Chiller Questions

robn

robn

Member
I am running a Pacific Coast 1/2 hp chiller on a 480gal tank.....total water volume is probably 525 gallons.....I run 1000W of MH 5 hrs a day....ambient temp is 78.
The tank runs from 76.7 to 74.5 ......it takes the chiller 4 hours to cool to that range.
1) Is this about normal or should it be cooling faster than that? The chiller is rated for a 10 degree pulldown on a 450 tank, but these ratings don't really say how long it takes to accomplish this pulldown.
2) Would it be better to add another chiller or sell this one and get a 1hp (or something) instead?
Thanks!!!
 
scsinet

scsinet

Active Member
The pulldown ratings on chillers are based on average conditions and circumstances, and are absolute maximums, so it's usually assuming the chiller is running constantly. Your situation may be different, but I'd say the timeframe you are seeing is not that unusual.
My suggestion would be to change the temperature to 78-80. I can't think of a reason to run the tank this cool, you're just running up your electric bill.
 
robn

robn

Member
I hear you, but the reason I'm running the tank at that temp is for the Horn Shark that prefers cooler water......
 
scsinet

scsinet

Active Member
Ahh...
Well if I were you I wouldn't upgrade to a 1hp, I'd add another 1/2 HP and switch them together using a Ranco controller or something similar. This way if one fails you aren't completely without a chiller for your shark. Just daisy chain them together plumbing wise.
 
newbostonconst

newbostonconst

Member
SCSInet, You always have good ideas, but I would put them in parallel, that way u have a larger delta T through the heat exchanger. It should run more efficient that way. Good luck.
 
robn

robn

Member
Thinking from a "let's keep the electric bill to a minimum so the wife does not kill me" standpoint, wouldn't it be better to run 1 larger chiller? The one I run now is 9.9 amps on 110V......I found a 1.5 hp that pulls 10.3 on 220V.....just curious what would be the better choice....
Thanks to both of you for your replies
 
newbostonconst

newbostonconst

Member
Originally Posted by robn
Thinking from a "let's keep the electric bill to a minimum so the wife does not kill me" standpoint, wouldn't it be better to run 1 larger chiller? The one I run now is 9.9 amps on 110V......I found a 1.5 hp that pulls 10.3 on 220V.....just curious what would be the better choice....
Thanks to both of you for your replies
Electric Motors overall are more efficient at high voltages, but as for as comparing 2 units it depends on how each is designed. If the larger unit is going to short cycle (come on for a min and then turn back off) then it is definitely better to have the smaller unit. But in your situation I think, as SCSInet said, it might be better to have 2 units. Allot depends on the amount of plumbing, pumps needed, and the amount of your time that is needed to install. It maybe easier to unbolt one, and install a larger one in its place.
 
scsinet

scsinet

Active Member
The efficiency difference between one motor and two smaller ones is going to be more significant than the efficiency difference between 120 and 240v. What you are seeing is more a consequence that a larger single compressor produces more BTU per watt than two smaller ones of half size than of efficiency gains with the higher voltage. SO, I won't lie to you, you'll consume more electricity by using two smaller ones.
However...
First, you are probably going to spend far more by selling your unit (at a significant loss most likely) and buying a larger one than you would by adding a second unit, so you have to figure how long it will take to make up the difference in power.
Second, if you were to daisy chain them, but (and here is where I change from what I said before) use two controllers, with one set behind the other, you will acheive a sort of two stage cooling setup, where one will kick in only if the other falls behind. Every month, you flip them, swapping the setpoints on the thermostats, thus evening the wear and tear on both units. This setup may also work with paralleling them, though I'm thinking not as well.
With your investment, I'd hate to see a failed chiller result in a dead tank, especially with an expensive item like a shark in there. Always try to have multiple points of failure... straight from the department of redundancy department

The reason I suggested daisy chaining them rather than paralleling them is that should the water flow in them become uneven, due to perhaps differences in the bends of the plumbing, a piece of debris causing a clog, etc, you might not noice it since the flow will still make it through the other unit. The one with restricted flow could freeze, effectively destroying the machine. There are advantages and disadvantages of doing it each way. Not sure which situation is better... efficiency versus the slight chance of that happening though.
 
newbostonconst

newbostonconst

Member
If they are in series (daisy chained) and the water line gets plugged they both stop working.
From an efficiency stand point, say the first one drops the temp from 85 to 70, the second one is not going to drop from 70 to 55. That is were the efficiency loss is. Also I don't think you want water that is ~twice as cold entering the tank.
Can't the units can be staggered and switched the same if they were in series or parallel? Would you even really need a special controller for this? It is a great idea though.

