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cold showers on desuperheater
Last Post 16 Dec 2010 09:31 PM by docjenser. 73 Replies. |
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geome
Advanced Member
Posts:987
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| 27 Oct 2010 09:56 AM |
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Joe, first, thanks for keeping your response amicable. I will as well.
"I bring to the table before and after hot water kw consumption data. What is more valid? Can you or your installer document the same?"
What I do have is my word that when my DSH's run, that the DSH Out is Always discernibly hotter than the DSH In.* Also, our DSH's Always run when our geothermal units run (in heating or cooling mode.) Does our installer have data, probably not, or he would have volunteered it to me.
I can say, that we are both very happy with our results. Could we both be happier with our results if we added a buffer tank, perhaps, but at the cost of increased space, installation cost, and additional risk of leaks. I don't disagree that a buffer tank has advantages (some of which you mentioned), but there are disadvantages too. Some people believe the benefits outweigh the disadvantages (and that's perfectly fine with me.) The reverse is true for me since our unit is working wonderfully. I would feel differently if our DSH system was not contributing to hot water production, but it is, so I'm happy. I wish more happy single tank owners with DSH's would chime in, but unfortunately, most people on this forum write in about problems, not success.
*Was this the situation with the data case you referred to (where the DSH Out was Always hotter than the DSH In, and the DSH Always operated when the geothermal system was running)?
What were the other particulars with this data case (manufacturer of geothermal system and water heater, hot water usage per day, upper and lower thermostat settings on water heater, tank size, loop EWT, etc.?) |
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| Homeowner with WF Envision NDV038 (packaged) & NDZ026 (split), one 3000' 4 pipe closed horizontal ground loop, Prestige thermostats, desuperheaters, 85 gal. Marathon. |
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docjenser
Veteran Member
Posts:1400
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| 27 Oct 2010 10:13 AM |
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Posted By geome on 27 Oct 2010 08:24 AM
For some reason, manufacturers and some installers (including our installer that has a single electric tank setup in his house) don't agree that 2 tanks are always necessary. There are also instances here where homeowners are happy with their results with a single tank setup, and don't want a second tank for various reasons. There seem to be benefits to a 2 tank setup, but there are drawbacks too (previously discussed in depth.)
I guess the problem is that not many installers seek feedback. If you actually monitor what is going on you will be surprised how much of an energy hog a "wrong" setup can be. Sure some are happy, since the overall performance of the system is still great and the water is warm. I have one of the early 410a Synergy units (must have been made before they realized there is a DSH problem and applied some controls), which I use for A/C, hydronic heat and year around hot water, and my desuperheater was turning on every time the unit turned on. After putting the welserver system for monitoring on it, I realized that in A/C mode every time the DSH was running my tank temp was dropping, resulting that it was taking heat from the tank and putting it in the ground loop. Now I turn off my DSH in the summer time, and the interval before my tank calls for heat again more than tripled! |
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| www.buffalogeothermalheating.com |
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geome
Advanced Member
Posts:987
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| 27 Oct 2010 10:23 AM |
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Posted By docjenser on 27 Oct 2010 10:13 AM
I guess the problem is that not many installers seek feedback. If you actually monitor what is going on you will be surprised how much of an energy hog a "wrong" setup can be. Sure some are happy, since the overall performance of the system is still great and the water is warm. I have one of the early 410a Synergy units (must have been made before they realized there is a DSH problem and applied some controls), which I use for A/C, hydronic heat and year around hot water, and my desuperheater was turning on every time the unit turned on. After putting the welserver system for monitoring on it, I realized that in A/C mode every time the DSH was running my tank temp was dropping, resulting that it was taking heat from the tank and putting it in the ground loop. Now I turn off my DSH in the summer time, and the interval before my tank calls for heat again more than tripled!
Thanks doc. I do not dispute that a buffer tank can correct some problems, or add some efficiency to a DSH system that is otherwise functioning correctly. I think we're more on the same page than not. I just don't think it is the perfect fit for everyone, all the time, if their single tank DSH system is working as intended (contributing to hot water production.) |
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| Homeowner with WF Envision NDV038 (packaged) & NDZ026 (split), one 3000' 4 pipe closed horizontal ground loop, Prestige thermostats, desuperheaters, 85 gal. Marathon. |
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docjenser
Veteran Member
Posts:1400
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| 27 Oct 2010 10:40 AM |
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Posted By geome on 27 Oct 2010 10:23 AM
Posted By docjenser on 27 Oct 2010 10:13 AM
I just don't think it is the perfect fit for everyone, all the time, if their single tank DSH system is working as intended (contributing to hot water production.)
No, I don't question that, although I simply refuse to put them in as a single tank system.
