How should this valve be positioned? Heater bypass

You only need the check valve if you want to be able to take the heater offline or if you have a tab feeder.

If your flow will be over 70 gpm, I would do the 5 psi check valve bypass.

You can add the additional Jandy check valve if you want to be able to take the heater offline.

Do you have a tab feeder?

How do you chlorinate?

Do you have a SWG or plan to get one?

Some heat pumps like the Pentair UltraTemp have an internal bypass that helps manage excess water flow, but it looks like the Aquacal does not.

The UltraTemp internal bypass is a 12 psi check valve, so it really won't do what it is supposed to do because the head loss never gets to 12 psi.

The chart shows the head loss topping out at about 9 psi.

Some heater manuals require a check valve for a tab feeder or a SWG.

The Aquacal recommends a Hartford loop for a tab feeder but there are no requirements or recommendations for a SWG.

For a tab feeder, you really need a corrosion resistant check valve to protect a heater as a Hartford loop really won't prevent backflow of corrosive chlorine from a tab feeder when the pump is off.

In fact, I would never have tabs in a tab feeder with the pump off.

The second the pump turns off, the liquid in the feeder begins to migrate out from the feeder and it will destroy everything it touches.

Tab feeder liquid is very acidic and it is a very strong oxidizer, which is an especially corrosive combination far more corrosive than acid or chlorine by itself.

If a feeder contains tabs, the only way to protect the system is to keep the pump running continuously.