Sunday, March 1, 2015
I read two statements in Kyle Gargaro’s HVACR News editorial that really jumped out at me. He said that 40% of the thermostats sold in 2014 had internet capability. Later he stated that in the coming years the number of devices connected to the internet would exceed the number of people. I found that a little unnerving. Then I thought, I am not connected to the internet, my computer is – and it is definitely a thing. So what is so weird about my thermostat being connected to the internet? Digital thermostats are really just small computers with a very specific task. The difference is just in the human interface and the much narrower scope of operation. However, the real idea of the internet of things is not so much to allow us to talk to our thermostat. There is not really a lot to say to your thermostat. It is the possibility of our things communicating with each other so they can accomplish their tasks cooperatively. For example, the alarm clock can tell the thermostat, coffee pot, hot water heater, and toaster when I plan to arise. They can all use that information to make sure they each perform their function in a timely manner, so I have warm water, a warm house, hot coffee, and toast all at the right time. Or an internet connected electric meter can tell the thermostat when electric rates will increase and decrease, allowing the thermostat to consider the ideal time to turn back my system. I heard a great use the other day on NPR. A cardiologist has his patients wear a bracelet that monitors their blood pressure. The wrist device is connected to their phones via Bluetooth and they can upload their blood pressure history to his office. He can see not just the blood pressure when they walk in, but what it has been for a week or a month. The connected things allow the doctor a much better view of their health, so he can make more informed decisions. Suppose you had all the system’s relevant voltages, pressures, and temperatures before you got in your truck? Or a tool that takes those readings, provides a diagnosis, and offers possible corrective actions? These actually exist now, but they are the exception rather than the rule. I think they may become commonplace when the internet of things takes off.
Sunday, February 15, 2015
Checking for proper airflow is not just a summer thing. Most techs know that poor airflow is the first thing you should check in the case of freezing up air conditioning coils or lower than normal suction pressures in cooling. We need to be concerned with airflow in the heating season as well. In fact, in the case of heat pumps, airflow is arguably more important in the heating season because the indoor coil is now the condenser. Sure signs of an airflow problem in a heat pump are low suction pressures and icing in the summer and frequent high pressure switch trips in the winter. I have heard several stories about systems which techs “fixed” by adding charge in the summer and taking it out in the winter. In effect, they are overcharging the system in the summer and undercharging it in the winter. Of course this kills both system efficiency and the compressor. In the summer, the overcharge causes liquid dilution of the compressor oil, and in the winter the undercharge makes the compressor run hot. Other signs of poor airflow include open fuse links on strip heaters, open strip heaters, or open thermal limits which eventually fail from opening and closing repeatedly. In gas furnaces, poor airflow will cause a higher than normal temperature rise. In the case of gas furnaces, it is possible to have too much airflow. Too much airflow will reduce the temperature rise below the minimum, which can cause condensation in heat exchangers which are not designed for condensation. Typical temperature rise for mist furnaces is between 40°F and 70°F. However, check the data plate on the furnace for the exact specification.
Monday, February 9, 2015
ShurTape has launched an initiative to follow three students at Athens Technical College through their studies in the Air Conditioning Technology Program. To support the students, Shurtape is challenging each of them to a series of missions. They complete the mission and report their findings on the ShurTape blog. The students are paid $500 for each completed mission, up to $5000 for the year. A mission can be to interview the owner of an HVACR company about HVACR careers, or discuss job safety with a tech in the field. They have chosen three students with different backgrounds and ages, who are at different points in the program. By following the three students blog postings, you can vicariously experience a little of life as an Air Conditioning Technology student and see how they progress in their career quest. I am quite pleased to be working with ShureTape in helping promote our industry. I really appreciate their support – I know Josue, Daniel, and Thomas do. To read more anut the program and the students taking part, go to http://www.shurtape.com/Blog
Friday, January 30, 2015
Dad turned 89 today. In celebration, my sister hosted a party at Stanfield Air Systems so the many folks who have come to know Dad over the years could celebrate with him. Friends from all walks turned out. The room was crowded with people regaling each other with stories about their life and work with Dad. Family, neighbors, employees, customers, and competitors all turned out to celebrate and wish him continued good fortune. Dad started Stanfield Air Systems in 1968. The company he started grew in reputation as the place to go, especially if what you wanted to do was a bit off the beaten path. Dad was among the first in our area to tackle high velocity systems, solar heating, and ground source heat pumps. Along the way he also installed Arkla-Servel gas fired air conditioners and Amana EG mini-boiler systems. How did he know about all these technologies? He read and studied. Studying your field was just part of your job. And if I am completely honest here, I think he really enjoyed doing different things. If you work hard at your craft and treat people fairly you collect a lot of friends. Today showed there are many folks in Athens who are very glad Lynn Stanfield moved here and started Stanfield Air Systems in 1968. Happy birthday Dad!
