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Masoud
Basic Member
Posts:180
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| 30 Aug 2010 08:13 PM |
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engineer wrote yesterday: "the in/out temps may be explained by very low flows resulting from natural convection "
This has been verified on my 3-ton Tranquility 27 (a similar make to Stuarts), with power to DSH pump was disconnected. I have observed: DSH IN hot OUT cold, OUT hot IN cold, both hot, both cold, and each warmer than the other. All only noticed near the heat pump connections, not near the pre-heat tank.
jonr wrote today: "I suppose if one wanted to force up the temperatures, they could bypass the ground loop circuit to some extent. Might even be worth it in some cases."
This is also true with my heat pump running in dehumidification mode (Climadry), mostly bypassing the ground loop. While actual EWT is around 65˚, and despite relatively short run times, hot water production is good.
Regards,
Masoud |
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decafdrinker
Basic Member
Posts:420
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| 30 Aug 2010 09:03 PM |
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"Your low LWT may well be keeping the DSH off, perhaps rightly so."
Is there any way to temporarily boost the LWT for the sake of testing? I can try switching to heating mode for a time and check then. LWT is a product of both EWT and the amount of heat drawn out of the house, which is a product of how warm the air is in the return duct as compared to the supply. Right?
If I let the house heat up, maybe turn the system off for the day, then turn it on when I get home, there should be a lot of heat to process. Would that be enough to cause the DSH to operate?
Assuming that everything is connected correctly, is the system just not gonna produce hot water coz it's too efficient and the ground loops are just too nice and cold?
I wish I could find someone to check this out. I'm meeting a lot of dead ends. Local companies don't want to check systems they didn't install. |
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docjenser
Veteran Member
Posts:1400
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| 30 Aug 2010 09:16 PM |
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Posted By stuart.wyss on 30 Aug 2010 01:31 PM
That might be a last resort, as I would not want to damage anything or risk voiding the warranty. Could I just bypass the thermostatic switches with a piece of 12 ga. wire? I mean, the worst thing that would happen is the pump would turn on and possibly the system wouldn't produce much HW if I was watching it. I'd certainly make sure the DSH wasn't exceeding 125 on the output.
I'm also looking into getting a WELserver...expensive....SIGH.
You would start taking BTUs out of your hot water tank...and putting it into the ground. That was the reason they put the switch there. |
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| www.buffalogeothermalheating.com |
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engineer
Veteran Member
Posts:2749
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| 02 Sep 2010 02:49 AM |
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Posted By stuart.wyss on 30 Aug 2010 09:03 PM
"Your low LWT may well be keeping the DSH off, perhaps rightly so."
Is there any way to temporarily boost the LWT for the sake of testing? I can try switching to heating mode for a time and check then. LWT is a product of both EWT and the amount of heat drawn out of the house, which is a product of how warm the air is in the return duct as compared to the supply. Right?
If I let the house heat up, maybe turn the system off for the day, then turn it on when I get home, there should be a lot of heat to process. Would that be enough to cause the DSH to operate?
Assuming that everything is connected correctly, is the system just not gonna produce hot water coz it's too efficient and the ground loops are just too nice and cold?
I wish I could find someone to check this out. I'm meeting a lot of dead ends. Local companies don't want to check systems they didn't install.
Find a way to reduce loop water flow and LWT will rise. Slow the loop pump, operate it intermittently, or introduce a restriction in the lines. Letting the house get really warm will temporarily provide extra load, but the system will manage that via modulation by the TXV, limiting rate of heat rejection. If you have a several hour continuous run you will somewhat saturate a closed loop system with extra heat. Both EWT and LWT will rise, possibly by 5-10 degrees as the system works off the accumulated heat in the house. Occupant comfort will suffer until the system catches up, so this is of limited practicality as a long term strategy. Someone knowledgeable needs to spend 10-15 minutes fingering tubes, pipes and pump in your system to ascertain what is going on. Too bad I'm not nearby. |
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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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decafdrinker
Basic Member
Posts:420
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| 02 Sep 2010 07:26 AM |
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Thank you everyone for your input. I finally found someone who has been in the business for over 20 years with Geothermal, and he's coming out next week. I will post the results. |
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docjenser
Veteran Member
Posts:1400
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| 05 Sep 2010 04:09 PM |
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Posted By engineer on 02 Sep 2010 02:49 AM
"Find a way to reduce loop water flow and LWT will rise. Slow the loop pump, operate it intermittently, or introduce a restriction in the lines."
Good point. if you have headered inside, you might be able to shut of some part of the loopfield. Or restrict flow with one of the shut off valves. Although A/C efficiency will suffer.... |
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| www.buffalogeothermalheating.com |
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decafdrinker
Basic Member
Posts:420
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| 08 Sep 2010 11:00 AM |
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So, to summarize about buffer tanks (and I apologize for repeating info that is scattered in various threads on this board).
The advantage of a buffer tank is that it's unheated, and therefore the desuperheater is able to efficiently dump heat into the unheated water. Then the "pre-heated" water goes from the buffer tank to the "finishing tank", where it's further raised (if necessary) and maintained at the temperature desired for the house, using gas, electric, AirTap, or something else.
Not having a buffer tank and maintaining the single tank with gas/electric/AirTap/something at the household temperature prevents the desuperheater from working efficiently, or even working at all, because the water is *already* at or above the temperature to which the desuperheater can heat. |
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Bergy
Basic Member
Posts:277
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| 08 Sep 2010 02:46 PM |
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In a nut shell... yes.
