I have a Water Furnace with a deSuperheater assisting a Bradford-White electric water heater.  There is no buffer tank-- the desuperheater feeds directly to the Bradford White heater.  I have problems with the water heater reset button popping, and the B-W info indicates that is a sign of too high a temperature.  Both thermostats and heating elements have been replaced in the water heater and I still have the problem.

Is it possible that the heat supplied by the desuperheater is tripping the reset button?  If so, what is the fix?

The output line of the desuperheater has a temperature sensor strapped to it. I would check there first and if I'm not mistaken the control board has logic in it that may be at fault.

Bergy

The solution is a buffer tank
I assume the safety switch trips when the water is a certian amount of degrees above the set point on elements
a desuperheater is taking water from that tank and adding heat to it , as long as the tank was at temp it will trip because you are adding to and above the set point

The good news is a buffer tank is the only right way to do it anyway

Good call Geo Fan!! I completely missed the "little" detail about there not being a buffer tank.

Bergy

I'm surprised to hear that desuperheat return water is hot enough to pop a water heater high temperature limit, especially this early in the cooling season. Last I checked they allow temps of 150 or so. The sensor is relatively distant from where desuper water enters the tank regardless of plumbing configuration, furthering my suspicion that the desuper water isn't responsible for the trips.

Did the replacement of the upper thermostat include replacing the assembly containing the reset button?

My first (internet free-and-worth-every-penny) thought is that the limit is defective.

Absence of a buffer tank is of some but not total relevance - if in fact this desuper somehow heats water to limit-tripping temps, a buffer tank full of such hot water would still trip the main tank's limit, though the trip might be delayed a bit.

WF desupers are supposed to cut out at 130 - circ pump is interlocked by a limit switch, further furthering my suspicion that the desuper is not responsible for this situation.

But, I could be wrong...

As Engineer suggests, it is not a given that the lack of a buffer tank will pop the limits, however.....it is a given that running without one will cost you money in most cases.
So...put one in and let us know if your limits keep popping.
j

If you're adding a new tank, flush the old tank well and use it as a buffer tank.

Regards, Masoud

I have nearly an identical set up as yours: a WaterFurnace Envision GSHP direct connected to a Bradford-White water heater.  My only differences are that my HWH is gas-fired, not electric, and my DSH is not turned on.

Here's a chart below to show you the relationship between the R410a refrigerant temperature going into the DSH versus hot water teamperature.  You'll see that the Envision's DSH doesn't get sourced with refrigerant temperature (blue line) much above 120° (F).  Thus, like Engineer postulates, I too agree it's unlikely the DSH is causing your HWH problem.

Best regards,

Bill

Im not fimiliar with the product line .
My assumption that the safety switch was based on the set point
In other words if its set to 115 , it will trip if water gets to 120
set to 105 trips at 110
as apposed to a fixed high limit

My attempt to defend my thought
It would help , if some one familiar with this product could offer more details about the saftey
Is it a high limit ? Is it pre set , or based on a differential ? Could it be a GFI ?

I'm fairly certain it is a simple high limit set 10 or so degree above the maximum thermostat setpoint which is typically 150 or so. Otherwise there would be many nuisance trips in cases where the thermostat is set at or near its high limit. Once years ago I recalibrated an electric water heater thermostat to allow a higher setpoint than 150 and sure enough, the limit popped at 160 or so. I don't remember why I did it - could have been for really hot water to kill a bunch of fire ant mounds or some oddball cleaning project. At any rate, the experiment taught me a bit about how water heaters work

The high limit is the second of three lines of defense for safety in a water heater; the first being the thermostat(s) and the last being the T/P relief valve.

I've never heard of a code requirement for ground or arc fault protection of water heater circuits, but who knows what the future will bring.

Do you have the lower element turned way down as single pipe recommendations suggest?
How old is the tank, can we rule out a wiring problem?
Is there any pattern to when it trips (i.e. only at night, after everyone showers, after the heat pump runs for...)?
j

Original poster here. Well, thanks for all of your insight. Maybe the reset button was not popping after all because all we did was replace the lower heating element in the water heater and all is well.

Funny, originally, you suggested you changed more than the lower element.
What's the real story?
j

The real story is I must be dumb, because I don't know. What I have been saying has been true, but I cannot explain a systematic reason for my recurring problem. I would feel better if I had a systematic explanation, but the symptoms have been as I said.

Not calling you dumb, but trying to figure out what's what. I think it's worth pursuing for our benefit (know what to look for) and yours (in case it happens again.
J

I know you were not calling me dumb. I wish I had more to offer to the dialog -- it is me calling me dumb.

On topic but off. We are running a geo-comfort water to water with the DSH line plumbed to a separate buffer/pre tank. Since it was a regular electric tank I went and checked and both the upper and lower over temps were tripped. I reset both of them and they haven't popped again yet (about a week now). I do have a thermometer on the DSH line and that thermometer tops out at 160 and almost every week it has maxed out. I believe the DSH pump kicks off at about 140F, but due to convection it still very slowly continues to warm the tank and I believe this is why ours was tripped out. Again since it isn't wired up we would never know otherwise. The regular T/P relief valve seems just fine.

Note also that the DSH cutout temperature may be measured on the inlet, so at the moment of cutout, DSH discharge might have been 5-10 above 140.

I'm amazed to hear of a DSH making so much water so hot.

If it's a WaterFurnace Envision unit, or another WaterFurance unit that uses R410a refrigerant, then it's not possible for the DSH to produce the hot temps being noted here.  Looking at the chart I posted earlier, you can see that incoming R410a refrigerant temperature, into the DSH, only ranges from 120 - 130 degrees (F) in cooling mode.

Best regards,

Bill

I assume he is in cooling mode now from his location, but I just want to point out that in heating mode at least, high discharge temps are very possible with R410a. On my W-W unit at the coldest loop temps and hottest radiant temps, the discharge temp is over 220F. As you say, his temps are probably far lower, but something to keep in mind.