I have seen many small window ac units that out perform larger units. It is all in the design.
220 volt motors are more efficient because the windings don't have to be as big to carry the same watts. Similar to power lines, the higher the voltage the small the wire needs to be to carry the same power.
 
scsinet

scsinet

Active Member
Originally Posted by NewBostonConst
If they are in series (daisy chained) and the water line gets plugged they both stop working.
That's right, but you'd know because you'd see the reduction in flow in your filtration system... you'd notice. Like I said, it's all about advantages and disadvantages. IMO there is no right or wrong way when you are looking at these two choices.
Originally Posted by NewBostonConst
From an efficiency stand point, say the first one drops the temp from 85 to 70, the second one is not going to drop from 70 to 55. That is were the efficiency loss is. Also I don't think you want water that is ~twice as cold entering the tank.
A chiller does not accomplish it's complete pulldown with one pass. Imagine his example... It takes 4 hours to effect a 6 degree pulldown. If his filtration is what you'd expect to find in a reef, 10x turnover per hour, that comes out to 0.15 degrees of differential per pass. It's probably more than that, because the tank is continuously heating the water, so maybe 0.5 degrees per pass. I agree that there would be a significant efficiency loss if the pulldown were that significant, but the water temperature leaving the chiller is not going to be that much cooler than the water entering when looking at one pass at a time, so I'm thinking that the efficicency difference would be slight.
I checked this one on my reef tank. My chiller takes about 20 minutes to pull the temperature down 2 degrees on the tank. When it had been running once for about 10 minutes, and the tank was 79.3 degrees, I pulled out an inflow and filled a container with water directly from the chiller, and measured it at 79.1 degrees. Of course, passing that water through the chiller 20 or 30 times and you get to where you want to be.
Imagine what would happen if water that was 5 or 10 degrees cooler was coming in through the inflows... what those cold currents would do to the fish.
Originally Posted by NewBostonConst
Can't the units can be staggered and switched the same if they were in series or parallel? Would you even really need a special controller for this? It is a great idea though.

I think so. What I'm not sure of is what the effect would be of 1/2 of the water passing through a chiller that's not running. It probably wouldn't have much of an impact so it would work either way.
Originally Posted by NewBostonConst
220 volt motors are more efficient because the windings don't have to be as big to carry the same watts. Similar to power lines, the higher the voltage the small the wire needs to be to carry the same power.
True but this makes no difference in the motor's efficiency, only it's weight. You siad it yourself, the actual power consumed by the motor does not change. It's simple Ohm's Law. W=V*A. If you have a motor that consumes 1200w at 120v, it's drawing 10 amps. Increase it to 240v and you get 5 amps, but still 1200w, still same power consumed. Since electricity is billed by the watt, you are paying the same amount to run it.
Bottom line is that in this situation, it's all about choices. Make no mistake, I'm certainly not suggesting for a second that my way is the "right way" and that everyone else here is wrong, and I don't want to spark a huge argument as I respect everyone's opinion, especially on this thread. There are advantages and disadvantages of each way of doing this, and you have to take some concessions with each.
 
newbostonconst

newbostonconst

Member
I am just trying to think this through and give good advice. Sometimes it takes arguing. I am learning a lot through all of this and appreciate your comments. You definitely have more experience then me in aquarium chillers.
Now, lets step outside.

