Nyle Refrigeration Kiln Wet bulb temp won't go down.

AdirondackMill · February 17, 2015, 10:34:05 AM

We're running two Nyle kilns we just switched one over from parlow controls to their new touch screen controls that run on a little computer that we can control through a wireless connection.
We have a load of 4/4 EWP in it and the moisture content avg is around 20% we're 10 days into this charge. That MC is a little higher than normal for a kiln load of 4/4 that has been in this long. Right now we're having issues getting our wet bulb temp to come down. We tried venting it on manual to see if it we could get it down and to see if it would then be able to get it to stay near the set point. No such luck. We wanted to make sure the compressor was doing its job, its putting out somewhere between 5600-6000 lbs of water per day. My contact at Nyle said it should be taking out 5400 lbs a day. So we're even more confused as to how this is happening. Dry bulb is set to vent at 130F and thats working fine. The Wet bulb is set at 95F but its running anywhere from 110-115F. Anyone have any other ideas how to get that WB temp down?

GeneWengert-WoodDoc · February 17, 2015, 09:12:06 PM

How are you measuring water output? I wonder about your numbers here.

What sort of air flow do you have across the wet bulb?

Is one of your measurements wrong? With EWP at 20% MC, there is not enough water left to provide 4500 pounds, so the air should be dry indeed. So is the equipment running 100%? If so, then what is keeping the air humid? So, is it really humid?

AdirondackMill · February 18, 2015, 09:11:01 AM

Quote from: GeneWengert-WoodDoc on February 17, 2015, 09:12:06 PM
How are you measuring water output? I wonder about your numbers here.

What sort of air flow do you have across the wet bulb?

Is one of your measurements wrong? With EWP at 20% MC, there is not enough water left to provide 4500 pounds, so the air should be dry indeed. So is the equipment running 100%? If so, then what is keeping the air humid? So, is it really humid?

We're collecting the water measuring volume using a 8.33Lbs/Gal conversion. Kiln has around 40-43,000 BDF of 4/4 EWP.
We flushed out and replaced all the refrigerant last night. We've tested the wet bulb, used a hydrometer and you can feel the humidity in the chamber when you're in it, its definitely different than normal. Airflow across the wet bulb is good that hasn't changed.

GeneWengert-WoodDoc · February 18, 2015, 03:16:22 PM

Hot water is only 8.0 pounds per gallon or "a pint is a pound the world around."

I thin that wwith a properly functioning compressor, you should easily be running 24 hours a day and removing huge amounts of moisture. So, something does not add up. Perhaps the control system shuts the compressor off at times due to pressure levels in the compressor.

LeeB · February 18, 2015, 08:53:56 PM

Beg to differ Gene. 8.33 ppg is the correct number for fresh water.

Den Socling · February 18, 2015, 09:36:47 PM

I agree with Lee. Where did you get 8.0? Google confirms 8.34.

GeneWengert-WoodDoc · February 18, 2015, 11:51:35 PM

I was thinking about hot water (180 F) which is indeed very close to 8 pounds. But, as pointed out correctly, for cold water, which is what a DH will have, the value around 8.34 is indeed correct. Thanks for catching this error.

LeeB · February 19, 2015, 01:09:06 AM

No problem. I don't know much, but I do know this one. That number is a major part of my bread and butter.

Denny · February 19, 2015, 07:23:42 AM

Vents working ?

AdirondackMill · February 19, 2015, 09:07:42 AM

Quote from: Denny on February 19, 2015, 07:23:42 AM
Vents working ?

Vents are working. We've actually been having problems with them freezing open in this weather. It drops both temps in a hurry.

GeneWengert-WoodDoc · February 19, 2015, 10:02:51 AM

So, let's review. You are removing over 5400 pounds a day, which indicates that the compressor is running 100% of the time and that the compressor is properly working with adequate gas, etc.

Your lumber is drying, but more slowly than expected. Your wet-bulb is higher than desired, with the set-point being lower. If the set point was reached, it would turn off the compressor.

The dry-bulb is at the correct temperature.

