Need some help sizing a pump

[Voltrax]

Hi,

I am running to a problem with a pump and am working with the original installer to get it resolved but have concerns and am looking for any insight which can be provided.

In 2005, the well was put in. Here is the info on the well:
375 Total Feet
Pump set at 250 feet
Water Level at 150 feet
Casing down to 140 Feet
Approximately 30 feet from the well to inlet in house.

Original pump was a Franklin Jacuzzi SandHandler 18gpm with a 1.5hp motor tied to a Constant pressure SubDrive 75.

The house has a 4 ton geothermal (open loop) unit which can pull between 8 and 10 gpm, otherwise typical household water usage. The PSI is set to 50psi constant pressure.

After 13 years the motor and pump have died.

The driller has put in a 10gpm Franklin tri-seal 4400 with a 1.5hp motor and says it is sufficient to run the geothermal and normal household usage. I have concerns that it is not and it may need a larger pump.

The driller calculates a the feet of head just shy of 400ft (385ish). Is this the feet of head referred to on the performance curves from the manufactures? If so, then the 18gpm pump was only putting out 10ish gpm according to the spec sheet I got. The driller says the 20gpm pump doesnt have the performance to hit that head figure and I would need to bump up the subdrive75 to the subdrive100 in addition to the pump raising the bill quite substantially.

Given the track record of the constant pressure pumps, it seems like mine is on borrowed time to begin with.

 

[Reach4]

The driller has put in a 10gpm Franklin tri-seal 4400 with a 1.5hp motor and says it is sufficient to run the geothermal and normal household usage. I have concerns that it is not and it may need a larger pump.

A 1.5 HP pump for geothermal does not seem efficient.

There is an easier method than the total head method; there are tables. The tables have the same info as the curves, but are easier to follow for the less experienced.

Either the 10 gpm 1HP or 1.5 HP would work. The 1 HP would reduce the water delivery as you were ready to run out of water.

The PSI column is the PSI in the house. You might typically use a 40/60 psi pressure switch setting.

The horizontal pressure loss is relatively small. Note that the depth to water from the table would be increased by any rise to the pressure switch. So if the well is downhill from the well, take that into account.

I snipped the table from a Franklin V catalog, but there is a similar table for4" TRI-SEAL PUMPS - 10 GPM on page 21 of http://www.franklinwater.com/media/238127/MF5060_FPS_Residential_Submersible_Catalog-1-.pdf

 

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[Voltrax]

Thanks for the information.

Is the depth on the chart the water level during a draw? So if its sitting at 150 and drops 20 during draw, I would be looking at the numbers for 160 or 180 which are 11gpm at 1.5hp (60 PSI)? Using the same chart for the old pump it was rated at 16gpm and 15gpm.

If the new pump is 11gpm and the geo uses 8gpm, is that sufficient for the rest of the household usage (two showers going at one time) given the pressure tank for the subdrive is only 4 gallons?

The well was rated at 50gpm when it was drilled, however it may be different now.

 

[Reach4]

Is the depth on the chart the water level during a draw? So if its sitting at 150 and drops 20 during draw, I would be looking at the numbers for 160 or 180 which are 11gpm at 1.5hp (60 PSI)?

Yes.

If the new pump is 11gpm and the geo uses 8gpm, is that sufficient for the rest of the household usage (two showers going at one time) given the pressure tank for the subdrive is only 4 gallons?

I would think so. I expect that as the pressure drops, the geo actually draws less than the 8.

8 seems a lot for the geo. Is that measured, or it maybe a max from a spec sheet?

 

[Voltrax]

Its limited with an 8 gallon restrictor. The spec says 8-12 depending if the second stage kicks in. The way that it is set up, I dont think it can go over 8gpm unless I put a second taco valve in without restriction.

 

[VAWellDriller]

To properly size this pump you have to know the drawdown...PERIOD...anything anybody says without that knowledge is speculation. I would go back with same flow series you had if pressure and flow were good for house and geo system. Maybe the original installer had a little more information. It will be cheaper that the 10gpm pump also. I run a Franklin 1.5hp 20 gpm on open loop geo at my house...got two 3 ton units and use a CSV.

