All,

Oh fellow InterWebers, I turn to you for guidance after my contractor has failed me ...

I recently had a 3 ton WaterFurnace Envision installed with a desuperheater, 80 gal buffer tank, and 80 gal electric hot water heater. Even with the water heater turned up one click past "Hot" (whatever that means), the water is only warm with temperature fluctuations as the hot water runs.

And here is the kicker, and something that I can't figure out for the life of me. When the heat pump is running (heating or cooling), the hot water at the faucet almost instantly goes from normal shower temperature (with only the hot water faucet on), to burn my you-know-whats off scalding hot. Then once the heat pump shuts off, it's back to luke-warm.

WaterFurnace has no idea, and the contractor is lost as well. Can anyone help me?

Thanks,
Ian

Can you post a picture of the plumbing to the tanks?

Sure thing ... I'll snap a few pics once I get home tonight or maybe tomorrow morning.

All,

Here is a picture of how my hot water heater is plumbed ... the tank on the left has the heating elements (ignore the flip-flopped panels on the tanks ... I accidentally swapped them when I was messing with the heating element settings)

Thanks,
Ian

Hard to really undertand where the piping is going exactly on your tank. But from what I can see the desuperheater is only on one tank. I would recommend replumbing the tank so u grab the coldest water from the tank on the left (out of the drain, put a tee there). That would be water in on the heat pump. Then water out would go to your cold inlet of your first tank (tank on right). All put a tee here for cold water in. This would create a loop between both tanks and circulate all the water in both. Then hot water from right tank to cold water on left tank. Only element that should be on for backup would be the top element on the left tank. This should crate even temperature between both tanks.

Can you tell us which pipes go between the heat pump in/out for desuperheater and the water heater. ie; top right pipe on right tank goes to desup in on water heater etc.... I don't see a mixing valve or expansion tank on this piping. Aren't they required? Thanks

istock1,

In our previous communication, we had asked you to have your contractor contact our technical support staff for further assistance; however, we are unsure if this has happened. Could you please provide the name of your contractor so that we may look into your inquiry further? Also, if they spoke with our technical support staff, could you please tell us whom they spoke with at WaterFurnace? We are more than happy to work with you and your contractor to find a resolution. If you do not wish to post this information publicly, please feel free to send us a private message.

WaterFurnace International, Inc.

WF,

Thanks for the reply. My contractor said that he contacted your technical folks and they didn't have any ideas, but did not tell me who they spoke too. They are Supreme Air LLC in Maryland.

Thanks again,
Ian

liveGeothermal: That is correct ... the dsh is only connected to the right tank.

geome: I'll check the dsh connections when I get home tonight ...

Thanks,
Ian

Posted By liveGeothermal on 13 May 2011 11:27 AM
Hard to really undertand where the piping is going exactly on your tank. But from what I can see the desuperheater is only on one tank. I would recommend replumbing the tank so u grab the coldest water from the tank on the left (out of the drain, put a tee there). That would be water in on the heat pump. Then water out would go to your cold inlet of your first tank (tank on right). All put a tee here for cold water in. This would create a loop between both tanks and circulate all the water in both. Then hot water from right tank to cold water on left tank. Only element that should be on for backup would be the top element on the left tank. This should crate even temperature between both tanks.

What are you talking about?? A Desuperheater is NOT hooked between the two tanks, it should be plumbed to circulate only through the BUFFER tank. It should be plumbed as shown...



Bergy

Posted By liveGeothermal on 13 May 2011 11:27 AM
Hard to really undertand where the piping is going exactly on your tank. But from what I can see the desuperheater is only on one tank. I would recommend replumbing the tank so u grab the coldest water from the tank on the left (out of the drain, put a tee there). That would be water in on the heat pump. Then water out would go to your cold inlet of your first tank (tank on right). All put a tee here for cold water in. This would create a loop between both tanks and circulate all the water in both. Then hot water from right tank to cold water on left tank. Only element that should be on for backup would be the top element on the left tank. This should crate even temperature between both tanks.

1) Desuperheaters (DSH's) are normally plumbed to one (the unpowered) tank in a two tank setup per manufacturer instructions, and not looped between two tanks.

2) It is typically recommended to pull cold water from the cold water line (via the dip tube low in the tank) to avoid pulling sediment into the DSH.

3) With liveGeothermal's plumbing suggestion, it is unlikely you will get sufficient hot water out of one heating element during shoulder months, and until the problem is fixed - the rest of the time as well.

4) Doing as liveGeothermal suggests may possibly even out the water temperature at the expense of a DSH system not working properly.  Better to get the problem fixed.  WF, and people here that know what they are talking about, will try to help you.

5) Following liveGeothermal's advise is ill-advised, despite his claimed experience.

Are bleeder valves installed at high points in the piping?

Good to know members on this board think back 20 years. Do what u want but I have customers who don't even turn on an element all year with this solution.

Posted By liveGeothermal on 13 May 2011 12:14 PM
Good to know members on this board think back 20 years. Do what u want but I have customers who don't even turn on an element all year with this solution.