Bergy
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joe.ami
Veteran Member
Posts:4377
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| 08 Sep 2010 10:27 PM |
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I would say, kinda.
I can't speak for all brands, but most I've worked with, say no buffer tank with electric systems only (not gas) and further encourage disabling of lower element. There are some here who suggest this may not be true of R-22 systems (I can't confirm or deny the claims).
That said, after purchasing a buffer tank for a customer or two after water heating electric consumption climbed with unbuffered install we will only install systems with a buffer tank.
Joe |
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Joe Hardin
www.amicontracting.com
We Dig Comfort!
www.doityourselfgeothermal.com
Dig Your Own Comfort! |
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engineer
Veteran Member
Posts:2749
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| 08 Sep 2010 10:39 PM |
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Stu,
That's actually an excellent summary of why a buffer or preheat tank is generally required for a geo (or, for that matter, conventional heat pump) recovery desuperheater to be effective. Your two paragraphs nicely sum up what I've tried to convey in 6-8 paragraphs here and elsewhere...nicely done. |
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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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decafdrinker
Basic Member
Posts:420
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| 09 Sep 2010 12:19 PM |
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Ok, so here's the "official" word from the experienced guy and what he wants to do. (I'm not posting it for debate, but more for progress on what my system is going through)
1. move the manifold to right where the pipes come in from outside, mount it right-way-up, run 1 1/4 inch pipes from the manifold across the ceiling to the Flo Center and the GeoMax (this will replace all 8 loop pipes coming across the ceiling into the upside-down manifold right next to the Flo Center)
2. move the water heater w/ AirTap right next to the GeoMax 2 and add a 50 gallon buffer tank. Cold water to be pulled out of the top, through the desuper, and go into the bottom drain. This will dramatically shorten the pex that runs from the desuper to the water tanks. Also, add valves/drains to allow purging of air from the desuperheater lines (there are currently no valves/drains and lots of 'high' places that air is probably trapped.
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docjenser
Veteran Member
Posts:1400
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| 14 Sep 2010 08:18 PM |
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OK...then we will not debate it but patiently wait for your progress report.
#2 sounds like a good plan
Don't know if #1 will help much, but again, waiting for your report! |
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| www.buffalogeothermalheating.com |
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decafdrinker
Basic Member
Posts:420
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| 15 Sep 2010 07:22 PM |
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I think #1 was more to neaten the system up....it's a somewhat sloppy install, plus moving the manifold frees up space to redo some of the duct work.
#2 I'm thinking will help significantly, especially as the pex will be insulated and it will travel no more than about 6 feet into the buffer tank, rather than the existing 25-30 foot 1-way distance. |
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joe.ami
Veteran Member
Posts:4377
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| 16 Sep 2010 09:17 AM |
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Circulator on that system is good for up to 50' one way according to manufacturer. Not saying this to criticize plan, just that the length mentioned is not a smoking gun and others with long runs should not conclude they have an improper install.
I agree with your guy, when workmanship is poor, just "neatening everything up" can yeild great results.
j |
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Joe Hardin
www.amicontracting.com
We Dig Comfort!
www.doityourselfgeothermal.com
Dig Your Own Comfort! |
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decafdrinker
Basic Member
Posts:420
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| 16 Sep 2010 10:38 AM |
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True. He wasn't overly concerned about the length, although it is all uninsulated pex in an unheated basement cooled even further by the AirTap which blows its cold air directly onto the pex lines!
He initially planned to just insulate it all, and wasn't concerned either about the 1/2" vs. 5/8" pipe sizing. But moving it frees up basement space actually, especially with the addition of the buffer tank.
The tank was also pumbed with cold coming out the bottom and he's switching that. Plus, there are many high spots in the desuper lines that could trap air and no valves or anything anywhere that would have allowed proper purging of air.
The desuper really only adds a few degrees of heat to the water as it circulates, so we're figuring that shorter, well insulated lines with no air trapped will possibly fix the hotter In than Out problem! |
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decafdrinker
Basic Member
Posts:420
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| 26 Sep 2010 06:30 AM |
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It's working!! The addition of the buffer tank has made a huge difference. Not only does the desuperheater actually work now (the hot line is hotter than the cold line), but the AirTap on the "finishing" tank is coming on fewer times now. The a/c only came on a few times yesterday, and the buffer tank was full of cold water from Friday's fix job, but the temp on the desuper in was 75, and the out was 96. Whoopeee! |
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engineer
Veteran Member
Posts:2749
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| 26 Sep 2010 09:09 AM |
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There should only be about a 5 degree difference across the desuperheater coil.
Then again, if you are referring to the desuperheater buffer tank supplying 96 degree water to the finishing tank during a time of low AC use, than yes, you are in high cotton |
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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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joe.ami
Veteran Member
Posts:4377
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| 26 Sep 2010 11:23 AM |
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I will add your name to the "why you need a buffer tank" mental notebook.
Congrats.
j |
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Joe Hardin
www.amicontracting.com
We Dig Comfort!
www.doityourselfgeothermal.com
Dig Your Own Comfort! |
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decafdrinker
Basic Member
Posts:420
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| 26 Sep 2010 03:03 PM |
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Joe,
I'm a believer!! Where do I sign?? |
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TomAndersen
New Member
Posts:13
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| 03 Oct 2010 12:48 PM |
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I turned off my single tank DSH three years ago after I noticed that there was some sort of loop where the hot water tank was dumping expensive electric heat into the heat pump. Electric bills went down. Now I am going to put in a buffer tank. This thread has been a good read. --Tom
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3 Ton open loop to radiant floor/(air coils for A/C) |
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