Spa Flow Rate vs Pump OverPressure

[mbeavers1]

Our pool was completed in late April and we used most of the settings from the builder in terms of pump speeds for our pool and spa. I was running my main pump at ~80 gpm when in Spa Mode and ~50 gpm for Pool Mode (min to activate flow sensor on Intellichem). I have left the pump run 24-7 over the summer to allow my Glacier cooler to run overnight to keep water temp in a comfortable range.

For the last couple weeks, I have noticed that when I activate Spa Mode, I get a VSF priming alarm on my control panel. With the pool running, I click over to Spa Mode. The pump RPMs, flow rate, and power usage all initially increase. After a short time, the flow rate drops off to ~50-55 gpm and a VSF Priming Alarm sows up but RPMs and Power Usage all stay significantly higher than in Pool Mode. Filter pressure is showing ~22 psi (cleaned approx <3 weeks ago). I do not believe there is a "priming issue" because there is no air in the viewing glass.

I have been trying to get the builder to come out to check it, but no luck. After talking a bit to Pentair and a bit of troubleshooting, I think I have some sort of flow restriction on the spa side. Here is what I have done:

Take Operating Parameters
1. Took base line pump operating rates in Pool Mode at 50 gpm. Measured 50 gpm, 2450 rpm, and 875 Watts
2. Took operating rates in Spa Mode with flow rate set at 70 gpm. Measured 55 gpm, 3065 rpm, and 1584 Watts (VSF Priming Alarm observed on Control Panel and Pressure Limit Alarm showing up on the pump panel) and ~22 psi on filter
3. Took operating rates in Pool Mode with flow rate set at 70 gpm. Measured 70 gpm, 3050 rpm, 1750 Watts, and ~22 psi on filter (No alarm observed).

Isolate Pump from Controls
1. Switch pump to "Service Mode"
2. Manually actuate valves to Spa Mode
3. Run pump at rates up to 3450 rpm without any alarms showing up on the pump panel. Measuring 63 gpm.

This seems to indicate that I am either limited by the friction pressure in the plumbing or there is a restriction in the system somewhere causing excess back pressure. I believe that I have 2" suction and discharge lines - trying to confirm from PB.

Seems pump is operating normally though I am surprised that at max pump RPM, I can only push 63 gpm through my spa. I believe I have 6 jets (need to count), so that is ~10 gpm per jet.

I am an engineer....am I "over-engineering" this or does it seem like I should have more rate.

 

[ajw22]

I think you are getting what you can expect from a residential system. I don’t believe anything is wrong other then your expectations.

@mas985 can take you through the engineering.

 

[Jimrahbe]

M,

I also believe that you do not have a priming issue.. Just so that we have all the facts... Did your spa work fine initially and now does not, or is this the first time that you have run into this issue or at least looked at it closely?? Have you made any recent valve position changes?

In the pool mode do you have a bunch of water features on that you do not have on when in the spa mode?

How about posting a few pics of your equipment pad..

Oh!! and welcome to TFP and a great job of filling out your signature on your first post..

Thanks,

Jim R.

 

[mas985]

Our pool was completed in late April and we used most of the settings from the builder in terms of pump speeds for our pool and spa. I was running my main pump at ~80 gpm when in Spa Mode and ~50 gpm for Pool Mode (min to activate flow sensor on Intellichem).

Intellichem should be able to run at 25 GPM. Does it alarm? Is there a bypass somewhere around the SWG?

3. Run pump at rates up to 3450 rpm without any alarms showing up on the pump panel. Measuring 63 gpm.

What is the filter pressure? How are you "measuring" flow rate?

Seems pump is operating normally though I am surprised that at max pump RPM, I can only push 63 gpm through my spa. I believe I have 6 jets (need to count), so that is ~10 gpm per jet.

What size are the jet nozzles?

Are you running the jets off the Whisperflo or the Intelliflo?

