Heat Controller FP1 lockout (low temperature)
Last Post 19 Jun 2011 07:10 PM by joe.ami. 25 Replies.
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jfuerstUser is Offline
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26 May 2011 09:47 PM
I have a 5 ton heat controller unit that is only about 3 years old. Recently it has been tripping a low temperature lockout (FP1) sensor. When the unit does operate without tripping the sensor it does not produce the kind of heat that it should. Odly enough the longer it sits without running the more likely it is to trip the sensor... Once it survives a cycle, it usually skirts the very edge of the limit to stay running, but does stay running.
I have the following information:

5 ton heat controller HTV-060 series
5 210' closed loop vertical wells
Incoming water temp 52.9*
Outgoing water temp 51.91*
pressure drop ~7PSI = ~25gpm or so
The FP1 sensor (low temperature sensor) ~15*

The entering water temp never falls below ~50* and for the first 3 years the FP1 cutout NEVER tripped when set to 32* cutoff. We had the service company out and after talking to the factory changed the cutout to 10* which seems to have "fixed" the problem for a few months but now it is tripping the 10* limit too.
Attached is a capture of one of these lockups.
What do I look at next?

Attachment: lockup.JPG

docjenserUser is Offline
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27 May 2011 01:14 AM
What antifreeze do you have?
Where are you located. Do me a favor and turn on the A/C and see if the lockout occurs again in A/C mode. Listen for some noise in the pipes 10-30 seconds after the compressor engages in A/C mode. Can you get us source temp delta in A/C mode? Let it run for a few minutes, and switch it back into heat mode. See if the lockout continues.
Need more info.
Thanks


www.buffalogeothermalheating.com
jfuerstUser is Offline
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27 May 2011 02:03 AM
I have Methanol mixed in with the water (can't remember what %age but the incomming water temp has never been below ~48* in the dead of winter any way)
I am located in Colorado just outside Longmont.
I turned on the AC and instead of the FP1 lockout I get the FP2 lockout. Also the air temperature didn't seem to cool down but a handful of degrees.
The heat cycle that followed did not lockout, but the FP1 temp ran ~20* which skirts the lockout point and I cant understand with incoming water above 50* and having sat unused for about a month.
I did not make out any odd sounding noises during the run cycles
Loop In: 53.94*
Loop Out 54.84*

By the way the manual advertises:
FP1= Water Coil Low Temperature (but I believe this is measuring the refrigerant temperature)
FP2= Air Coil Low Temperature (not sure but it works inverse to FP1)
Also I have a fresh air filter installed.

Attached is capture showing the immediate lockout in AC Mode followed by a cycle in Heating Mode...

Attachment: AC_HEAT.JPG

jonrUser is Offline
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27 May 2011 07:47 AM
As an aside, what does the manual recommend in terms of gpm per ton?


BergyUser is Offline
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27 May 2011 08:24 AM
With a water side delta T of ONE degree.... 25 GPM X 1* X 485=12,125 Btu's.  About 25% of the unit's capacity.  A service tech is needed to find the cause of the low Btu output.  My guess is a refrigerant leak.

Bergy


joe.amiUser is Offline
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27 May 2011 10:53 AM
Low water flow or pressure may be causing problem. What is the pressure?
refrigerant could be problem as well, but start with water side.
j


Joe Hardin www.amicontracting.com We Dig Comfort! www.doityourselfgeothermal.com Dig Your Own Comfort!
jfuerstUser is Offline
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27 May 2011 11:23 AM
The recommended water flow depends... The manual says 3gpm/ton but the factory via phone said min 4gpm/ton. I don't know why the 30%+ variance in opinion but I meet both.

There is a pressure tank/diaphragm on the system that keeps the loop pressure around 40psi. In this last measurement the pressure was 48 & 41 psi on the p/t ports on the unit loop in/out.

So assuming that this is a refrigerant leak, is that something that I should expect to be fixed, or is this something that I will have to live with being refilled annually?

