Joined on March 30, 2008
Last Post on August 26, 2014
@ August 26, 2014 7:58 PM in Stupid is as Stupid does.I saw a recent article in the ACHR news about one of these hoodlums that they caught red handed. The officers actually witnessed him cutting the lines. They turned him over to the federal authorities where getting charged with theft was the least of his worries. They brought out the EPA laws on illegal release of refrigerant and used that against him. For anyone unfamiliar with these laws, lets just say he will have completely empty pockets and about a decade to ponder the wisdom of his criminal career.
@ August 26, 2014 7:49 PM in Scorched Air vs HydrocoilDuring heating, the RH of the conditioned space depends on three things. The out door RH, the tightness of the structure and the internal latent loads. As air passes through any type of heat exchanger and gets warmed up the RH drops. The hotter the air exiting the HX, the lower the RH. The Absolute Humidity or grains of moisture per pound of dry air will not change. When the hot air exits the duct, it will mix with the air in the surrounding space. As it does so, it will be cooling off and the RH will be increasing.
IMO the largest enemy is infiltration and exfiltration. It does go both ways. Also, air is a gas and it will act like gasses do. When it is heated it expands and when it cools it contracts. Now consider what happens when you heat all the air in an entire house. It expands and pushes out through every nook and cranny that it can. As it cools it contracts and sucks in air through every nook and cranny. The outside air during the winter typically has a low RH. When this air is brought into the house and is warmed up to room temp, the RH drops even lower.
Any kind of air heating system will act this way to some extent. That is why we call it scorched air.
On the other hand, a system that uses some type of radiation to warm the space will ultimately establish and maintain a MRT. Once the MRT is established, the expansion and contraction of air will be negligible. Depending on the internal latent loads and the tightness of the house, no additional humidification may be needed.
That is why hot water radiant heating systems are the best, period. They are more comfortable with less effort.
@ August 24, 2014 9:08 PM in NO A/CPressure switches, Thermal switches.
Microchannel condenser coils are easily overcharged and will trip the high pressure switch. By the time you are out there, the switch will have reset and the weather might have cooled off a bit too making everything look normal. A dirty condenser coil could do the same. Slightly bad bearings on a fan motor may feel loose when the motor is cool but after the motor is running for awhile and heats up they can increase the friction on the shaft and end up tripping the motor on thermal.
What is the compressor discharge temp? Lower then normal suction pressure combined with a high superheat could cause the compressor to trip on thermal.
@ August 20, 2014 9:13 PM in Caleffi Boiler Mix Valve.That's what keeps us humble!
@ August 19, 2014 10:45 PM in Caleffi Boiler Mix Valve.The response time increased exponentially once I connected the neutral wire on the boiler circulator! Daggone it!!
Don't tell me you haven't done something like that! I'll know you are full of mud and your nose will grow an inch longer!
@ August 19, 2014 6:43 PM in Caleffi Boiler Mix Valve.How long does it take to respond with 180 degree boiler water?
@ August 14, 2014 7:54 PM in Gas drip leg/reservoirTrue, I could do that. It would mean switching to 1-1/4" pipe versus 3/4" . I'll have to see how much difference in cost between the 2.
@ August 13, 2014 10:49 PM in Gas drip leg/reservoirThe genset I am installing needs a minimum of 7"wc. It is 150 feet away from the gas meter. Hence I chose to switch to a 2psi system. Now I will have the underground riser coming up right at the genset with a regulator to bring the 2psi down to 10" wc. There will only be room for a foot or 2 of pipe from that point to the genset valve. I need a minimum of 10' of pipe betweek the regulator and the genset or, as I was hoping, a small canister like buffer that could be placed in line.
@ August 13, 2014 10:39 PM in Gas drip leg/reservoirThat is precisely what I was looking for.
@ August 13, 2014 9:04 PM in Gas drip leg/reservoirI am installing a standby 20kw genset. The gas piping will run underground 150' to the genset. The gas pressure in the underground line will be 2 psi. I need to install a regulator on the line by the generator to bring the pressure down to 10" wc. This will not allow sufficient piping between the regulator and the genset gas valve for buffering. I was wondering if anybody knows of any inline reservoir that would be available for this situation? It would be ideal if it could serve as a drip leg as well.
While on the subject, anybody have pipe sizing tables for SDR11 IPS. Specifically for 2 psi. but I would like the charts for low pressure and 10 psi as well?
@ August 13, 2014 6:58 AM in Heart attackI certainly hope he pulls through, Terry. It sucks loosing someone close.
@ August 11, 2014 8:15 PM in 6 dead 25hp ac comps in 12 years on one systemSounds like somebody made the same mistake 6 times. What was the cause of the 6 failures?