We just fix too many systems where the customer is not happy, but the installer does not think there is a problem.
Sometimes unreal expectations by the customer, but most of the time legitimate issues where the original installer behaves ignorant. |
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| www.buffalogeothermalheating.com |
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jpespisa
New Member
Posts:48
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| 27 Oct 2010 10:44 AM |
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As you can see from my welserver WEB page I am tracking electricity cost for the HP and hot water heater very closely. I'm also tracking when the HP, Well Pump, and Hot water heater are on. I will admit that I have noticed that the DSH will trigger the hot water heater to turn on for a few minutes. I expect it's due to the cool water that's in the 70' of pipe when it's first injected into the bottom of the water heater. Surprisingly this is a very rare occurrence. And only really occurs during the shoulder season. It's a small sacrifice for the benefits I receive from the DSH during the winter months.
I did consider adding buffer tank for a while, but now that I have installed a solar water heater which has its own buffer tank it really didn't make sense.
I estimate I was spending $60-$80 dollars a month on hot water before the HP was installed. The highest it's been since then is $40. Obviously the solar water heater has a big effect during the summer months. But the HP does most of the heavy lifting during the winter months. I know I can improve this by reducing the pipe length. Now if I can get my brother (Master Plumber) to give me hand, I might actually get this done.
http://welserver.com/WEL0167/ |
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| http://welserver.com/WEL0167/ |
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geome
Advanced Member
Posts:987
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| 27 Oct 2010 11:02 AM |
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Posted By docjenser on 27 Oct 2010 10:40 AM
Posted By geome on 27 Oct 2010 10:23 AM
Posted By docjenser on 27 Oct 2010 10:13 AM
I just don't think it is the perfect fit for everyone, all the time,
if their single tank DSH system is working as intended (contributing to
hot water production.)
No, I don't question that, although I simply refuse to put them in as a
single tank system. We just fix too many systems where the customer is
not happy, but the installer does not think there is a problem.
Sometimes unreal expectations by the customer, but most of the time
legitimate issues where the original installer behaves ignorant.
I can see all this happening. If I was an installer, I might do the same thing. It's a shame the DSH benefit from a single tank setup seem to be hit or miss. |
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| Homeowner with WF Envision NDV038 (packaged) & NDZ026 (split), one 3000' 4 pipe closed horizontal ground loop, Prestige thermostats, desuperheaters, 85 gal. Marathon. |
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geome
Advanced Member
Posts:987
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| 27 Oct 2010 11:14 AM |
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Posted By jpespisa on 27 Oct 2010 10:44 AM
As you can see from my welserver WEB page I am tracking electricity cost for the HP and hot water heater very closely. I'm also tracking when the HP, Well Pump, and Hot water heater are on. I will admit that I have noticed that the DSH will trigger the hot water heater to turn on for a few minutes. I expect it's due to the cool water that's in the 70' of pipe when it's first injected into the bottom of the water heater. Surprisingly this is a very rare occurrence. And only really occurs during the shoulder season. It's a small sacrifice for the benefits I receive from the DSH during the winter months.
I did consider adding buffer tank for a while, but now that I have installed a solar water heater which has its own buffer tank it really didn't make sense.
I estimate I was spending $60-$80 dollars a month on hot water before the HP was installed. The highest it's been since then is $40. Obviously the solar water heater has a big effect during the summer months. But the HP does most of the heavy lifting during the winter months. I know I can improve this by reducing the pipe length. Now if I can get my brother (Master Plumber) to give me hand, I might actually get this done.
http://welserver.com/WEL0167/
Thanks jpespisa. Where are the WEL sensors located on your DSH? If I am reading the chart correctly (and I may not be) it looks like for the last 12 hours the DSH is providing roughly a 1.5f increase between sensors? Is your DSH plumbed to your water heater (and not the solar tank)? |
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| Homeowner with WF Envision NDV038 (packaged) & NDZ026 (split), one 3000' 4 pipe closed horizontal ground loop, Prestige thermostats, desuperheaters, 85 gal. Marathon. |
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docjenser
Veteran Member
Posts:1400
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| 27 Oct 2010 11:24 AM |
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I don't think it is so much a hit or miss. Since the DSH performance in A/C mode depends on the EWT from the loop, it is also a question of run time, ground temperature etc.
I can see a benefit in souther climate, although a two tank set up is still much preferred. In heating dominated climate, for me, a one tank setup is a no starter.
It is my reputation on the line, I simply hate it when a customer is not absolutely raving about their system...... |
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| www.buffalogeothermalheating.com |
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jpespisa
New Member
Posts:48
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| 27 Oct 2010 12:00 PM |
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Hi Geome,
My WEL sensors are located right at the HP. Unfortunately we are experiencing unusually warm temperatures up here in MA. So my HP has not turned on in the last 24 hours. I'm only displaying the last 12 hours on the charts. So you’re not going to see anything of interest until the HP kicks on again. Probably this weekend. I typically observe ~10 degree temp different between EWT and LWT.
