Author Topic: furnace repair or replace? (Read 29551 times)

prettymuchfi

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furnace repair or replace?
« on: January 08, 2013, 08:21:49 PM »
In this "throw it away" "planned obsolescence" world we live in, I'm always dubious when told "you should get a new one". So, as I look at my ~ 1989 "Day & Night" furnace and hear the HVAC guy say this, I'm not convinced. So I'm asking my fellow mustachians for insights...

Existing furnace & related: Circa 1989 "Day & Night" downdraft furnace (electronic ignition), estimated 60000 BTU (3 ton?). Location: SF Bay area (i.e. not cold), 1800 sq foot house. Used 4 months of the year for average of $80/mth.

Current problems:
  • sticky relay on control board means the blower fan doesn't always turn off
  • blower is out of balance so it causes vibration in the house and is quite noisy and somewhat annoying
I had an HVAC guy look at it and he quoted a new Trane furnace for $4k plus $2k install for a new 96% variable speed (yada yada) furnace, sealing the existing ductwork to bring it up to California efficiency code, permits, inspection, new PVC vent piping etc. "Not worth repairing this old thing".

Random thoughts:
  • I don't think the extra efficiency of the new 96+% furnaces pays off in the 20yr lifetime of the furnace as our usage is so low
  • surely fixing the blower balancing / motor / bearings (whatever is wrong?!) would be easier, and quite likely a DIY job as its separate from the gas work
  • while I'm at it, replace the control board. It seems like there are plenty available for < $100 that will fix the relay
  • Home Depot charges $1600 for a no-name furnace, but the Home Depot recommended installers don't install them - just Trane or Rheem for 2x the price. I'm guessing that for ~$1500 I could eventually find an installer who would do it for $3k total replacement cost

Gotchas:
  • I don't have the manual and can't find the model # on the furnace. This is making it hard to identify things exactly and get online DIY pointers

We really would appreciate the increased comfort from stopping the vibration and likely lowering the noise, but none of this has to be fixed "right now". Indeed, this could perhaps become a nice summer project.

Any thoughts? Thanks!!

Another Reader

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Re: furnace repair or replace?
« Reply #1 on: January 08, 2013, 09:26:38 PM »
I had exactly the same problem and there is a thread on this. Long story short, I elected to replace my 1989 Day and Night with an 80 percent efficient Trane. The bill was $2,000 for 100k BTU's (4 ton). The payback where I live in Silicon Valley on the 96 percent efficient furnace is about the furnace's life. Plus the condensing furnaces need to be separately vented.

The model number is inside the furnace, I think below the circuit board. The manual is probably on-line. You will need the model number to see if anyone stocks the circuit board. To have the HVAC folks do it is $300-$500, if they can get the board.

Interested in how this works out for you. I kinda wish I had replaced the control board of the old one, but it's a crapshoot.

prettymuchfi

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Re: furnace repair or replace?
« Reply #2 on: January 08, 2013, 09:42:00 PM »
Thanks, I found your thread here: http://adm-karpinsk.ru/forum/ask-a-mustachian/cost-benefit-analysis-of-a-high-efficiency-gas-furnace/msg30392/. Yes, very similar problems.

TBH, the blower imbalance and resulting vibration is more of a problem for me than the control board. Right now I can hit the side of the heater to help the relay along and then its good for a few weeks (but of course its a problem just waiting to happen).

Good tip re the control board #. I'll turn off the power and take the case off of it and hopefully that will reveal the model number, and at least the control board part #. Maybe from that I can work back to the furnace model and find replacement details for the blower. It all *looks* pretty simple as DIY projects go, but I'm sure there are gotchas!

Crawling around under the house and sealing the vents might be worthwhile too. I've avoided going down there for too long :)

Another Reader

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Re: furnace repair or replace?
« Reply #3 on: January 08, 2013, 10:28:04 PM »
My house was built in 1988-89. The furnace guy said the ductwork was done correctly. It's not the same ductwork that would be installed today, but it was sealed properly. One of the other estimators pointed out where the builder had created a problem by using too small of a manifold leading to the main run. The airflow is restricted as a result.

If I recall, the model number is on the horizontal sheet below the circuit board on a separate plate. I have a parts list somewhere for mine. If you have the dual butterfly filters, the 12 x 20 filter size is difficult to find.

