EDIT: Bypass Causing Bubbles?? | Heater Bypass Saves $20/mo | ~40-50%

[matthewsunshineflorida]

The clickbait title is comparing the cost to run my pump at 40gpm (say for solar) for 8 hours a day at around $0.35/kwh. In reality, for most of us running at a lower speed with cheaper electric (currently around $0.13 here), that's only a small savings. However, I wanted more pressure in the spa jets and more flow through the solar without running the pump so high.

The flow was monitored via FlowVis and the power was monitored via a Klein CL900, which doesn't have the most precise range at low current (one decimal point), so the bottom range of the pumps isn't as precise.



I also plumbed in a tee for a temperature sensor and one for a poor man's acid injection because I like the ideal of small doses rather than large swings every handful of days (borates helps a ton with the frequency though). I didn't have room for a check valve and a 3 way valve wouldn't work without adding a bunch of elbows. Just couldn't think of a better way to do this! Figure if I get an intellivalve for the bypass, I'll just put it on the bypass valve to open and partially close for heater mode, leaving the heater always open.


Also, the pump now has to run at about 1800RPM to close the solar VRV, which is now all the way up to 45GPM and only ~400w so $10/mo if run for 6 hours a day all month long.

 

[mas985]

If you can move the VRV closer to the pump, you might be able to reduce the RPM even further.

 

[matthewsunshineflorida]

If you can move the VRV closer to the pump, you might be able to reduce the RPM even further.

I was wondering about that - I would prefer to be able to run solar starting at about 25gpm (probably 1100 RPM) and ramp up like I had before the bypass. It's about 12ft up on the supply side so I'm not sure how much further down is ideal?

I'm also realizing I might have a suction side leak - good bit of bubbles at low pump speeds. Unnoticeable with the bypass off which is so strange! I tried briefly setting the SWG to 1% but they seem unchanged. I guess I'll fully close the solar valves and see what changes if I suck from the main drains vs skimmer vs spa?

 

[mas985]

I was wondering about that - I would prefer to be able to run solar starting at about 25gpm (probably 1100 RPM) and ramp up like I had before the bypass. It's about 12ft up on the supply side so I'm not sure how much further down is ideal?

You could drop to as low as 6' above the pump.

I'm also realizing I might have a suction side leak - good bit of bubbles at low pump speeds. Unnoticeable with the bypass off which is so strange! I tried briefly setting the SWG to 1% but they seem unchanged. I guess I'll fully close the solar valves and see what changes if I suck from the main drains vs skimmer vs spa?

Are you sure that isn't the VRV opening? If the pressure is very close to 0 PSI at the VRV, it can suck in air. Raise the RPM and see if it goes away.

A suction side air leak would show up in the pump basket. Especially at lower speeds.

 

[matthewsunshineflorida]

You could drop to as low as 6' above the pump.


Are you sure that isn't the VRV opening? If the pressure is very close to 0 PSI at the VRV, it can suck in air. Raise the RPM and see if it goes away.

A suction side air leak would show up in the pump basket. Especially at lower speeds.

Good call on that - you're right that it's the solar. No bubbles when the solar is on, no bubbles when it's off in the morning, but when it turns off after hitting temp - I get bubbles as it drains. Isn't that strange? There's a check valve on the return side, and a 3 solar way valve on the supply side (my understanding is it has a tiny reverse check valve to allow draining). I also have isolation valves and if I turn off both of those, the bubbles stop. Obviously, while it's draining, the VRV is allowing air into the system, but the valve is closed so I'm not sure how that air could be pushed back through the returns.

When the pump is up higher, it doesn't allow the solar to drain so no bubbles - and since the bypass caused the pump to ramp up higher, turning that on pretty much eliminates the bubbles as well.

Not a huge issue, but I'd like to at least understand why - since I'll be fighting the ph a little more.

 

[mas985]

Not a huge issue, but I'd like to at least understand why - since I'll be fighting the ph a little more.

Pressure in the supply pipe drops with increasing elevation (i.e. static head). The higher in elevation the VRV is located, the more pressure at the pump (i.e. higher RPM) is required to keep the VRV closed. This is why I suggested lowering the VRV.

 

[matthewsunshineflorida]

Pressure in the supply pipe drops with increasing elevation (i.e. static head). The higher in elevation the VRV is located, the more pressure at the pump (i.e. higher RPM) is required to keep the VRV closed. This is why I suggested lowering the VRV.

I think I get that but (apologies if I'm not understanding!), but I'm saying when the solar is OFF, the supply side solar valve closes and the return side is a check valve so theoretically no water can get up through the supply side and only down from the return side. If the pump pressure is low enough, the solar can drain even while it's on (which seems like a good idea to me) because it drains through both the check valve and through the reverse check valve built into the 3 way solar valve. This is when I get bubbles.

In that scenario, I get how air is being released into the system through the VRV to prevent a vacuum condition as water escapes the panels, but I don't understand why air is pushed all the way through them back down into the pool. Once the panels are fully empty, this behavior stops, so it's almost as if the solar draining is also pulling air behind it, even though there's no pump pressure to push air down like that?

 

[mas985]

No, my bad. I misunderstood what you were saying.

When the solar valve is OFF, then you should not get any bubbles at least from the solar VRV. However, is there any air in the pump basket during this time? If so, then it is likely a suction side air leak.

 

[matthewsunshineflorida]

No, my bad. I misunderstood what you were saying.

When the solar valve is OFF, then you should not get any bubbles at least from the solar VRV. However, is there any air in the pump basket during this time? If so, then it is likely a suction side air leak.

Nope, you were right about that - no bubbles in the pump basket, and I can completely eliminate the behavior if I turn the two pentair 2 way valves off separately to entirely isolate the solar system. Thought I had a suction side leak but you were absolutely correct that it clearly has something to do with the VRV and solar - I just don't quite know how.

 

[mas985]

Ok, then the only thing I can think of is that the solar valve is not actually shutting off the flow to the solar panels. Have you taken it apart to look at the internal check valve? Those can and do fail allowing water to fill the solar panels and drain down. Just not as quickly as it would when open.