geothermal pool heater

[jb27733]

I work for a PHC company, we have been installed geothermal units for a few years. Our System Engineer (salesman) sold a 5 Ton water to water heating a 50 gallon storage tank. It has one zone of floor heat for the winter and one zone set up for pool heat in summer. It has a weil mclain 95k btu pool heat exchanger. I set the tank temp to 110 deg, the geo is heating the storage tank ok, but i am getting 2 deg drop on return back to tank from the pool heater. I've changed the speed on the grundfos pump to low,(3 speed up 26-99) installed a by-pass aroung the heat exchanger. this is the only way I can get any temp drop on the water, I'm not making any headway on the heating. I'm leaning to the size of the pool heater needing to be bigger, due to the fact that the geo is getting short run times (5 min) and maintaing the storage tank at 110 deg. I can't get the pool heater to use all the heat i'm putting in to it. Any input would be appreciated.

[dan sw fl]

... System Engineer (salesman) sold a 5 Ton water to water heating a 50 gallon storage tank. ... It has a weil mclain 95k btu pool heat exchanger. I set the tank temp to 110 deg, the geo is heating the storage tank ok, but i am getting 2 deg drop on return back to tank from the pool heater.

I've changed the speed on the grundfos pump to low,(3 speed up 26-99) installed a by-pass aroung the heat exchanger.

.. , I'm not making any headway on the heating.
I can't get the pool heater to use all the heat i'm putting in to it. Any input would be appreciated.

Raise the hot water storage tank temperature.
What is the desired pool water temperature?
What is the current pool water temeprature?

Where are you located?
Current outside air daily average temp is ?

What is the pool loop water flow to the HX?
What is the storage tank loop water flow to the HX?

Weil McClain 95K pool HX should be able to maintain pool (~16'x 32') water temperature > 22'F above average Daily outside air temperature.
i.e. daily high 70', low 50', average 60'F, pool should be able hold 82'F
if the heating system is set-up properly.

[progressive]

How is the pool zone isolated from the floor zone?

[jb27733]

After getting no help from weil mcclain, they didn't even want to talk to me about using their heaters for geo, they are designed for boiler use. So I talked to another supplier in MN. who has used flat plate heat exchangers for geo pool heat. Flat plate has a handy sizing calculator on their web site to size everything up. I need to increase the size of the heat exchanger surface area since I am only supplying 110 deg water at 12 gpm. I have a target temp of 80 deg. the pool is flowing 80 gpm thru the hx. We are in the midwest. The pool will have to be covered when not in use. So after getting some crap from the pool guys for not using a 82% efficient boiler, if the numbers come out right, I will use 60k btu geo running 17hours a day at 350% efficiency to heat a 44,000 gallon pool to 80 deg.:cool:

[Ecacophonix]

I do a good amount of work in oil & biodiesel from algae (http://www.oilgae.com), so geothermal is not exactly my expertise, but I wish to know whether geothermal can scale...from what I understand it might be a good idea for local consumption, but that's about it?

All the same, interesting discussion...am hoping that the country I live in (India) also gets to speed on geo

NS @ Oilgae.com - Oil from Algae (http://www.oilgae.com)

[firecontrol]

I need to increase the size of the heat exchanger surface area since I am only supplying 110 deg water at 12 gpm.

I have a target temp of 80 deg. the pool is flowing 80 gpm thru the hx. We are in the midwest. The pool will have to be covered when not in use. So after getting some crap from the pool guys for not using a 82% efficient boiler, if the numbers come out right, I will use 60k btu geo running 17hours a day at 350% efficiency to heat a 44,000 gallon pool to 80 deg.:cool:

The 12gpm @ 110°F with a drop of 2°F is only delivering about 11,500 btu's/hr
according to my calculations and my guess is that this won't go very far to heat even maintain a small pool.

If the HX that you have will take 80gpm flow on one side of it hopefully it'll take the same on the other side. With a potential of somewhere around 60,000 btu's/hr available from the geothermal unit you will need to up the flow on the tank side to the HX to 377gpm if you want to continue to only drop 2°F across the HX on the tank side.

:confused: Now if I did all the math right I'm thinking that increasing the temperature in the tank to a point that will allow for more temperature difference between the pool water temp you'll get more transfer.

It's projects like this that have taught me to do the math before I leave for the jobsite.

[dan sw fl]

After getting no help from weil mcclain, they didn't even want to talk to me about using their heaters for geo, they are designed for boiler use. So I talked to another supplier in MN. who has used flat plate heat exchangers for geo pool heat. Flat plate has a handy sizing calculator on their web site to size everything up. I need to increase the size of the heat exchanger surface area since I am only supplying 110 deg water at 12 gpm. I have a target temp of 80 deg. the pool is flowing 80 gpm thru the hx. We are in the midwest. The pool will have to be covered when not in use. So after getting some crap from the pool guys for not using a 82% efficient boiler, if the numbers come out right, I will use 60k btu geo running 17 hours a day at 350% efficiency to heat a 44,000 gallon pool to 80 deg.:cool:

You do not need to flow 80 GPM through the HX. A by-pass of 18 GPM (@ ~7psi [16 feet ] pressure drop) is more than enough with an 8'F temperature difference across the HX itself. The heated return can be mixed with the non-heated return will a resultant increase of ~1.8'F.
Plate HX: 5"x 12" x3", 24 plates. weight < 11#.