Grundfos SCALA2 Water Pump with External Pressure Tank

[vcs]

Grundfos SCALA2 Water Pump with External Pressure Tank

This is a example utilizing an External Pressure Tank in conjunction with a SCALA2

The SCALA2 utilizes a 10psi pressure range between starting and stoping.

Do the following 2 steps with the SCALA2 turned off and no pressure on the system:

1. Fill the SCALA2 Internal Pressure Tank to 36psi* see footnote.

2. Fill the empty External Pressure Tank to 42psi^ see footnote.

Turn on the SCALA2, press single center light, this starts SCALA2 at 42psi, stops it at 52psi.
————————————————————————————————————————————

The following tests were performed to show the the benefit utilizing the External Pressure Tank

TEST #1- SCALA2 WITHOUT EXTERNAL PRESSURE TANK:
Opened faucet, let 8 ounces of water per minute go down the sink drain. With the SCALA2 operating WITHOUT the External Pressure Tank - the SCALA2 cycled on/off EVERY 1-1/2 minutes.

TEST #2 - SCALA2 WITH EXTERNAL PRESSURE TANK:
Opened faucet, let 8 ounces of water per minute go down the sink drain. The SCALA2 operating WITH the External Pressure Tank - the SCALA2 cycled on/off EVERY 2 HOURS.

Even though the entire capacity of the pressure tank is not used - this is due to the SCALA2's pressure range of 10psi - the pressure tank addition makes a significant difference. This will not only save energy by eliminating the demand of constant start/stop cycling due to ice makers, drinking water treatment systems, turning faucets on/off, leaks, etc, it will also extend the life of the SCALA2.


Footnotes:

This is the Grundfos recommended setting for the Internal Pressure Tank listed in the Grundfos SCALA2 Instructions at the bottom of page 13 - 70% of the outlet pressure or stoping pressure. In above with the single center light setting the outlet/stopping pressure is 52psi. (0.7 x 52psi = 36psi)

^ The External Pressure Tank used is an Amtrol WX-302, 24”dia, 48” height. Set External and Internal
pressure tanks when SCALA2 is turned off and there is no pressure on system.

09/06/2021

 

[Valveman]

Wow! A WX302 is an 86 gallon tank that holds 20 gallons of water. You don't really need anything but a pressure switch to control the pump when you have a tank that large. The whole advertising gimmick with the Scala is that you don't need a pressure tank? But I agree they will last longer when used with a big pressure tank, you just don't get very constant pressure or save any money with a tank that large. Even if the large tank is saving energy, which I agree it will, for house use it will take 77 years worth of energy savings to pay off that 500+ dollar tank.

I replace a lot of those Scala pumps with a regular jet pump and a PK1A kit using a 4.5 gallon size tank. This cost much less than a Scala, will give you real constant pressure, and last 30+ years. Of course that is why manufacturers push the short lived VFD pumps like the Scala instead of a long lasting and inexpensive CSV. You are spending your time and money re-engineering the Scala when all you should have to do is use a PK1A so water comes out when you open a faucet.

 

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[Cclodomir]

Grundfos SCALA2 Water Pump with External Pressure Tank

This is a example utilizing an External Pressure Tank in conjunction with a SCALA2

The SCALA2 utilizes a 10psi pressure range between starting and stoping.

Do the following 2 steps with the SCALA2 turned off and no pressure on the system:

1. Fill the SCALA2 Internal Pressure Tank to 36psi* see footnote.

2. Fill the empty External Pressure Tank to 42psi^ see footnote.

Turn on the SCALA2, press single center light, this starts SCALA2 at 42psi, stops it at 52psi.
————————————————————————————————————————————

The following tests were performed to show the the benefit utilizing the External Pressure Tank

TEST #1- SCALA2 WITHOUT EXTERNAL PRESSURE TANK:
Opened faucet, let 8 ounces of water per minute go down the sink drain. With the SCALA2 operating WITHOUT the External Pressure Tank - the SCALA2 cycled on/off EVERY 1-1/2 minutes.

TEST #2 - SCALA2 WITH EXTERNAL PRESSURE TANK:
Opened faucet, let 8 ounces of water per minute go down the sink drain. The SCALA2 operating WITH the External Pressure Tank - the SCALA2 cycled on/off EVERY 2 HOURS.

Even though the entire capacity of the pressure tank is not used - this is due to the SCALA2's pressure range of 10psi - the pressure tank addition makes a significant difference. This will not only save energy by eliminating the demand of constant start/stop cycling due to ice makers, drinking water treatment systems, turning faucets on/off, leaks, etc, it will also extend the life of the SCALA2.


Footnotes:

This is the Grundfos recommended setting for the Internal Pressure Tank listed in the Grundfos SCALA2 Instructions at the bottom of page 13 - 70% of the outlet pressure or stoping pressure. In above with the single center light setting the outlet/stopping pressure is 52psi. (0.7 x 52psi = 36psi)

^ The External Pressure Tank used is an Amtrol WX-302, 24”dia, 48” height. Set External and Internal
pressure tanks when SCALA2 is turned off and there is no pressure on system.

09/06/2021

Very interesting. I run a scala2 in my first house with no problems (without an external tank).

You're post was so helpful that I just bought a second one for my mountain home and pair it with a GouldsV350 external pressure tank. The guys at the store also told me I could pair them, but they weren't helpful on the PSI settings.

Quick question, so it's essential that the PSI in the external pressure tank is 6psi above the scala2? Because 36psi setting in the scala2 equates to the second green light from the bottom.

Let's say I want to set my scala2 at the middle green light which is 51psi. How much psi to put in my GouldsV350 pressure tank?

Thank you for advising.

 

[Valveman]

Even if you have had no problems and purchased one of the first Scala pumps that came out, they haven't even been available long enough to have a track record. There are a few on lightly used water systems that may last a few years, but most do not. Adding a huge 119 gallon pressure tank to a pump that is not supposed to need any tank is a waste of money and space. With that huge tank even a cheap jet pump would outlast a Scala, and would be much less expensive to purchase.

 

[Cclodomir]

Even if you have had no problems and purchased one of the first Scala pumps that came out, they haven't even been available long enough to have a track record. There are a few on lightly used water systems that may last a few years, but most do not. Adding a huge 119 gallon pressure tank to a pump that is not supposed to need any tank is a waste of money and space. With that huge tank even a cheap jet pump would outlast a Scala, and would be much less expensive to purchase.

I hear you, but :
#1: I already have the pressure tank
#2: The site has zero grid power and fully runs on solar
# 3 House is under decent tree canopy, no full sun
#4 No city water. I have a shallow well

I basically want pressure while minimizing the amount of time my pump turns on. I currently run a 1/2hp jet pump at 40/20 psi (tank is at 18 psi), while it works it runs for 10 minutes straight every time , and I drain my precious energy.

 

[Valveman]

The Scala maybe easier to start on a battery system, but it runs longer to produce a gallon than a regular pump/pressure tank, and will use more energy in the long run. Your best bet maybe a 12V RV pump as they are DC and use very little energy. Just converting DC to AC with an inverter has considerable energy loss.