EcoRenovator  

Go Back   EcoRenovator > Improvements > Geothermal & Heat Pumps
Advanced Search
 


Blog 60+ Home Energy Saving Tips Recent Posts Search Today's Posts Mark Forums Read


Reply
 
Thread Tools Display Modes
Old 01-03-17, 01:42 PM   #1
Fathompin
Lurking Renovator
 
Join Date: Nov 2015
Location: Dayton Ohio
Posts: 12
Thanks: 1
Thanked 1 Time in 1 Post
Default Open-Loop Geothermal 2-stage Operation

My Brother has an open-loop well geothermal system that was giving him problems. I was called in to help because he was not real happy with the last service call. I found his problem, but now I have a few questions about the operation of his system that perhaps could be answered on this forum (and then I won’t have to do too much outside digging for the answers)…thanks in advance:

Two-stage heating and cooling:
Considering the higher efficiency of a low-load heat pump setting in a two load system, how does that compete with well pump cycling over longer time period? He has a pretty big well pressure tank (> or = 30 gals?) and a well that has pumped plenty of water over 20 years use. His thermostat is not set to the two stage load operation now (but can be) and I wonder if that was on purpose or not. If it is on purpose, then I assume somebody decided that drawing a lot of water could keep the well pump cycling less; i.e. pumps over shorter time periods, potentially shorter cycling times, and definitely longer off time intervals. Compared to low water flow for the low load heat pump setting, the pump will cycle constantly over longer time period and this may not be best approach. Hence, what is the best practice in this case?
(for example, if he installed a cycle stop valve on the well, I'd probably choose to maximize water flow at all times and reduce well pump time on.)

Also, out of curiosity I'm just wondering; is wiring the well water valves directly to the thermostat "Y & Y2 call for heat/cool" the best practice? I ask because when the compressor shuts off (due to problem, I know not the usual operation), thermostat calls for heat means the well pump keeps pumping and dumping water until somebody notices the red light on. Off-hand, I don't see a better way to control the water valve from the heat pump controls, I only see that the best way is a parallel connection from the thermostat call for heat/cool to the valves and the heat pump control, especially the two-stage setup, because the valves need to stay independent, which is what Y and Y2 are.

Thanks.

Fathompin is offline   Reply With Quote
Old 01-06-17, 09:45 AM   #2
jeff5may
Supreme EcoRenovator
 
Join Date: Jan 2010
Location: elizabethtown, ky, USA
Posts: 2,428
Thanks: 431
Thanked 619 Times in 517 Posts
Send a message via Yahoo to jeff5may
Default

Way not enough info. All we can really tell from your post is that something somewhere used to work and now it has problems. You came over and looked at the rig and said: "HMMMM...THAT'S STRANGE."

And that's what we know.

Oh, and it's not yours.
jeff5may is offline   Reply With Quote
Old 01-06-17, 08:28 PM   #3
Fathompin
Lurking Renovator
 
Join Date: Nov 2015
Location: Dayton Ohio
Posts: 12
Thanks: 1
Thanked 1 Time in 1 Post
Default

Oh, OK then....never mind.
Fathompin is offline   Reply With Quote
Old 01-06-17, 08:48 PM   #4
stevehull
Steve Hull
 
Join Date: Dec 2012
Location: hilly, tree covered Arcadia, OK USA
Posts: 826
Thanks: 241
Thanked 165 Times in 123 Posts
Default

what brand of heat pump?

Steve
__________________
consulting on geothermal heating/cooling & rational energy use since 1990
stevehull is offline   Reply With Quote
Old 01-07-17, 10:00 AM   #5
Fathompin
Lurking Renovator
 
Join Date: Nov 2015
Location: Dayton Ohio
Posts: 12
Thanks: 1
Thanked 1 Time in 1 Post
Default

Quote:
Originally Posted by stevehull View Post
what brand of heat pump?

Steve
It is a Bryant 5 ton.