The removal of about 22 pounds of water per MBF will drop the moisture by 1% MC. It looks like you are losing about 8% MC per day, so that is 176 pounds per MBF. With 30 MBF, that would be 5200 pounds per day. Do you have 30 MBF? If you have less, then it appears that there is either an error in the water output measurement or there is another source of water in addition to the lumber.

pine · February 19, 2015, 11:52:29 AM

Quote from: GeneWengert-WoodDoc on February 19, 2015, 10:02:51 AM
So, let's review. You are removing over 5400 pounds a day, which indicates that the compressor is running 100% of the time and that the compressor is properly working with adequate gas, etc.

Your lumber is drying, but more slowly than expected. Your wet-bulb is higher than desired, with the set-point being lower. If the set point was reached, it would turn off the compressor.

The dry-bulb is at the correct temperature.

The removal of about 22 pounds of water per MBF will drop the moisture by 1% MC. It looks like you are losing about 8% MC per day, so that is 176 pounds per MBF. With 30 MBF, that would be 5200 pounds per day. Do you have 30 MBF? If you have less, then it appears that there is either an error in the water output measurement or there is another source of water in addition to the lumber.

Quote from: AdirondackMill on February 18, 2015, 09:11:01 AM

We're collecting the water measuring volume using a 8.33Lbs/Gal conversion. Kiln has around 40-43,000 BDF of 4/4 EWP.
We flushed out and replaced all the refrigerant last night. We've tested the wet bulb, used a hydrometer and you can feel the humidity in the chamber when you're in it, its definitely different than normal. Airflow across the wet bulb is good that hasn't changed.

Using Gene's numbers of 176 pounds per MBF and AdirondcksMills previously stated charge size of 40-43,000 BDF I would think instead of 5200 pounds per day for Gene's 30 MBF, it would be closer to 7040 pounds per day 176x40 =7040. If true then the DH is not removing as much water as Gene's calculations show there should be.

What is the DH rated for as to charge size. Are you pushing the upper limit?

AdirondackMill · February 19, 2015, 01:45:58 PM

This is where it gets a little tricky. When we put the first kiln in(the one we're discussing) it came with one compressor as it was put in to dry 6x8 & 8x8 log home cants. We built the chamber to Nyles specs and they installed the drying system all in the thought that we were going to be drying timbers forever. As things often do stuff changed. Before long we were getting requests for dry 4/4 & 8/4 and we decided to start drying boards for our own log siding and T&G. So we built another Kiln right next to the first. Now when this one was built they put in two compressors. They claimed that the single compressor would still do the work of the other two if we were to load that kiln with boards instead of cants. So now we're not totally sure that, that is true. So I would say we're definitely running it close to its limits.

5quarter · March 10, 2015, 01:27:04 AM

I know next to nothing about commercial kiln drying operations, so naturally I'll jump in with my 2 cents. All other things being equal, drying 40mbf of 8x8 timber should take considerably longer to dry than 40mbf of 1x8 lumber, mainly because the rate of moisture loss is directly related to the total surface area of the wood. What you should be seeing is an increase in the drying rate with 1x and 2x material over 8x. have you had other identical charges prior to this one in the kiln? if so, then it's probably equipment failure somewhere. as you suggest, maybe your compressor is plumb worn out. Hope you get it figured out.

AdirondackMill · April 02, 2015, 11:06:28 AM

Quote from: 5quarter on March 10, 2015, 01:27:04 AM
I know next to nothing about commercial kiln drying operations, so naturally I'll jump in with my 2 cents. All other things being equal, drying 40mbf of 8x8 timber should take considerably longer to dry than 40mbf of 1x8 lumber, mainly because the rate of moisture loss is directly related to the total surface area of the wood. What you should be seeing is an increase in the drying rate with 1x and 2x material over 8x. have you had other identical charges prior to this one in the kiln? if so, then it's probably equipment failure somewhere. as you suggest, maybe your compressor is plumb worn out. Hope you get it figured out.

New(refurbished) compressor is all it took.
Thanks