I did recently add another sensor next to the water heater to track the temp of the water coming from the HP. This is how I determined the 5 degree drop I'm observing. BTW I just updated the welserver to better display that sensor. Also added day high and month to date high readings.
My DSH is plumbed to the 80 gallon electric water heater. I actually thought about plumbing the DSH to my the solar buffer tank but I have two issues with that. 1- The solar buffer tank is further away from the HP then the electric tank. 2- In the summer the water in the solar water buffer tank can reach 150-160 degrees. I wasn't sure what effect this might have on the DSH. I assume it would shut down fairly quickly.
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| http://welserver.com/WEL0167/ |
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geome
Advanced Member
Posts:987
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| 27 Oct 2010 12:41 PM |
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Thanks jpespisa. I was just out for a bit, and realized your system hadn't been running, or it would have been running for 12 hours straight (strange for this time of the year.) :-)
Based on what you have observed, is the DSH contributing to hot water production, or is it a wash from the 5 degree drop (both ways?) due to the length of run?
It will be interesting to see the results after the length is reduced too. Sorry if I missed it earlier, what brand is your geothermal system, and solar system? How does your vault work with your setup? |
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| Homeowner with WF Envision NDV038 (packaged) & NDZ026 (split), one 3000' 4 pipe closed horizontal ground loop, Prestige thermostats, desuperheaters, 85 gal. Marathon. |
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docjenser
Veteran Member
Posts:1400
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| 27 Oct 2010 01:04 PM |
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Keep in mind,
the DSH performance in heating mode is unquestionable, it will always add some BTU, but it will compete with the electric heat element in the water tank with a single tank setup, and therefore shut off the circulation relatively fast. The buffer tank does not have any competing heatsource, thus the DSH can run longer and and the water typically is colder for a longer period of time, adding efficiency. Unfortunately I erased my WEL graphs which show he "stealing" of heat when the DSH was running in the summer time. |
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| www.buffalogeothermalheating.com |
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jpespisa
New Member
Posts:48
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| 27 Oct 2010 01:35 PM |
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The DSH is definitely contributing to my hot water production during the heating season. In the summer the HP cycle times aren't long enough for the DSH to engage.
If you look at the water_tmp_HWG graph when the HP has been running overnight you will notice a pattern that looks like a set of stairs. Each step shows an increase in the EWT and LWT temp from/to the DSH. The LWT will typically reach 110-115 degrees by the morning. It will quickly drop once the family gets up an starts using hot water.
I’m hoping to increase the LWT temps by reducing the pipe length and insulating the PEX tubing. I only insulated the PEX in the unfinished part of the basement. This will hopefully reduce the heat loss I’m now observing . BTW I did turn down the thermostat on the lower heating element on the water heater. I noticed the water in the bottom of the electric water heater is much colder then the top. This may explain why I rarely observe the water heater kicking on when the DSH turns on.
The HP is a ClimateMaster TT27-72 (6 ton). The solar system I purchased as a kit that I installed myself. It uses two 8x4 AET collectors and 80 gallon solar tank/heat exchanger.
The vault is basically a dry well. I have an open loop SCW design. I use my artesian well for both domestic water and the HP. Unfortunately my well is under sized for my HP. So on the really cold days I quickly cool down the water in my well. To overcome this issue I have to start bleeding water in order to maintain the well water temperature. The bleed starts when the EWT temp reaches 47 degrees. I bleed at a rate of 3GPM to prevent the well temps from dropping any lower. The bleed line tees off the pipe exiting the HP to the vault/dry well.
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| http://welserver.com/WEL0167/ |
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geome
Advanced Member
Posts:987
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| 27 Oct 2010 01:36 PM |
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Got it - "everything's better with buffer (bacon)" :-)
Earlier, I should have said there were many variables instead of hit or miss (I was in a hurry.) |
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| Homeowner with WF Envision NDV038 (packaged) & NDZ026 (split), one 3000' 4 pipe closed horizontal ground loop, Prestige thermostats, desuperheaters, 85 gal. Marathon. |
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geome
Advanced Member
Posts:987
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| 27 Oct 2010 02:13 PM |
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jpespisa,
Thanks for the info. Have you tried reducing the cycles per hour in cooling mode 1? Several of us here like the results and have commented on better DSH production, but to my knowledge no one that did that has a WEL system. The results would be be interesting to see in a heating dominated climate. Your piping plans and insulation sound good to me. |
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| Homeowner with WF Envision NDV038 (packaged) & NDZ026 (split), one 3000' 4 pipe closed horizontal ground loop, Prestige thermostats, desuperheaters, 85 gal. Marathon. |
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docjenser
Veteran Member
Posts:1400
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| 27 Oct 2010 02:46 PM |
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I feel that I am getting too much into things here...cycling length has a big impact on DSH performance.
