DesuperHeaters and Water Heaters
Last Post 07 Nov 2008 10:33 PM by joe.ami. 68 Replies.
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Palace GeothermalUser is Offline
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21 Sep 2008 08:05 PM
I finally hooked my WEL unit up to my desuperheater and water heater.  Now we have some more data to digest.

I have an A O Smith Power Shot Power Vent 50 Gallon natural gas hot water heater.  It costs me about $15 dollars per month for hot water for our family of 5.

I have a 4.5 ton Florida Heat Pump  GT054  with a desuperheater,   (HWG) ,  tied into the bottom of the  hot water heater, (HWH), using a concentric fitting.

I have attached a graph below which shows the following:

The water coming out of the HWH is about 118°

After the HWH has finished a heating cycle,  the temp coming off the bottom of the HWH is about 90°.

After the HWH finished, the HWG raised the temp of the water in the bottom of the tank from 90° to about 110°.

I forced my heat pump to run for about 2 hours solid while gathering this data.

During this time,  the HWH went through several heating cycles.

At no time was the water going into the HWG warmer than the water coming out.

Which to me means that at no time was the flow of heat going the wrong way (from the HWH into the ground loop)

As Bill was so careful to point out in his thead,  this data only applies to my system.  You may or may not get the same results on your system.

As a side note,  I really enjoy being able to share info with and learn from the other posters on this forum.

Attachment: ScreenHunter_26.jpg

Dewayne Dean

<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system
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21 Sep 2008 08:44 PM
You guys are really making me want to get a wel to see how my DSH is compared to yours


Green Bay, WI. - 4 ton horizontal goethermal, 16k gallon indoor pool, 3kw solar PV setup, 2 ton air to air HP, 3400 sq ft
Bill NeukranzUser is Offline
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22 Sep 2008 09:34 AM

Dwayne, I'll look at this today to and try to learn from it.

I may even be able to change my WEL measurements to match the technique above, to enable closer comparison.

This is interesting, and helpful.  Thanks for the posting.

Best regards,

Bill



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22 Sep 2008 11:00 AM
Posted By geodean on 09/21/2008 8:05 PM

... with a desuperheater (HWG),  tied into the bottom of the  hot water heater (HWH), using a concentric fitting. ...

What is "a concentric fitting?"

Is it anything like what's in the image below (my DSH's connection to the 'bottom' of my HWH)?

Thanks and best regards,

Bill


Attachment: IMG_9951.jpg

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22 Sep 2008 11:04 AM

Dewayne, does this diagram match the piping hookup of your DSH to your HWH?

Thanks,

Bill


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22 Sep 2008 11:32 AM

Dewayne, I'm a little uncertain on your terminology, as it looks like your FHP GSHP unit may be labeled a little differently than my WF unit.

Does this diagram (below) accurately match up your measurement points to the value descriptions in your WEL chart (above)?

Thanks!

Bill


Attachment: system2.jpg

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22 Sep 2008 02:25 PM
Posted By geodean on 09/21/2008 8:05 PM
 
...

During this time,  the HWH went through several heating cycles.

At no time was the water going into the HWG warmer than the water coming out.

Which to me means that at no time was the flow of heat going the wrong way (from the HWH into the ground loop)

...

OK, I set up a chart just like Dewayne's: http://welserver.com/WEL0043/DesuperDHWHours7.gif .  I used the exact same name, scaling, naming conventions, etc., as best as I could figure out.  (Dewayne's is at http://welserver.com/WEL0114/DesuperDHWHours7.gif .)

I also created a new chart, that looks at the difference (delta) between my compressor discharge R410A refrig temp and the HWG Out (red line), and the delta to the HWG In (blue): http://welserver.com/WEL0043/DHWHours7Deltas2.gif .

I'm assuming for the moment that my guesses shown in the above connection diagram are correct - I'll fix things if Dewayne reports back that I misunderstood something.

I'll let the data accumulate for a while, and then offer some updates to my earlier stated observations.

Some preliminary new observations:

Dewayne's got what looks to be a pretty fancy (efficient) gas-fired HWH.  His power-vented unit looks to have much more frequent gas-burning cycles than I have (my HWH is the old-fashioned direct-vented type).  As a result, I'm guessing his HWH tstat keeps his DHW Out in a tighter temperature band than mine does, with a lower 'high' DHW Out temp, and, probably does all this more efficiently than mine.

Dewayne's DHW Out temp sure drops at a faster rate than mine.  I wonder if he has a HW circulator for his residence.

I looked up the details on Dewayne's FHP GT054 GSHP unit - it has R22 refrigerant.  Thus, I believe his compressor discharge R22 temp going into his HWG is more on the order of 150°F.

Thus, with Dewayne's fancy HWH controlling the DHW Out in a pretty tight band centered at what looks to be about 110°, with highs limited to about 120°, I don't see where there's possibility to transfer heat from the HWG In or Out lines to the R22 refrig line.

I.e., the worse case delta (smallest) between Dewayne's incoming R22 refrig and his HWH Out looks to me to be about a positive 30°.