Based on jeff5may’s feedback, let me simplify my question: This system has high and low load capability and I noticed low-load operation was not being used - either by accident because it was not set up properly, or on purpose. So I was wondering, should I fix that or not? I think I would favor NOT using a low load mode because in that case the well pump would run longer, cycle more, and potentially wear out quicker. But, on the other hand the low-load operation may be much easier on the heat pump compressor lifetime, and if so, there may be clear, best practice thinking that the compressor should take precedence over any trade-off between compressor and well pump operation….an not a consideration of any efficiency savings based on electricity usage per BTU.

The second question about the water pump valves, I noticed that the heat pump has controls to shut off the compressor, but when it does the water pump still runs. Again if I’m going to ignore low-load operation, I could easily wire the pump valves so that when the compressor is off the pump is off. I realize this is not a typical problem, just wondering about common practice for what controls are used for the water valve (in the current system the water pump valve is operated by the thermostat calling for heat).

I also noticed the Bryant operation manual does not go into any detail about recommended water flow, simply stating 7 gpm, whereas for a 5 ton system I think that is a little low and 7 gpm might be what they recommend for low-load operation. I can use the heat of rejection formula to dial in water flow for the high load operation and stick with 7 gpm for low load, if I decide to use that. In my mind, 12 gpm seems appropriate for 5 ton with 58 degree entering water temperature.

Thanks for your consideration.
Fathompin is offline   Reply With Quote
Old 01-07-17, 08:15 PM   #6
pedro
Lurking Renovator
 
Join Date: Oct 2012
Location: Indy
Posts: 12
Thanks: 0
Thanked 2 Times in 2 Posts
Default

They are more efficient when they run longer so a bigger Geo unit with dual stage should use both stages. To take advantage of this a couple things should happen.

Do you know how many hp the well pump is? Do you know the cycle time on the well pump? The amount of time off compared to the amount of time it is on.

I have a 3.5 ton. 1/2 hp well pump. I have done some modifications over the years to help everything out. When I moved here they had 2 small well tanks. They also had the geo lines plumbed with 1/2" Pex which was way to small so it was using full house pressure to push the flow through. High flow low pressure is better. I ended up redoing things over the years. Now I flow around avg of 5 gpm at 15 psi. I cycle on and off close to every 5 minutes while the geo is running. Usually only one cycle while the geo cycles. Right now it is 13F and it is cycling twice for each geo cycle. My entering water temperature is around 56F. I can flow less keeping exit water around high 30s at only 3.25 gpm but output goes down. At that flow around 36,000 btu. Around 5 gpm I get around 40,000 btu.

To take advantage of the two stages you need a way to flow 2 different amounts of water. My valve is triggered off the heat / cool call and is a basic 1" sprinkler valve.

So my geo wasn't using high pressure house water I installed a bigger 86 gallon (it doesn't hold that much but that is what they call it) tank that the submersible fills and it runs 15 - 35 psi. That pressure feeds the geo and there is a pressure regulator set to 15 psi that feeds the geo line. The house then has another pump that is feed off the large pressure tank and pumps another smaller well tank at 40 -60 psi for the house.
pedro is offline   Reply With Quote
Old 01-07-17, 08:16 PM   #7
pedro
Lurking Renovator
 
Join Date: Oct 2012
Location: Indy
Posts: 12
Thanks: 0
Thanked 2 Times in 2 Posts
Default

Need two more posts.
pedro is offline   Reply With Quote
Old 01-07-17, 08:17 PM   #8
pedro
Lurking Renovator
 
Join Date: Oct 2012
Location: Indy
Posts: 12
Thanks: 0
Thanked 2 Times in 2 Posts
Default

Here is live data on my geo
pedro is offline   Reply With Quote
Old 01-07-17, 08:24 PM   #9
pedro
Lurking Renovator
 
Join Date: Oct 2012
Location: Indy
Posts: 12
Thanks: 0
Thanked 2 Times in 2 Posts
Default

Quote:
Originally Posted by pedro View Post
Here is live data on my geo
Link now included. I monitor entering water temp, leaving water temp and GPM. I also monitor geo power and well pump power. (got a new monitoring unit as I found the current one is a little off due to the power factor). I also monitor supply and return temps. I then calculate the heat of absorption for the water flow and the overall output of the Geo. From all that I also calculate COP which is a little low because the geo power reads a little higher than what it is. I found on avg going from 3.25 - 3.5 gpm to 4.75 to 5.25 gpm raised COP about .25 or so plus I was putting about 4000 BTU/h more but my pump when from 33% on to 49% on.