If you are getting that small of temperature drop, series or parallel won't make a difference in efficiency. From the spec of some of the chillers I've seen, the units give from 10 to 30 degrees temperature drops depending on the amount of flow through the unit. If you are only getting a ½ degree I would think you are forcing too much flow through it and wasting a lot of energy in pumping. These small changes in efficiency don’t seem like much, but when something runs 24-7 it adds up quick.
I think I would run a small pump for each, rather then one large one. That way if one stops working for some reason the tank won’t over heat and loose everything. People use the same idea buying 2 small heaters rather the one large one.
Yes, a 1200w motor at 120v uses the same power as a 1200w motor at 220v, but in general practice with electric motors you are going to get more of that power turned into turning force on the 220v motor. The 110v motor usually produces more heat thus less turning force. This is because in your equation when A is bigger then V, more heat is produced trying to push the electrons through the wire, and when V is bigger you are pushing fewer electrons through the wire. It is like trying to pump a million gallons through a small hose. All you are going to produce is heat. Hope this makes sense. Ohm’s law is V=I*R.
 
robn

robn

Member
Do you think my chiller needs a freon charge? I'm just trying to get a good gauge of its performance.....
 
zman1

zman1

Active Member
Sure that's a possibility. Seeing frost on the evaporator can be (not always) an indication of a low charge. If your condenser coil is dirty restricting airflow can reduce efficiency dramatically.
I think Scsi mentioned this. The manufacturer ratings are based on running 24 hours with 3x turnover through the chiller with florescent NO lighting. Also, your ambient room temp impacts performance. Ambient max is 95F
Sure you could connect two chillers in series and make it work similar to a two speed compressor. An example for discussion purposes. If the tank were 83F both chillers run. When the tank drops to 80 then one chill turns off and the other single chiller brings it back down to 78. This is an extreme range and not practical but to illustrate. The same for arising temp. The first one in series is off and the second one turns on at a temp , but it is not keeping up and tank is still heating then the first one kicks on to assist for a range then drops out. Or time delay one and have it kick in to assist only after the one running hasn't brought the temp down fast enough. What you will have to do is make sure you don't short cycle the compressor on one of the chillers this can damage it. On, Off, ON, Off. Running two in series is doable and simular in a round about way to High efficiency split systems two speed compressors. The biggest item for HE split sytem are just larger coils.
 
scsinet

scsinet

Active Member
Originally Posted by NewBostonConst
If you are getting that small of temperature drop, series or parallel won't make a difference in efficiency. From the spec of some of the chillers I've seen, the units give from 10 to 30 degrees temperature drops depending on the amount of flow through the unit.
Manufacturers rate chillers based on the total amount of differential you can expect the machine to maintain on a given body of water given average conditions such as heat load, ambient temperature, etc.
Running water slowly through a chiller is a bad idea, and in fact manufactuers stipulate minimum flow rates to prevent freezing of the heat exchanger. I think we are both on the same page here, I'm just advocating caution to not run water through TOO slowly.
I go back to my earlier comment that you should not expect a chiller to accomplish a complete pulldown of 10+ degrees, or even 5 degrees, on one pass. If you do that, assuming your chiller is on your main return line (which is where most manufacturers recommend that they be placed, as the last device before the tank), then you are blowing water with a 5 or 10 degree differential into the tank, which WILL cause tremendous fish stress. IMO you don't want more than a 1 degree differential, so as to give the water time to mix and adjust gradually to the change, as so shockingly quickly changing the temperature in any direction can be a problem for your fish.
Originally Posted by NewBostonConst
I think I would run a small pump for each, rather then one large one.
Sure. The only thing you have to watch for is if a pump fails but a chiller keeps going (if you use an outboard controller). If you do this you should have a flow switch on the chiller to shut it down in the event of flow loss to prevent freezing and destruction of the heat exchanger.
If you use an outboard controller you should do this anyway though.
Originally Posted by NewBostonConst
Ohm’s law is V=I*R.
Ohm's law is the relationship between voltage, current, power, and resistance. V=I*R is an expression of the relationship between voltage, current, and resistance, which is a part of Ohm's law.

W=V*A is an expression of the relationship between power, voltage, and current (For the benefit of other readers, you could also express this W=V*I, as I and A both mean current/amperage). This is also a part of Ohm's law.

Also:
V = sqrt(W*R)
R = W / (A*A)
I = W/V
W = (A*A) * R
... to name a few others.. There are actually over a dozen ways to express it.
It's all Ohm's law, so we're both right.
 
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