the Burkert for about $120 US, which seems like a fairly reasonable price.

In the data sheets there's a kv or cv value, which I'm presuming is some coeffecient of flow, can somebody shed some light on the value? There's a Burkert valve with a very high coefficient that's probably the best option if I'm understanding this correctly.

Magnatrol
http://magnatrol.thomasnet.com/item...&seo=110&bc=100|1003|1015|1021|3001013|3001 014

Burkert 6213's
http://www.valinonline.com/product.asp?prodid=160805
cv - 10.5

SMC VXEZ2350 -
http://www.smcworld.com/2002/npp/pd...p-E06-8-VXE.pdf

Danfoss EV250B -
[http://www.danfoss.com/North_America...n_lang%3den_us
kv - 6.0

Buschjost 82370 - model 8237300.9382
http://www.buschjost.com/pdf/E82370.pdf
kv - 5.8
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post #3 of 10 (permalink) Old 01-12-2008, 05:16 PM
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I realize you're using gravity to drain, but couldn't you put a pump inline with the solenoid to speed things up? I use a pump, a 3/8" solenoid, and after going up about 8 feet, across a 20 foot run, then down 8 feet or so to a drain, I can still manage 20 gallons in 30 minutes. I just have the pump and solenoid on the same timer (through an Aquacontroller Jr).
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post #4 of 10 (permalink) Old 01-12-2008, 05:22 PM Thread Starter
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That's about the same rate I'm getting with my existing valve, problem is I've got up to 40 gallons to do...maybe I'm impatient but I'd like the drain to be as quick as possible.

What are you using for a booster pump? It may be that a booster pump/cheap solenoid is a better combo than a single expensive solenoid. Also, is your solenoid direct acting?

In my setup of inline plumbing my canister filter will provide some additional push, however it won't be the kind of pressure required to get much more rate through the solenoid.
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post #5 of 10 (permalink) Old 01-12-2008, 05:45 PM
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Quote:
Originally Posted by original kuhli View Post
That's about the same rate I'm getting with my existing valve, problem is I've got up to 40 gallons to do...maybe I'm impatient but I'd like the drain to be as quick as possible.

What are you using for a booster pump? It may be that a booster pump/cheap solenoid is a better combo than a single expensive solenoid. Also, is your solenoid direct acting?

In my setup of inline plumbing my canister filter will provide some additional push, however it won't be the kind of pressure required to get much more rate through the solenoid.
You know what, it's actually a 1/4" (fairly cheap ~$30) solenoid from autotopoff.com (link) with 3/8" JG ends on it. I'm using 3/8" polyethylene tubing. The booster is an Iwaki MD-15R, one of their smaller pumps. I already had it (for maybe 10+ years now) from a previous water cooling setup in a computer. I also have it inline after the main pump and filter, so some head is coming from there too ...
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post #6 of 10 (permalink) Old 01-12-2008, 09:30 PM
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I don't mean to sound like a dick, but you can't afford that SMC part, unless you have money coming out the wazzuu. Its almost 400 big ones.

33G: Eheim 2224, Finally have pressurized Co2 and Reactor
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post #7 of 10 (permalink) Old 01-13-2008, 12:29 AM
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Quote:
Originally Posted by original kuhli View Post
In the data sheets there's a kv or cv value, which I'm presuming is some coeffecient of flow, can somebody shed some light on the value?
Correct. "cv" = Coefficent of Volume. And it is indeed a measure of the freedom of flow through the valve. The higher the number the better.

Specifically, the cv number is the amount of liquid, measured in gallons per minute, that will flow through the valve when it has a pressure differential of 1 psi across it.

Along the lines of the example you gave, with an inlet pressure of 6.5 psi, and the outlet of the valve going to free air (so no pressure is needed to push fluid through after the valve), the pressure differential across the valve is, of course, 6.5 psi. Use a valve with cv=1 and you'll get a flow of 6.5 gpm. Use a valve with cv=2 and you get 13 gpm, etc.

I guess I'll go ahead and post a little bit of info on solenoid valves, that I was going to post in a separate message here:

Solenoid valves come in different types, with different characteristics. Major types include:

direct-acting solenoid valves The most intuitively obvious type. The solenoid rod acts as the valve stopper; i.e., when the magnetic coil pulls the rod out of the way, the fluid is able to flow through the resulting opening inside the value body.

Advantages: They require no differential pressure in operate; e.g., they'll work in even graivity feed situations where little/no head pressure is available. They work well in low-flow/low-pressure application. Operating time is very fast (measured in milliseconds); e.g., the low rider guys use these in their hydraulic systems that make their cars bounch up and down. Many can take a bit of back pressure in the closed state, although most do have a preferred direction, and may leak a bit when exposed to significant back pressure.