You can see live data on my unit here: https://dweet.io/follow/yumyum
pedro is offline   Reply With Quote
Old 01-08-17, 04:49 AM   #10
stevehull
Steve Hull
 
Join Date: Dec 2012
Location: hilly, tree covered Arcadia, OK USA
Posts: 826
Thanks: 241
Thanked 165 Times in 123 Posts
Default

Fathompin,

Now I understand better your issue. First, how old is this Trane unit?

A 5 ton gthp dual stage allows operation in each stage. You have problems with it only running in stage 2 (all 5 tons) AND the water runs all the time. These are both issues. Here are my thoughts.

First, a 5 ton units will use about 10-15 gallons per minute when running (2-3 GPM/ton) on stage 2 (high speed). The unit is a lot more efficient when running on stage 1 (low speed). Your unit is likely about 3.5 tons on stage 1 and the full 5 on stage 2.

You really DO want it to run most of the time on low speed. Longer operation is actually better for it and far more efficient. The high water flow is a separate issue.

I have never seen the well pump directly connected to the thermostat. This is very odd. The thermostat Y1 and Y2 tell the Trane unit to: 1) turn on the fan, turn on water flow (low or high) by activating 24 V AC lines and 3) energize the appropriate compressor speed (low or high). If the unit turns on in low speed (Y1) and the change in house temperature in the next few minutes is not great enough, then Y2 is turned on. The unit should shut down by turning off in order: 1) compressor, 2) shutting of water flow and then 3) turning off fan.

First, I would disconnect the thermostat. The problem may be the thermostat that is in only turning on in stage 2 (Y2).

So first use Y1 and see if stage 1 turns on (forget about high and constant water flow for the moment). Does Y1 energize stage 1 and the fan? Does Y2 turn it on at full speed? You can check the speed by looking at current in one of the AC supply 240 legs (with clamp on meter).

If it does not turn on with Y1, but WITH Y2, then there is a problem internal to the Trane circuitry. If it works on Y1 (turns on at low speed) and Y2 turns on to high speed, then the problem is the thermostat.

Now to water flow. Many open loop geothermal heat pumps have two energized 24 V ac lines. One turns on at low speed and both turn on at high speed. This is so that two electric solenoid valves can control water flow through the unit appropriate for the compressor speed.

In your case, valve 1 on would let about 6-10 GPM through the unit. On speed 2, a second valve would open (on a parallel water branch) and allow about 5-7 more GPM. The goal is to have a temperature difference between water in and out of ~ 10 degrees F.

Yes, running the well pump is costly and best practice is to use the water flow appropriately. But if you have and endless supply of water (like an artesian well then who cares). But you reference a well pump and I assume you have an air tank as well.

Some installers are lazy - they only hook up one solenoid regardless if the unit is on stage 1 or 2 (low or high speed). You need to check to see if there are two solenoid valves.

The fact that the water does NOT turn off and the unit has a red malfunction light indicates a problem. It could be simple - or it may mean replacing the board. Again, you can check this by individually turning on Y1 and Y2 and looking at the voltage at the solenoid (have water manually on the entire time).

To trouble shoot this, you will need to be able to manually turn on maximum water flow (10-15 GPM) for testing. You do NOT want to energize the compressor for ore than a couple seconds if you have no water flow.

So, go look at the unit and find out if there are two solenoid valves in parallel controlling water flow for the two speeds. Check Y1 and Y2 manually (thermostat out of the controls). See if there are two solenoid lines and do they individually work at each stage.

Let us know and we can help you from there.


Steve

__________________
consulting on geothermal heating/cooling & rational energy use since 1990
stevehull is offline   Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 02:28 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Ad Management by RedTyger
Inactive Reminders By Icora Web Design