Old Gas Furnace: Replace or Keep Until Dead?

[gathermewool]

I recently purchased a small, 2-floor (with own basement) condo built in the 60's and, as you can imagine, I have a bunch of things on my TO-DO list. I know there are better sources of info on the etherwebs for home improvement(I've just begun my research,)but I'm hoping to tap into the years and years of experience of the members on this forum, as well!

So, I'm pretty sure my furnace is original - the home inspector agreed that it was likely, and that while furnaces typically have a lifespan of only 20-25 years, that this Rheem (sp) furnace is well built, with a cast iron heat exchanger, and that it didn't need to be replaced immediately. He suggested that I maintain my CO detectors in good working order and not to replace the furnace until it begins to show signs of failure.

The last service was performed a few months ago, and here are the numbers listed by the service company:

O2: 11.9%
CO: 30ppm
Eff: 77.9%
CO2: 5.1%
T-STK: 363F
T-AIR: 75.6F
EA: 117.1%
CO(O): 70 ppm

Any help in interpreting these numbers would be appreciated. Things like efficiency (which seems pretty low) and T-STK/T-AIR are self-explanatory, but others, like CO vs CO(O) I'm not sure.

MORE INFO:

1. The furnace runs at what I would consider a consistent frequency (not all the time, on-and-off-and-on again.)

2. It's loud at times (squeaks and rattles, though I've been using silver tape to quiet'er down a bit however, as I type this it fired up and I can only hear air flow, no rattles or squeaks. The motor has a serviceable bearing that required occasional lubrication (old, I know,) that was recently replaced.

3. When we first moved in, the first floor was 3-5F warmer than the master bedroom on the second floor. The first floor has two supply vents in the living room ~ 2' apart on the same wall. The return is on the opposite wall. There are no supplies in the dining room or kitchen. The second floor has a supply in the master and second bedroom, as well as the bathroom. I've blocked one of the 1st floor vents and also the vent in the second bedroom (we don't use it,) which has made a pretty substantial difference.

For those interested, I used three of those flat magnetic jobs from Home Depot for the 1st floor vent, and silver tape on the second floor. The louver dams don't work due to age or excessive layers of paint, btw.

4. Poor service? The first thing I noticed while walking through the place prior to buying was that that filter did not fit the space available between the return duct and the furnace inlet. I measured the slot at 14"X27"X1.5". A 16"X24"X1" filter was installed, which leaves a pretty substantial gap for:

a. unfiltered air to enter the inlet
b. unfiltered BASEMENT air (not preheated return air) to enter the inlet.

Is this something the service company should have figured out or is the size just too unusual (I haven't found any filter thus far that fit this, though I have found a 16"X25" and a 24"X30" filter...

Sorry for the long post, guys. I'm very new to these types of things, and if you guys don't mind I plan to post a bunch of questions about how to fix things that obviously need fixing or updated, but how-to is beyond this newb!

 

[JHZR2]

Can you put in a modulating/condensing unit, to get 95-ish % efficiency? If so, you'll save fast, especially if federal/state/utility rebates and incentives are available.

Otherwise IMO keep till dead.

 

[JayhawkRoy]

If there are no incentives to replace, highly recommend a service contract with a reputable company to service your unit annually. I have one that does the furnace in fall and air conditioner in spring. My experience is that the annual service is worthwhile. It insures that the older furnace is operating at an optimum level. You could also address the furnace filter issue at the same time. What you measured is an abnormal size. Haven't checked lately, but you may be able to find a larger (possibly reusable) filter and cut it down to exact size.

 

[dishdude]

If you only plan on living in this condo for a couple of years, I'd nurse it until it dies. If you plan on being in it forever, I'd casually shop for quotes until I found a price and contractor I was happy with, and had some extra cash laying around to replace it with.

It's tempting with your first place to upgrade and replace everything, but you never get a return on your investment when you turn around to resell it.

 

[FXjohn]

get every last second out of it. my furnace was built in 1963.

