Balancing SCW water flow for two units

What is the best way to balance two units running on a single SCW? I have a 5 ton and a 2 ton running each with their own thermostat through a single water feed. I have tried to balance the flow with both systems running simultaneously to provide the minimum amount of flow required during that time. When only one system is on then there is a lot more flow to it since they both feed from the same line. Should I separate and run a line to each independently?

There are ball valves that I can turn to adjust flow.

 

Lots of different ways to do this, but yes at some point each unit should have its own feed and solenoid.

 

Each has its own solenoid but when only one unit runs it has so much more flow than it needs that when the solenoid shuts it creates a water hammer effect that I don't hear when both units are running. Should I have a pressure regulator in line for each of the systems to keep the pressure constant?

 

It seems this thread is dead but I thought I'd try and give it a "bump." I have a similar situation; I have a 5 ton unit in the basement that struggles to cool the third floor during the summer. It would be simple enough to abandon the single trunk line that feeds the attic duct work from the basement, and replace it with a small unit in the attic. Balancing the two systems for "both on" and "both off" seems simple enough; combine the discharge lines from each unit into one, and locate the solenoid valve downstream. In this case, water would flow through both units when either is energized. I'm not sure how wasteful this is but my hang up is how to control water flow to the units individually without cycling my well pump. If it matters, I have a SCW system that is also used to fill the pool and run my small irrigation system; no drinking water. The cut off is set to 60PSI. Any suggestion on how to set this up or where to look would be great.

 

I ended up putting in a relay circuit that opened both solenoid valves any time either of the units was on. This keeps the flow constant but is wasteful on water.

 

I think that is what I'm going to do, except with one valve. I'll put a flow limiter behind the 5 ton but before the discharge water recombines with the 1.8 ton. That should ensure enough flow to the attic unit. It'd be nice to conserve the energy from pumping so much water around but I can't figure it out and there really isn't anyone in the area familiar with geothermal.

 

I did some poking around and it seems there are "constant pressure" pump motor controllers that should balance the different water loads. At $1K for the Franklin though, I wonder how long it would take to get the return on investment vs just running it as previously described. I need to find out what size pump motor is down there to get to estimate yearly electrical costs on that end of the HVAC system. I guess the "constant pressure" systems are pretty common on GT-HVAC; any user experience?

 

I ended up abandoning the geothermals after the return line froze this winter and ruined both compressors. I went with two brand new high efficiency heat pumps and my bills have been 35% lower than with the geothermal. Lots of numbers are bantered around about the efficiency of geothermal however if you look end to end at the overall system consumption including pumping costs I think you will find there is a lot of nonsense out there. I'm much happier without the geothermals and so is my wallet.

 

Yes, I'm getting the same feeling. Everything is in place and relatively new so hopefully I can run it as is for a while. BTW, I was given some friendly advice from a local to avoid the "constant pressure" system.

 

"I ended up abandoning the geothermals after the return line froze this winter and ruined both compressors. I went with two brand new high efficiency heat pumps and my bills have been 35% lower than with the geothermal. Lots of numbers are bantered around about the efficiency of geothermal however if you look end to end at the overall system consumption including pumping costs I think you will find there is a lot of nonsense out there. I'm much happier without the geothermals and so is my wallet."

there is no question that geo is the most efficient way to heat a home. air source heat pumps depending on climate may run a close second and with lower installation cost may when the ROI discussion.
It sounds as though you are the victim of poor design and that stinks. I'm glad you are happy with your new system.

 

I'm curious what others opinions are on two setup options. I have two W2A units, a Climate Master Genesis 1.8T and Edwards Engineering "Tetco" ES-II 5 T, fed by a SCW well that's ~6-700 ft deep with static water 30 ft down. The well is a big producer in that I'm able to draw about 20k gallons in the spring to fill my pool. The pump produces about 18 GPM through a garden hose, I think it is a 1HP high efficiency "Jacuzzi" but I'm not entirely sure. My question is, is it better to pump water through both heat pump regardless of whether one, the other, or both are calling for flow. Or should I have each control an it's own valve. The first solution wastes energy by pumping excess, unused water while the second will probably result in my well pump cycling, especially when only the smaller, 1.8T system is calling for water. Are these the only solutions available? Any help would be greatly appreciated.

 

I would be more concerned with the coil eroding over time with constant flow before I would worry about the pump. A properly sized storage tank minimizes cycling.

 

Thanks, I didn't know coil erosion was even a consideration. For clarity, they would not have flow constantly, just in tandem when either call for water flow. I assume the suggestion of a properly sized storage tank means shunt a portion of the flow to a bladder tank. I currently have a 50 gallon bladder tank and still had to run at 60 psi for the well pump to run continuously while the single Tetco 5T unit was running. I can't imagine what kind of storage capacity to shunt for cases where only the small unit was running. I'm not trying to be a negative Nancy or strike down your suggestions; they're appreciated. I'm just trying to get more of the relevant parameters out there so I can get this thing running.

 

If you can get past the feeling you are short cycling your pump, please consider powered valves and flow controls for each HP to minimize the cost of pumping water. Even in a system running to conserve water, power consumption can amount to around 20% (varies by many factors) of your running electric costs.

 

http://welserver.com/WEL0424/

Variable speed, constant pressure well pump, with solenoids for every heatpump.

 

I can appreciate the engineering and craftsmanship that went into the job there BuffaloGeo. I've been looking over your site for quit a while. Unfortunately, as much as I'd like to, I cannot afford that kind of retrofit with the pump, controller, and install. I did ask about it locally and every well driller in this area said to avoid the variable speed pumps. Their opinion is that they are too susceptible surges due to lightning strikes. I can't tell if this is a real concern or just superstition, but with a $5,000 price tag, it really isn't an option considering the existing pump is 8 years old. Do you use the Taco Geo Valves on SCW/Open loop systems, or a normal valve and flow detector?

 

The variable sped pumps we use are much less than $5K, at least for a 7ton 2 Heatpump system. You need about 12 gpm flow, no need for a $5K pump.
For the last 5 years they are running pretty flawless. We used taco valves, but are more using now the Johnson Control Valves coming with the 7 series, and now start going towards Belimos. We use variable valves who use a 0-10 Volt input signal and are controlled by the Delta T at the heatpump.

 

I agree with Doc for those that can afford.

For middle class middle Americans with 1 or 2 stage HPs, an irrigation valve (opens immediately and closes slowly) from local orange or blue box store (get spares for when they get tired, they are cheap) and a Hays flow control of your required flow rate (harder to find but is a must) will do nicely with a conventional on/off well pump.

 

I had 2 Taco's fail on me after 4-5 years, thus the change. No issues so far with the Belimos or Johnson Control. Time will tell. Yes, they are about 2x as much as the Tacos, but way cheaper of me having to go back to the job and change them out. I think with geo the emphasis should be to never really plan on going back to a job. I rather pay twice as much for the premier material, than having to put money in a warranty reserve or increased overhead due to future repair costs.

 

I haven't used the orange headed Taco in over 10 years. It never made sense to me to use a heat motor to open a valve carrying 54f water. I switched to Taco EBV at that time. Todays version is the Taco Zone Sentry. I have never had an issue with them for 1 or 2 stage equipment.

A failed orange headed Taco is usually caused by corrosion from condensation on the mechanical end switch. As the plunger drops, the end switch swings in to make contact. It can be cleaned and made to work in a pinch but I replace them whenever I can.