We have exactly this scenarios with two of our customers. One home owner overshoot and run 1 hours minimum running cycles.
I am not saying this is the way it should be, but I have not much control over the thermostat settings by the owner. He wants it that way.
http://welserver.com/WEL0288/
Buffer tank =125 degrees
Manual J =79 KBTU/H
DSH did never turned on in A/C mode, because ground loop was too cold. It is one of those early R-410 units, with a DSH shut off unless the compressor discharge temp is above 125 degrees.
http://welserver.com/WEL0336/
Manual J = 92 KBTU/H
Shorter cycling
Buffer Tank = 65 degrees
Never got over 93 degrees in A/C mode.
Different indoor setpoint, but both 6 ton systems in heat dominated climate. Unfortunately no chance to run them in A/C mode now. Too cold outside. |
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| www.buffalogeothermalheating.com |
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jpespisa
New Member
Posts:48
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| 27 Oct 2010 04:40 PM |
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Thanks for the suggestion Geome. Actually it was your recommendation to me on an old thread to change the thermostat cycles to two per hour. That dramatically improved my DSH performance in heating mode. That change worked quite well with no reduction in over all comfort.
To be honest I’m not too concerned about DSH performance during the cooling mode now that I have the solar water heater in place. I’d probably just turn it off if I could.
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| http://welserver.com/WEL0167/ |
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geome
Advanced Member
Posts:987
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| 27 Oct 2010 05:01 PM |
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Now I remember. At least I'm consistent. :-) Glad it's working. |
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| Homeowner with WF Envision NDV038 (packaged) & NDZ026 (split), one 3000' 4 pipe closed horizontal ground loop, Prestige thermostats, desuperheaters, 85 gal. Marathon. |
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joe.ami
Veteran Member
Posts:4377
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| 27 Oct 2010 09:47 PM |
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Posted By geome on 27 Oct 2010 09:56 AM
Joe, first, thanks for keeping your response amicable. I will as well.
Geome, thanks for the laugh, I've had a heavy work load and was thinkin' on the way home my brevity may have sounded terse  . I did have a conversation with some one recently where I mentioned my responses are sometimes handicapped by the contractor "no fail" perspective. I don't want to spend energy on something that may work, It has to work; or it costs me money. You may recall the case I cite that I installed the buffer tank at my expense after op cost rose. If you have the means at some point, a welserver or the like on your water heater tested both with and without the DSH running might be interesting. It is a fair point that the heat pump jacks up electric bill enough to conceal a rise in DHW cost if not monitored seperately. Remember, I was a contractor that "drank the water" or hot water, until the revelation of independant monitoring. j |
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Joe Hardin
www.amicontracting.com
We Dig Comfort!
www.doityourselfgeothermal.com
Dig Your Own Comfort! |
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WF_Inc.
New Member
Posts:88
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| 28 Oct 2010 03:51 PM |
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In any desuperheater application, heat from the DHW tank can be taken and added to the unit refrigerant circuit if the DHW temperature is higher than the refrigerant discharge temperature.
In the past manufacturers used R-22 refrigerant and the temperature differential was not an issue. However, with manufacturers being forced to move to 410A refrigerant there are some conditions when the discharge temperature is lower that the DHW temperature. To prevent heat being taken from the DHW tank WaterFurnace uses their DHW and Freeze protection thermistors to measure the water and refrigerant temperatures. If the DHW temperature is higher than the refrigerant discharge temperature, the unit microprocessor control will not allow the desuperheater option to function.
In any single tank installation, make sure the lower element is either turned off or disconnected. If you need additional hot water or want to take full advantage of the desuperheater option, install a second tank for more DHW storage capacity.
WaterFurnace International, Inc. |
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engineer
Veteran Member
Posts:2749
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| 28 Oct 2010 08:49 PM |
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While I agree with that analysis, it basically mandates a buffer tank. Turning off the lower element is simply not an option in nearly all instances. Doing so deprives the home of about 75% of the total capacity of the water heater. In times of no DSH production a 60 gallon water heater with no lower element would have only the top 15 or so gallons warm, barely enough for a single short shower. Few families would abide that situation. |
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Curt Kinder <br><br>
The truth is incontrovertible. Malice may attack it, ignorance may deride it, but in the end, there it is - Winston Churchill <br><br><a href="http://www.greenersolutionsair.com">www.greenersolutionsair.com</a>
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