Water based heat pump

[Dennis Robitaille]

Came across a first for me today. A water based heat pump (I think).

Manufacturer was Stiebel Eltron. I could not find much in the way of operating details on their web site. So looking for operating info.

There was no exterior unit.
It had a huge water holding tank in the basement (around 250 gallons)
The water for the unit appeared to come off the well for the domestic water supply. The water pump seemed to run part of the time when the HVAC unit ran.
(I always thought a GEO system was a closed system.)

[James Duffin]

Came across a first for me today. A water based heat pump (I think).

Manufacturer was Stiebel Eltron. I could not find much in the way of operating details on their web site. So looking for operating info.

There was no exterior unit.
It had a huge water holding tank in the basement (around 250 gallons)
The water for the unit appeared to come off the well for the domestic water supply. The water pump seemed to run part of the time when the HVAC unit ran.
(I always thought a GEO system was a closed system.)

So you say there is a water makeup valve feeding water to the tank when the level in the tank gets low?

[Dennis Robitaille]

I believe so.

[Scott Patterson]

A ground source, pond, water tank, etc heat pump does not use the water that it's lines are surrounded by other than to dissipate heat/cold.

Now if you have an Apollo type system, it does use the hot water from the water tank for potable water.

[Jerry Peck]

(I always thought a GEO system was a closed system.)


A ground source, pond, water tank, etc heat pump does not use the water that it's lines are surrounded by other than to dissipate heat/cold.

There are closed system and open system geothermal heat pumps.

Closed systems are as Scott described - the coolant (could be water, could have anti-freeze in it, etc.) circulates through piping in the water/earth/etc., and cool or heats from the heat stored in that heat sink (the water/earth/etc.).

Open systems can draw water from a well, a lake/canal/river/etc., or even a large holding tank as in the photo which is supplied with water from any source. This draws the water in, through the evaporator coil, then takes the water back out and into the heat sink source. This replenishment could be via sprinklers, water injection well at some distance from the suction well, pumping the water out into a canal/river/lake/etc., where the water either directly or indirectly finds it way back to the heat sink.

The most common systems I've seen have been open systems which return the water either through sprinklers (there are at least two of these on my street, and several more in the town where I work) or through simply being piped back into a canal/lake/river (there were many of these systems in South Florida where the water was pumped out of the ground and then pumped back into a canal).

An open system is good when you have an endless supply of water.

A closed system is good when you have to protect the piping and heat source from freezing.

[Raymond Wand]

Looks like the heat pump has a super deheater installed and plumbed into the electric hot water heater.

Typically you need 3 GPM per ton of heating/cooling I am wondering if the well is not capable of producing enough water and the tank is being used as storage so the well pump does not run continuously during heating and cooling. Or the tank could be used for house supply as not to diminish the GPM requirement of the heat pump.

[Dennis Robitaille]

Thanks guys.

[Dennis Robitaille]

Ray,

The electric water heater was shut off electrically.

[Raymond Wand]

Dennis

If there is a super deheater installed on the HW tank taking waste heat from the heat pump, it can heat the supply water from the well to approx 110-115 deg. F., the longer the system runs. The owner may have shut off electricity because he feels the water is hot enough solely from the heat pump.

I have 4 ton ground source heat pump with super deheater to electric HW tank which boosts my well water which is approx. 47 deg. F to 115 deg. F. Then the HW tank elements heat the water to 130 deg. F.

Couldn't be definitive on my assumptions but only from what appears to be secondary lines to and from the HW heater.

[David Bell]

That company also manufactures solar kits. Do the PVC lines in front of the air handler go to a coil or something else?

[James Duffin]

I believe so.

I would be concerned about a constant flow of fresh water entering the system. The fresh water will dilute the freeze protection and mess up the water chemistry. This will foul the coils very quickly. If the closed system needs make up water there might be a leak somewhere.