Hi All,
Been a while since I posted, but still visit this site periodically.  I love the great discussions on this forum.

Our system is now 2.5 yrs old.  Climatemaster 4T, TTV049 with Desuperheater, R-410A;  3 x 260 vert closed loop with methanol/water; 2 26-99 pumps.  I run just one circ pump while in 1st stage.

System has been running great, but lately I have noticed the discharge air temp getting a tad lower compared to past winters.

Now:  IAT=67, OAT=84-85(1st stage), OAT=87-88(2nd stage)

Last winter: IAT=67, OAT=90(1st), OAT=93(2nd)

Well Loop temps were similar both years.  I checked pressure drops to determine water flows and all looks good there.  About 9 GPM (1st), 15 GPM(2nd)  approximate.  Same as before.

Our loop temps have been similar to other winters, now running in the mid 40's on the inlet side.  Delta T is about 3-4 degrees (approx) measured with a stab in meat thermometer.

I have also noticed the power consumption is a little lower via our TED 5000 monitor.  I have a probe dedicated to the GEO.

I first noticed by walking past our bedroom floor vent, and the air felt tepid, not slightly warm as it usually does.  So I put the temp probe in the duct at the unit in the basement and checked to confirm.

So, I know I need to confirm my air flows to ensure nothings changed on the air side, and I also need to get some more accurate readings on the loop flows and delta T's.  I will do that shortly, to get a better BTU reading. 

The original contractor did do an annual service in the fall of 2011.  He connected guages to the refrigerant side at that time.  I was a little miffed that he did that, but bit my lip.  Everything seemed fine.

Nothing has been touched on the unit since that visit.  I do the filter and clean the condensate pump out as needed. 

Question on my mind, is there an easly way to measure status of the refrigerant charge, without connecting gauges?  I will get the contractor for that.  Can I measure the subcooling directly or some other temp checks on the refrigerant lines to see if my charge is in the ballpark.  I have a fluke with temp probe and have abiltiy to work around electronic stuff safely.

Any quick checks I can do?  Any thoughts are appreciated.

I'd like to get some good data before I call the contractor in (if at all possible).

Thanks!

The Heat of Extraction (HE)/ Heat of Rejection (HR) must be calculated. To do a HR/HE three things are needed. First, a needle probe pressure guage. Second, a digital probe thermometer. Third, the specification manual for your heat pump.

With the Desuperheater disabled and the unit running in second stage heat, measure the loop pressure in and out (Delta P). Measure the loop temps in and out (Delta T). Look up your unit in the manual and find the specs for High Heat. Find the pressure drop tables and convert the Delta P at your ENTERING water temp into GPM. Multiply GPM X Delta T X 485 (for closed loop w/Glycol) or 500 ( for open loop pure water).

As an example... Yesterday I calculated the HE/HR on a GeoComfort E036 closed loop w/ Glycol. Pressure in = 25 PSI Pressure out = 20 PSI. Temp in = 45 Deg Temp out = 40 Deg.
Delta P = 5 PSI
Delta T = 5 Deg
Acording to the manual 5 PSI @ 40 Deg Entering Water Temp equates to 10 GPM

10 GPM X 5 Deg X 485 = 24,250 Btu/Hr. is the Heat of Extraction
The manual shows the heat pump should put out about 23,750 Btu's @ 40 Deg EWT. (Plus or Minus 10%) 24,500 is within 10% so the unit is operating properly. There is NO NEED to connect a guage set to the unit's refrigeration circuit unless the HR/HE indicates a problem.

Bergy

Looks like I'm sliding down the cliff. This morning DAT was 78 (1st stage) and 83 (2nd). I will be calling the original contractor to come take a look. To me it looks like a refrigerant leak since performance degraded over a week or so period of time.

I am hoping (praying) that the Climatemaster warranty comes through.

Posted By chrisbiker on 31 Jan 2013 08:25 AM
... This morning DAT was 78 (1st stage) ...

If indeed you have a refrigerant leak, by this time in heat mode (LAT = 78° F) you've lost a pretty good amount.

One way to confirm a refrigerant leak is to measure the temperature of the compressor's discharge refrigerant line.  If you've got a leak, and have already lost a good amount, and you're in 1st stage, then this measurement will have become very high (> or much greater than 170°).  Use this chart to get a general sense of what should be normal.  (The chart's for a WF equipment, and is one of the charts produced by my performance monitoring system, at WEL0043, but,  it should still be applicable when you're running in 1st stage, and if your equipment is R410A.)