 

[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.

 

[nickaluch]

All the numbers look great.I would for sure just let it ride.New furnaces are no way built like that one.Get a service contract and cut your own filter to fit.You can try amazon to get a exact size filter.The new furnaces are 80 to 97 % eff now and your not far off on those numbers.The price of gas is so cheap now your payback could be many many years.I just had a new heat and ac put in my house and it was not cheap.My old bryant unit was installed in 1953 and ran like a champ with no problems.Just some 20 weight oil in the bearings and a filter change.The only reason I had a new furnace put in was it was instaled in the middle of my basement and I wanted to make a man cave down there.Had the furnce moved against the wall to open the room.Also a new furnce wont correct your vent and return problems.If you do decide to go new do your homework.

 

[gathermewool]

Originally Posted By: JHZR2
Can you put in a modulating/condensing unit, to get 95-ish % efficiency? If so, you'll save fast, especially if federal/state/utility rebates and incentives are available.

Otherwise IMO keep till dead.

I don’t have a handle on any of the replacement options as of yet. Would you suggest I request several opinions on replacement options at this time or is this something I can garner from research alone?

Originally Posted By: JayhawkRoy
If there are no incentives to replace, highly recommend a service contract with a reputable company to service your unit annually. I have one that does the furnace in fall and air conditioner in spring. My experience is that the annual service is worthwhile. It insures that the older furnace is operating at an optimum level. You could also address the furnace filter issue at the same time. What you measured is an abnormal size. Haven't checked lately, but you may be able to find a larger (possibly reusable) filter and cut it down to exact size.

I’ve got to figure out what incentives are in place for efficient replacements, as well. The previous owner, who owned for the past four years, has had it serviced each year, with nothing of note reported. I plan to do the same, given the age.

Originally Posted By: dishdude
If you only plan on living in this condo for a couple of years, I'd nurse it until it dies. If you plan on being in it forever, I'd casually shop for quotes until I found a price and contractor I was happy with, and had some extra cash laying around to replace it with.

It's tempting with your first place to upgrade and replace everything, but you never get a return on your investment when you turn around to resell it.


When the wife and I began our search we were debated stretching ourselves conservatively thin to buy a “forever” home or take a small chunk out of savings and buy a starter home. Looking at the numbers, it made a lot more sense to buy a cheap starter condo, which, including all expenses (not , however, including unplanned maintenance, obviously) cost about as much as a decent apartment for the two of us and her worthless, ahem, errrr, um, adorable little shih tzu.

So, our plan is to begin our family in this condo, and then move on to something bigger in the next 3-5 years after the 2nd or 3rd kid is on its way and room becomes limiting. We plan to rent the condo out, which then begs the question: which is worse, being able to survive with heat from a few ceramic heaters in key locations or having to deal with tenants who may not be able to do the same should the furnace decide to die after we decide to rent? Also, what about the risk of HX cracking and CO pumping into the people space? If we decide to drive this bad boy into the ground, would it then make sense to add the caveat **drive this bad boy into the ground OR until rented out?

One more thing to note, is that we saved a lot in closing costs by buying a cheap little condo, so we have the savings available now to replace the furnace now (and then any other major issues that may crop up,) so if it makes more sense, financially or safety-wise to replace sooner than later, it won’t be an issue.

Thanks again, guys and gals!

 

[gathermewool]

Can some one explain the 2 CO numbers: CO and CO (O)?

Oldhp makes it seem dire, but aren't these numbers based on exhaust gases, not heated-air supply?

Gas is relatively cheap here. Bill for the past month is $60, though I expect it to double for the remainder of the winter months due to the following:

I've been so busy with work (7 days/week, 11-14 hrs/day,) that since closing in the beginning of December, I've spent only half of that time "living" (sleeping) in my old apartment, keeping the new-to-me condo thermostat at 55F. Even after finally moving in and sleeping/showering here, the heat has been set between 64 and 68F, with only minimal shower usage (gas water heater.)

