Originally Posted By: dnewby This post was automatically imported from our archived forum.
Hello to all…
What happens to a furnace and AC when you check the furnace and then turn on the AC. Does the extreme temp change damage the heat exchanger? Do all you home inspectors check the furnace in the summer time. Thank you.
Originally Posted By: dedwards This post was automatically imported from our archived forum.
Donna,
I absolutely do check the furnaces. By referring to a heat exchanger I have to assume you are talking about gas furnaces as electric furnaces do not have them. There are a couple of caveats though about checking gas furnaces.
1. I NEVER light any pilot lights or turn on any gas valves. They are OFF for a reason and you do not know why. It may be because it is unsafe. Too many home inspectors get themselves into trouble going over the line IAW with the SOP.
2. I never override any normal operating controls. I have been asked to use a jumper to override a faulty thermostat. Never do that! The buyer isn't expected to use a jumper so neither should you. It has to be checked using the normal operating controls.
3. If the venting, flues, etc. are not safe I do not proceed any further. I recently went to a home where they had just replaced the roofing. The roofers screwed up and swapped the roof flue for the furnace with the roof vent cap for the range hood. Something looked screwy so I went back inside and the two were very close to one another in the home and got mixed up. Big difference in appearance and function.
I do check furnaces. I have done thousands and it has never damaged any of them. For one thing it isn't on long enough. Second, they are designed to be used. In the deep South (Im origially from MS) it isn't at all unusual for us to have very cold nights and the next day for it to be in the 70's or even higher. I usually check the furnace after I have run the AC and gotten all my information that I need. Call for heat, watch the burners (to observe the flame pattern and ignition) come on via whatever source of ignition, allow the temperature to come up enough to kick on the circulating fan. Normally I do not need to set the thermostat any higher than 80 or so for it to fire. I also used the temperture control on the thermostat to shut off the heat mode not the selector switch as this is all done by the temperature sensor and not by mode switch. This tells me that the sensor is actually working as designed. It is only for a short burn and then I shut it down, go back to cooling mode and use that opportunity to reset the thermostat at where the owners had it. If they are there I announce it to them that I am doing that. This confirms for me so I am not asking myself later if I forgot to reset the thermostat and it makes an impression on them so they will remember it too. These are just habits I developed to save me time and steps. Time is money and once you make it routine it comes almost automatically.
Heat pumps, I check only the Emergency Heat section of the system after I have checked the cooling mode. If the heat pump was working in the cooling mode chances are extemely remote that it won't work in the heat mode as you are using all the same components. The only thing that you will not be checking is the reversing valve outside in the condenser unit. The heat pump is no longer even on line in Emergency heat mode. YOu are basically using an electric furnace in Emerg. Heat. The outdoor unit fan or compressor should not be running. Check for a rise in heat at the registers and you should or will probably smell the dust/crud burning off the heating elements. I sometimes will check the amperage at the element wiring but you should only do that if you have been trained and know what to do and where to do it.
I do recommend if there is a local community college or a vocational tech school locally that offers HVAC training at night to go take it. HVAC is probably one of the most misunderstood systems HI run across daily. It is a hugh confidence builder and worth every penny. It is usually only a couple hours a night for a couple of nights a week.
Hope this helps.