johncomyn
Registered Users
New Member
Posts:23
 |
| 10/08/2009 9:01 AM |
|
| Now that we are heading into the heating season again, my heat pump is running more frequently.
I notice when taking a shower that the hot water seems cooler when the heat pump has been running some overnight. Could my desuperheater be lowering the temp in my hot water heater? And if that is happening would it be turning on my Hot Water Heater unnecessarily?
In the cooling season on days, which were few, that the heat pump ran for cooling the hot water was considerably hotter.
I have a 4 ton ClimateMaster Tranquility Heat Pump hooked up to a electric 60 gal hot water heater without a preheat tank.
I have a drawing in this thread of how my hot water heater is hooked up http://www.greenbuildingtalk.com/Forums/tabid/53/view/topic/forumid/13/postid/42787/Default.aspx
Thanks
John
|
|
|
|
|
|
|
craigb93
Registered Users
New Member
Posts:31
|
| 10/08/2009 9:17 AM |
|
Think about how a GSHP works.................makes hot water to put in the ground while it makes cold water to cool your house. The reverse occurs in heating mode. The desuperheater temperatures mimic this sequence.
Probably time to turn OFF your desuperheater for the duration of the heating season.
Dick |
|
|
|
|
heatoftheearth
Registered Users
New Member
Posts:44
|
| 10/08/2009 9:41 AM |
|
Posted By johncomyn on 10/08/2009 9:01 AM
Now that we are heading into the heating season again, my heat pump is running more frequently.
I notice when taking a shower that the hot water seems cooler when the heat pump has been running some overnight. Could my desuperheater be lowering the temp in my hot water heater? And if that is happening would it be turning on my Hot Water Heater unnecessarily?
anks
John
Yes and Yes.
My first fix would be to use your current tank(dis able power leave plumbing) as the preheat tank and add second tank and power it.
Second fix would be to disable the DSH
this poster had a similar problem Dont Know how or if he resolved it
https://gbt.buildcentral.com/Forums/tabid/53/forumid/13/postid/65704/view/topic/Default.aspx
|
|
|
|
|
johncomyn
Registered Users
New Member
Posts:23
|
| 10/08/2009 10:19 AM |
|
So how can I check what is happening? Measure temperatures at the Heat Pump DSH in and out?
Could it be that I am losing heat from my hot water heater to the heat pump? This would cause my hot water heater to cycle on unnecessarily and cost me lots of $?
How do I dis-able the DSH?
Thanks
John |
|
|
|
|
Masoud
Registered Users
Basic Member
Posts:116
|
| 10/08/2009 10:31 AM |
|
The Tranquility 27 DSH should not be stealing much heat from the hot water tank. There is a limit (125˚ F, if my memory is good) for entering water temp to DSH pump, at which it is turned off. But John still needs a pre-heat tank to get most from his 4 ton GSHP.
Regards,
Masoud, not a pro, a Tranquility 27 owner.
|
|
|
|
|
Ona
Registered Users
Basic Member
Posts:130
|
| 10/08/2009 11:59 AM |
|
johncomyn ~ I am a homeowner (not an expert) who had geothermal through last winter in a heating dominated area (Upstate NY). My hot water never became cooler. Based on what my installer told me, I am suprised that hot water would become cooler if installed correctly. I have a 3 ton WaterFurnace envision. Last winter I had plenty of hot water, as a matter of fact, I noticed that I had less volume of hot water when the geo system was not running in the spring, but I've never noticed a "cooler water" situation.
Also, last winter my hot water heater used 2-5 kWhrs/day to heat my hot water, when my geo system was no longer needed in the spring we were using 10-12 kWhrsday to heat my hot water. This informs me that my desuperheater was in fact working throughout the winter. I understood that a desuperheater "stole" a little from the geo heating process to preheat hot water even in the winter. Again, I am not an expert, but this was my experience for my first winter on geo. |
|
Ona
just trying to make my old home better
www.geochoices.com |
|
|
geome
Registered Users
New Member
Posts:59
|
| 10/08/2009 3:40 PM |
|
John, I'm not an expert either, but we have a single tank setup too. Do you either have a water heater timer, or have the lower water heater thermostat set significantly lower than the upper thermostat? One thing we noticed is when the geothermal system (and desuperheater) runs for short periods of time, it mixed the colder water at the bottom of the water heater with the hotter water at the top of the tank. This cooled the hotter water at the top of the tank (and warmed the cooler water at the bottom of the tank) and made it seem like the desuperheater was stealing hot water from the tank, even though it wasn't. We knew this was the case because the desuperheater out was always hotter than the desuperheater in. We overcame this problem by running the water heater timer two times per day at times just before anticipated hot water usage. I suppose someone could also increase the lower thermostat setting (closer to the upper thermostat setting) until the geothermal/desuperheater runs more (due to it being colder outside), and then reduce the setting again to get more benefit out of the desuperheater. We are very happy with a one tank setup, but two tanks are definitely better if you don't mind a second water in the house.
