View Full Version : Geothermal unit has issues...and I'm hot! Help please..
07-11-2010, 12:28 PM
I have a Carrier Geothermal unit in my home, it's about 4 years old. It is a 50YCV, H and D vertical upflow, horizontal and downflow packaged system.
Last year I once again started having problems, basically it would short cycle. It would run normal and blow cold air from anywhere between 5 minutes and 1 hour, then the unit would "click" and start blowing warm air and never return to cold without me turning the unit off and on using the thermostat. I started it up yesterday and it ran just fine for about 8 hours until I shut it off.
I've had a couple people look at it and I get different answers. One says the compressor, another says some of my vents in my house need to be restricted.
I ask is it possible that I have a minor issue since it worked just fine for hours yesterday? I mean, if it was mechanical problem wouldn't it happen all the time. I'm hoping I have a clogged drain or something else. I have replaced the filters so they are clean.
Any help would be greatly appreciated.
07-11-2010, 05:02 PM
Clogged drain would take all low voltage power off unit if equipped with float switch.
Has anyone looked at the possibility of high entering water temp?
07-11-2010, 07:44 PM
Hey Watercop, thanks for input. I'm on a well system and the water is always really cold. And since I've had the unit running today for about 30 minutes I went and just looked at the temp gauges. The inlet is at 58 degrees and the outlet is at 80 degrees.
As far as my drain thought, I noticed that my condensation line is dripping to what appears to be normal. It's not terribly humid here in Idaho today, but a little moisture is in the air.
I also failed to mention that the water that the system uses goes into a pond type retention on my property. If I remember correctly from last year, I think my short cycle problem started when the pond was at capacity. With that in mind, is it possible that if the pond is at capacity, could it restrict water going into the pond causing the system to stop because of the lack of water discharge or moving through the system?
07-11-2010, 08:33 PM
A 22 degree delta T on the water side is very high. It looks like you might have a low water flow situation.
07-11-2010, 09:17 PM
Thank you Bergy. Um, I'm guessing that when you say Delta T you are referring to the temperature difference between inlet and outlet?
I just looked at the system and I have one incoming pipe that splits into two pipes that have what looks to be electric adjustable valve/solenoid type things. I also have a manual lever on each pipe to control water flow which are before the valve/solenoids. After the valve/solenoids, the pipes then go back into one pipe before the temp gauge. I also noticed that both manual levers were set at like 85% closed. I opened both levers to the full position and waited about 20 minutes. The outlet temp dropped to roughly 69-70 degrees and the inlet temp did not change. I did not mess with the round knobs on the valve/solenoids but I did determine they were set at max open--max counter clockwise rotation.
I also saw that my float gauge went from 7.5 GPM to 11.5 GPM after I made the above changes.
Am I on the right track?
07-12-2010, 10:25 AM
The twin pipe/solenoid set up is first stage/ second stage operation. In first stage only one of the valves are open and both open for second stage. Open loop systems require 1.5 to 2 GPM per ton.
You need to have a "competent" Geothermal service contractor evaluate your unit. They should first set the proper water flow rates then perform a heat of extraction/rejection for your unit. (Make sure they provide you with those numbers.) If the numbers are not within plus or minus 10% of factory specs further troubleshooting into the refrigeration circuit is required.
Heat of extraction/rejection requires the following information (Must be done with desuperheater OFF and the unit running in second stage)...
Delta T(temperature) of incoming/outgoing water.
Delta P(pressure) of incoming/outgoing water.
In the unit spec manual Delta P at incoming water temperature will show GPM.
GPM x Delta T x 500=Btu/Hr Heat of extraction/rejection.
They should also measure the air flow Delta T. (AT THE UNIT) and the compressor's Amp draw. You should keep a record of each time this information is gathered, it will show changes in performance that may need service attention.
07-13-2010, 11:18 AM
I'm sorry, I've given you some incorrect information. For an open loop system, running 1.5 Gpm/ton, a 22 degree Delta T is NOT high. It is on the high side of normal.
07-13-2010, 11:53 AM
Hey Bergy, no problem on the confusion. I will tell you I have not noticed anything different after I opened the valves up. I have since moved them back to what they were. I ran the system yesterday for about 5 hours and had no problems. I don't think I'll be running it today as it's cooler outside. I somehow still think my short cycle problem that I experienced last year has something to do with the water level in my pond, or lack of water more specifically. I'll be curious to see if the system starts given me issues as the pond gets higher water.
Thanks all for your help.
07-20-2010, 12:46 AM
If EWT is low enough, there is no actual need to run 1.5 GPM per ton. Water could come in at 60 and leave at 100 and still be within bounds for system operation albeit at some loss of capacity and efficiency.
I have 71 EWT in an open loop system and sometimes restrict flow so as to fill a pool with 95-100 degree water or shower the kids out on the deck using the system leaving water. That costs me about 1 amp in additional compressor current.
Last winter I pinched down water flow so as to produce 40 degree water to feed a snowgun...not many Florida kids get to sled in winter...system still met house heating load in low stage but daily running hours rose by 2-3, costing an extra 50 cents or so, but the pics of kids on a snow hill south of Jacksonville are pretty much priceless.
My point in all this is not to get too wedded to rules of thumb such as GPM per ton - every individual system situation varies
OTOH if water comes in at 90 the flow needs to be much higher to keep capacity and efficiency reasonable.
I see absolutely no purpose or correlation with restricting one or more vents in the house.
Powered by vBulletin® Version 4.2.0 Copyright © 2013 vBulletin Solutions, Inc. All rights reserved.