2nd backup pump in parallel with 1st. Do I need a 3 port on both inlet and outlet?

[a34536]

I have a 2nd pump plumbed in parallel with the 1st. The 2nd pump is smaller than the 1st. I only use 1 at a time, and I manually switch both 3 port valves to block off inlet and outlet of the pump not in use.

My question is, If I want to automate the switching between the 2 pumps, do I need an actuator on each 3-port and replicate what I do now manually, or can I open one 3 port to both pumps and put an actuator on the other to switch between them. I already have the electrical switching in place, so just asking about the water flow.

If I just use 1 actuator should I put it on the inlet or outlet 3-port?

If the actuator fails and the pump electrically switches to the other, I'll automatically detect that no water is flowing and switch off the pump after 30 seconds, but for that time period, the pump is either pushing or pulling against a closed valve. Is one better than the other?

Cheers.

 

[1poolman1]

Not sure why a back-up pump, but actuator in the of the pumps and check valve after each of the pumps. Place a T fitting in place of the second 3 port.

 

[willygee]

Dual parallel pump back up unit....I'm liking this. I keep a spare V Green motor and a retired 12 year old single speed (works fine) for my 2 speed Hayward Tristar.

 

[a34536]

Not sure why a back-up pump

A very fair question! Pump1 is a single speed 3 phase pump that I run from my UK domestic single phase supply using a commercial inverter motor drive which gives me fully variable speed which I have integrated into my home automation, along with all the actuator switching for solar, ASHP, etc. Been working well for 7 years, and way way lower cost than buying a variable pool pump in the UK.
If either the pump or the inverter fails however, then there's likely to be a delay while I get replacement parts. If this happens during the pool season, then I have a problem.

My old pump was single speed single phase and still works fine, so I plumbed it in as pump2. I'd now like to automatically switch to it once per week to keep everything operating properly.

Here's what it all looks like. I'm doing some mods which is why there are a couple of valves that go nowhere!

 

[Bperry]

A very fair question! Pump1 is a single speed 3 phase pump that I run from my UK domestic single phase supply using a commercial inverter motor drive which gives me fully variable speed which I have integrated into my home automation, along with all the actuator switching for solar, ASHP, etc. Been working well for 7 years, and way way lower cost than buying a variable pool pump in the UK.
If either the pump or the inverter fails however, then there's likely to be a delay while I get replacement parts. If this happens during the pool season, then I have a problem.

My old pump was single speed single phase and still works fine, so I plumbed it in as pump2. I'd now like to automatically switch to it once per week to keep everything operating properly.

Here's what it all looks like. I'm doing some mods which is why there are a couple of valves that go nowhere!

View attachment 459049

Why not just keep the backup pump in a box and switch it out if there’s a failure with the original? A few days or a week without a pump on isn’t a big deal as long as you can manually dose chlorine.

 

[willygee]

Why not just keep the backup pump in a box and switch it out if there’s a failure with the original? A few days or a week without a pump on isn’t a big deal as long as you can manually dose chlorine.

One in the box untested...parallel pump military ready...

 

[Bperry]

One in the box untested...parallel pump military ready...

Cool. Just making sure the OP realizes that military readiness isn’t required for a residential pool and would be just fine for some time even without a pump running. But I get some folks are into the super tech thing.

 

[flynwill]

I would be very cautious about using automated 3-port valves in this application, if either valve fails to move when you select the backup pump the pump could be "dead headed" and bad things occur (burst pipes, burned out pump).
I would suggest adding 2 check valves. One in series with the output of each of the two pumps, and then set your two existing 3-port valves to the "all open" position.

 

[a34536]

bad things occur

Yes, this was my concern.

I don't really have the space for the check valves without rearranging more of the plumbing.

I've decided I will add the actuators to the 3 ways, but will keep the switching of those actuators as a manual activity. I can then visually verify the valves have moved using a camera I already have set up in the pool shed before switching the 2nd pump on. Yes I am being lazy!