Another way to confirm a refrigerant lead, if it's associated with the evaporator coil, is to use a flashlight and look for a shiny liquid substance at various places on the coil.  This is refrigerant oil, and if present, will confirm you've got a leak at least associated with the coil.  Take some time and do this examination thoroughly - it's easy to otherwise miss the oil.

If your compressor refrigerant discharge temp is over 180°, in first stage, and it's R410a equipment, I'd stop running the unit (if you can) to preserve not losing the compressor to burnout.  I would at a minimum prevent the unit from shifting to 2nd stage while you're waiting for repair to arrive.

Best regards,

Bill

Bill,
This is exactly what I was looking for. Thank you so much!

I will check the unit ASAP for compressor discharge temps and oil on the coil. I will remove the Y2 wire as well or just shut er down. The Tech will be at the house tomorrow morning to take a look. $110 for the visit. Not sure where this will end up, but hopefully Climatmaster and my installer will not make this too painful.

Any suggestions from anyone is much appreciated.
Chris

Hi,
Checked unit.  There is a little oil at the bottom of the coil.  I guess thats not good.

I check the compr. discharge temp in first stage.  It was around 125-126 deg. F after running five minutes and stabilized.  I wrapped the probe with some foam pipe tape to get a good reading.  This is way under 175.

If you see oil along with all of the other information,coil is almost certainly source of refrigerant leakage. You might try some soap bubbles around the area where the oil is present.If you get bubbles then you have pinpointed the leak.You are at a point where you are going to need a professional service company.

Here is a pic of the discharge temp check showing 125 Deg. F.

I have the tech coming tomorrow so I will know more after that.  The unit has performed flawless for 2.5 years.  Why would a coil just go bad all the sudden?


Any advice that could possibly help me navigate the Climatemaster Warranty is greatly appreciated.  I would hope this is fully covered?  Unit has a 10 yr warry.

Thanks,
Chris

Pic posting not working for some reason...

Update: Tech confirmed leak in the coil. Parts being ordered. The good news is everything is going to be 100% covered by warranty, even todays visit. I am very satisfied with our Geo contractor. Great bunch. Confirms what everyone says, got to go with a trusted contractor.

I still worry about long range durabiltiy of the coils. Seems like this is not isolated to Geo or any particular manufacturer. Is it the copper itself, wall thickness, or what that is the issue these days? If this happens later on, I will likely not be in warranty and that will be painful.

Coil itself still looked brand new on the outside, just a tiny leak somewhere.

By chance do you have spray foam insulation?

Evaporator / indoor coil leaks are an industry wide problem. There is an issue called "formicary corrosion", sometimes called "ants nest corrosion" owing to the appearance of the damage under high magnification.

There is supposedly a link between formicary corrosion and spray foam insulation...we've worked several coil leaks in homes with foam.

R410a operates at significantly higher pressures than R22, particularly in heating mode, exacerbating leaks.

I'm suprised to read that compressor discharge temp was as low as 125*F after such a pronounced loss of charge.

It sounds like you have an excellent contractor. I hope they continue to exhibit excellence by:

1) establishing a nitrogen (or other inert gas) purge while brazing in the new coil
2) Deeply evacuate system and confirm vacuum level with a micron gauge - maximum is 500 but I like to see 300 or a bit less. (Much below that may boil refrigerant oil)
2a) Techs who merely run the vacuum pump for a set amount of time, such as over lunch, are slackers and should be run off
3) weigh replacement charge from an inverted jug of new refrigerant placed on a digital scale.

Excellent initial diagnosis and advice from others here. You can't control what you don't measure, per Lord Kelvin.

Curt
No we do not have spray foam insul but we did do air sealing in the attic with some spray foam cans to seal up penetrations. Followed with r50 fiberglass blow in. Interesting point you bring up about the corrosion.

Maybe the copper is thinner or has micro porosity issues these days... They need to solve it whatever the cause.

Maybe I measured the compr disch temp in the wrong spot. I measured on the bare copper pipe just adjacent to the two pressure switches. It was hot so I figured this was the correct one. The other pipe coming from the comp was all insulated and felt cool underneith. Maybe I did this wrong...

Thanks so much for your reply and your great tips to ensure the repar and re charge is done good. The braze purge and deep vac draw are great tips. I will print this for ref during the fix.

Posted By chrisbiker on 31 Jan 2013 01:04 PM

... I check the compr. discharge temp in first stage.  It was around 125-126 deg. F after running five minutes and stabilized.  I wrapped the probe with some foam pipe tape to get a good reading.  This is way under 175.

The fact that your measurement was not in the 140 - 165° range, or actually much higher due to refrigerant loss, is probably due to one of two reasons:

1.) You inadvertently measured the suction line's refrigerant temp, not the discharge line's temp.