 

[mbeavers1]

Thanks Jim:

The spa has always worked but I did not get the alarm initially. The thing that has me is "Why the alarm now?". I did not have this for the first several months and it seems to have simply appeared. This is the first time that I have really looked at it closely...because of the alarm.

I only have 6 valves (see poor picture....best I can do from the office). The two IntelliValves actuate between Pool Mode and Spa mode. The actuated 3 way valve cracks open when my Chiller is operated - currently closed. It acts at the "regulator" to control the water volume to the chiller. The final three are on the suction side of my pump from the main drains and skimmers - all open.

The thing I noticed last night is that my Intellicenter throws the "VSF Priming Alarm" but the pump actually shows "Pressure Limit" on the Intelliflo control pad. I can believe the Pressure Limit, but not the Priming.

 

[mbeavers1]

Intellichem should be able to run at 25 GPM. Does it alarm? Is there a bypass somewhere around the SWG?

What is the filter pressure? How are you "measuring" flow rate?

What size are the jet nozzles?

Are you running the jets off the Whisperflo or the Intelliflo?

1. At less than 50 GPM, the flow switch on the IntelliChem will not shift up and the unit will register "No Flow". I was surprised by this too, but played with the pump speed a lot to find the lowest rate. My pool is chlorine, so I do not have a SWG. It dispenses liquid chlorine. I have been tempted to "bypass" this, but dont want to take the risk of dumping HCl in with no flow. I would love to find a way to run the pump at an even lower speed than normal (~2400 rpm, 50 gpm, and 775 Watts).

2. Filter pressure when? In normal Pool mode at 50 gpm, it is around 12-14 psi. In pool mode at max pump speed of 3450 rpm at 70 gpm, the filter pressure is ~28 psi. When I switch to Spa Mode and RPMs increase to ~3050 RPM (flow rate is ~55 gpm), the filter pressure increases to ~22 psi. The "Flow Rate" is an output of the IntelliFlo pump. It reads on the pump control panel itself and is transmitted to the control system where it can be read in the app (see pic). I spoke to Pentair about this and it is related to the impeller speed. I assume this is a direct measurement (ie. mag pick up?), but Pentair did not elaborate.

3. Unsure on nozzle sizing. Need PB to give me this information. It is not on the spec sheet from the builder, only that there are 6ea. Is there an easy way to find out?

4. All pool and spa functions are on the IntelliFlo. The Whisperflo is for the 3ea sheers on the back wall (2ea 2ft long, 1ea 6ft long).

 

[mas985]

2. Filter pressure when? In normal Pool mode at 50 gpm, it is around 12-14 psi. In pool mode at max pump speed of 3450 rpm at 70 gpm, the filter pressure is ~28 psi. When I switch to Spa Mode and RPMs increase to ~3050 RPM (flow rate is ~55 gpm), the filter pressure increases to ~22 psi. The "Flow Rate" is an output of the IntelliFlo pump. It reads on the pump control panel itself and is transmitted to the control system where it can be read in the app (see pic). I spoke to Pentair about this and it is related to the impeller speed. I assume this is a direct measurement (ie. mag pick up?), but Pentair did not elaborate.

They use a calibration table to calculate flow rate. For each pump RPM and Wattage, there is only one flow rate possible. But it should identical to the input setting unless the RPM is maxing out which is what could be happening. The flow rate settings for your setup may not be possible because of the head loss in the plumbing. Can you also post the pump pressure reading from the display?

3. Unsure on nozzle sizing. Need PB to give me this information. It is not on the spec sheet from the builder, only that there are 6ea. Is there an easy way to find out?

Depends on the type of jet that is being used. If you have a part number for the assembly, you can determine if from that. Are the exterior fittings eyeballs or screw in assemblies?