Sunday, January 25, 2015
With the abundance of condensing furnaces, drain problems are no longer limited to the summer months, but are now a year round concern. Although the drain on a condensing furnace is a relatively small detail in the overall scheme of things it can shut a system down if not run properly. Normally, there are two furnace drains: one for the condensing heat exchanger and one for the vent. Some furnaces combine then inside the furnace while others require the installer to take care of that. The vent should slope towards the furnace so any water condensing inside the vent runs back to the drain. This also prevents water dripping out the vent and creating an ice dam. The drains need to be trapped, but only once. After the drain leaves the trap the pipe should never rise. Sometimes sags in PVC drain lines cause unintended secondary traps. Secondary traps will keep the water from draining out, creating a mess. Many manufacturers now provide a manufactured trap. If a furnace has a built in manufactured trap you should not add another one. Multi-poise condensing furnaces pose a special problem: you have to know which end is up (literally) to know how to position the trap and drain. Often these furnaces come configured for upflow installation but must be reconfigured for downflow or horizontal installation. Make sure the drain gets moved to the right location for whatever position the furnace is installed in. In general, you should not run the air conditioning condensate drain and the furnace condensate drain into a common line. The positive pressure from the coil can travel through the drain to the furnace drain and cause the vent safety switch to trip. It is OK to run both into the same condensate pump basin, so long as it is open to the air and not sealed tight. If you use a condensate pump, make sure that it is rated for furnace duty. The condensate from furnaces is moderately acidic and can eat up some pumps that are not designed to handle furnace condensate. If the drain will run through unconditioned space that may drop below freezing, it will need to be wrapped with a heat tape to prevent it from freezing. If the furnace is located in an area which can be damaged by water overflow, such as an attic, it will require a secondary drain pan underneath the furnace. Finally, remember water runs down hill. The drain should slope away from the furnace until its outlet.
Thursday, January 15, 2015
WE are experiencing lot of cold, rainy days here in Georgia. The temperatures hover just above freezing into the mid 40's. This type of weather is perfect weather for heat pump defrost problems. Heat pumps have to defrost more in weather just above freezing than in much colder weather. If the temperature is so cold that water freezes out of the air, there won’t be much water in the air. If there is not a lot of water in the air, heat pump will not develop very much frost. On the other hand, if the temperature is 40 degrees and raining, there is a lot of water available. The coil in the heat pump will be below freezing even when it is 40 degrees outside, so the water will form frost on the coil. The system is more likely to need frequent defrosting at temperatures just above freezing than at much colder temperatures. This is not to say heat pumps won’t got into a defrost cycle at very cold temperatures, but there is much less ice to defrost. The first thing to check on an iced over heat pump would be to make sure the outdoor fan motor is operating. If the outdoor fan motor is not moving air across the coil, it will frost very quickly in cold, wet conditions. The normal defrost periods would not be able to keep the coil clear. An undercharge can also make a system freeze up faster and keep it from clearing the ice when it does go into defrost. If water created when the coil is defrosted cannot drain away from the unit, a large ice floe can build up underneath the unit. This can create an ice chunk around the bottom of the unit. Heat pump condensers should be elevated enough to allow the water to drain. Sometimes the defrost thermostat just clips onto the coil. Occasionally they become loose and cannot sense the coil temperature, so they will not initiate a defrost cycle in weather that is above freezing. To check a defrost thermostat, just ohm it out. Generally, the defrost thermostat should close when it senses a temperature cold enough to initiate a defrost cycle. This can be checked by disconnecting the defrost thermostat from the circuit and ohming it out. If it is in the correct location, making good contact, and the coil is iced over, the defrost thermostat should be closed (0 ohms). If it is open (OL) it is bad. A thermistor defrost sensor is also checked by resistance, but these typically change resistance with temperature rather than opening and closing like a switch. You have to check the measured resistance against the manufacturer’s specs. Usually, these fail open, so if you have a measurable resistance, the defrost sensor is probably OK. Most defrost boards today have s test function. Jumping across the test pins accelerates time. If the defrost thermostat is closed, jump the test pins. If the board is good, it should initiate a defrost cycle. Do't automatically assume that the problem is a bad defrost board.Changing the board won't help if the problem is caused by one of the other causes.
Thursday, January 8, 2015
In case you missed it, there are now new minimum efficiency standards for residential air conditioning equipment. As of January 1, 2015 the long discussed regional air conditioning standards went into effect. They are called regional standards because the minimum legal efficiency of the equipment is determined by the region of the country in which it will be installed. For Northern states, nothing changes – the minimum stays at 13 SEER. For the southeast, the minimum is increased to 14 SEER. For the southwest, the minimum is a bit more complicated. The SEER rises to 14, but minimum EERs are also introduced. The minimum EER for the Southwest is 12.2 for systems less than 45,000 Btuh and 11.7 for systems 45,000 Btuh and greater. So a 13 SEER system that is legal in Indiana is illegal in Kentucky. A 14 SEER system that is legal in Texas might not be in Arizona, depending on its EER. Although the minimum efficiencies are already in effect, the enforcement mechanism has yet to be determined.
It is interesting to note that it is possible for a unit to have a higher SEER than another unit, but for the lower SEER unit to have a higher EER. That is the reason for the dual SEER/EER conditions.
Rheem has a good page with a map and a table explaining the new standards
There is a very informative presentation on the California Energy Commision’s web site by Steve Kavanaugh explaining the reasoning behind using both SEER and EER for minimum efficiency standards.