Heat pump install date August 2007 Updated and replaced 80 gallon tank with Pside-Kick
kit and 4.5 gallon pressure tank December 2012
My well is a low producing well that only makes 4 GPM. The well has a couple of hundred gallons of storage on top of the recovery rate of 4 GPM. So my well pump can produce up to 10 GPM for short periods of time. My heat pump needs a minimum of 4 GPM for long periods of time. The peak domestic use for the house is 10 GPM. I would have needed 14 GPM to supply both at the same time, which the well and pump is not able to do.
So I tied in my domestic water to the discharge side of the heat pump instead of the inlet side. Now all the water goes through the heat exchanger before it gets used for domestic use in the house.
When the house is using more than 4 GPM while the heat pump is running, the extra flow through the heat pump reduces the temperature differential, and makes the heat pump more efficient. When the house is not using any water, and the heat pump is on, 4 GPM is being dumped into an earth tank for livestock use. This way a 10 GPM pump is adequate to supply the heat pump and the domestic use. I was able to use a 1/3 HP well pump. This 1/3 HP pump supplies the heat pump, the house, a barn, a guest house, a little irrigation, two small wildlife watering stations, and an ornamental fountain, before the excess goes to the livestock tank, where I also raise fish. This not only makes the most use of the limited water available but, also requires a smaller well pump, which saves energy on pumping cost for the Geo system.
The well pump was already running 24/7 at a cost of about $70 per month, to supply the water for livestock. I am just pulling the heat out of the water and supplying the houses before it goes to the livestock tank, which basically means my heat and domestic water supply is free.
The showers in the main house are the only place where we notice the change in temperature for using the discharge water from the heat pump. When the AC is on, the cold water in the shower is almost perfect without adding any hot water, which saves energy and hot water. When the heat is on, the cold water in the house is a little colder, so we have to add more hot water to adjust the shower temperature. With a 50 gallon water heater, we still have plenty of hot water. The change in the water temperature for the house is not even noticed by the toilets, sinks, ice maker, or washing machines.
The discharge water from the heat pump at the main house travels about 1,200 feet to feed domestic water to the barn and guest house. By the time it gets there it is already back to ground temperature, and no one at the guest house notices a temperature change from the heat pump at the main house.
The only concern I had was the quality of the water discharging from the heat pump (copper) coming through the heat exchanger to feed the house domestic supply.
Got the water tested. (August 2009) Copper was 33 ppb, and the EPA says the acceptable level of copper is 1300 ppb. This sample was taken after the heat exchanger and all the way to the other side of the house, which is all copper pipes. The system is less than 2 years old, so it should get even better with age as the green patina covers the inside of the copper pipes. Everything else tested below the detection limit of 5 ppb.
Update; 12/03/14
This system is now about 8 years old and we have had no problems. Teeing in the domestic water on the discharge side instead of the inlet side of the heat pump has saved a considerable amount of water and energy. In this way the same water gets used at least twice for the same expense.
The well pump has never shut off except during a few power outages, and then only for short periods of time. Pumps like to run 24/7, so the pump should last many times longer than a well pump that cycles on and off frequently.
Conclusion;
Teeing the water for the house domestic use on the discharge side of the heat pump has many benefits. It allows the use of a much smaller, less expensive pump, which saves considerable energy and water compared to the traditional way of teeing in the house supply on the inlet side of the heat pump.
