Hi, We are installing a Waterfurnace envision 5 ton system in an open loop configuration. I have a variable speed well pump and a return well. The installer stated that he would be putting a ball valve inline on the return side to control flow. This is where im not sure I trust these guys. It is a 2 stage that can flow as much as 15 gpm so I am assuming that it does not need maximum flow when in is in it's first stage. That would just be wasting electricity by over working the well pump. So my question is, how does this thing need to be plumbed on the return side. There must be some way to control the flow with a solenoid valve. ???
Quite honestly, I do not see much benefit to restrict flow on the source side in almost any application. Heat extraction is a function of flow and temperature delta, the higher the flow, the lesser the delta T. Usually, we do everything we can not to restrict flow, so the whole concept of flow restrictors does not make much sense to me. The manufactures recommend them, so some installers put them in, but nobody could ever explain to me why. The only reason I could see on the load side if you want your delta T to be a certain minimum.
For open loop systems, Waterfurnace recommends about 1.5 gpm/ton; so, for a 5 ton Envision, anything more than about 8 gpm is a waste of power at the well pump. I seriously doubt that there's enough difference in "optimum" flow rates between stage1 and stage2 to make it worth the effort to adjust pump output depending on stage. A flow restrictor possibly makes sense in an open loop system -- where lifting water from the well can be a significant operating expense. (Can't imagine a case where a restrictor would make sense in closed loop.)
In an open loop system you need to limit the amount of water through the unit to what the unit really needs, anything more is a waste. example: variable speed pumps ramp up to meet pressure/flow setting. If the unit is not throttled the unit and more importantly the injection well will see the maximum flow rate the pump and piping will deliver. If the unit needs 3gpm per ton that is 15 gpm max, the pump and piping can deliver 35gpm, what a waste. Also the injection wells we drill are designed to handle the capacity of the units not the capacity of the well pump that may also supply domestic and irrigation in my kneck of the woods.
Plumbing WF recommends a parallel piping configuration - 1 for each flow rate requied. There are a number of options. I have some pics but can't figure out link structure on this iPad I'm on.
With a variable speed pump and a control board, don't you set the pump to the amount of water you need for first and second stage, or multiple stages? I understand that some manufacturers have parallel configurations, but that also assumes constant speed pumps. This thread was started with a description of a variable speed pump. So if you can control the amount of water pumped up, why would you want to restrict flow after that?
You wouldn't. For any given gpm, lower pump discharge pressure = lower cost. On edit: gallons x deltaP = energy gpm x deltaP = power ...not just a good idea, IT'S THE LAW, Looby
In most cases the variable speed pumping equipment serves other distribution than the heat pump. If it were for the heat pump only, control of gpm and pressure would be easy. Given that the flow rates for 1st and second stage are so close, if the pump were for the heat pump only you would save money by not using a variable speed product and go with a conventional pumping equipment sized exactly to the 2 stage.
That is my point. I do not see any application I can think about to restrict flow, not even an open system. And I agree, with 1st stage needing about 2/3 of the flow of 2nd stage, why wouldn't you save all the money and get a nicely sized pump for your delta P and the flow you need to put both 1st and 2nd stage within the delta T parameters of your heatpump, and move on. The only time I have used variable speed pumps is in multiple heatpump applications served by one open well source.
In principle, I agree -- IF you can dedicate a single well pump to geothermal. However, if the same pump must service both geo and domestic water, it gets more complicated. Geo requires high daily volumes at low pressure, domestic supply requires much lower daily volumes at much higher pressures. If you have to supply both from the same storage tank, you'll have to restrict flow through the GWHP. Yes, flow restriction = wasted energy, but sometimes that's less expensive and/or less complex than the alternatives.
Applications That is my point. I do not see any application I can think about to restrict flow, not even an open system. Irrigation.
I like the sound of the parallel piping for each flow range. But isn't the smaller piping just a form of restriction? The variable speed well pump is so we can supply water for the house also and the well pump kicks up to allow for anything we throw at it while not wasting energy when it doesn't have to. But lets face it, every gallon pumped out of the well has a small price attached so why pump more through the unit than we need to. I see no reason to pump 30% to much through it when it doesn't need it. I have to recoup the cost of the unit everywhere I can. I can see why you wouldn't want restriction in a closed loop but this is an open loop fed by a bladder tank which is filled by a well, bladder tank empties to a certain level and well pump kicks on to refill. Why kick the pump on more than we have to?
So you are using the flow restrictor to empty your bladder tank slower (thus pumping up lesser water), but not to restrict the flow from the pump. Ok, I must revise myself. This would make sense......
Solution Ok, I talked to Water furnace tech support today posing as a dealer installer Problem solved, we y off at the output on the unit. Flow restrict one side at optimum flow for stage 1 and put a 3 wire slow open solenoid on this side. On the other side of the y we put a 2 wire solenoid wired to CC and ground, then restrict this side to additional flow needed for the sum of the two to equal optimum flow for stage 2. In stage 1 only one side opens and in stage 2 both sides open. Seems like it would save a lot of water over 20 years. Almost a 3 GPM difference.
Thanx for the Waterfurnace work around. From a conservation standpoint, water and electric usage 3gpm over any extended period of time is a good thing. For my customers amusement I have been recommending that open loop systems be installed with gpm water meters to measure usage. Those numbers are a lot bigger than anybody realises
more common I'm just shocked that this isn't more common. You would think most people that put in a geothermal unit would be pretty serious about saving every penny that they can. Otherwise you are just stepping over a dime to pick up a nickle.
We are in the process of installing a closed loop vertical system in our home as we speak. We used to have an open loop system in a previous home. Make sure the well pump is designed for the load you are giving it. We had a single pump that supplied the geo and the home water source. We had to replace the pump almost every year. When it went out, no heat, no AC, NO WATER! This was 15 years ago, and the manufacturer would not stand behind the pump because of how we were using it! I'm sure things are better now, hope you have better luck with the open loop system. Also make sure the injection well is going back into the same aquifer. If not, you might pump the supply side dry.
Well pump We have addressed the supply issue with a variable speed pump with lots of capacity. They are supposed to last much longer. I turned the well on for the first time today and ran water out in the driveway for a while. I was surprised how much water noise there was in the house. The geo unit isn't plumbed yet, do you guys think I should plumb it seperatly from the house and run it along the ground in my crawl space rather then under the floor joist?
Water noise and water hammer can be issues to address. Talk to your plumber and well guy about how to illeminate the "roar" in the pipes. Solutions are often simple and inexpensive.