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Jack

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Re: furnace repair or replace?
« Reply #4 on: January 09, 2013, 07:10:31 AM »
Do you have air conditioning, and if so, is it similarly old? Since the climate is relatively warm/mild, might it be worth considering ditching the furnace entirely and getting a heat pump instead?

tooqk4u22

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Re: furnace repair or replace?
« Reply #5 on: January 09, 2013, 11:35:35 AM »
Just got mine replaced-it was 24 yo. Go with Another Readers guy because the deal seems amazing.

My circuit board went bad but it was $900+ to replace - to me it was a no brainer to get a new heater just not worth putting that much money into something that old and inefficient. At $500 and in a moderate climate like SF I may have been tempted - although not if I can get the deal that Another Reader got - no sense spending 25% of a new one on the old one.


prettymuchfi

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Re: furnace repair or replace?
« Reply #6 on: January 09, 2013, 10:07:49 PM »
Do you have air conditioning, and if so, is it similarly old? Since the climate is relatively warm/mild, might it be worth considering ditching the furnace entirely and getting a heat pump instead?

Good thoughts. No, we don't have AC or need it. I looked at heat pumps, but with no backyard and close neighbours, the noise is likely to be a problem unfortunately :(. And, of course, there isn't much economic justification to spend the extra money, especially without AC.

prettymuchfi

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Re: furnace repair or replace?
« Reply #7 on: January 09, 2013, 10:15:48 PM »
My circuit board went bad but it was $900+ to replace - to me it was a no brainer to get a new heater just not worth putting that much money into something that old and inefficient.

I fear the prices that the HVAC people are extremely self-serving. They told me "oh, about $500 + labour" for a new board, but I'm pretty sure my board is available online for <$80 and the labour is ~1/2 hr and simple enough for me to do.

At $500 and in a moderate climate like SF I may have been tempted - although not if I can get the deal that Another Reader got - no sense spending 25% of a new one on the old one.
I wonder about the 25% making no sense in my scenario. If $1000 gets the old one back to running shape for > 5 years, then, in my moderate climate, I'm back to being ahead on a new one (even assuming a new one will last 20 years and cost $4k). Sure there's some hassle with a breakdown sooner, but we're not going to freeze here while we sort it out fortunately!

prettymuchfi

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Re: furnace repair or replace?
« Reply #8 on: January 13, 2013, 08:31:00 PM »
Some updates on where I'm at and why.

Random data points affecting my reasoning:
  • New furnaces are horribly complex beasts with corresponding high failure rates.
  • New efficient furnaces require new exhaust piping, holes in the wall etc
  • My existing furnace is a simple beast. There's one circuit board, an electric motor hooked up to a blower and "some gas stuff"
  • It appears most of "the gas stuff" I should stay far away from - with the possible exception of the flame sensor & thermocouple
  • The 2 HVAC service companies I've talked to have no interest at all in fixing what I have. They would much much rather install a new system.

I'm really disappointed with the HVAC companies. Its feeding my already boundless cynicism.

The control board I was quoted $500 + labour to replace is available on Amazon for $45 and although it has quite a few wires, its all very low tech and easy to work on if you've ever done any assembly stuff before (e.g. building your own computer). Part: http://amazon.com/Fan-Blower-Control-ICM271-Electronics/dp/B000TMK310/, Photo of similar board to mine and thread: http://diychatroom.com/f17/bryant-carrier-relay-board-78018/.

My other concern of "vibration" seems to be an unbalanced blower. One HVAC company said "it would cost at least $1000 to take out the motor and fix the vibration". I found a good description of how to re-balance it here: http://diyforums.net/how-to-balance-furnance-blower-motor-heater-making-noise-5244114.html, and several good youtube videos on replacing the whole motor and blower myself if it comes to that. Its basically two screws and the whole thing slides out. You can literally replace the whole thing if you want, but there are also easy to find new motors, blowers etc. E.g. electric motors for my furnace are < $200 (and possibly < $50 - I haven't pulled it out yet to get the exact part #). One estimate on a forum said something like: "It takes an experienced tech about 30 mins to change out a motor. A DIY type should allow 2-3 hours. The hardest part is if the blower is frozen to the motor shaft. Use WD40 and patience - not a bigger hammer".

After working on computers or cars, this stuff is all very low tech.

Don't get me wrong. I wouldn't want to be diagnosing some strange fault, but at the price of these components, its possible to treat them as a black box and just replace the whole part -- which seems to be the most common suggestion for the control board (just replace it!). Except for the gas stuff - which I don't want to go near!

