Quote:
Originally Posted by michael
...The source water comes into the device at 57 degrees and exits at about 48. I can increase the difference by throttling down the water flow somewhat...
|
I have nearly gotten into fistfights over this one, BUT...
When you reduce the water flow, it is true that you will allow the temperature to go higher in the water that comes out, because you have increased the dwell time. However (this is where the fistfight begins) by decreasing the flow, you will reduce the total heat output per unit of time.
At the same time, increasing the flow rate through a pipe will increase the power required exponentially... to be exact, to double the velocity through the same pipe pipe, will require you to quadrupal the power required, due to fluid friction.
So, there is a 'sweet spot' where power required is balanced by heat rate obtained.
Quote:
Originally Posted by michael
Clearly this heat pump cannot be connected directly to a radiant floor...
|
This will actually depend on the mass of your floor. Your floor might have enough mass, as installed, to balance the heat pump. If not, a buffer tank would be required to add more thermal mass to the floor system. The buffer tank is smaller and is intended to hold enough heat to smooth out the on-off cycling of the heat pump. This could be compared to a capacitor in an electric curcuit.
Quote:
Originally Posted by michael
...to build up a cushion of stored heat for periods of high demand.
|
The water tank can serve this function, but your language suggests that now you are interested in using the tank not as a buffer tank, but as hot water heat storage. Now, you are using your water tank as a storage battery.
Quote:
Originally Posted by michael
...I'm beginning to grasp how important it is to size a heat pump carefully to the size and heat retention rate of a particular house.
|
Awesome!
Quote:
Originally Posted by michael
This particular heat pump was built to be a water heater either with an indirectly fired water tank or with an electric or gas tank that had been converted, and it would still be a good candidate for that.
|
I sure wouldn't give it away!
Quote:
Originally Posted by michael
A little studying has convinced me that heating DHW, at least for my family, is the absolute least of our heating worries, and pales by comparison to heating the house. Because we are in a controlled water district even though we have our own well, we monitor and report our water use every month. We use an average of 60 gallons of water per day for all domestic use, i.e. drinking, cooking, washing, bathing, etc. Of that 60 gallons, only a portion is heated, and I would estimate that at 20 gallons a day. That would consume about 1/10 gallon of diesel in our water heater with an annual cost of less than $150. I'd be happy to save some of that $, but it's clear to me that going to extreme measures to reduce DHW heating cost is putting effort in the wrong place. Got to get house heat, which is more than ten times the cost of DHW, under control, and that's why I'm chasing after the idea of a GSHP.
|
Great insights here.
Do you know if there are any local restrictions on 'Pump & Dump'? In other words withdrawing water from a well, extracting the heat, and then returning the water?
Best,
-AC