2.) Too much refrigerant has already been lost, as indicated by the fact that your supply air temp was not normal (normal would be 90 - 110°).  Since you had already gone past the point where there was still enough refrigerant for the systems to function (elevated compressor discharge line refrigerant temp along with still normal supply air temp), now the compressor is just 'spinning freely' such that there's no heating action occuring.

My bet is on the second reason.  I should have thought of this.  If supply air temp is not being heated, as you told us, then it would be difficult for the compressor discharge refrigerant line to have an elevated temp.

I have a chart, from a speech I gave over a year ago, that shows what happens with compressor discharge refrigerant line temp at points of refrigerant loss start and continuously (slowly) thereafter (associated with an evap coil leak).  See page 14 of this PDF document for an illustration in heating mode, and page 15 in cooling mode.  In both cases, refrigerant loss had not become so great as to significantly affect (yet) supply air temp.  But the charts show how much harder the compressor's working to maintain the supply air temp in spite of the lowered levels of refrigerant.

Eventually, the compressor would have 'given up,' compressor discharge refrigerant line temp would have come way down, and supply air would have no longer been heated, similar to what you have experience.

Best regards,

Bill

Posted By chrisbiker on 01 Feb 2013 11:09 AM
Update: Tech confirmed leak in the coil.   ...

I still worry about long range durabiltiy of the coils. Seems like this is not isolated to Geo or any particular manufacturer.   ... that is the issue these days? If this happens later on, ...

I will likely not be in warranty ...

Not surprised a coil leak was found.  This has been the most common location of refrigerant leaks of R410a type geo systems since the systems came on to the market.

You should be concerned about the longevity of the replacement coil.

If the problem is environment caused, then absent addressing the environment, you may be regularly replacing your coil until coil manufacturers eventually figure out the adjustments needed to make them last much longer.

If the problem is manufacturing related, then eventually the coils will be perfected to the point that a longer life is achieved.

There's a third problem area that's often overlooked.  Operating temperatures and pressures may well be the culprit, not environment.

For example, I have 2 geo units side-by-side, both installed at the same time.  They're both been in service for 5.5 years now.  One has had a coil replaced, the other is still on the original coil.

The unit that's still on the original coil runs with cooler supply air in heating mode (about 90 °F), even with slightly warmer return air, than the one that's had its coil replaced (105° supply air).  You can see the supply air (black and dashed brown lines) and deltaT differences (blue and dashed violet line) here.

Air pressure through the coil may also be part of the situation.  The unit I've had a coil replaced on has zoned dampers - the original coil unit has no zoning.

What you want to hope for is that the manufacturers finally figure out the problem before your 10 year warranty is complete.  And that if you have a problem coil that it's replaced before your 10 years is up.

If you're a one geo unit residence, where a geo outage means you don't have any heating or cooling, you may want to consider putting in a monitor on the compressor discharge line temperature.   At least with this investment you'll have an early warning you're going to eventually lose your heating/cooling due to leaking refrigerant.

In my case, I have a 13 month chart that monitors the daily high for each compressor's discharge refrigerant line temp, and, an email alarm set up such that if the temp gets too high in either heating or cooling mode I'm notified.  I had plenty of warning time to contact my HVAC professional, for him to confirm the leak (visible oil on the coil), order the parts, and gracefully schedule a full day for installation repair.  All total about a 4 week cycle.

Overall, after you get away from the (hopefully few) HVAC professionals who don't do a good job with design and/or installation, and/or the 'fringe' brands that are not constructed to the same quality standards as 'the big boys,' I'd say evap coils that have gone bad have had more negative impact on the small scale residential geo market than any other single item.

The 'big boy' manufacturers have no choice but to say it's not a manufacturing defect, and that instead it's the environment.  They already have been paying a lot of money to have coils replaced over the past few years.  But, in fact they're quietly working to figure out how to make coils that last longer.  They have to, because it's been an excessive expense to replace the coils, and the negative rumblings from existing customers has affected the potential market.

Meanwhile, hope that you get a better performing replacement coil than what you had (that it has some manufacturer improvements versus a coil that's been sitting in a distributor's warehouse for a couple of years now), and that you get a good coil installation (it's definitely not a trivial repair exercise).  Good luck!

Best regards,

Bill

Bill- good presentation you made. Lots of good tips in there. I may look into monitoring my compressor temps as it really can give advanced warning as you indicate. Good stuff.

What environmental factors can influence coil longevity? No sure what I should look for and actually act on.

Our house is typcial for a 25 year old colonial of std construction. I did beef up the attic insul and did some air sealing. We run the circ fan all the time, so I would think that would help keep the coil dryer in the A/C season and perhaps limit corrosion. I run a April Air humidifier in the winter. Nothing really special about our house.