@ August 7, 2014 5:29 PM in problems with Mitsubishi split systemMost probably low on refrigerant. That oily spot he found would be a leak. The connection he tightened would likely be a flare connection. When a flare leaks, it is usually best to undo the connection, cut off the old flare and then re flare the pipe.
If this were me, I would first check every connection for a leak. Then I would recover the freon and see how much was left in the system. Then repair the leaks and weigh in the freon charge that was calculated by system design.
@ August 6, 2014 9:30 PM in Compressor Overheating and Rfrig. OilIt's a fun read!
I would say that the highest discharge temp that I am inclined to be comfortable with is right around 230°F. This would be the measured temp. The actual discharge temp will be 50° - 75° higher than that. That would put the actual discharge temp up around 280° - 305°.
As the document states; Refrigeration oils have been highly refined in an effort to elevate the temperature at which chemical decomposition will occur. As such, they are vulnerable to losing the lubrication film necessary to prevent metal to metal contact between bearings and journals, or piston rings and cylinders, prior to the temperature at which decomposition begins. With mineral oil this will occur approximately between 310ºF and 330ºF. When these temperatures are achieved, the probability of extreme piston and ring wear is imminent.
ALL THE SH's ARE CRITICAL!! The comp discharge temp is a product of "Heat of Compression" and all the combined SH's, including the evaporator. We can do nothing about the heat of compression, but we can run a "tight ship" on the rest of the SHs.
Another point that was of interest to me;
Chemical decomposition: This happens at elevated temperatures, and is accelerated in the presence of other contaminants such as air or water. 18 is an important number to remember, for the rate of chemical reaction doubles with every 18ºF temperature increase.* For example, a chemical reaction that takes 10 years to complete at 100ºF, will only take 5 years to complete at 118ºF. At 136ºF it would be complete in 2-1/2 years, and so forth. The process by which the refrigerant and/or oil chemically breaks down can occur in a matter of seconds if there have been enough 18° temperature increases.
Good stuff to know!!
@ August 6, 2014 1:20 PM in An interesting discussion.Lets talk about which components you are using and why.
I'll start things off with Air Separators.
I have been using Caleffi for a while now. I used to use Spirovent. I chose Caleffi because it not only is serviceable and works well, it also has an interesting side effect. Whenever possible, I place the separator at the highest point of the near boiler piping. The circ will be pumping away from the separator and will have shutoff flanges. The return piping will have a ball valve at a level higher then the boiler.
This allows me to add water conditioner easily without any tools. I shut off the circ flange valve and shut off the ball valve on the return and also the PRV. Then I drain a gallon or so of water from the boiler drain. At this point I unscrew the cap from the top of the separater leaving a nice big hole to dump in my corrosion inhibitor. Next I replace the cap and turn on the valve to the PRV. All the air immediately exits the system. Then I turn the circ flange valve anf the return ball valve back on.
We are back in business! It only takes minutes, no tools required ;-)
@ August 6, 2014 9:47 AM in Compressor Overheating and Rfrig. OilHere is a good read. It explains in great detail about the importance of controlling the comp discharge temp and what happens if you don't.
@ August 4, 2014 7:05 PM in Then there was Mueller.Did a little research on this critter. It is supposed to have a 5HP comp!!! Not a 6! Also I must take my SH readings at the suction port on the comp, (3°- 4°) after the SLAHX, not before. That means the evap will be completely flooded which is what they want. That means I'm still undercharged and a little more Freon should help bring the discharge temp down some. I am not expecting normal levels.
I ordered the replacement service valves. The parts don't come through the normal channels. I deal with a Dealer/Service company who buys direct from the manufacturer. That is how it is, the dairy equipment service industry is sewed up. They give me a healthy discount on parts though and I had a great conversation with one of their technical guys named Jim. They are fully stocked and can get me anything I need!
Good point on the SLAHX. I have Rustoleum and an insulation blanket that's begging for a home.
I particularly enjoy working on Dairy Equipment. On average the systems (not just refrg.) are more complex and interesting than the normal humdrum ;-)
@ August 4, 2014 6:48 AM in Then there was Mueller.Doesn't have a S/G. I need to replace the high and low side service valves. Same time I do that I plan on replacing the drier and adding a S/G.
The unit uses R-22. The condenser settled in around 108° @ 78° ambient. The evap never really settled down completely. One snapshot I took was with the condenser temp as previously stated, evap temp @ 23°, 3° SH before the SLAHX, and about 51° refrigerant temp @ the suction port of the comp. Discharge temp registering @ 245°.
