Joined on October 17, 2010
Last Post on July 21, 2014
@ July 21, 2014 8:22 PM in FREE ,FREE, NO CHARGE ,Schrader Tee.You are wrong in this case Spence. Pressure drop does indeed figure into the Subcooling calculation when your lift exceeds the 15-20' that the manufacturer factors into their published data. As we were stating in the adjoining thread, the compressor is just a pump and the refrigerant is a liquid. No different than in a hydronic system.
If you don't allow for the pressure drop in high lift situations, you will have a full liquid sight glass at the condenser and a mix at the top of the column.
Tech, I could have shown you a handful of TXV's with tap tees installed from today's startups, but it is a Federal facility and they get really, really nervous if someone pulls out a camera. But that is ok, I got a ton of those Schrader tees rolling around in a box in my van.
Spence, give it a try sometime. Once you do it, you will see what we are talking about.
@ July 21, 2014 8:16 PM in Height vs SubCooling vs Freon ChargeThe compressor is a pump. My dad and grandad called it the pump.
For example. We installed and I still service a Liebert XD system with RPU's. This is a pumped refrigerant system. There are no compressors in the system so to speak. Refrigerant moves around the system via (2) special Grundfos pumps. The refer is kept just above the dew point because moisture in Data Centers is the Cardinal Sin and this is a major data center.
Aside from the lack of a compressor, it is the same basic principle. Refrigerant is cycled through the system where it hits an expansion device where the rapid pressure drop causes the refrigerant to rapidly cool and begin to change state. As it moves through the coil, it absorbs heat from the server racks and becomes a gas. A great example of how a compressor is just a pump.
In this system, we use chilled water as a condenser, but there are other options.
@ July 21, 2014 8:07 PM in Not Cool: Techman & Meplumber:Sorry for the delay, we have been pulling 14+ hour days trying to punch out on a project. My service guys and I have a massive amount of equipment on this project (boilers, RTU's, a MultiStax chiller, and more air handlers than I can count) to startup and commission.
Ice, I am not sure that I helped that much, but it looks like you are learning more in a few days of tinkering with your system than some of my apprentices have in years. As Tech said, the first thing that I would have done was throw the gauges on. The low suction would have indicated the low airflow and hence a high delta across the coil. You are on the right track.
@ July 12, 2014 7:58 PM in Not Cool:Chris, it sounds like you have an airflow problem, possibly in combination with something else going on. To help me get my head around it, I have a homework assignment for you.
Can you get me the model # of the air handler and the condenser? Also, any chance of posting a couple of pictures of the air handler and condenser install? Can you take a temp probe and give us the suction and liquid line temps at the condenser and the air handler? Can you guess at the line length between the evap coil and condenser? That would be a start so we could give you some guidance.
@ July 12, 2014 7:53 PM in nuisance lock out of mini splitThis "Jack from the Internet" was THE manufacturer's representative for a major mini-split manufacturer from their introduction into the United States. He is more qualified to talk about mini-splits than anyone else on this website. I have been doing air conditioning for my entire adult life and most of my teenage years (30 years all together) and I still look to Jack if I get stumped on a mini-split problem.
He answered your question. Your employer or the design engineer chose the wrong equipment. Period.
Mini-splits are often put in these rooms because they are a cheap alternative. All of them and I mean all of them automatically reset after a power outage. There is something else going on, that you are not seeing. As Terry told you, some of these lower end units have to have the remote within line of sight when the power is restored. Otherwise, they lose their setpoint reference. The default in some of the units is 77 deg cooling. Unless the remote can "resend" the setpoint, it will default to the higher setpoint.
Do what was described above. Find the remote, put it in a drawer and recycle the power. If the unit doesn't come back on, then that is your problem. Then to prove it, place the remote in line of sight of the evaporator and repeat the test.
@ July 8, 2014 9:44 PM in Pipe connections to Condenser - Best Practices?In my very experienced opinion, the guy did a fine job with the tight criteria that you gave him.
The braze joints near the floor are because you can't bend roll copper that tight, so he used standard refrigeration long sweep 90's. This is an accepted practice. Those long sweep 90's are the flow equivalent of a manual bend in the coil of pipe.
None of us want to turn that tight, but you really gave him no choice and it appears that he did it as well as could be expected. His braze joints show that he used the proper amount of heat as to not "Cook" the joint.
I would say that he did a good job. As icesailor said, there are a lot of really poor installs out there, this isn't one of them.
@ July 8, 2014 9:34 PM in 17-1/2 ton evaporator weight.While it doesn't weigh 750 lbs (that would be the weight of the whole air handler), the coil only, will weigh around 200 lbs and be fairly awkward to carry.We just replaced the coil only in a 15 ton Trane air handler. Due to the location inside a bank, we had to hand carry it.
If this is just a coil replacement, I would recommend at least 3 people to be safe. If this is the whole air handler, you could always break it down into sections and carry it piece at a time, but it is still a job for 3 or 4 guys just to keep it safe. Remember, you only have one back. Don't wreck it while you are young, just to save a few bucks.
@ July 4, 2014 10:38 PM in stupidityThis guy is creating an incredibly unsafe environment. As an owner, I need to know when a recently hired or promoted manager isn't doing what's in the best interest of the company.
I lean on my older techs for that. They know that the door is open and I know that they won't sugar coat it. This guy is on the verge of a MAJOR accident. As Jamie said, those OSHA regs are there for a reason. If they find your company in violation after a death or major lost time accident, the fines will be very steep.
You did the right thing. Good job.
@ July 3, 2014 9:25 PM in Height vs SubCooling vs Freon ChargeGreat point.