Disadvantages: Lower cv values than other valves. Prices climb fast with higher values; e.g., the cheapest McMaster-Carr has is $28, with a cv=0.2, and >$200 fir cv>2. In other words, these type of valves have the lowest flow per dollar of any type of valve.

pilot-operated valves The typical sprinkler valve falls in this group. The solenoid rod is used to control the flow of fluid into a chambe that acts on a (much larger) diaphram or piston, which is what actually stops or allows the flow of the fluid. Operation of the diaphram or piston is determined by the differential in pressure between the fluid being controlled, and the pressure in the chamber colntrolled by the solenoid. In effect, the diaphram/piston acts as an "amplifier" of the solenoid for controlling the flow.

Advantages: Good flow rates at low cost. For example, $10 commodity lawn sprinler valves can have cv values in the range of 3-4. Reasonably quick operating times (~1 second).

Disadvantages: Most do not operate at low pressures; e.g., lawn sprinkler valves are typically spec'd to require at least 15 psi to operate. This is due to the fact that the fluid pressure itself is used to move the element (diaphram or piston) that controls the flow. Also, inherent in their design is that they cannot take any backpressure in the closed state. Any backpressure merely pushes the diaphram out of the way, amd the fluid flows past.

Hydronic ball zone valves I just stumbled across this type of valve. I haven't seen any posts about this being put to aquarium use, but I think it may be ideal for many aquarium applications.

Unlike the previous two types, these are not solenoid valve at all. Ever thought that a simple way to make an electrically-controlled valve would be to simply take a ball valve, and mount a small electric motor on it? That's exactly what these are. They're commonly used for zone control in HVAC heating systems that use water, such a underfloor radiant heating system.

Advantages: High flow at relatively low cost. Due to their use in HVAC systems, they a high-volume mass-market devices (as usual, eBay is the best source). CV=10 for 3/4" valves are not uncommon. Operates at low pressure, and some will take backpressure.

Disadvantages: Slow operating time; ten seconds is not uncommon. Not quite as "fail-safe" as other types (may fail in the open position).
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post #8 of 10 (permalink) Old 01-13-2008, 02:17 AM
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Hydronic ball zone valves I just stumbled across this type of valve. I haven't seen any posts about this being put to aquarium use, but I think it may be ideal for many aquarium applications.

Unlike the previous two types, these are not solenoid valve at all. Ever thought that a simple way to make an electrically-controlled valve would be to simply take a ball valve, and mount a small electric motor on it? That's exactly what these are. They're commonly used for zone control in HVAC heating systems that use water, such a underfloor radiant heating system.

Advantages: High flow at relatively low cost. Due to their use in HVAC systems, they a high-volume mass-market devices (as usual, eBay is the best source). CV=10 for 3/4" valves are not uncommon. Operates at low pressure, and some will take backpressure.

Disadvantages: Slow operating time; ten seconds is not uncommon. Not quite as "fail-safe" as other types (may fail in the open position).
Cool info. Thanks ... If they're cheap enough, two plumbed in parallel would add redundancy to significantly decrease the possiblility of failing in the open position.
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post #9 of 10 (permalink) Old 01-13-2008, 03:17 AM
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You can get a 1" In line sprinkler selenoid valve from Lowes for 13 or so dollars. I got one for my misting system in my paludarium. Same Idea, I think.
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post #10 of 10 (permalink) Old 01-13-2008, 09:45 PM Thread Starter
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Indeed my valve is a reputable version of a sprinkler valve, I paid about $80 for the reliability that I hope it will bring. The reality is that these aren't going to give the flow rate that the inlet size would indicate, they're considerably smaller orfices within and in my experimentation the flow rate hasn't been what one would expect.

My plan had been to go for the largest valve possible at a reasonable price. Given that I'm in Canada and some evil foreign distributor is gouging the hell out of us things like this always cost double anything you have available if its available at all. Home Depot and Rona don't carry solenoids in Canada. I'd hoped that a good solenoid would be cheaper than a smaller diameter solenoid and booster pump (and it is).

My hope was that the valve would be enough with gravity, for some people it may be, especially those with smaller tanks. In my experience thus far I've determined there are two methods:

1. Large 'full port' type d or type g solenoids with gravity as the drive.

2. Any solenoid with a booster pump. The downside is you now have two point for leaks and electrical failure where you used to have one.

If I were to do this again I'd pay for a 'full port' version and keep the booster pump out of the system and cabinet.
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