I ask because the last time we had the geothermal guy out here he spent an hour on the phone with the factory, cut a jumper to (in my opinion hide the real problem), billed us, and stated that they don't carry this brand any more and went home.
I want to be well prepared this time around so that I get my moneys worth...
You know you only get the efficiency savings of unit if it:
a) Works
b) Works properly
c) you arn't having the service guy out every 6 months


joe.amiUser is Offline
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27 May 2011 12:13 PM
If it is a refrigerant leak it needs to be found and repaired. Not gassed up annually until your part warranty expires.
50* entering water temp in the winter suggest very modest demand vs equipment and loop size.
Calls your installers credentials into question.
May want other opinions.
J


Joe Hardin www.amicontracting.com We Dig Comfort! www.doityourselfgeothermal.com Dig Your Own Comfort!
jonrUser is Offline
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27 May 2011 01:44 PM
I wouldn't let a repairman leave until the water flow and delta T indicate that the unit is producing full rated btu output. As others have said elsewhere, excessive gpm can cause problems - I'd keep it around 3 gpm/ton.


acwizardUser is Offline
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27 May 2011 02:00 PM
There are some definite installation and design problems here.What pump are you using, what size tubing,methanol brings up another whole series of questions. Post some pictures of whatever you have installed.


jfuerstUser is Offline
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27 May 2011 02:16 PM
Okay. I called the service guy and he told me that we are passing too much water through the unit and need to slow it down to just 3 gpm/ton. It is a drive from where they are to where we are so I am okay (and hopefully capable) of taking suggestions via phone and implementing them.
Not believing this story I called the factory to fact check this request and they began by saying I don't have enough flow (should be 11gpm/ton WTF!!). I FIRMLY pointed out their spec page and explained what the installer/technician said and he changed his tune to agree that we need to tune it down to 3gpm/ton (saying he was confused with another furnace series??).

I turned off one of the 2 water pumps which lands me right at a 4psi drop and right at 15gpm/ton. Using the equation from Bergy above I get the following results in heating:
485*15*(52.81-50.34)=17,969 BTU or about 1.5T
out of my 5T unit. which is probably the same as what I was getting before as the flow rate of 7psi drop is not published so I guessed based on the published part o the table.

Essentially, what further information do I need to have to confidently demand that the furnace is not performing like it should?
The math seems to say it is not working
The run times suggest it is not working
The electric usage suggests it is not working
The lockouts when the conditions are ideal (to me any way) suggest that it is not working
am I crazy or does the information suggest I am getting the run around from the tech and factory?


acwizardUser is Offline
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27 May 2011 06:45 PM
What you need is professional help at the jobsite. Almost all geos operate somewhere around 3gpm/ton. How are you measuring flowrate and pressure drop.Need to know more info on pumps.No one in their right mind would oversize a pump by degree in which you are stating.


docjenserUser is Offline
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27 May 2011 11:12 PM
Your refrigerant circuit is not extracting/rejecting the BTUs from/into the source water. You need a technician to troubleshoot the refrigerant circuit, most likely the refrigerant level. Heatcontroller HTVs have a 6 year warranty. They are climatemaster clones which use supply shop distribution. You need 3 gpm/ton flow, 15 gpm total for a 5 ton model. Call the factory and ask them how they intend to honor their warranty. I assume your original installer is not around anymore.


www.buffalogeothermalheating.com
acwizardUser is Offline
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28 May 2011 12:36 AM
If it were a refrigerant problem, the unit more than likely would not run . It would be off on low pressure switch.Refrigerant circuit has nothing to do with flow rate. It only has something to do with heat transfer.


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28 May 2011 01:41 AM
Posted By acwizard on 28 May 2011 12:36 AM
If it were a refrigerant problem, the unit more than likely would not run . It would be off on low pressure switch.Refrigerant circuit has nothing to do with flow rate. It only has something to do with heat transfer.


