Waterfurnace Synergy 3d/Envision question
We built a home last spring with an open loop system using Waterfurnace components. In the basement I have a 5 ton Synergy 3D unit and an Envision unit. This provides radiant heat to the basement as well as forced air on the main floor and domestic hot water.
Although my overall utilization has been higher than I anticipated, my question is related to the domestic hot water situation. The envision unit is connected to an 80 gallon storage tank which in turn is connected to a 40 gallon tank (which has an electric heating element). The envision unit is set to 125 degrees and the storage tank approximately the same
I have a circulating pump which pulls water to the farthest shower in the house. In observing the unit my perception is that the Envision unit turns on for 20 minutes then off for 20 minutes fairly continuously throughout the day during periods when no hot water is being used. This seems inappropriately high and subsequently may be the source of my high energy utilization? Could I be missing something? Is there a particular change I can make to improve the situation? I apologize if I haven't provided enough information.
Any assistance would be appreciated.
What is the model number of your envision unit. Is it a water to water or water to air unit? Since you are saying it is "set" to 125 degrees I can guess you have an NSW unit(full model number would be helpful) and if you have an NSW unit then not sure why you would need an 80 gallon and 40 gallon tank, that seems excessive. WaterFurnace makes a 120 gallon storage tank(rebranded state equipment) because two tanks, you will have temp sensing issues.
Something seems odd about how its setup. If you could post a pic it would be helpful to tell if you have desuperheaters or dedicated water to water systems and how the Synergy is connected to the radiant.
Thank you for the response. My model numbers are:
Envision - NSW025C10HLSS0SA
Synergy3D - SDV049E101NTL0SA
As it turns out I seem to be unable to post pics/links since I have not had enough posts yet. I'd be happy to send you an email with the links if you are willing and PM me.
The system is supposed to provide hot water for the main house with 4 showers as well as an in-law house that is 30' away with 1 shower. The theory in construction was that using one heat pump would be most efficient and as I understood it the 2 tanks would 'back each other up' better to provide continuous hot water if there was a significant draw on the system (Grandpa in the shower in his house while using a shower at the main house).
The in-law house does have its own heat pump to provide heat/AC.
Thanks again for any input/advice that you can offer.
Although there can be many piping configurations, one of the more common methods is to draw from the smaller tank and keep it hotter. The larger tank is kept at a temp below the smaller tank and feeds the smaller tank.
Sort of defeats any potential energy savings to keep both tanks at the hotter set point.
You're correct that the smaller tank with the heating element feeds the water out to the house and the bigger tank with hot water provided by the heat pump sends water over to that smaller tank.
You're suggesting that I should turn the envision unit down from 125 to 115 or 120 and keep the smaller tank at 125 or so?
I think it takes 3 posts to be able to post links so I should be able to get those pictures up after this...
I think you are confusing something. Hot water for the radiant system and domestic hot water. Domestic hot water (Desuperheater) is piped to a water heater for the home, ideally there should be two tanks. first a buffer tank then the main water heater. This allows the Desuperheater to warm the "Buffer" tank whenever the Geo is running.
Water for the radiant system should be piped to a buffer tank, when the tank gets below your set-point the Geo starts up to heat it up.
Your domestic water and radiant water should NOT be mixed together... EVER!!
I still don't see why they are using a two tank configuration when you can get a single 120 gallon tank and install elements in it. Typically a two tank setup is for a desuperheater, not a dedicated water to water heat pump. With that NSW025 you shouldn't need anybackup and the 120 gallon storage tank allows for 4,500 watt elements. I could see the two tanks causing a temperature sensing issue which would cause the cycling.
I am not suggesting to turn anything down, I am suggesting you shouldn't have two tanks with those model numbers you provided and that the two tanks could be causing the short cycling issue if the heat pump is having problems sensing the water temp due to constant water flow from your EWPK2. Also in most NSW configurations the pump will cycle every 20-30 minutes to take a water temperature sample.
As mentioned in post #6, there are concerns when using hot water for both domestic use and radiant heating. It can be done, but I would recommend consulting a licensed engineer skilled in the art. I think what has to happen to keep the bacteria down is that the radiant heat has to be hot enough so that nothing will grow. What can happen in practice is that the radiant heat temp may be turned down in an effort to save energy, and that's when bad things can potentially happen.
But back to the dual tank setup. You would have to look at your original criteria; where were the savings you were looking for going to come from? Think about that question.
Here is a typical setup . . .The smaller [and hotter] tank provides the domestic hot water. I keep my hot water heater at 150*F, which others will tell you is too hot, but my water heater is small so [due to the smaller surface area] the heat loss is less [it's also indoors, which further reduces the heat loss and even helps in the winter]. And when using the hot water, more cold water is mixed with it so less hot water is used from the tank, so it lasts longer.
If your radiant heating is mixed with the domestic water, then your setpoint for temp for that smaller tank needs to sterilize the water in your radiant heating so you don't get weird bugs growing inside of your body. You could have design problems here, but I'm getting off topic [a heat exchanger is one common solution]. Let's pretend you do not have radiant heating for the time being.
So, the smaller tank is kept hotter and feeds the hot water needs. Then, in summer, you want the house to be comfortable so the A/C kicks on. The heat rejected from the heat pump goes into the larger tank to give you 'free' hot water. The larger tank is just there to catch all of the heat rejected from the heat pump when the heat pump is in cooling mode. The larger tank might even get hotter than the smaller tank, rare, but it could happen; an additional air cooled coil is required to reject heat that the larger tank cannot absorb [that is likely already plumbed in].
Do you sort of get it? You see, there is no savings to be had in the winter. In winter, you would likely use the heat pump to just keep a minimum temp in the larger tank. Might only be 75 or 80*F, sort of depends on how much hot water is used from the smaller tank and how fast that smaller tank can recover to meet the needs of the household.
So, here's your homework . . . Back to paragraph number two . . . Where was your original savings intended to come from?
Originally Posted by aweise
Thanks for the detailed response! I still don't have the clearance to post links to pictures but will show you my system whenever HVAC-talk lets me.
Bottom line is that your assumption is correct. There are 3 tanks in my basement. One for the radiant which I haven't really touched. I think its set at 120 or so. The two tanks for domestic water are as you describe. A large one connected to the heat pump and a smaller one with the heating element from which I draw for hot water.
I was under the impression that heating water with the heat pump is 'cheaper' than using the electric heating element, therefore I should be trying to keep the temp in the larger tank essentially the same as the smaller tank - therefore using the heat pump more than the electric. I will give it a shot to turn up the electric tank and turn down the heat pump. Thanks again
Pictures of the system. 80 gallon tank visible on L. Synergy in the middle. Large storage tank for in floor heat on the R
In floor heat manifold. Envision unit on the L
80 gallon tank with connection to envision unit coming out the front. 40 gallon tank is directly behind it.
Back of synergy unit. 40 gallon tank is visible. In floor heat storage tank is in the foreground.
Not sure if these pictures are helpful. Thanks again for your assistance.