Two pumps in parallel

[wilde]

We have a spa with 12 jets - 8 managed by a dedicated whisperflow (spa return) and 4 managed by an intelliflow (filter and heater). Even when the intelliflow is at the maximum 3450rpm, those 4 spa jets have maybe half the pressure of the remaining 8.

If we replumbed the 2 pumps to be in parallel (spa return from intelliflow redirected to connect with the whisperflow intake; whisperflow return split with new line connecting to the 4 jets now managed by the intelliflow) would that be a viable solution to balance out the pressure on all 12 jets? I'd be willing to lose a little pressure on the 8 to get the pressure up on the 4.

 

[Kiss4aFrog]

Welcome to the forum

Would you be running both pumps each time the heater kicks on to maintain the spas temp and do filtering ??

 

[wilde]

I don't think so, only the intellifow would be used when heating/filtering - which woudl allow a low flow rate to be used for that purpose. The whisperflow would only kick in when the jets are activated.

This is how things operate now - the main issue being that since the jet circuits are separate, the four jets that provide the heated/fitlered water are operating at very low pressure. If the two jet circuits could be connected, then perhaps the pressure would be consistent.

 

[wjr75]

My spa has all the jets connected to a seperate 2hp pump. The filter and heater has 2 floor main drain returns and two outlets at the bottom of the tub.

 

[Kiss4aFrog]

The problem I see is if you connect them in parallel after the filter and heater and don't run both at the same time you have the intelliflow leaking backwards through the whisperflow reducing it's pressure to the four jets. What I don't know is how much water will flow past/through the whisperflow's pump with it not operating and how much volume and PSI you'll lose in the filter and heater circuit ?? Only real concern is having adequate flow in the heater when it's running unattended and on a timer or temp demand.

Unless you add a manual or solenoid controlled valve to isolate the intelliflow when running the heater.

 

[mas985]

The easiest and most effective solution would be to put in a bypass for the Intelliflo which would bypass some of the water around the filter and heater. This would increase the flow rate to those 4 jets by quite a bit.

 

[wilde]

The 4 jets powered by the intelliflow are what provide the heated and filtered water. The remaining 8 jets are powered by a 2hp whisperflow (water just circulating to and from the spa, no interacting with the rest of the system).

If placed in parallel, regarding reduced pressure on the 4 intelliflow-driven jets when the whisperflow is not running, that wouldn't be a concern because the whisperflow would be on whenever in "jet mode". Also, when the whisperflow is off, the reduced flow from the 4 jets would be made up by the intelliflow sending water through the other 8 jets as well - so the same amount of hot water should get into the spa when in heat mode (whisperflow not running).

Ah, a variable bypass does seem like it may also be a solution. It could still send some water through the heater, etc., but most could be sent directly to the jets. A bypass might be a little more straightforward, but wouldn't the parallel pump solution provide more balanced pressure across all 12 jets?

Below is a quick diagram of my current situation (left), and what I'm proposing to put the pumps in parallel (one plumbing line connecting the intelliflow spa return to the whisperflow spa return).

 

[mas985]

A bypass might be a little more straightforward, but wouldn't the parallel pump solution provide more balanced pressure across all 12 jets?

The two pumps have different head curves and when you put pumps in parallel, there are interactions between the pumps that are not always predictable so the pressure and flow rate for each return might be balanced but overall performance could be significantly reduced. With your solution, the 8 will suffer in flow rate and you might increase the flow rate of the 4 slightly. However, with the bypass, the 8 will have the same flow rate as they do now and the 4 will have an increased flow rate. You can also adjust the flow rate of the 4 with both the bypass and RPM so it can be identical to the 8 if you so desire. So I think the bypass is a much better solution.



P.S. There is no OW in Whisperflo or Intelliflo

 

[wilde]

Thanks mas985. I'd want to have this automated with spa activation.

If just after the Intelliflo a bypass is installed with a valve actuator, can the "on" spa state of the actuator be set to something other than 100% bypass? (obviously the "off" pool state would be 0% bypass)

 

[mas985]

Yes, with an actuator, you can set the stop anywhere.