At 7 psi, the flowrate for a HTV060 is not 25 gpm, but more between 17-18 gpm. 14 gpm at 50F are 3.5 psi, 15 gpm are 4.3, 17 should be around 7 psi. Pressure drop increases more than exponentially. So the flow is may be 10-15% higher than optimal spec, but nothing unusual. So as a result the delta T should be 15% lower. At 50F a HTV060 has a rated heat extraction of 46 KBTU/H in second stage, and 33 kBTU/h in first stage. However, at 17 gpm and a delta t of 1.1 F indicates a heat extraction around 9 kbtu/h. I am aware that a refrigerant circuit has nothing to do with flow. His flow rate is fine. I am also aware that the refrigerant circuit has something to do with heat transfer. His heat transfer (e.g. heat extraction from the source water) is off, that is why the data points to the refrigerant circuit. Sure, the unit could still run with low ( or in this case to consider, too much!) refrigerant.
Which reminds me, there was a typo in the 2008 Heatcontroller installation manual, falsely directing the installer to cut jumper JW2 when actually jumper JW3 is the low temp water coil setting. Make sure the technician has not accidently cut JW2, which is the air coil low temp limit setting and is actually regulated (triggered) through the refrigerant temp. That is what I was going after with the a/c mode. Check which jumper is cut and report back. Thanks


www.buffalogeothermalheating.com
acwizardUser is Offline
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28 May 2011 04:59 AM
The pressure drop is off the scale of normal operation. Both low temp water and low temp air sensors are reading refrigerant temperatures. Only the low temp water jumper should have been cut (10F).What is baffling is there should be a history of errors LP lockout code3.This is the code which would be seen for refrigerant fault.The refrigerant charge needs to be looked at. The superheat and subcooling temperatures will be a dead giveaway if the charge is low,or high . I do believe there are multiple problems occuring here. Not only does the flow, refrigerant charge, percentage of antifreeze need to be checked but the airside may be contributing to the problem as well.


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28 May 2011 06:30 PM
17-18 gpm flow instead of 15 gpm will not cause a lockout. So you disconnected a pump, and were right at 4 psi (which by the way is a great way to save some dollars for pumping power down the road!). However, the heat extraction is the same (namely low), so the heatpump is not extracting enough heat out of the source water while running. Check the jumper first before you do anything. Yes, check the antifreeze, may be someone filled it up with 100% Glycol to cause high PD but low flow. But than you would see a higher delta T. So that is not it. Anything on the airside would not explain why the heat extraction out of the source water is that low. So that is it not either. Now your are back to the refrigerant circuit.


www.buffalogeothermalheating.com
jfuerstUser is Offline
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28 May 2011 08:23 PM
So, for the first 2.5 years of this heat pump everything was fine... About 4 months ago we started getting the FP1 lockout and called the tech. Turns out after he talked to the factory the wrong jumper had been cut and so he cut the remaining jumper. As it stands right now both JW2 AND JW3 are cut.

This is what started my curiosity into the problem because immediately our electric bills doubled and the heat pump ran 2x longer, couldn't keep uo when it used to, etc. We have actually been supplimenting our heat on cold days with our emergency backup pellet stove since then... My main question at the time was "How come it ran just fine for 2.5 winters without the jumper being cut and now all the sudden requires it to be cut?" Likewise why would it be getting lockouts when the incoming water is 50* anyway? The whole story just seems fishy to me.

It seems like there has been a steady degradation in the unit since slightly before the first lockouts occurred. Again, after the jumper was cut the lockout problem went away (but not the performance issue) until just recently when it cropped back up again. Everyone that I talk to (including the factory) is adamant that it is a water flow problem (which I 100% disagree with) I am convinced that it is a refrigerant issue as docjenser and others have suggested.