At the beginning of the new year, my wife will move in as well, which MAY mean that the thermostat may not stay at the to-me balmy 64-66F that I prefer, hence the predicted $120/month gas bill. My wife also likes to cook, so that must be included as well.

I really do appreciated all of the quick responses. You guys are a fantastic pool of knowledge.

 

[Keith_Stone]

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.

Those are flue gas measurements, not conditioned space which CO should be near zero.

 

[gathermewool]

Originally Posted By: nickaluch
All the numbers look great.I would for sure just let it ride.New furnaces are no way built like that one.Get a service contract and cut your own filter to fit.You can try amazon to get a exact size filter.The new furnaces are 80 to 97 % eff now and your not far off on those numbers.The price of gas is so cheap now your payback could be many many years.I just had a new heat and ac put in my house and it was not cheap.My old bryant unit was installed in 1953 and ran like a champ with no problems.Just some 20 weight oil in the bearings and a filter change.The only reason I had a new furnace put in was it was instaled in the middle of my basement and I wanted to make a man cave down there.Had the furnce moved against the wall to open the room.Also a new furnce wont correct your vent and return problems.If you do decide to go new do your homework.


What you say is very similar to whaut the inspector said. The original blower motor bearing was very noisy, so the bearing was replaced by the previous owner. How often should I add lubrication?

I've noticed that the ventilation doesn't seem very efficient - why the [censored] would they put two supplies on one side of the room, with the only return on the opposite side of that same room? It's not too bad, and should I decide to keep the thermostat at 70-72, I'm sure it wouldn't matter much, but as-is, it seems odd that I have to block off vents to keep things in balance.

I wonder if fitting a properly-sized filter on the inlet and silver-taping the gap might help a good bit.

 

[nickaluch]

Look at your gas bill.About one third has nothing to do about how much gas you use.Thats half the reason a new super duty efficent boiler is not ALways the rite choice.PAYBACK TAKES MANY MANY YEARS

 

[Rock_Hudstone]

If you decide to replace I'd at least wait until the warmer months.

This is the busy time of year for heating contractors, not likely you'll get the best possible price right now.

 

[gathermewool]

Originally Posted By: nickaluch
Look at your gas bill.About one third has nothing to do about how much gas you use.Thats half the reason a new super duty efficent boiler is not ALways the rite choice.PAYBACK TAKES MANY MANY YEARS


Agreed, which is why my question is partially (maybe majorly) about whether there's a safety concern in running a furnace until it fails instead of replacing it after a certain number of years.

I know there's a lot that can be done with regard to insulation, but there is only so much I can do with a condo.

 

[daves87rs]

Mine is 14, almost 15, and holding up pretty well. Would love to get a new one myself, but plans are to run this thing until it dies....

 

[gathermewool]

Originally Posted By: daves87rs
Mine is 14, almost 15, and holding up pretty well. Would love to get a new one myself, but plans are to run this thing until it dies....


Makes me wonder whether mine, which is going on 50 years old (possibly,) is well past due for replacement.

 

[nickaluch]

Have a furnace company come check and tune up your furnace.You can pick his brain on on how safe the furnace is.Call the company that did the last service.

 

[doitmyself]

Looks like a 14 x 30 x 1 is about as good as you can get, without going to an expensive custom made filter.

http://airfilterbuy.com/product-category/size/14x30x1/

On older furnaces be aware of the MERV rating you select in regards to flow restriction. The big box stores imply good/better/best regarding filtering efficiency without taking into account older furnaces that might be negatively affected by too much flow restriction (i.e. motor overheating).

I would do lots of research if you want to try over MERV 8 on an older furnace, IMO.

 

[gathermewool]

I'll call the company who last serviced it and see what they have to say.

I do plan to keep researching all that I can. Maybe it was intentional that they chose a too-small filter (yea, right.)

 

[nickaluch]

Amazon is where i get my stupid sized filter