Any tips of what to look for that can influence corrosion on the coil?

Also, during the coil replacement, do they need to add oil? How do they know if the oil remaining in the system is correct? I would think they would need to add some, but I am curious how they know the correct amount? Maybe its a non issue?

Thanks.

Posted By engineer on 02 Feb 2013 08:35 AM 
... I hope they continue to exhibit excellence by:

1) establishing a nitrogen (or other inert gas) purge while brazing in the new coil
2) Deeply evacuate system and confirm vacuum level with a micron gauge - maximum is 500 but I like to see 300 or a bit less. (Much below that may boil refrigerant oil)
2a) Techs who merely run the vacuum pump for a set amount of time, such as over lunch, are slackers and should be run off
3) weigh replacement charge from an inverted jug of new refrigerant placed on a digital scale.

...

In the Dallas area, for the residential market, excellence is no longer defined with the inclusion of point 1 above, establishing a nitrogen (or other inert gas) purge while brazing ...

It just isn't done anymore, in this region, for residential settings.  My guess is it was a cost cutting move.  Even the best respected residential HVAC professionals (in the Dallas area) these days say it (nitrogen purge while brazing) is not necessary as long as careful attention is paid to all details of the repair operation, and, a new filter/drier is installed.

If a consumer, needing a repair requiring opening up the refrigeration system, insisted upon this first item of the above list, here in the Dallas area, the response would be more than likely 'we just don't do it - it's not necessary if the repair is done properly, and if a new filter/drier is also installed.'

Best regards,

Bill

Posted By chrisbiker on 04 Feb 2013 09:43 AM
... What environmental factors can influence coil longevity? No sure what I should look for and actually act on.

Do a Google search 'formicary corrosion' and you will learn plenty.

A PhD person says: a majority of the problems occur when environmental acids corrode (the) coils; protective coatings are an option; heat transfer is decreased 10% with coatings.

Carrier says it is dedicated to continued field and laboratory testing and research efforts to identify an effective method of preventing coil failures caused by agents in the household environment.  To date, no solution has been identified that is functional, cost effective and feasible to manufacture.

American Heating and Cooling says: coil damage is caused by organic acids in the air that is cooling or heating your home.

But ...

A lot of the articles you'll pull up doing this Google search are either undated, or, are dated in the 2007 - 08 time frame.  It's pretty hard to find material on the subject that's been published recently.

Plus, I'm hearing that, in the Dallas area, the frequency of replacing leaking coils has substantially subsided, at least for one major manufacturer.

My conclusion is that it's the geo R410a systems installed starting around '06 through at least a few years following, that are the biggest potential problems.  Indeed, the manufacturers have been quietly working to manufacture coils that satisfactorily perform in today's residential environments.

Best regards,

Bill

I don't buy that. Every equipment mfg insists on the N2 purge. Failure to include it causes flakes of copper oxide to form on inner tube walls, and R410a's refrigerant oil carries them throughout the system. The filter drier may catch them, at some increase to its own pressure drop, but some may clog TXV orifice before lodging in the filter drier.

40 CF of N2 costs $12, and a nifty regulator gizmo to dribble a tiny bit of N2 through the system while brazing runs about $50, so I continue to insist my guys do it. Same with the microns...too many systems have noncondensibles running around the refrigerant circuit simply because tech was too lazy, ill-equipped or pressed for time to do it right. With the proper hardware and hoses, maybe $200, it takes just 3-4 minutes to pull a vacuum to my spec.

well I guess I'll just have to see what the installers going to do. I will likely ask if he will purge but I guess I cannot force him to. I hope that he does is all I can do.

is there a special way to determine if the oil in the system is correct?
or is that a non issue.

thanks guys for all your tips and suggestions. I do appreciate it. Parts come in Friday and the repair will be next Tuesday.

I agree with Curt. Industry practice is to always purge with nitrogen during brazing.With that said , if there was only one or two connection points not purging probably would not make a whole lot of difference.All manufacturers recommend purging with nitrogen when replacing major components along with changing all refrigerant filter-driers.As Curt explained about the copper oxides can mix with the refrigerant oil and if there is enough of this contaminant can cause eventual failure of the compressor.The refrigerant oil is a specific amount that was added at the factory. It is very difficult to know just how much oil has been lost. What the technician must be aware of is how much oil is trapped in the coil being replaced.Adding oil one must be cautious.There are all types of oils on the market.The exact same type as per the factory specs is the only acceptable oil that could be added.Too much oil is just as bad as not enough.