@ August 3, 2014 10:08 PM in Then there was Mueller.Saturday I went out to trouble shoot a Milk Cooler. There was a lot of ice forming on the bottom of the bulk tank and the compressor was running abnormally long. I put on my gauges and yes, it is low in Freon. I charged it appropriately. I ended up with normal condenser p/t for the ambient conditions and about 3° superheat at low load condition, (bulk tank @ 36°). That is what they want, a flooded evap to alleviate thermal stress on the cooling plates on the bottom of the tank. The condenser is a unique setup. I had to noodle over it a bit till it made sense. Starting at the compressor, the discharge line first passes through a free-heater (water heater with a desuper-heating coil in it), then it makes it's way back to the condensing unit and enters the condenser which has standard fan head pressure controls. Once it exits the condenser, it passes through a "suction line accumulator heat exchanger = aka SLAHX" and then on to the TEV. Through the TEV and on to the evap plates and then back to the SLAHX and back to the compressor suction port.
The TEV threw me for a loop at first. It is designed to maintain a specific subcool 10° at the condenser. In this manner it is possible to keep the condenser operating at maximum BTU output regardless of ambient conditions or evap loads. This is important because milk needs to be cooled quickly and the milk that is already in the tank should not be allowed to warm up during consecutive milkings.
So that's all good. Here is the problem. 245° to 250° comp discharge temp. It didn't seem to vary much with the suction line temp. Granted, the suction line picks up some heat going through the SLAHX but I was measuring temps both before and after to get a better feel for things. The comp is a Techumseh AGA5568EXN. That is a H/Back Pressure Air Conditioning compressor. I did notice the compressor's nominal capacity is about 9k BTUh higher than the max output of the evap, which occurs at the max rated influx of warm milk.
I will attach Pics. https://www.dropbox.com/sh/p871yhxaodphd8z/AAAc1VEK8ZCVUv1XFik4dPjna
Oh, and I did find 2 leaking service ports which account for the low charge.
@ July 31, 2014 9:17 PM in Brazing without nitrogen?!Interesting stuff, CuO
It has been beat into my head that it is an abrasive and nitro should always be used. "Which I do, unless I'm in one of those unique situations that the books conveniently ignore." In fact, apparently CuO is used to polish optical equipment; cool.
Then there is this paragraph that I barely understand. It makes some interesting points about CuO enhancing fluid viscosity and thermal transfer.
1.1. Characteristics of CuO NPs
CuO is the simplest member in the family of Cu compounds and exhibits a range of potential physical properties, such as high temperature superconductivity, electron correlation effects, and spin dynamics [15,16]. As a semiconducting compound with a monoclinic structure, CuO has attracted particular attentions in the field. It possesses useful photovoltaic and photoconductive properties because CuO crystal structures have a narrow band gap . Besides the property, CuO NPs hold novel characteristics. CuO NPs can also improve fluid viscosity and enhance thermal conductivity, and these novel properties make them a potentially useful energy-saving material that can improve the effect of energy conversion . CuO NPs have been applied in different areas, including gas sensors , catalysis , batteries , high temperature superconductors , solar energy conversion , and field emission emitters . For industrial catalysis, CuO NPs may be able to replace noble metal catalysts for carbon monoxide oxidation , which would reduce production cost and improve the catalytic efficiency. The suspension has excellent thermal conductivity and can be used as a heat transfer fluid in machine tools . CuO is much cheaper than silver oxide and can be mixed with polymers more easily to obtain composites with unique chemical and physical properties. Because they can reduce friction , and mend worn surfaces, CuO NPs are used as an additive in lubricants, polymers/plastics, and metallic coatings . Moreover, the extremely high surface areas and unusual crystal morphologies endow CuO NPs with antimicrobial activity, and they dose-dependently inhibit
Here is the whole article http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCIQFjAA&url=http%3A%2F%2Fwww.mdpi.com%2F1996-1944%2F5%2F12%2F2850%2Fpdf&ei=muXaU_TyJY6lyASb_oLYBg&usg=AFQjCNHsfETPS9nTYUK-fduYRHsSZNcUHA&sig2=KDklJ6vFhfRVMX49kp4lgg&bvm=bv.72197243,d.aWw
@ July 30, 2014 6:32 PM in increasing length of AC cycleSome are and some aren't. Mostly it will be controlled by a minimum off time. The EcoBee does allow more in depth settings.
Hope that helps.
@ July 25, 2014 5:42 PM in New Boiler InstallBefore you put a new boiler in, the same way the old one was, perhaps it would be a good idea to determine why the old boiler failed. That way you can make the appropriate changes when you install the new boiler.
Where did it leak?
Was it a cold start?
How does the interior walls of the iron pipes or heat exchanger look?
Was the system frequently purged?
Is there a lot of rust debris in the bottom of the fire box?
We're there any chemicals in the system, glycol...ect?
Is your DHW tied in as well? If so, how? A separate zone or and indirect coil?