When is it safe to restrict outgoing flow from external pumps?

[Nickeleye]

I have an Eheim 1262 pump that I am considering using with a 30g tank with a chiller that says that it would like 500 GPH minimum flow to 800 GPH maximum flow. The Eheim pump puts out 900 GPH at zero head so I'm not sure if this would create problems with the chiller or not. My question is if placing a ball valve after the output from the pump and slightly restricting the flow would damage the pump. I read somewhere that there are certain types of pumps that won't get damaged from reducing outgoing flow a little, but then are are some types of pumps that do get damaged from restricting the flow. Can anybody offer me some more information regarding this?

Thanks.

[ribs]

IMO, sounds like you've chosen the right pump for the application.
There's restriction on the return already, plus adding the restriction thru the chiller, I think your flow rate will probably be sufficient after the above-mentioned items, using the pump you've chosen.
Start with it full open tho, adjust back only if necessary, worry later, and only if you wind up closing the output valve 50% or more.

[Nickeleye]

I should now point out that according to other sites, the chiller is spec'd out for 300-500/600 GPH (depending on the site). That being said, I measured how high the outtake from the tank would be and it's roughly 4.5 feet. That should reduce the flow for the chiller, correct?

[ribs]

The reason I mentioned keeping the valve full open to start with is because of the inherent restrictions already placed on it.
At 4.5 feet, and a chiller plumbed inline......try to find the pump curve for the ehiem (I don't have it readily available) and make a judgement call using that. You'll have enough restriction at 4.5' and a chiller to drop an "average" pump down to at least 600gph. The difference, you can adjust using the output valve.

[kgross]

To answer your question on restricting pumps any centrifical pump will not be hurt with a restriction on the output, unless you restrict the flow so much to cause the pump to overheat (this normally only happens if you basicly stop the flow completely).

Kim

[Nickeleye]

I'm actually most curious about the amount of flow going through the chiller. It mentions anywhere between 300-600 GPH. I'm just not sure the reasoning behind the chiller's specifications. I'm not sure if they recommend those GPH specs due to more efficient cooling or if you go too high you might blow something up in the chiller. That's an extreme example, but I think you get the idea.

[Nickeleye]

Kgross, thanks for the input. So if I install a ball valve between the pump and chiller I could just adjust as necessary.... if necessary at all.

[kgross]

Yes that is correct. With the chiller and the head you have, I don't think you will need to restrict the flow actually.

Personally I always put ball valves on my pumps just incase I need to turn them down for any reason, like I need to work on the overflow or something and I don't want the tank to overflow.

Kim

[Nickeleye]

Kim,
Again, thanks for the advice. Why do you think my chiller would not need the reduction in flow? I'd like to use the larger pump, which would be putting a whole lot of flow into the chiller... wouldn't it? Maybe I'm looking at it all the wrong way. The water has to come down about 4.5 feet into the pump so does that count for reducing the flow or is it only upwards that you worry about? I'm just trying to figure out if the input of the chiller is actually going to see 900 GPH or if it's going to be getting less.

[ribs]

Originally posted by Nickeleye
Maybe I'm looking at it all the wrong way. The water has to come down about 4.5 feet into the pump so does that count for reducing the flow or is it only upwards that you worry about? I'm just trying to figure out if the input of the chiller is actually going to see 900 GPH or if it's going to be getting less.
Is there a sump in this setup?
As I posted above, you will not get 900GPH out of the pump you've mentioned as there's a chiller and 4.5" head. The only adjustments I'd foresee is to get the proper chilling, and that would be slight adjustments on the output of the pump you've chosen to get the best chiller cooling effect. Again, sounds like the right pump for the job, with alittle adjustment (if any) if you feel like fiddling. Sounds like you're good :)

[kgross]

The only reason the chiller would need the slower flow rate is if the water is flowing through the chiller to fast the chiller is not able to cool it off enough, no time for heat transfer. Normally this is not a problem unless you are trying to put a lot of water through your chiller. Your 900 gph pump is 900 ghp at 0 head correct, so as soon as you start hooking stuff to the pump, ie pipes, and the chiller you will be restricting the flow because the the friction loss. The best suggestion I could give you would be to put the valve on the pump and then if the chiller is not able to cool down the tank, slow down the flow slightly until it is able to cool the tank.

Kim