Tuesday, November 6, 2018

Tripped Rollout Switch

Anytime you have to reset a rollout switch on a furnace, warning alarms should go off in your head. The switch is not the problem, it is a symptom of a very serious problem. Just resetting the switch and going on is like turning off a fire alarm and leaving the fire burning. You need to find out why the rollout tripped. Rollout switches trip because flames are burning back where they are not supposed to be. Possible causes include a stopped up vent, a stopped up heat exchanger, low gas pressure, or a cracked heat exchanger. All of these conditions are very serious and have the potential to do great harm. Figure 1 shows a common rollout switch.
Figure 1 Rollout Switch
In the case of the plugged vent or heat exchanger. The flue gas cannot exit quickly enough, builds up and pushes the flames out of the heat exchanger into the area where normally there is only secondary combustion air. Although 80% gas furnace heat exchangers seldom become restricted, the condensing, secondary heat exchangers on 90% furnaces often become restricted. Either way, you must have a clear heat exchanger and vent to operate the furnace safely.

A cracked heat exchanger  can also lead to tripped rollout switches. A cracked heat exchanger can allow positive pressure air from the blower into the heat exchanger and reduce the draft. If the hole is big enough, the pressure in that cell of the heat exchanger can become positive, and push the flames out of the heat exchanger into the area where normally there is only secondary combustion air. Figure 2 shows an example of this. Look carefully at the burner on the left. See that there is no bright inner cone. That is because the flames are coming back out of the tube. The burner to the right of it looks normal.
Figure 2 Flames rolling out (left burner)
Low gas pressure can cause the flame to retreat from the burner port, back into the burner body, often all the way to the orifice. Figure 3 shows an example of flames burning back at the orifice due to low gas pressure.
Figure 3 Flames burning back at orifice

Whenever you find a furnace with a tripped rollout switch, you need to determine why the rollout switch has tripped. I know no professional would ever jump out a safety device, such as a rollout switch. But just to make certain – NEVER “fix” a furnace by jumping out a rollout switch. The switch is not the problem – it may be the reason nobody died.

Friday, October 26, 2018

EPA Proposes NEW Rules Change

I am a little late getting this out. On October 1, 2018, the EPA proposed a rules change that would effectively wipe out all regulations on non-ozone depleting refrigerants.
Really, the only ozone depleting refrigerant that is widely in service now is R-22, which will be pretty much extinct in a few years. For all of today’s refrigerants, such as HFCs and HFOs, this rule change would mean anyone could purchase refrigerant, no certification would be required to handle refrigerant, no refrigerant recovery would be required, no mandatory leak checks, pretty much no regulations. This would put technicians following best industry practices at an economic disadvantage compared to folks who don’t both purchasing things like recovery machines. It would open up the path for Home Depot and Lowes to sell systems to the public, since purchasers would no longer be required to be certified. I believe it would lead to more mangled equipment, as well as mangled DIY folks who watched a You-Tube video on how to change their own compressor. I urge you to write in to the EPA and tell them that you want to keep the current regulations, passed on November 18, 2016. All comments must be received by November 15, 2018.
Here is a link to the full text of the proposed rule changes

Here are the instructions for submitting a comment
Submit your comments, identified by Docket ID No. EPA-HQ-OAR-2017-0629, at www.regulations.gov. You will need to copy and paste the Docket ID 

Friday, August 17, 2018

Bristol Compressors Closing

It is sad whenever a company in HVACR cannot make a go of it. Bristol Compressors has announced that they are closing after more than 40 years in business. They developed some innovative products, such as the Inertia Compressors with suction valves built into pistons that separated allowing suction gas to travel through the piston head, or the Twin-Single compressors that had a unique crankshaft which moved both pistons up and down in one direction and only one piston in the other direction.  More details on the closing here https://www.coolingpost.com/world-news/bristol-compressors-announces-closure/ 

Wednesday, August 1, 2018

Chemours (Dupont) Buys ICOR International

I just got an email info blast from ICOR in which it states that ICOR is now a wholly owned subsidiary of Chemours. Tht surpised me, so I looked a littel further into it and found an article on :Cooling Post" dated April 8, 2018 which confrms that Chemours bought ICOR. Here is the link to the Cooling Post artcle
Here is the link to the info blast that ICOR sent me.

Basically it is warning against cheap refrigerant from unknown sources. As always, if you stick with legitimate supply houses you are pretty safe. If you get it off the back of someone's truck at midnight in the parking lot behind the bar, well you might not be getting what you think you are getting. Even ordering over the internet is risky if you are are buying it from someone outside of the normal distribution chain. There is now counterfeit refrigerant out there, so just because the jog says Honeywell or Chemours does not mean that it really is from that manufacturer. Some of the counterfeit stuff has hydrocarbons in it and could be quite dangerous in a system that is not designed for explosive refrigerant.

Thursday, July 26, 2018

New Low GWP Non-Flammable R410A Replacement

This will be a short post because I don't know a lot of details yet. Honeywell is developing a new three part zeotropic refrigerant that can replace R410A. It has a relatively low GWP of 733 compared to 2088 for 410A, and most significantly, is non-flammable. Honeywell's trade name for it is Solstice N41, the ASHRAE number is R466A. It reportedly contains the same two chemicals as in R410A (R32 and R125). A third is added - trifluoroiodomethane (CF3I). This third component is currently used a a fire retardant. It also helps reduce the GWP of the mixture. The new refrigerant is not claimed to be a "drop-in" for R410A, but required design modifications are said to be minimal. The refrigerant is currently undergoing ASHRAE testing, but has received a preliminary A1 rating.  I have now told you all I know, and it did not take very long. Here are links to two articles about this new refrigerant.

