Old Gas Furnace: Replace or Keep Until Dead?

[gathermewool]

Originally Posted By: nickaluch
Amazon is where i get my stupid sized filter


16X27 is available, but very expensive. I'd rather tape the gap and allow some unfiltered air through - we have a good HEPA filter we run in our bedroom, anyway.

 

[JR]

Keep it, proper. maintenance and tlc and it will live many more years. we have a oil burner from the fifties in the farm house. grandma burns fuel oil in it. we stock on hand a ignitor, fuel filter, and some odds and ends. we put a new pump and blower motor five years ago. runs like a new one.

we have several smaller oil burners around the farm in out buildings.
we burn undyded off road ulsd in those.

ken

 

[zzyzzx]

If you have been running unfiltered air thought it, and it has an AC coil (central AC was not mentioned, and you are in CT so I have no idea if you would have that there, but my guess is not) then you might need to get the AC coils cleaned. Finding the right filter size should be possible. I had to find the right size as well. Home Depot and Lowe's carry more filter sizes than WalMart. Just because there is no paper filter the size you need, doesn't mean that there won't be a fiberglass one the right size next to it (again, ask me how I know that!!!).

Get a CO meter that has a digital readout for your bedroom, and possibly other living areas (depending upon how paranoid you want to be). If it's not gong to kill you then keep the furnace until it dies. If you happen to use the furnace a lot, it might pay to get a more efficient one, but I don't run mine enough to justify the expense, plus my vintage 80's furnace is already an 80% furnace, so it's really not worth it. Your 1960 furnace might be pretty inefficient. Plus you can't always install a higher efficient one without what I would consider to be too much work, plus they have more stuff to break. Mine is easy to fix.

 

[gathermewool]

Forced heat only, no cooling coil.

 

[Danno]

Had a 21 year old Carrier gas furnace. It had a main blower motor, combustion blower, and hotwire ignition changed over the years. Replaced it last month with 97% eff. Keeprite and AC as well, rated at 16 SEER.

$6,700 all in and got rid of the monthly service contract on the existing furnace.

Decided to prioritize reliability over cost.

 

[HTSS_TR]

My house was built in 1970. The original 43 years old furnace still running well, we moved in 1997 and never had the furnace serviced.

The furnace is in the middle of 4 bedrooms, it has 2 filters size 10X30, I bought the largest filter size 20X30 and cut it to half instead of buying two 10X30 filters. Since we rarely turn on the heat, the furnace is running at around 10-20 hours a month from Dec through Feb, so the filters(1 larger filter) lasted 2-3 years.

You should buy 20X30 and cut to 14X27.

 

[Pop_Rivit]

If it were me, I'd replace the furnace after this heating season.

You won't get a complete payback from energy savings in your 3-5 year time frame, but you will get some lower utility costs for a couple of years. Add to that a higher resale value when you do sell. A 3-5 year old high efficiency furnace is a selling point, a 45+ year old furnace is a liability.

By finding a contractor and getting prices after the heating season you'll be able to get a better price than if you do it during the heating season. When the old furnace does completely fail, it will be during a cold snap in the middle of winter when you need it most.

 

[Slick17601]

Originally Posted By: oldhp
The CO should be ZERO. This is a timebomb waiting to kill you. There is a crack in the heat exchanger, that could get bigger at any second, like when your asleep. Replace.


+1

 

[gathermewool]

Originally Posted By: Slick17601
Originally Posted By: oldhp
The CO should be ZERO. This is a timebomb waiting to kill you. There is a crack in the heat exchanger, that could get bigger at any second, like when your asleep. Replace.


+1


+1 what? Did you read the replies to oldhp's post and still agree with his assessment or did you simply skim and his post jumped out at you?

I'm going to get some one on the phone and see what they think first thing next week. It'll be interesting to hear what they have to say.

 

[Tdbo]

Originally Posted By: Pop_Rivit
If it were me, I'd replace the furnace after this heating season.

You won't get a complete payback from energy savings in your 3-5 year time frame, but you will get some lower utility costs for a couple of years. Add to that a higher resale value when you do sell. A 3-5 year old high efficiency furnace is a selling point, a 45+ year old furnace is a liability.

By finding a contractor and getting prices after the heating season you'll be able to get a better price than if you do it during the heating season. When the old furnace does completely fail, it will be during a cold snap in the middle of winter when you need it most.


I would agree with this. At that age the furnace has exceeded its life expectancy and potentially could pose a hazard. I would also recommend a 90+ efficiency unit. I managed to cut my heating and cooling costs in half by replacing the unit.

 

[oldhp]

Is the CO% coming out of the vents that you are breathing?Argh...replace-replace-replace.
This is from the EPA.

Health Effects Associated with Carbon Monoxide
At low concentrations, fatigue in healthy people and chest pain in people with heart disease. At higher concentrations, impaired vision and coordination; headaches; dizziness; confusion; nausea. Can cause flu-like symptoms that clear up after leaving home. Fatal at very high concentrations. Acute effects are due to the formation of carboxyhemoglobin in the blood, which inhibits oxygen intake. At moderate concentrations, angina, impaired vision, and reduced brain function may result. At higher concentrations, CO exposure can be fatal.