 

[Voltrax]

They were the original driller, but they don't seem to have that figure. The pump that was in it is no longer made which is where the problem occurs.

 

[VAWellDriller]

Every brand of pump makes something close now... some have 18gpm series pumps some call then 15 or 20 gpm series. There are minor differences among brands but a 15gpm series 1.5 hp would be slightly more conservative pick regarding drawdown as compared to the old 18gpm.

 

[Voltrax]

Just to update, the driller fixed the pipe they cracked by over torquing it and left the 10gpm pump installed. With Geothermal running and two showers on, the pressure goes from 60psi to 40psi so its not sufficient and it hasn't been sized appropriately. I am trying to work with them but am having some problems getting them to correct it. I'll post a resolution when I have one.

 

[Reach4]

Just to update, the driller fixed the pipe they cracked by over torquing it and left the 10gpm pump installed. With Geothermal running and two showers on, the pressure goes from 60psi to 40psi so its not sufficient and it hasn't been sized appropriately. I am trying to work with them but am having some problems getting them to correct it. I'll post a resolution when I have one.

Sounds like a non-problem to me. Would you notice if you were not looking at the pressure gauge? I am not a plumber or other pro.

Nice that the cracked pipe was found and fixed. Was that schedule 80 PVC down the well?

 

[Valveman]

It would actually be better if it dropped to 20 PSI when running the Geo. 20 PSI is all the Geo system needs, and any extra pressure is just wasting energy as the pump is larger than needed. If you increase the size of the well pump, the energy consumption will also increase. Since you need about a 1/2HP more pump to get the pressure from 40 to 60, you might consider adding a little 1/2HP jet pump to boost pressure just to the house. This would actually drop the pressure to the Geo to 30 or maybe 20 PSI, which is still OK. But the booster pump would pick up water from the well pump at 20-30 PSI, and boost it to 50-60 like you want when the house needs water. In this way you are still using the smallest pump possible to keep the Geo system efficient, and the extra 1/2 horsepower pump only comes on a few minutes a day when the house is using water.

 

[Voltrax]

Sounds like a non-problem to me. Would you notice if you were not looking at the pressure gauge? I am not a plumber or other pro.

Nice that the cracked pipe was found and fixed. Was that schedule 80 PVC down the well?

I noticed before looking at the gauge, with the geothermal on, and a tub drawing water, PSI is down to 20, anything additional, and it drops further.
The pipe was PVC, not sure what schedule it was.

 

[Voltrax]

It would actually be better if it dropped to 20 PSI when running the Geo. 20 PSI is all the Geo system needs, and any extra pressure is just wasting energy as the pump is larger than needed. If you increase the size of the well pump, the energy consumption will also increase. Since you need about a 1/2HP more pump to get the pressure from 40 to 60, you might consider adding a little 1/2HP jet pump to boost pressure just to the house. This would actually drop the pressure to the Geo to 30 or maybe 20 PSI, which is still OK. But the booster pump would pick up water from the well pump at 20-30 PSI, and boost it to 50-60 like you want when the house needs water. In this way you are still using the smallest pump possible to keep the Geo system efficient, and the extra 1/2 horsepower pump only comes on a few minutes a day when the house is using water.
View attachment 50159

There is a pressure reducer valve of either 40 or 50 psi in-front of the geothermal. I dont know if 20 is efficient for it, but it doesn't need 60. The info I got today was in 2005, resting water was at 120ft and is currently at 190ft. This has also been the wettest year on record, so there is quite a drop. They are proposing dropping the pump from 250ft to 300ft and upgrading to a 2hp motor from a 1.5hp.

 

[Valveman]

Heat pumps need flow, not pressure. Usually there is a 20 PSI regulator on the inlet to the heat pump. This keeps the flow through the heat pump consistent as the house pressure varies from 40 to 60 with the pressure switch. Going form a 1.5HP to a 2HP will increase your heating/cooling cost by at least 25%. Like I said, you heat pump will work fine at 20 PSI. You may need to adjust the flow control for that pressure, but it will work fine. I would add a 1/2HP jet pump to the line going to the house, and not change the well pump.