I was home when the methanol was added to the loop and can't remember exactly but I believe that it is 15%. It is in no way 100% because originally I did not want any antifreeze because all 5 of the wells went through lots of water from 25' to 200' and didn't believe that I needed it. The loop contractor wanted a 20% mixture and I remember settling at 15%.

I called the tech again and he will be here at the end of next week. We are a 1 hour drive from him and 2.5 hours from the next contractor that services heat controller units (that I know of). I am gathering as much information as I can to knowledgeably stand my ground when he gets here.


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28 May 2011 09:26 PM
Posted By jfuerst on 28 May 2011 08:23 PM
So, for the first 2.5 years of this heat pump everything was fine... About 4 months ago we started getting the FP1 lockout and called the tech. Turns out after he talked to the factory the wrong jumper had been cut and so he cut the remaining jumper. As it stands right now both JW2 AND JW3 are cut.

This is what started my curiosity into the problem because immediately our electric bills doubled and the heat pump ran 2x longer, couldn't keep uo when it used to, etc. We have actually been supplimenting our heat on cold days with our emergency backup pellet stove since then... My main question at the time was "How come it ran just fine for 2.5 winters without the jumper being cut and now all the sudden requires it to be cut?" Likewise why would it be getting lockouts when the incoming water is 50* anyway? The whole story just seems fishy to me.

It seems like there has been a steady degradation in the unit since slightly before the first lockouts occurred. Again, after the jumper was cut the lockout problem went away (but not the performance issue) until just recently when it cropped back up again. Everyone that I talk to (including the factory) is adamant that it is a water flow problem (which I 100% disagree with) I am convinced that it is a refrigerant issue as docjenser and others have suggested.

I was home when the methanol was added to the loop and can't remember exactly but I believe that it is 15%. It is in no way 100% because originally I did not want any antifreeze because all 5 of the wells went through lots of water from 25' to 200' and didn't believe that I needed it. The loop contractor wanted a 20% mixture and I remember settling at 15%.

I called the tech again and he will be here at the end of next week. We are a 1 hour drive from him and 2.5 hours from the next contractor that services heat controller units (that I know of). I am gathering as much information as I can to knowledgeably stand my ground when he gets here.


Voila - your unit cannot run normal. You need to use a wire with 2 clips and bridge JW2-FP2 (make sure you shut the breaker off to the unit). Installation page 29, there should be 2 jumpers, JW2 is the lower one of them. Chances are that after that, everything will be normal. Your antifreeze might be on the low side, and your flow is fine, don't worry about that. I would insist getting a new control board. It was clearly misprinted in the installation manual. Heatcontroller should stand up for it.


www.buffalogeothermalheating.com
BergyUser is Offline
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29 May 2011 09:57 AM
Make sure your service tech does the following...

Make sure the unit is running in SECOND stage heat WITHOUT the strip heat and WITHOUT the desuperheater running. Have the service tech record the following information and keep it WITH the Geo so future inspections can compare the performance information.

Delta P (Pressure In minus Pressure Out.)
Delta T (Temperature In minus Temperature Out.)
Air side Delta T (AT THE UNIT,  NOT AT THE REGISTERS).
High voltage to the unit.
High Voltage out of the contactor.
Low Voltage from the transformer.
Amp draw of the compressor.

You can now look in the spec manual and find the pressure drop at the measured Entering Water Temperature (EWT).
For instance, a GeoComfort GXT048 at 50* EWT with a Delta P of 7 PSI has a flow rate of 12 GPM. The heat of extraction should be
42,000 Btu's and the heat of rejection should be 65,100 Btu's(+ or - 10%) Remember, heat of extraction is GPM X Delta T X Brine factor (Brine is 500 for water and 485 for anti-freeze).

If the Heat of Extraction/Rejection is within 10% of book the refrigerant circuit is OK and a gauge set should NOT be hooked to the refrigerant circuit. If it is outside of 10%, further testing will be required to determine the cause of the refrigerant circuit's poor performance.


Bergy


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