Nameplate SC is a range that applies under a certain "normal" set of installation conditions. It won't work in every situation. Most of the US manufacturers factor a maximum of 15'-20' lift in the SC range. If you exceed the factored lift, then you have to make a field correction to the SC target. By applying the 1/2 PSI rule, you can trim your charge accordingly.
@ June 22, 2014 10:05 PM in TXV not set properly?Paul, you would use a chart like this one. All small tonnage units come precharged with enough refrigerant to cover the matched evap coil and a 15' lineset. There will be a factory charge weight on the condenser. You then use a weight chart to figure out how much extra to add for the additional lineset length. See below:
@ June 22, 2014 8:41 PM in TXV not set properly?With a lineset that short, why not just calculate it and charge by weight? You cannot go wrong charging by weight.
Up here in the great white north, we have to do that more often than by SH or SC. Since the charts all stop at 50*, we wouldn't be able to charge but a few weeks a year without weighing it in.
I think that you are overcharged. There is a slim chance that you have a restriction, but I would tell one of my guys to pull the whole charge out and weigh it in for the 20' lineset and then reevaluate. Especially since you have no height difference to worry about.
@ June 20, 2014 10:12 PM in Aquatherm pipingCharlie,
We had an engineer up here spec'ing it pretty regularly for a while. It does have its advantages, but I am not a fan of the larger diameter stuff. Over 4" the set time makes it a bear to work with in position. Everything looks great when you are doing it on the ground. But when you are 15' - 20' in the air, things get interesting. Also, above 4" plan on spending some serious cash in a hurry.
In my opinion, for closed systems, I am still a fan of Victaulic on large diameter stuff. We are doing an 8 story addition to a hospital now. We went through the process to submit on Victaulic even though Aquatherm was on the original spec. Aside from the cost savings, our comfort level, despite a bunch of jobs using Aquatherm, was higher on the large diameter chilled water and hydronic piping using the Victaulic connection system. This job has a lot of 16" and above piping.
@ June 16, 2014 11:52 AM in SubCoolingAgain, I am old and use rules of thumb that my dad and grandad taught me. I always use 1/2 PSI/foot pressure drop for the liquid column lift (probably incorrectly, I apply this to all refrigerants.) Amazing how the old dudes that came before us knew this stuff without the access to the science that we use today.
My grandad was installing air conditioning and refrigeration in the late 40's and early 50's, then dad followed him. Almost all of my "Rules of Thumb" were beaten into my head by them.
Grandad's #1 rule when I started working with them and learning the trade: First thing every morning, put your P & T chart in your shirt pocket along with a notebook. You are useless without them.
Still today, it is part of my morning routine (even on my off days, haha).
@ June 14, 2014 8:56 AM in Expanion rateTerry, the rule of thumb that we have been using for AC and Refrigeration is 1" per 100' of horizontal run, properly supported. It isn't as exact as Jamie's number, but hasn't bitten me in the rear yet. I will do an expansion loop only if the horizontal run exceeds 150' and it is a heat pump application. In AC only, the temp rise is below the point where it will cause a sufficient expansion to stress the joint.
@ June 13, 2014 7:55 AM in internal coil cleanerAs Terry said, there is stuff out there, but I won't use it. I will ocassionally use an RX-11 flush if it was a total burnout (smells burnt and test acid from the start), then blow N2 through the system SEVERAL times.
Terry's procedure is dead on and the only way to insure that you are out of the woods.
@ June 13, 2014 7:52 AM in Whoops!Harvey, that poor TXV is probably hunting all over the map. Don't you hate that?
@ June 13, 2014 7:50 AM in R410A pipe sizing chartWe do most of our work on 15 ton and up. "Go with what you know." Haha.
You will want to trap that riser at the bottom, but you shouldn't have to do an inverted trap at the HX. 15' isn't that big of a rise for 15 ton, but....
I am assuming that this is a 2 compressor machine. The concern is velocity with only one compressor running. Who is the manufacturer? They should have some refer velocity data at the outlet of the condenser. If they are moving 3800 fpm at the outlet, and the riser is really close to it, then I don't sweat the riser velocity so much. Also, if you have the total equivalent length, I can dial it in exactly.
I would sleeve the 1 5/8" in 4" PVC with 1" insulation on it. You can split a 90 at the top of the riser where it goes into the building and then glue the seam. We would then put the LL in a 3" PVC pipe, also insulated (with at least 1/2"), and use split ring hangers to secure it to the building. Makes for a nice straight run where people can see it.
@ June 12, 2014 11:04 PM in R410A pipe sizing chartI would need a little more information, but my gut reaction is 1 5/8" suction and 7/8" liquid. If it was R22 it would be 2 3/8" suction and 7/8" liquid. I would have to double check my charts when I get to the office tomorrow. The question is the velocity on the rise to compensate for the oil. I like to keep my velocity on the vertical above 1500 fpm and keep the Delta on the suction below 4 F (preferably 2-3 F).
Hope this helps.
@ June 8, 2014 9:17 AM in txv issueCharlie, to me this screams liquid line restriction. As the Professor stated, the TXV is doing what it is supposed to do. Check the filter drier or look for a new kink in the liquid line.
@ June 5, 2014 9:37 PM in Head Pressure ControlsThat is great Terry. Plenty rolling around in my head, if you can figure out what question to ask in order to pry it out.
@ June 5, 2014 6:52 PM in Head Pressure ControlsIt would depend on the refrigerant. The head pressure control for 410A would be set much higher than it would for 22 or 407, etc...
And, if it is being used for low ambient operation, then those settings would be different still.
Did you have a specific application that you were thinking about?
@ June 4, 2014 10:14 PM in AIR HANDLER RHEEM central air systemYou have something going on that we cannot possibly troubleshoot in a forum. Troubleshooting this would require testing the high voltage feeding the units. Locate a competent local HVAC professional and let him tackle this one.