 

[mbeavers1]

They use a calibration table to calculate flow rate. For each pump RPM and Wattage, there is only one flow rate possible. But it should identical to the input setting unless the RPM is maxing out which is what could be happening. The flow rate settings for your setup may not be possible because of the head loss in the plumbing. Can you also post the pump pressure reading from the display?

Depends on the type of jet that is being used. If you have a part number for the assembly, you can determine if from that. Are the exterior fittings eyeballs or screw in assemblies?

@mas985

The pump pressure when in Spa mode is 28 psi (2960 rpm, 53 gpm, 1544 watts). The pump is throwing a Pressure Limit alarm. The filter pressure is only reading 21 psi. Thats quite a difference in pressure and with the filter being downstream, it should be slightly lower due to head loss in the pipe/fittings between the pump and filter. That being said....who knows which pressure is correct, but experience tells me the trusty dial gauge.

The exterior fittings are eyeballs so I cant actually see the jets without draining the spa.

 

[mas985]

So at that operating point, there is 66' of head. According to my pump models, (2960 rpm, 53 gpm, 1544 watts, 66' of head, 0.0227 PC) is a valid operating point but the plumbing has a lot of head loss for that RPM. I would say it is excessive. If I model a 6 jet spa assuming 3/8" jets and 35' runs with your equipment, I would get the following operating point: (2960 rpm, 74 gpm, 1773 watts, 63'' of head, 0.0115 PC). Your plumbing curve (PC) is almost 2x a typical spa plumbing curve (Head (ft) = PC * GPM^2) so something is causing excess head loss.

What is the distance from the pool to the spa?

What is the filter gauge height relative to the spa water level?

Did you take any pictures with the underground pipe exposed?

Can you ask the PB what model TEE and jet they used?

Can you take multi-view pictures of the pad?

Also the pump pressure is reflective of total head loss (return AND suction). This means that the suction head loss is close to16' of head which is quite high for 53 GPM.

 

[mbeavers1]

So at that operating point, there is 66' of head. According to my pump models, (2960 rpm, 53 gpm, 1544 watts, 66' of head, 0.0227 PC) is a valid operating point but the plumbing has a lot of head loss for that RPM. I would say it is excessive. If I model a 6 jet spa assuming 3/8" jets and 35' runs with your equipment, I would get the following operating point: (2960 rpm, 74 gpm, 1773 watts, 63'' of head, 0.0115 PC). Your plumbing curve (PC) is almost 2x a typical spa plumbing curve (Head (ft) = PC * GPM^2) so something is causing excess head loss.

What is the distance from the pool to the spa?

What is the filter gauge height relative to the spa water level?

Did you take any pictures with the underground pipe exposed?

Can you ask the PB what model TEE and jet they used?

Can you take multi-view pictures of the pad?

Also the pump pressure is reflective of total head loss (return AND suction). This means that the suction head loss is close to16' of head which is quite high for 53 GPM.

@mas985

Pool and spa connected but spa on far end away from equipment pad (see attached picture), maybe 75ft - pool length is 40ft

Unfortunately no pictures of plumbing but there are only a few turns. Plumbing comes from pax makes 1 90 then runs straight all the way to the end of the pool and makes a 90 to spa. (Runs under decking between pool and house in pic).

The bottom of the filter is essentially at the decking level and spa water level is about 12" higher, so gauge maybe 2ft higher.

Will check with PB on jet sizes.

 

[mbeavers1]

@mas985 I also noticed over the weekend that 1 of my spa jets has a drastically different flow rate than the other 5. Possibly plugged? I am trying to get information from my PB, but he is simply saying that its a limitation of the plumbing and that there isnt any issue.

 

[mbeavers1]

@mas985 struggling to get jet size. PB said they are Hydro Jet bodies (see pic). He said air comes through the middle and water at a right angle. Looks to be about 0.5-0.625" jet size. Also, drained spa to see if i could see anything stuck in there but looks clear. With spa running, its clear that jet is weaker. I have a video but cant upload apparently. Any other ideas?