Also, if you have a dual stage compressor, our installer told us that the output water temperature of the desuperheater will be hotter in second stage compared to first stage heating and air conditioning.
I would start by checking the input and output temperature of the desuperheater water lines before taking any action.
|
|
|
|
|
engineer
Registered Users
Veteran Member
Posts:1157
|
| 10/08/2009 4:29 PM |
|
I agree that 2nd stage operation will provide both more Btuh and higher temps from the desuper.
Some systems have a sensor that decides when refrigerant conditions are unsuitable for DSH production, typically when system is in cooling mode with fairly low EWT - refrigerant just doesn't get hot enough to heat domestic water. This condition would be much worse in a single tank arrangement.
I've said it before and I will again now: It rarely makes sense to purchase and deploy the desuper option without it having its own unpowered storage or buffer tank.
Ona - your KWH numbers are excellent data...do you have a buffer tank? |
|
Without data, you only have an opinion. |
|
|
Bergy
Registered Users
Basic Member
Posts:116
|
| 10/08/2009 6:59 PM |
|
Gas fired water heaters and desuperheaters do not play well together. A gas water heater does not have the temperature stratification needed by the desuperheater. If your tank is set for 130* the water temps you pull into the desuperheater will be about 125*. You need an un-powered electric tank in front of the gas unit if you want to take full advantage of your desuperheater.
Bergy
|
|
|
|
|
bgillett
Registered Users
New Member
Posts:18
|
| 10/09/2009 6:53 AM |
|
| I have noticed the same thing w/ my water being cooler. I had to turn my water heater up to get the same temp that I had during the summer. I have a preheat tank and a natural gas water heater. I haven't talked to my installer yet because I wanted to see what happens as it gets colder. Our system was installed last November so this is the first time I have had this happen. Also, I rarely used the AC so I dont' think that this is happening b/c I am not getting the extra btus that I was getting when the heat pump was in cooling mode. |
|
|
|
|
geome
Registered Users
New Member
Posts:59
|
| 10/09/2009 7:56 AM |
|
Experts, I'm confused. Why would people with preheat tanks notice any water temperature difference at any time during the year (regardless of desuperheater usage) unless the thermostat is either set too low on the "finishing" water heater, or the recovery rate of the finishing tank can't keep up with hot water demand (too small of a finishing tank)? I can see the recovery rate being less when the geothermal/desuperheater isn't in use (since the water from the preheat tank is colder).
|
|
|
|
|
johncomyn
Registered Users
New Member
Posts:23
|
| 10/09/2009 3:08 PM |
|
Thanks, for all the replies!
I tried testing the in and out fittings from the GSHP for temperature. The "in" was at about 80 degrees and "out" at about 82 degrees it jumped around abit up into the 90's at one point. All I was using is a digital probe thermometer against the fittings externally on the unit, not sure how accurate this will be. The hot water tank was not used all day before that, so I presume temp is much lower at the bottom of the tank.
Maybe what geome said makes sense, the flow of water from the desuperheater is mixing the cold from the bottom with the hot.
Top element is set to 125 and bottom to the minimum guessing 100 degrees.
I have a 60 gallon hot water heater and do have another 40 gallon which I plan to hook up some time as the hot water heater and use the 60 gallon for pre-heat.