Levels in Homes
Average levels in homes without gas stoves vary from 0.5 to 5 parts per million (ppm). Levels near properly adjusted gas stoves are often 5 to 15 ppm and those near poorly adjusted stoves may be 30 ppm or higher.

 

[Cujet]

Your tech probably used a portable "flue gas analysis tool". Those tools use 2 sensors, an O2 and a CO sensor. From those 2 sensors, they can determine and infer all sorts of information. Hence the very normal combustion data you have.

Your furnace is operating normally and, if properly maintained, (at near 80% efficiency) should provide economical heat.

Yes, there are furnaces that peak near 98% efficiency today, under laboratory conditions. Installed efficiency is often much less for all the obvious reasons (airflow restriction, ductwork heat losses, exhaust gas path, intake air path and so on) .

Don't make the assumption that you will be going from near 80%, to 98%. It's much more likely that you will see no more than a "real world" 10% improvement in efficiency when you upgrade to a common, reliable, modern, 95%+ rated furnace.

The post above concerning filter restriction is something to be very mindful of. Effectiveness of the unit is closely tied to a low restriction filter. In my house, I have 2ea. 24x24 airfilters, one above the other, feeding the same plenum. That way, there is very minimal restriction. I use MERV 4 filters and my unit and ducts remain internally very clean. It's not the job of the air handler to purify the air down to the sub micronic level.

 

[supton]

The CO that the OP mentioned is what was in the flue, not in the air outside the furnace. I'm not sure why one would assume otherwise?

 

[gathermewool]

I appreciate all of the useful posts. It's very tough figuring things out online when there are so many posts by those who obviously know absolutely nothing about the topic at hand.

I think I'll continue to have the furnace serviced annually, fit a properly rated and sized filter (and seal up the GIANT gap between the return ventilation and blower inlet. I really appreciate the low efficiency filter recommendations - makes a lot of sense. Cujet (and others,) with the space I have, would it make sense to install two lower-efficiency filters in series in the plenum and seal up the gap?

Based on the suggestions here and how badly the system seems to distribute heat, I'm going to agree with Cujet, that installing a new, much-higher-efficiency furnace may not make a significant difference if it's pumping through inefficient ducting.

I'm going to guess that even in this little 1,000 ft^2 condo, replacing the ducting from the basement up to the second floor would be very costly. Any other suggestions to help things out?

Remember, I've blocked flow to one of the three (I wrongly mentioned only two before) vents on the first floor, as well as the vent to the second bedroom on the second floor, but the master bedroom still doesn't come up to temperature quickly after turning the heat up. For example, when we come back after being gone all weekend and turn the heat back up from 55F to 65F, the first floor comes up to temperature quickly and the heat shuts off (single zone, thermostat on the 1st floor,) but the master bedroom remains pretty cold if the door is shut. I can feel heat coming steadily from the bedroom vent, but maybe the vent is too small...

Thanks again for all of he thoughts and help.

 

[Thermo1223]

I did a lot of this with my grandmother's old oil furnace.

It is not the fact that the ductwork is inefficient just designed to just move heat not airflow. Now her furnace had a belt driven blower so not ideal at all. The air temp was significant higher at certain points with the low flow. Now that it was replaced with a high efficiency furnace the air temp is lower but more stabilized over all outlets even without a proper duct design. Airflow was much improved as well but noise rose as well so be prepared for that. Replacing ductwork isn't material expensive it is the labor especially if wall cavities were used before.

You will always gain efficiency by going newer but at a price. I would replace it but I would not go all out if you don't plan on living there for ever. It also would entail a complete redesign if you go higher than 90% because you cannot use the current exhaust stack. It must be PVC and ducted out another way plus you need a drain to deal with the condensate.

So what I personally would consider replacing it. I would get a couple of estimates with a heat load calculation done because odds are the unit is oversized now. They always did that back in the day, now they know as they did with my grandmother's house that if you undersize the unit slightly longer runtimes equal better overall efficiency(IE no short cycling), mostly the reason it fails to heat the upstairs properly. I would stick with standard 80% furnaces but get one with a variable speed blower. This style automatically adjusts fan speed based on requested CFM and uses very little electric as well. This would also allow you you get thicker less restrictive filters that last a lot longer. They are about 4 inches thick but way less restrictive than the 1 inch filters at the home stores. I would not run anything other than a step above the blue fiberglass filters on an older furnace.

See the combustion efficiency is 77% but the actual heat you are getting out of the old heat exchanger could be far less. Modern ones use stainless steel which heats up & cools down a lot quicker. Just like cars they use electronic ignition which is alot easier and safer than a pilot light driven furnace.

Don't sweat it this winter but I would budget for it come the fall or summer.

 

[PandaBear]

Originally Posted By: Thermo1223
I would get a couple of estimates with a heat load calculation done because odds are the unit is oversized now. They always did that back in the day, now they know as they did with my grandmother's house that if you undersize the unit slightly longer runtimes equal better overall efficiency(IE no short cycling), mostly the reason it fails to heat the upstairs properly.