So, for Dewayne's set up, my guess is that using a pre-heat tank would be more efficient (delta probably goes from 30° to about 50 - 60°), but not a necessity to avoid inefficient GSHP operation.

Just guesses at the moment - I'll watch the data for a while.  Type of refrigerant and performance style of the gas-fired HWH look to be substantial influencers to the subject.

Best regards,

Bill  


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22 Sep 2008 03:28 PM
Posted By a0128958 on 09/22/2008 11:00 AM
Posted By geodean on 09/21/2008 8:05 PM

... with a desuperheater (HWG),  tied into the bottom of the  hot water heater (HWH), using a concentric fitting. ...

What is "a concentric fitting?"

Is it anything like what's in the image below (my DSH's connection to the 'bottom' of my HWH)?

Thanks and best regards,

Bill


Below is a concentric fitting.  The water goes to the HWG and returns from the HWG through the fitting.


Yes my piping matches your diagram except with the  exception of the concentric fitting .


I do not have a recirc pump.  My HWH tank temp does not drop as fast as the graph shows.  I am taking the reading on an uninsulated copper pipe about 12" above the HWH.  I think the section of pipe just falls to room temp.  When I use a  little bit of hot water, the  temp reading jumps back up with out the HWH firing.

The only time the graph make any sense is when the heat pump is running.

My heat pump will probably not run at all  now for a few days.  Fall weather is here and no need for cooling.


The thing that surprised me most about this was that after the HWH had cycled on and off,  the water coming out of the bottom of the tank was only in the 100° range which allowed my HWG to keep adding heat.

Since my hot water heating costs are so low and adding a preheat tank is going to cost me $300-$400 plus our cooling load is small,   I don't think I will  be adding a pre heat tank any time soon.


Sorry to be so long getting back to you,  I was out working.

Attachment: Resize of DSCN9114.JPG

Dewayne Dean

<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system
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22 Sep 2008 03:44 PM
I need to look up somewhere a more in depth of how this all works because I'm not following all of it.
From what I'm seeing a0128958's desuperheater is taking in 101 water and moving it up to 102 to put back in the tank, which doesn't sound right.

Correct me if I'm wrong, but the idea is the geothermal takes regular water from the tap (or well), and heats it with either waste heat (cooling mode), or extra heat available from the system (heating mode), and puts it into the tank or a holding tank giving it a temperature around 80 or 90. The regular heater tank takes it up the rest of the way to 120.


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22 Sep 2008 04:29 PM
I'm a new user, and have a question for bill regarding his illustrations of the hot water hook-up. Mine seems to be hooked up the same as yours. I have a Climate Master Tranquilty and in the drawing they show the hook-up slightly differently. They show the cold supply (DHW in) entering at the bottom of the tank connected with a tee to (HWG in). The cold water in is the only difference to your drawings.

I guess my question is doe it matter?

It shows it here on page 16 http://www.climatemaster.com/downloads/97B0045N01.pdf.

Thanks

John


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22 Sep 2008 10:03 PM

I think I got it wrong. This is how my hot water tank is connected.


Not sure if it matters how the tank is connected.

What do you think?

John


Attachment: Graphic2.jpg

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22 Sep 2008 10:13 PM
The second best design ( the best would be to have a separate preheat tank ) would be to pull the water from the bottom, return to the top. Right now you are pulling and returning from the bottom. How much difference does it really make ? My guess is not very much. Mine is almost the same as yours as the concentric fitting pulls and returns at the bottom as well. The important factor here to make sure that the heat flows from the heat pump to the water heater. Under some conditions, the reverse can happen which is a total waste of energy.


Dewayne Dean

<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system
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22 Sep 2008 10:19 PM
The Cimate Master install manual says

"The HWG high limit temperature switch is set at 125°F [52°C] and is located on the HWG heat exchanger “Water In” line. If the HWG is connected incorrectly or if circulation is reversed, the aquastat will sense leaving water temperature and prevent HWG operation. UNDER NO CIRCUMSTANCES SHOULD THE LIMIT BE DISCONNECTED OR REMOVED!"

Don't know if that is what you mean?

Thanks for you reply.

John


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22 Sep 2008 10:31 PM
The problem occurs when the water in the hot water heater is hotter than the temp of the desuperheater. Then heat is taken from the hot water heater and transferred to the heat pump.

It sounds like Climate Master might have addressed this situation.


Dewayne Dean

<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system
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23 Sep 2008 11:49 AM
Posted By geodean on 09/22/2008 10:13 PM
The second best design ( the best would be to have a separate preheat tank ) would be to pull the water from the bottom, return to the top. Right now you are pulling and returning from the bottom. How much difference does it really make ? My guess is not very much. Mine is almost the same as yours as the concentric fitting pulls and returns at the bottom as well. The important factor here to make sure that the heat flows from the heat pump to the water heater. Under some conditions, the reverse can happen which is a total waste of energy.

I don't understand.

In my case, my HWG is pulling from the top, and returning to the bottom.  At first glance, to me, this would appear to be the most desired connection configuration.

