I no longer believe the thump is from a check valve. I realized the intake pressure going up to 40 from 30 when the pump stopped was the pressure of the moving water get trapped on the house side of the system check valve. This time I could hear the inlet check valve close with a very small click. I removed the outlet check valve and reinstalled the inlet check valve. Initially the pump stopped thumping and ran better but it did not last, it began thumping again within the hour. My biggest question is this something that a functioning inlet check will fix or is it likely a design flaw and should I just get a refund and get a different pump. I'm waiting on the RMA to go through to refund/replace, the pump. The intake pressure jumps around quite a bit during this and I think it confuses the pumps controller and it runs erratically trying to maintain a constant output. When there is a call for water the pump starts and the check valve slams open causing the thump.

It appears that inlet check valve is allowing enough flow backward to pressurize the line between the pump and the check valve where it comes into the house (about 15' of 3/4 cpvc). I finally got around to trouble shooting it today. When I set the pump any higher than 40psi it thumps when it kicks on and then runs erratically, changing rpms sometimes stopping for a split second, which results in another thump when it starts up. 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.I bought and installed a Scala2 pump to help with my low pressure due to elevation. Of course that is why manufacturers push the short lived VFD pumps like the Scala instead of a long lasting and inexpensive CSV. This cost much less than a Scala, will give you real constant pressure, and last 30+ years. I replace a lot of those Scala pumps with a regular jet pump and a PK1A kit using a 4.5 gallon size tank. 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. 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. You don't really need anything but a pressure switch to control the pump when you have a tank that large. Wow! A WX302 is an 86 gallon tank that holds 20 gallons of water. Pressure tanks when SCALA2 is turned off and there is no pressure on system. ^ The External Pressure Tank used is an Amtrol WX-302, 24”dia, 48” height. In above with the single center light setting the outlet/stopping pressure is 52psi. 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. 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. The SCALA2 operating WITH the External Pressure Tank - the SCALA2 cycled on/off EVERY 2 HOURS.Įven 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. Opened faucet, let 8 ounces of water per minute go down the sink drain.

TEST #2 - SCALA2 WITH EXTERNAL PRESSURE TANK: With the SCALA2 operating WITHOUT the External Pressure Tank - the SCALA2 cycled on/off EVERY 1-1/2 minutes. TEST #1- SCALA2 WITHOUT EXTERNAL PRESSURE TANK: The following tests were performed to show the the benefit utilizing the External Pressure Tank Turn on the SCALA2, press single center light, this starts SCALA2 at 42psi, stops it at 52psi. Fill the empty External Pressure Tank to 42psi^ see footnote. Fill the SCALA2 Internal Pressure Tank to 36psi* see footnote.Ģ. The SCALA2 utilizes a 10psi pressure range between starting and stoping.ĭo the following 2 steps with the SCALA2 turned off and no pressure on the system:ġ. This is a example utilizing an External Pressure Tank in conjunction with a SCALA2 Grundfos SCALA2 Water Pump with External Pressure Tank

Grundfos scala 2 testbericht