Thanks
John |
|
|
|
|
geome
Registered Users
New Member
Posts:59
|
| 10/09/2009 6:14 PM |
|
| Again, I'm no expert, but your hot water needs will determine if it is better to have the larger or smaller tank as the powered finishing tank. If your typical maximum hot water usage (for instance - times when people in your house take showers simultaneously or consecutively) exceeds what the smaller tank can provide (look at the first hour rating and recovery rate to help guide you), you may want to consider the larger tank as the powered tank. Of course, it's possible that the smaller tank could have a better first hour rating and recovery rate, but I'd check the specs to be sure. When your desuperheater/geothermal system doesn't run a lot in the spring and fall, choosing the tank with the better first hour rating and recovery rate should give you more available hot water. In the summer and winter, this may not be an issue since the buffer tank should be hotter from the geothermal system running more. |
|
|
|
|
engineer
Registered Users
Veteran Member
Posts:1157
|
| 10/09/2009 8:53 PM |
|
You shouldn't be confused - both your remarks are accurate.
Deficiencies of the finishing tank may be hidden by a highly effective desuper + buffer combination until a period of HVAC non-use (such as spring or fall mild weather) makes the finishing tank carry the whole hot water load.
|
|
Without data, you only have an opinion. |
|
|
bgillett
Registered Users
New Member
Posts:18
|
| 10/10/2009 5:57 AM |
|
| Here is where I am confused. My hot water was worked fine during the summer, when I basically didn't use the AC, does it make sense that I would have to turn my water heater up now that my GEO system is running? The only thing that I could think of would be a lower temperature in the basement, but I don't think that would make a large difference. |
|
|
|
|
newdeal
Registered Users
New Member
Posts:28
|
| 10/10/2009 6:15 AM |
|
| maybe your water heater stopped working properly and so you are only using the temperature the desuperheater is putting out |
|
|
|
|
geome
Registered Users
New Member
Posts:59
|
| 10/10/2009 6:22 PM |
|
The mixing problem I mentioned would only apply to a single tank setup. bgillett, is your hot water not as hot, or is it possible that your cold water is colder? The pressure tank for our well is located in a vented crawlspace. When it is cold outside, the water that sits overnight in the pressure tank gets even colder. Then we have to use more hot water to compensate when taking showers. Not sure if this is happening in your situation, but it would explain your heat going on and the hot water seeming to be not as hot (when mixed with cold water).
If cold water isn't the issue, I'm not sure what the problem could be. Are your desuperheater lines only going into the buffer tank? Maybe check the hot water temperature compared to the thermostat setting on the gas water heater? |
|
|
|
|
Masoud
Registered Users
Basic Member
Posts:116
|
| 10/11/2009 10:15 AM |
|
In regard to Ben's water heater,
I saw a similar problem exhibited by a friend's old gas water heater that had a broken dip (aka cold fill) tube. The dip tube's job is to deliver cold water to the lower section of of the tank, without much mixing with hot water.
I can also think of a bad thermostat on the tank, or one that simply needed adjustment. I'm not a plumbing expert.
Regards,
Masoud
|
|
|
|
|
bgillett
Registered Users
New Member
Posts:18
|
| 10/11/2009 7:11 PM |
|
| The pressure tank is in the basement, so I don't' think that is an issue. The gas water heater is only a year old so I don't know. It could just be that the crawl space is colder and the lines run through it. I just thought it was weird timing. I will watch my utility bill to see if the gas portion of the bill changes. |
|
|
|
|
joe.ami
Registered Users
Veteran Member
Posts:1418
|
| 10/12/2009 6:36 AM |
|
Hi Ben,
You now have let your installer know what's going on.
Lower entering water temps, greater usage and lower surrounding temps could all contribute. Analyze possible changes in these things as well as improvements to the home that may be causing draft changes with the chimney (greater insulation and less drafts elsewhere make tank more likely to employ colder combustion air from crawl).
Try different setting on tank (mechanical controls relax as well).
Keep me posted (in private e-mail so as not to hijack thread).
More to the general question a foot note to Bergy's observation:
10/08/2009 6:59 PM
Gas fired water heaters and desuperheaters do not play well together. You need an un-powered electric tank in front of the gas unit if you want to take full advantage of your desuperheater.
Bergy
I'm not aware of a manufacturer who suggest use of a DSH on a gas water heater with no buffer. There may be warranty issues.
Joe
|
|
Just a Mechanic;
Geothermal; Savings Underfoot |
|
|