The solution you were presenting beats the purpose of installing a buffer tank to capture heat from the desuperheater most effectively. Would you care to explain how your customers, with the setup you were describing, heat their hot water in the shoulder season, when the heatpump is not running for space conditioning, without any additional heat elements turned on? The plumbing you were suggesting indicates a lack of understanding how desuperheat works, especially with R410a and the newer control boards. You might be installing (or in your own words: supervising) this for the last 20 years, but that does not mean it is efficient and to the benefit of the customer.

Posted By gonegeo on 13 May 2011 11:28 AM
Can you tell us which pipes go between the heat pump in/out for desuperheater and the water heater. ie; top right pipe on right tank goes to desup in on water heater etc.... I don't see a mixing valve or expansion tank on this piping. Aren't they required? Thanks

No mixing valve required. Here is a modified Bergy sketch to include a checkvalve, which is crucial to assure that you do not have thermal siphoning from the desuperheater, which in heating dominated climate can get your upper part of your buffer tank dangerously hot. Keep in mind that the safeties shut of only the circulation pumps, not the DSH circuit it self. I have seen DSH running up to 180F and with the siphoning, have heated up the buffer tank to 160F. The checkvalve prevents the siphoning. All unlikely with a 3 ton and a 85 gallon buffer tank, but there is always the first. In addition to clarifying the flow, could you let us know if the dip tube was removed and any backflow preventer was removed. Where are you located?

Call your local munciple office and find out the rules about the mixing valve. In some areas it is manditory a mixing valve is installed.

Even in spring/fall which typically during daytime don't require heating and cooling still usually require it at night. Most people only use the hot water during night and in the morning. By shower time in the morning both tanks are hot for morning usage. During several field test with many different types of equipment. This has proven to reduce costs. Having both tanks in a loop helps the desuperheater provide both tanks with hot water not requiring the elements to turn on and maintain temperature. Most of the cost for hot water is the maintaining. Typically the furnace during the year runs much more often than using water. Also putting 2" of insulation board underneth the hot water tank helps from your concrete floor from leeching the heat out of the tank. Only part of the tank not insulated is the bottom.

Hope that helps some of u

Thanks to everyone for their input so far ... this discussion has been really helpful (at least to me)

Doc: I am not sure what to look for to check if the dip tube and backflow preventers were removed. Could you tell me what they look like? And I'm in Maryland.

If your in the Wash DC - Baltimore area and want a second opinion give Love's Heating and Air a call.  They installed my WF w/buffer almost 2 years ago.
CH

LiveGeothermal,

In your piping scenario you are drawing the hottest water into the desuperheater. The finish tank will have water of at LEAST 120* drawn into a unit that will shut off the desuperheater at 130*.  As you draw the hot water down the elements in the finish tank will begin to energize, fighting the desuperheater for the privilege of heating the water.

You also are drawing calcium and other debris into the desuperheater, not a good idea for the circulators impeller.  Also, there is not one manufacturer recommending your piping... Why?

Bergy

Homeowner here with 4 ton Geothermal - buffer tank & finishing tank (plumbed according to Bergy) and it works perfectly.

(If I'd have plumbed BOTH tanks in series to the DSH, and not put any elements on, I'd have no hot water! My system has run a total of 10 hours in the last 13 days (0 hours in the last 4 days). Mild weather in the coming week points to the system continuing NOT to run.)
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istock1 - do you have a probe thermometer (like a digital meat thermo?). You might want to tuck the probe into/under the insulation of all the different pipes and try to get a fairly accurate reading of what the water temp is at different points of the loops with the system on, and/or with a hot water tap running somewhere.

IE - with the system on
on the Geo unit - DSH out, DSH in
on the buffer (1st unpowered) tank - pipe *to* DSH in, pipe *from* DSH out
You should also be able to feel a difference between the DSH in and DSH out on the geo unit when it's running (out should be hotter than in)

then with a hot water tap open in the house somewhere:
measure the temp of the pipe that goes from the buffer to the finishing (powered) tank
the temp coming out of the finishing tank to the house
the temp at a couple different faucets around the house (maybe one close to the system, medium, and faraway).
(to measure water at the tap, have the water flowing into a mug or something, let it continue to flow and overflow the mug, put the probe into the mug.)

You could also drain a little water out of each tank from the bottom T, and measure the temp with a probe. Be careful!!! It could be very very hot!!

Posted By liveGeothermal on 13 May 2011 03:07 PM
Even in spring/fall which typically during daytime don't require heating and cooling still usually require it at night.

Well, with thermostat settings of 80 heating and 60 cooling, this might work year round. 

Posted By decafdrinker on 13 May 2011 05:39 PM
If I'd have plumbed BOTH tanks in series to the DSH, and not put any elements on, I'd have no hot water! My system has run a total of 10 hours in the last 13 days (0 hours in the last 4 days. Mild weather in the coming week points to the system continuing NOT to run.

I'm with decafdrinker.  Our system has not been running much either.  Last time I checked, the DSH process is slow and needs a good deal of run time.