Iron Filter & Ground Source Heat Pump

[cdods]

When I converted to a GSHP last year I was unable to get a straight answer how how to plumb both the Iron filter and GSHP, so I just disconnected the Iron Filer. My iron bacteria problems are back - so it's time to figure this out.

The iron filter is a Culligan Rust Master (air injection) iron filter. For a number of reasons I can't have the water for the GSHP pass through the air injection "pump".

So I've come up with the following idea. Can anyone tell me if this will or won't work, or provide me with some alternatives. If you think it will work, I'd like some advice on sizing the pressure tank for the GSHP as well as how to figure out what good pressure settings would be on this pressure tank.


The idea: Tee the well discharge to two pressure tanks, one for the household water (which will run through the iron filter), and one connected to the GSHP.

After between the tee and and the household pressure thank, I'd place first a check valve (to prevent the GSHP tank from pulling water backwards through the air injector, and then the air injector).

The two pressure switches (one on each pressure tank) would be connected in parallel), such that if either or both of them dropped below the cut-on pressure, the well pump would be turned on.

So it would look like this:

------ GSHP Pressure Tank
well -|
---- Check Valve ---- Air Injector ---- Household Pressure Tank

Thoughts, comments and advice all are appreciated.

Thanks.

 

[Valveman]

You can’t size a pressure tank to work with a GSHP. Even a huge pressure tank would still cause the pump to cycle far too often, while the pressure and flow through the heat pump would be continually varying. You need to size the pump to the GSHP. Attached is a drawing of the most efficient way I know to set up a heat pump. Using this drawing, you would only need the filter after the booster pump to the house.

 

[Sponsor]

 

[cdods]

Valveman,

Thanks for the advice. When my well pump dies, I may very well go to a two pump system as you've described. However at the moment the current single pump system works, and doesn't seem to cycle too often.

I'm specifically interested in whether the two pressure tank system I've described will cause any any problems.

 

[Valveman]

You might make that work. I would put the pressure tank after the GSHP, so the temp of the water in the tank is not a problem. This line will also need a check valve.

Splitting the flow through two pipes may not be enough volume to make the air injector work.

Are you injecting air into a bladder type tank? This could be a problem.

I hear a lot of people say their pump doesn't cycle very much. When I pin them down, they say "oh, only every 5 or 10 minutes". Cycling every 10 minutes is 144 cycles per day. Every 5 minutes is 288 cycles per day. I also hear a lot of people say their heat pump actually cost them more than a standard furnas, because they have to buy a new pump every 2 or 3 years. I have one myself, heat pumps are a good idea as long as you don'e cycle your pump to death regularly.

 

[dancour]

Your math may be right "Cycling every 10 minutes is 144 cycles per day", but who runs their pump 24 hours a day?

 

[Gary Slusser]

You can't filter IRB, and air isn't going to kill IRB, it can make the problem worse. IRB is a large group of both aerobic and anaerobic bacteria.

 

[NHmaster]

Full circle, back to that chlorine thing again

 

[Valveman]

Your math may be right "Cycling every 10 minutes is 144 cycles per day", but who runs their pump 24 hours a day?

Heat pumps usually run many hours per day. If yours runs only 12 hours per day, then that is 72 cycles per day. Running 6 hours would be 36 cycles per day. Only 36 cycles per day is still 13,140 cycles per year. 12 hours per day would be 26,280 cycles per year and so on. The fewer number of cycles, the longer your pump will last. The longer your pump last, the more a heat pump can save.

 

[dancour]

Sounds like a salesman with a calculator. "Only 36 cycles per day is still 13,140 cycles per year."

Well, who runs their heat pump 365 days a year ?

PS I did buy a CSV ....

 

[NHmaster]

people with heat and A/C run their heat pump every day.
Pump cycling and it's associated cost are one of the factors that GWHP salesmen will often try to avoid revealing.

 

[Valveman]

Sounds like a salesman with a calculator. "Only 36 cycles per day is still 13,140 cycles per year."

Well, who runs their heat pump 365 days a year ?

Where I live it is either hot or it is cold. There are very few days where I would not touch the thermostat. Somedays we even run the heater at night and the AC during the day. My heat pump runs an average of about 6 hours a day. You can use your calculator to add up the cycles per year but, it is still a lot of cycling. Cycling is the major cause of pump system failure, which is the most common reason for a heat pump not to be able to save money.