It's pretty late here now, but I'll give you a quick (edit: not so quick) description of what the system is, and what I'm trying to do, and do a diagram tomorrow.
I have a newly installed Geo-Thermal “Water to Air” Heat Pump in my home. You may be more familiar with a conventional "Air to Air" Heat Pump, which extracts Heat from the air, multiplies it and distributes it to the house. However, air temperature is constantly varying, and those heat pumps lose their ability to produce useful heat once the ambient air temperature falls below a certain point. Geo-Thermal Heat pumps, on the other hand, use the energy from beneath the earth, which is fairly constant.
There are many ways to tap the earth's energy, but in my system, (Water to Air), two deeply drilled water wells are used, which provide water that is a constant 55 deg. F. This water is pumped out of one well and delivered to the Heat pump, which uses a process like "reverse" Air Conditioning, to extract the heat, multiply it and transfer it to a coil over which air is blown and distributed to the house via a fan. Then the water is returned to the earth into the second well. Very efficient, very "Green" and very cheap to run, and here the Gov. helps offset the initial high cost of the system. Payback from not burning fossil fuel is very quick.
The only problem is my well water is very dirty, hence the need to purge (clean) the dirt from the water filter regularly. (there are also "closed loop" Geo systems that don't use well water, but circulate a Glycol solution in and out of the earth, However the "Open loop" system I use is much more efficient)
In-between the cooling and heating season, the system isn't used, so as the well "sits" it becomes very dirty, as it also does after a very heavy rainfall. Once the heating season arrives in the fall (as it is here now) the well starts to get used. The water it pulls up is very, very dirty, and clogs the water filter in just a few minutes. There are several filters "in-line" , but the first one filters out the "big" stuff and this filter has a valve on it that can be opened briefly, which will "purge" the dirt off of it, rather than having to disassemble it and clean it. As the days and weeks go by, the well runs cleaner and cleaner, therefore the times that this purge operation is needed gets to be less and less. Hence the need adjust the "off" interval for the 24VAC purge valve to be longer and longer.
Sequence of events:
When the T-Stat calls for heat, it opens a well water zone valve (there are 2 zones-downstairs and up). The well pump then sees the pressure drop in the pipes and starts to pump water out of the ground. The Geo-Thermal heat pump, having been also called into action by the T-stat, starts its process and I'm now getting warm air throughout the house.
But, if the water filter gets too dirty, the flow is reduced below the needed amount, and the Geo-Thermal heat pump shuts down prematurely. Hence the need to purge (clean) the filter.
As my drawing shows, because the T-stat and zone controller use 24VAC to operate the water zone valve, I tapped off that to provide 24V to the solenoid "purge" valve. The drawback is that without a timer controlling it, the purge valve is open all the time during the entire heating sequence, and a portion of the needed well water is diverted out the bottom of the filter housing, and thru the purge valve’s piping. The well pump is able handle this "leak" with no problem, but as you can imagine, I'm wasting a portion of the water into the sump pump pit. But, it is keeping the filter from getting clogged. By the filter assembly’s design, the dirt exits, rather than attaching to the filter.
Over the next few weeks, the well will run cleaner and cleaner, so, that's why the timer "Off" time can be adjusted to be longer and longer. The valve opens to purge the well for only a short burst, (<5 sec) then stays closed. The off (closed) period gets to be longer and longer, as the well gets cleaner and cleaner.
So to conclude, my drawing is functional (if I have the proper timer), and can work, but not optimally. Because the timer is always powered, its timing events are not coordinated with the start up of the Heat pump. Ideally, I'd like the timer's short "ON' period to begin and be simultaneous with the start of the heating sequence. That way, I'm always assured that any dirt that may have gathered in the well during the "down" time (between calls for heat) will be expunged immediately, and the timing cycle will then continue: The "off" duration will be adjusted and set manually on the timer, as I observe the filter in its clear glass housing over the upcoming days and weeks.
Whew, didn't think I'd take so long to explain it. Hopefully I didn't lose you!
