Does Pentair MasterTemp 400k BTU heater really have a maximum allowed flow rate?

Vegas Mike

Member
Mar 30, 2019
17
Las Vegas, NV
Just bought a house with pool needing work (not the one in my signature). A pool contractor told me the Pentair MasterTemp 400k BTU has a maximum allowed flow rate, so I need to add a diverter valve ahead of it. This seems wildly untrue, but anyone doing something like this? Will be replacing an ancient controller with Pentair EasyTouch 8, and plan to repair and keep the old Pentair MasterTemp. Has a Pentair variable-speed pump. And switching to SWG too.
 

jimbethesda

Gold Supporter
Jul 2, 2018
213
Austin, TX
From the manual (located at https://www.pentair.com/content/dam/extranet/product-related/product-manuals/pool-and-spa-equipment/mastertemp/MasterTemp_Pool_and_Spa_Heater_Installation_and_Users_Guide_English.pdf)

“A manual bypass valve should be installed across the heater when the pump flow exceeds 120 GPM (454 LPM). See “WATER FLOW RATE” on page 13- Table 1 for setting of the manual by-pass valve.”

Also, did you look into IntelliCenter instead of EasyTouch? “Ancient” is relative, but I would call EasyTouch ancient. IntelliCenter is Pentair’s latest automation panel and is similarly priced. I would at least consider it...I love mine.
 

Vegas Mike

Member
Mar 30, 2019
17
Las Vegas, NV
Thanks JimBethesda! I found your reference in the MasterTemp manual. The pump is a Pentair Intelliflow 2, so from the pump curves I could get 150GPM if the pump is at maximum speed, 3450RPM. On my original home the maximum speed I use is 3050RPM. Don't know how much head loss to attribute to filter and piping, but I'm guessing it does not really exceed 120GPM. So looks like you have the same configuration -- do you have a manual bypass valve in front of your heater?
 

Vegas Mike

Member
Mar 30, 2019
17
Las Vegas, NV
Found a pump head calculator from Pentair, Pump Calculator. Using 7psi drop when my CCP420 filter receives 120GPM, maybe 50 foot of 2" piping and some elbows, I get 40 feet head. At that head, IntelliFlow 2 pump at 3110RPM can produce 125GPM. So looks like a manual bypass is unnecessary. I appreciate your help! And thanks for the tip on IntelliCenter.
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
12,725
Pleasanton, CA
Head loss is going to be much higher than 40'. You are missing several items that cause head loss including the heater, skimmers, eyeballs, valves, etc. At most the flow rate will not exceed 100 gpm.
 

JamesW

TFP Expert
Mar 2, 2011
16,359
A pool contractor told me the Pentair MasterTemp 400k BTU has a maximum allowed flow rate, so I need to add a diverter valve ahead of it. This seems wildly untrue, but anyone doing something like this?
Everything has limits on how much flow, pressure, temperature, stress, weight, force, voltage, current etc. it can take.

Why would you think that the heater could take an unlimited amount of flow?

In any case, the heater definitely has a limit on how much flow you should put on it.

There should not be any reason for you to ever exceed about 40 to 63 gallons per minute. So, the limit should be irrelevant.