Thursday, July 12, 2018

Air Conditioning Energy Ratings

BTUh, kWh, EER, CEER, SEER, SACC – when it comes to understanding air conditioner capacity and efficiency there are certainly plenty of arcane acronyms to sort through. The systems set up to allow objective comparison of air conditioners are hindering that very goal because of the many different measurement systems and terminology. Before discussing the different terms I would like to quickly explain what an air conditioner does: it pumps out heat. Much like a sump pump pumps out water from a basement or crawl pace, an air conditioner pumps heat out of your house. You need a sump pump that can pump water out as fast as it leaks in, or your basement will flood. With air conditioning, you need one that can pump heat out of your house faster than it leaks in, or your house will still get hot. The key point is that the air conditioner moves heat. In the United States we measure heat in British Thermal Units, or BTUs. The rate at which in air conditioner is able to pump out heat is given in BTUs per hour, or BTUh. This tells us how many BTUs of heat the unit can remove operating for an hour. The air conditioner’s electrical use is measured in kilowatts hours, or kWh.

EER Energy Efficiency Ratio
The EER is the easiest measure to understand. It is the cooling capacity in BTUh divided by the energy use in kWh. It tells you how many BTU of heat removal (cooling) you get for each kWh of energy. However, there are some things not taken into consideration. First is that it is a steady state test, meaning the unit is up and operating at full efficiency before any measurements are taken. No consideration is given for the energy used at startup, shut down, and while plugged in but not running. Also, all measurements are done at design condition, which is 80°F, 50% rh inside and 95°F outside.
SEER Seasonal Energy Efficiency Ratio
The Department of Energy devised this measurement for rating central air conditioning units in 1978 to address some of the issues not addressed by EER. Namely, cycling losses and operation at more than one temperature. The idea is that SEER is supposed to show the BTUh/kWh over a season, not just at one steady state condition. To simulate seasonal operation, SEER testing includes cycling and operation at  three different test conditions: 80°db/67°wb inside and 95° outside, 80° db/67°wb inside and 82° outside, and 80°db 57°wb inside and 67° outside. A unit’s SEER is generally higher than its EER because the SEER includes operation at milder conditions. Currently, the minimum SEER in the northern half of the US is 13 while the minimum SEER in the southern half of the US is 14.

CEER Combined Energy Efficiency Ratio
The DOE devised CEER in 2014 specifically for window air conditioning units. CEER is similar to SEER in that it measures efficiency at two operating conditions: 95° and 83°. It also includes the energy used while the unit is plugged in but not operating. A unit’s EER and CEER normally end up being very close to each other with the CEER being slightly lower.

SACC Seasonally Adjusted Cooling Capacity
The SACC was devised in 2017 to measure the efficiency of portable air conditioners. By portable, they mean the ones on wheels where the whole unit sits in the room and an exhaust duct is placed in the window to carry hot condenser air out. It is similar to the CEER in that it measures capacity at both  95° and 83°. It also includes adjustments for heat gains (cooling losses) from the exhaust duct plus loses due to infiltration caused by having to stick the exhaust duct out the window.

How do you convert between these different methods? You don’t because they each have different testing specifications. There are some formulas offered, but they can’t determine the differences in how different units will respond at the varying testing conditions.  The best you can do is understand each rating and use them to compare units with similar ratings. Just as the EPA mileage estimates don’t really tell you what your mileage will be with that new car you just bought, these ratings will not really tell you the energy use for your new air conditioner for a year. So which rating system do I believe is the most reliable? Honestly, the simplest and oldest one: EER.

Friday, February 2, 2018

Understanding Loads in Series

We don’t often see loads wired in series with each other in HVACR, but you do occasionally run across a circuit which has two loads wired in series. Loads in series spit the voltage based on their individual resistance compared to the overall resistance. So if each load is about the same resistance, they will split the voltage in half. However, if one load has a much higher resistance than the other, the loads with the higher resistance will get the most voltage.

This diagram is a partial diagram of a residential refrigerator-freezer. It shows the defrost control, freezer fan, and defrost heat circuits. During normal operation the freezer fan is in series with the defrost heater, as shown in diagram 1. The heater has a resistance of around 28 ohms while the fan has a resistance of around 280 ohms. But since the fan is an inductive load, its total impedance (effective AC resistance) is much higher – more like 2800 ohms. The current for the circuit is very small 120 volts / 2828 = 0.04 amps. Voltage across each device is calculated by multiplying the current times the resistance. The heater voltage drop is 28 x .04 = 1 volt. The remaining 119 volts are all used by the fan. Essentially, the defrost heater is acting like a wire.

When the defrost control switch moves to the defrost position, the fan shuts off and the defrost heater energizes. The fan shuts off because now the same leg of power is applied to both sides of the fan. With no voltage difference from one side to the other, no current flows through the fan. The heater now has its own source of power ad receives a full 120 volts. The heater will stay energized until the defrost termination thermostat opens, breaking the circuit.

When the defrost control takes the freezer out of defrost (diagram 1) the fan will remain off until the coil is cold enough to close the defrost termination thermostat.