Heater head loss?

[friendswoodnewbie]

I have been trying to find out what the approximate heater head loss will be for our pool build and have not been able to find good numbers anywhere.

It is a Pentair Mastertemp 400 - I guess very common heater these days....

A Pentair support guy told me it would about 13 ft of head at 30 gpm just for the heater
He also said the head loss would be 14 ft of head @ 50 gpm. That sounds very strange to me:?:

Based on mas985 estimate and other trustworthy information, I had expected the head loss over the entire system to be <6 ft of head @ 30 gpm.

I am getting a manual bypass over the heater which certainly seems like a good idea if it truly has 13 ft of head @ 30 gpm....

Does anybody have better data?

 

[JasonLion]

How did you come up with <6 feet of head?

 

[mas985]

It is really tough to find any data on heaters. I asked Hayward about mine and they gave me 3.25 PSI (7.5') @ 60 GPM. This is about twice what a cartridge filter would produce so I am thinking it isn't too far off.

The head loss in pool plumbing is mainly determined by equipment, valves and fittings. Straight pipe has a minimal impact on overall head loss unless there are extremely long runs. Anyway, because of this, you can use a simple formula to model entire plumbing systems and/or any single piece of plumbing including heaters:

Head Loss (ft) = Hf * GPM^2

For entire plumbing systems, the CEC has defined Hf (head factor) as:

CurveA -> Hf = 0.0167
CurveB -> Hf = 0.05
CurveC -> Hf = 0.0082

The above numbers are for entire plumbing systems but the same methodology can be used for a single component. Here are some of the values that I tend to use for various pieces of equipment:

Heater -> Hf = 0.002
Cart Filter -> Hf = 0.001
Skimmer -> Hf = 0.001
SWG -> Hf = 0.0001

According to Pentair's numbers, Hf would be 0.0144 for just the heater which is more than an entire plumbing system for CEC CurveC so I don't think that can be correct. 14' @ 50 GPM Hf would be 0.0056 which is still pretty large and would be a majority of CurveC head loss so I don't think thats very close either. What I have found with customer support is that it is hit or miss and sometimes you have to ask several times before you get someone who actually has a clue.

BTW for CurveC which would be typical of a plumbing system with 2" pipe and single runs, here are the corresponding head loss values for various GPM values:

30 GPM -> 7.4'
40 GPM -> 13.1'
50 GPM -> 20.5'
60 GPM -> 29.5'
70 GPM -> 40.2'
80 GPM -> 52.5'
90 GPM -> 66.4'

 

[friendswoodnewbie]

Mark,
I guess you answered both Jason's question and mine in one post :-D
Since I have 2 and 2.5" plumbing and separate runs I would think the 6 ft of head @ 30 gpm sounds realistic.
Do you know how a DE filter compares to a cartridge filter? I would expect it to be higher since it has finer filtering and lower flow area - both leading to higher head loss.
Actually Pentair has a curve of the head loss over the Quad DE 100 filter. Maybe I will just assume that the heater is comparable to that?

 

[mas985]

Yes, 6' @ 30 GPM is realistic and would have a plumbing curve Hf of 0.0067 which is close to my plumbing.

DE filters usually have higher head loss than a cartridge but it depends on the type of backwash valve. Pentair filters will usually have a pressure loss curve included with the filter manual. They also have the losses for the backwash valves if it is not included in the manual.