My guess is, when the HWG is not running, and the HWH's gas-burner is off, and no HW is flowing, the water in the tank is at one homegenous temp.

When the HWH's gas-burner turns on, or when HW is flowing, I would think the water is hotter at the bottom of the tank than at the top.  Thus since I'm pulling from the top and returning to the bottom, it would appear that I'm pulling the colder water out to be heated by the HWG when it's running.  Which appears to make sense.

But I'm not familiar with HWH technology.  And thus I'm sure there's good reason why what appears to be is not correct.

And with respect to the 'concentric fitting:'  how does any water get in/out of the HWH when the water is being pulled and returned at the same point?

(Plumbing is not my expertise.)

Thanks,

Bill


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23 Sep 2008 12:05 PM
Posted By johncomyn on 09/22/2008 10:03 PM

I think I got it wrong. This is how my hot water tank is connected.


Not sure if it matters how the tank is connected.

What do you think?

John


John, your HWG is connected to your HWH identically to how mine is.  And is consistent with the WaterFurnace HWG installation instructions.

Below is an image of the top of my HWH, showing how my connection is just like what you illustrated.  My DHW Out (HW) pipe connection is on the left, and the DHW In (CW) is on the right.  The pipe connected to the DHW In (CW) pipe, going upwards, goes to the HWG In connection at my GSHP in my attic.

Best regards,

Bill

Attachment: IMG_9945diag.jpg

Energy reduction & monitoring</br>
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23 Sep 2008 12:25 PM

Bill, my HWH is electric, not sure if it makes a difference.

The Climate Master litreture says "On tanks with both upper and lower elements and thermostats, the lower element should be turned down to 100°F [38°C] or the lowest setting; the upper element should be adjusted to 120-130°F [49-54°C]."

I think the CW in at the top of the tank runs in a pipe internally to the bottom of the tank, so in my case it would be circulating the cooler water at the bottom of the tank, I could be wrong in my assumptions.

Anybody please correct me if I am wrong. Just trying to make sure I have it connected correctly.

John



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23 Sep 2008 12:40 PM
I am not a plumber either,  but here is my take on this.

The hottest water in a HWH is always at the top since heat rises.  The cold water "in" line on a HWH extends close to the bottom of the tank.  This enables the hot water to be replaced from the bottom up.   If you use a few gallons of hot water,  the water at the bottom of the tank is now cold.

If you are pulling water from the cold line,  you are pulling from the bottom of the tank.

As far as  "the water in the tank is at one homegenous temp",  my tank is not that way and I doubt that others are.

If you look at my chart you will see that the HWG in temp is as much as 15° lower than the HWH out temp.

The question that I have is where is the best place to return the water from the HWG.  In the top of the HWH or the bottom?  It seems to me that by leaving the  cooler water at the bottom undisturbed  you would get better performance from the HWG.

Most heat pump manufacturers show the plumbing done either with a concentric fitting or the way that Bill's system is piped.   So maybe they know something that I  don't.

A concentric fitting  is made up with two pipes of different diameter and different length.  The smaller pipe being the longest and extending further into the HWH.   This  allows  for the water to go out to the HWG and back thru the same fitting.


Dewayne Dean

<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system
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23 Sep 2008 12:46 PM
Sorry if this is nitpicking, but just to clarify, heat does not rise. Heat transfers/conducts/radiates. Hot air will rise. Hot water will rise/stratify... Not that this matters much...


Clark Timothy ([email protected])<br>Geothermal Heat Pumps: Heating and Cooling that's Dirt Cheap!<br>www.pinksgeothermal.com
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23 Sep 2008 12:46 PM
Posted By geodean on 09/22/2008 10:13 PM
The second best design ... would be to pull the water from the bottom, return to the top.

OK.  John's comment above helps me to better understand HWH design principles.  Incoming CW is piped (internally) to the bottom of HWHs.  That makes sense, now that I think about it, because that's where the gas-burner is.

So, noting this, the cooler water is at the bottom, not the top, and thus is consistent with what Dewayne comments as the the second best design - pulling water from the bottom, and returning it to the top.

I did some research on the WaterFurnace side of the subject.  It turns out this is how WF instructed the HWG to be connected, for many years.  Recently, though, (past few years) WF reversed the HWG's water loop flow.  I believe this is because of scale and sediment concerns.  Looks like it's a trade-off.  I.e., I'm pulling from the top, where the water is not as cool as at the bottom, but, I'm avoiding pulling into the HWG as much sediment dirt and debris as I'd otherwise get from the bottom.

So, perhaps 'second best design' is 'pull from the bottom / return to the top' from a performance point of view, and it's 'pull from the top / return to the bottom' from a long term reliability / maintenance point of view.

Interesting.

Best regards,

Bill


Energy reduction & monitoring</br>
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href="http://www.americaneei.com">
(www.americaneei.com)</A></br>
Example monitoring system: <A href="http://www.welserver.com/WEL0043"> www.welserver.com/WEL0043</A>
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