I have a newly installed Geo-Thermal “Water to Air” Heat Pump in my home. You may be more familiar with a conventional "Air to Air" Heat Pump, which extracts Heat from the air, multiplies it and distributes it to the house. However, air temperature is constantly varying, and those heat pumps lose their ability to produce useful heat once the ambient air temperature falls below a certain point. Geo-Thermal Heat pumps, on the other hand, use the energy from beneath the earth, which is fairly constant.
There are many ways to tap the earth's energy, but in my system, (Water to Air), two deeply drilled water wells are used, which provide water that is a constant 55 deg. F. This water is pumped out of one well and delivered to the Heat pump, which uses a process like "reverse" Air Conditioning, to extract the heat, multiply it and transfer it to a coil over which air is blown and distributed to the house via a fan. Then the water is returned to the earth into the second well. Very efficient, very "Green" and very cheap to run, and here the Gov. helps offset the initial high cost of the system. Payback from not burning fossil fuel is very quick.
The only problem is my well water is very dirty, hence the need to purge (clean) the dirt from the water filter regularly. (there are also "closed loop" Geo systems that don't use well water, but circulate a Glycol solution in and out of the earth, However the "Open loop" system I use is much more efficient)
In-between the cooling and heating season, the system isn't used, so as the well "sits" it becomes very dirty, as it also does after a very heavy rainfall. Once the heating season arrives in the fall (as it is here now) the well starts to get used. The water it pulls up is very, very dirty, and clogs the water filter in just a few minutes. There are several filters "in-line" , but the first one filters out the "big" stuff and this filter has a valve on it that can be opened briefly, which will "purge" the dirt off of it, rather than having to disassemble it and clean it. As the days and weeks go by, the well runs cleaner and cleaner, therefore the times that this purge operation is needed gets to be less and less. Hence the need adjust the "off" interval for the 24VAC purge valve to be longer and longer.
Sequence of events:
When the T-Stat calls for heat, it opens a well water zone valve (there are 2 zones-downstairs and up). The well pump then sees the pressure drop in the pipes and starts to pump water out of the ground. The Geo-Thermal heat pump, having been also called into action by the T-stat, starts its process and I'm now getting warm air throughout the house.
But, if the water filter gets too dirty, the flow is reduced below the needed amount, and the Geo-Thermal heat pump shuts down prematurely. Hence the need to purge (clean) the filter.
As my drawing shows, because the T-stat and zone controller use 24VAC to operate the water zone valve, I tapped off that to provide 24V to the solenoid "purge" valve. The drawback is that without a timer controlling it, the purge valve is open all the time during the entire heating sequence, and a portion of the needed well water is diverted out the bottom of the filter housing, and thru the purge valve’s piping. The well pump is able handle this "leak" with no problem, but as you can imagine, I'm wasting a portion of the water into the sump pump pit. But, it is keeping the filter from getting clogged. By the filter assembly’s design, the dirt exits, rather than attaching to the filter.
Over the next few weeks, the well will run cleaner and cleaner, so, that's why the timer "Off" time can be adjusted to be longer and longer. The valve opens to purge the well for only a short burst, (<5 sec) then stays closed. The off (closed) period gets to be longer and longer, as the well gets cleaner and cleaner.
So to conclude, my drawing is functional (if I have the proper timer), and can work, but not optimally. Because the timer is always powered, its timing events are not coordinated with the start up of the Heat pump. Ideally, I'd like the timer's short "ON' period to begin and be simultaneous with the start of the heating sequence. That way, I'm always assured that any dirt that may have gathered in the well during the "down" time (between calls for heat) will be expunged immediately, and the timing cycle will then continue: The "off" duration will be adjusted and set manually on the timer, as I observe the filter in its clear glass housing over the upcoming days and weeks.
Whew, didn't think I'd take so long to explain it. Hopefully I didn't lose you!
It gives me something to do - I'm currently unemployed... but with a bit of luck that will change soon - I went to a screening test for a new job last week, and they said I did really well and they want to interview me tonight, so fingers crossed 