I feel the same way. My 1500 sqft 2/F house has a 4 burner heater that cycles on and off every 15 minutes, and the duct work and exhaust goes through the wall between 2 bedrooms. When it comes on it would wake everyone up, even the fetus inside a pregnant woman's womb (my daughter). Every contractor I've talked to said it is way oversized for the house.

 

[Cujet]

I'm not surprised at the improper airflow. Guess what modern large buildings do to maximize and equalize airflow? They have "in duct" restrictors that modulate to adjust the flow rate. You are doing much the same thing by closing down vents. Just make sure you don't have leaking ducts.

You may want to take some time and adjust all of the registers to promote airflow to the bedroom.

Also, can you leave your bedroom door open? That may be a wintertime requirement for adequate airflow.

In my home, I need to leave both the bathroom and bedroom door open a bit to get proper cooling in there.

As for a better air filter, I'm a fan of as much filter area as possible. The filter frames are cheap, and often easy to replace with larger ones.

 

[Thermo1223]

Originally Posted By: PandaBear
Originally Posted By: Thermo1223
I would get a couple of estimates with a heat load calculation done because odds are the unit is oversized now. They always did that back in the day, now they know as they did with my grandmother's house that if you undersize the unit slightly longer runtimes equal better overall efficiency(IE no short cycling), mostly the reason it fails to heat the upstairs properly.


I feel the same way. My 1500 sqft 2/F house has a 4 burner heater that cycles on and off every 15 minutes, and the duct work and exhaust goes through the wall between 2 bedrooms. When it comes on it would wake everyone up, even the fetus inside a pregnant woman's womb (my daughter). Every contractor I've talked to said it is way oversized for the house.


Ya it was such the way with her house. They used the worst company for the job IMO after all the quotes I got but at least they didn't oversize the furnace again. Thankfully that house will be someones else's responsibility shortly.

The better company to do the job that I wanted suggested moving the thermostat off a wall with heat register nearby. It was one of those

moments. The wall would transfer heat right to the thermostat. It was moved to an interior wall w/ no register nearby and now the house gets warmer than it ever did before. 70F acutally means just now! Not 70F on that wall and 65F everywhere else.

 

[dishdude]

Originally Posted By: gathermewool
I appreciate all of the useful posts. It's very tough figuring things out online when there are so many posts by those who obviously know absolutely nothing about the topic at hand.

I think I'll continue to have the furnace serviced annually, fit a properly rated and sized filter (and seal up the GIANT gap between the return ventilation and blower inlet. I really appreciate the low efficiency filter recommendations - makes a lot of sense. Cujet (and others,) with the space I have, would it make sense to install two lower-efficiency filters in series in the plenum and seal up the gap?

Based on the suggestions here and how badly the system seems to distribute heat, I'm going to agree with Cujet, that installing a new, much-higher-efficiency furnace may not make a significant difference if it's pumping through inefficient ducting.

I'm going to guess that even in this little 1,000 ft^2 condo, replacing the ducting from the basement up to the second floor would be very costly. Any other suggestions to help things out?

Remember, I've blocked flow to one of the three (I wrongly mentioned only two before) vents on the first floor, as well as the vent to the second bedroom on the second floor, but the master bedroom still doesn't come up to temperature quickly after turning the heat up. For example, when we come back after being gone all weekend and turn the heat back up from 55F to 65F, the first floor comes up to temperature quickly and the heat shuts off (single zone, thermostat on the 1st floor,) but the master bedroom remains pretty cold if the door is shut. I can feel heat coming steadily from the bedroom vent, but maybe the vent is too small...

Thanks again for all of he thoughts and help.


Every 2 story I have lived in is like this, if you have central AC wait until summer, you'll be sweltering upstairs. From what I can tell, it's a combination of factors that a new furnace won't help - lack of proper sized air returns on the second floor, duct work that wasn't sealed with mastic (this was pretty common up until Energy Star rated homes came out) and of course being the farthest rooms from the furnace.

The proper way to fix it is to replace/seal the duct work and install a zoned system. Not at all worth it IMO. I was fine in the winter, but actually installed a $99 window AC to supplement the central unit in the summer.

 

[gathermewool]

This system is heat only, so we'll have to use a window A/C unit(s) during the hotter days of summer. I finally took some pics of the furnace and associated duct vents - notice how the return seems to have pushed down on and deformed the ducting inlet to the furnace. There's also residue from duct tape previously being used to seal off the gap where the filter goes, though none was used this past time, leaving a giant, gaping hole for unfiltered return AND basement air to enter:




[URL=http://s381.photobucket.com/user/gathermewool/media/DSCN0413_zps96d36fe2.jpg.html]


Some of the burner:



The inlet duct, blower and blower motor:


Should this backing plate be sealed with ducted tape or am I missing something?



I purchased some low-efficiency cut-to-fit stuff, but I'm not sure how to go about installing it (i.e., how do I install it so that it will create a decent "seal" and not get sucked into the blower area?


Finally, in order, the 1st floor supplies (one blocked with magnetic sheets,) 1st floor return, and the master bedroom supply: