Various speed pump motor issue

[bfang711]

I replaced the old single speed motor with a various speed motor. Now I noticed an issue. The way I set it up has been 3140RPM for 2 hrs, followed by 2100RPM for 4hrs, followed by 1300RPM for 6hrs. I think the setup can definitely make the whole pool of water circulate at least once per day. However, most cases are that when it runs at 3140RPM, the filter pressure is at about 30psi, and 15psi when it is @2100RPM and <5psi@1300RPM. When it is at 5psi, there is no water flow at all from the return line, and I can see instead of full of water, the pump basket are all air, which means the pump is running but without water being circulated at all during the last 6hrs of low speed RPM. (When I run @3140RPM, there are just several air bubbles in the pump basket, and @2100RPM, there are definitely a layer of air in it, but water still being circulated, not like @1300RPM. )

So my question is that, is this normal for various speed pumps? If it is not, what could be the issue? I actually haven't used the lowest 600RPM it provides. If I use that, then forget about it. there won't be any water pumped out at all. If it is normal, what is the rule of thumb of using various speed pump.

thank you very much.

 

[Davejavu]

Mine gets air in it at low RPM and according to Hayward, it's normal.

Here are a few thoughts:
- Do you have a priming cycle to make sure the pump gets water before lowering the RPM? I cannot get prime at 600RPM, so I run at 2100RPM for a few minutes before lowering down.
- It's possible it's sucking some air. To diagnose, start with making sure the o-ring on the pump filter basket cover is clean and lubed. Then start checking valves and pipes.

 

[bfang711]

Yes. it has a prime cycle. but only before the 1st stage, which is @3140RPM. So I don't think that will help, because even when it is full of water, after a while running @ low speed, the air will come in again.
I will definitely clean and lube the pump busket and check if there is any air leaking.

Thank you.

 

[VikingPoolMan]

You said at the 1300RPM setting, there is ALL air in the pump basket and NO water coming out of the returns? If that's the case, you are running the pump dry for 6hrs and that's not good? Or, do you you mean you see little water in the pump basket and feel little flow through the returns? I assume this is what you mean since you said you are getting 5psi in the filter? If that's the case, I don't see the problem.

 

[bfang711]

Well. I pretty much think there is no water coming out of the return line at all. I feel it with my hand, but cannot feel any water movement at the return. I remembered I ever opened the pump lid when it was running @ low speed and there was no water coming into the pump. so I think unfortunately it is running dry. I know it is not good, so I just switched back to high speed. at least it is good for the motor. I think there must be some air leak somewhere, otherwise this cannot happen.

 

[Davejavu]

Another tip is to re-read your instructions for installing the pump. Mine needed a long straight run (not a quick bend) into the pump in order to prevent pump cavitation at higher speeds. Check your manual for the max recommended RPM for your setup.

Also, the efficiency goes down significantly with higher RPMs. It is sometimes much more energy efficient to run 2 or 3 times longer with a lower RPM. Again, read the manual for guidance. And see this post: http://www.troublefreepool.com/threads/58668-Pump-efficiency-6-7x-better-at-1000RPM-vs-3000-RPM-!!

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Well. I pretty much think there is no water coming out of the return line at all. I feel it with my hand, but cannot feel any water movement at the return. I remembered I ever opened the pump lid when it was running @ low speed and there was no water coming into the pump. so I think unfortunately it is running dry. I know it is not good, so I just switched back to high speed. at least it is good for the motor. I think there must be some air leak somewhere, otherwise this cannot happen.

Check to make sure the pump drain plugs are lubed and tight too.