Increasing motor HP for additional GPM for heater

[nottinbe]

Hi everyone. I used this site extensively last year for the first time and using the methods and advice here kept my pool the cleanest I've ever seen it. That's after several years of using a PB and local chains and having moderate results at best. So, thanks! Now for my first post...

My old Raypak NG heater officially died at the end of last season. It was a 10+ year old 330k BTU model. I'm also taking the opportunity to repipe the mess that was the equipment pad. I would like faster heat-up times than we enjoyed with the previous model and was hoping to install two P-R406A-EN-C 400k BTU heaters in parallel.

To prepare for this I installed a FlowVis flow meter. It shows ~72 GPM, which is not enough to support the 40GPM minimum required per heater.

(Sorry if I get terms wrong, I don't fully understand the pump vs. motor terminology. I think the pump is the housing and the motor is what gets wired and inserts into it?)

I currently have this motor http://www.inyopools.com/Products/07501352022093.htm. The only identifying mark I can find on the pump is Jacuzzi written on the lid. I am wondering if I can simply swap my current motor for this one http://www.inyopools.com/Products/07501352022277.htm without changing the pump? Also wondering how much GPM increase could be expected by increasing the HP by 1.5?

Thanks so much.

 

[dschlic1]

No changing the motor will not increase the flow. The flow is related to the rotational speed of the motor, and all two pole motors turn at about the same speed. You will have to change motor and pump. Sorry.

 

[nottinbe]

So are you saying that I should be looking at RPMs and not HP?

Could you explain how HP relates to pumps motors and flow? If changing the motor to a higher HP doesn't increase flow, then it seems like it would follow that changing the motor to a lower HP wouldn't decrease the flow. So why wouldn't anyone just use the lowest HP motor available if HP doesn't affect flow?

I don't mind buying stuff. I just want to know what to buy, and understand the principles behind it. Right now I feel pretty confused.

 

[CJadamec]

No matter how much HP you throw at a pump if it is spinning the same speed you will get the same flow. You would need a different pump altogether to get more flow. On a single speed motor like you have the motor rpm is a fixed number.

An intelliflo pump would probably be a good choice to get you over 80 GPM and not kill your electric bill when you just need to skim the pool and not heat it.

 

[Gulfjasper]

Flow or gallons per minute (GPM) will be determined for the most part by impeller size and rotations per minute (RPM). The larger the impeller the more effort it takes to rotate, which means more HP needed.

 

[nottinbe]

Which Intelliflo would I need?

And could you help me understand what role HP plays? If increasing it doesn't increase flow, I don't understand why you wouldn't always just buy the cheapest pump with the lowest HP.

What is the impeller? Is that apart of the motor, or the pump?

 

[Gulfjasper]

The impeller is the "wheel" part of the pump that moves the water. If you require a pump that moves 80 gpm for your system. It will require a certain amount of Horse Power (HP) to rotate an impeller at the needed rpm to move that amount of water.

If you had a large impeller but a small motor (low HP) the motor wouldn't be strong enough to spin the impeller fast enough.

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I'm not familiar with what's needed for a heater. But like CJ said, a variable speed pump rated for your heater needs would allow you to run it slower when you're not using the heaters.