So, all that said, my next steps are:

  • order a new control board (to fix the start-stop problem when the blower is done, probably from a sticky relay on the board)
  • replace the control board
  • remove the blower
  • rebalance and reinstall the blower

If that all goes well (yes, a big IF), my furnace should be good to go for another 10 years or so. For $50 and a few hours of my time learning a new skill.

Another Reader

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Re: furnace repair or replace?
« Reply #9 on: January 13, 2013, 08:48:15 PM »
It's definitely worth a shot. One thing is for sure, the new Trane is made out of much lighter steel. If the thinner metal extends to the combustion chamber, then this one will not last nearly as long as the Day and Night. I'm waiting for this month's PG&E bill to see if there is any reduction in gas usage.

In general, furnaces can be kept operational until the combustion chamber cracks. Boards, blowers, motors, etc., can all be replaced. As the furnace ages, it becomes more important to inspect the combustion chamber regularly.

Actually, $2,000 is a typical price here, as long as you stay away from the big companies. Another Trane dealer advertises an 85k BTU 80 percent efficient model in the San Jose paper for $1,645 installed. If you do end up buying a replacement, don't bother with the high efficiemcy ones. They do not make financial sense and they are more prone to failure.

I'll be very envious if your plan works....let us know.

Self-employed-swami

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Re: furnace repair or replace?
« Reply #10 on: January 13, 2013, 10:37:51 PM »
I'm envious of everyone living far enough south, such that a furnace failure doesn't automatically = emergency!

Living in Canada, it has been 30 degrees Celsius below freezing a lot in the last month, and we had to replace the thermocouple (pilot light kept blowing out repeatedly). Seeing as I have been away for work for much of the time, for the piece of mind, I called a friend of my Dad's to come and check the furnace out and do the thermocouple at the same time.

Ours is a 1988 carrier vintage furnace.

He said that the motor sounds like it could go anytime now, and that we are best to try and limp it along until spring, when the scratch and dent sale comes along for dealers, and that he'd pick on up for us then. However, if our furnace dies before then (and it is still below freezing outside) we'll have to either repair ($1000 he said for this motor) or replace it with an off the rack model ($3-4000 depending). We can't go without heat when it is freezing outside, as we run the risk of freezing the pipes, and creating a whole other huge mess (not to mention, suffering the wrath of two very pissed off cats!)

Here's hoping ours doesn't die before spring, when we can get a cost-effective replacement put in.
A small business-owning SWAMI working herself towards FI.

prettymuchfi

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Re: furnace repair or replace?
« Reply #11 on: January 14, 2013, 11:33:48 AM »
Actually, $2,000 is a typical price here, as long as you stay away from the big companies. Another Trane dealer advertises an 85k BTU 80 percent efficient model in the San Jose paper for $1,645 installed. If you do end up buying a replacement, don't bother with the high efficiemcy ones. They do not make financial sense and they are more prone to failure.

Yes, it seems like the "loss leaders" are the 80% efficiency single speed models. I agree with your analysis completely. Given how little we spend on heating overall, the running cost difference between 80% and 95% efficiency does not nearly pay for the extra cost of the furnace and installation. Fingers crossed for the "fencing wire & duct tape" fix first though ;)

Here's hoping ours doesn't die before spring, when we can get a cost-effective replacement put in.

Ouch, -30C is way past my comfort level ;) I remember a night when fahrenheit met celsius (-40), and while those sort of temps are academically interesting in all sorts of ways (e.g. riding a bike on snow isn't slippery), its not "normal" for an Australian! Fingers crossed for you with your furnace. While mine is around the same age as yours, you probably use yours more in a year than mine has run its entire life!

Self-employed-swami

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Re: furnace repair or replace?
« Reply #12 on: January 14, 2013, 11:51:42 AM »

Ouch, -30C is way past my comfort level ;) I remember a night when fahrenheit met celsius (-40), and while those sort of temps are academically interesting in all sorts of ways (e.g. riding a bike on snow isn't slippery), its not "normal" for an Australian! Fingers crossed for you with your furnace. While mine is around the same age as yours, you probably use yours more in a year than mine has run its entire life!

Ours runs pretty steadily 8 months out of the year (I mean, coming on and off as needed to heat the house), and then maybe only in the night for 2 more months. Then the other 2 months of the year, it gets to +30 sometimes, and we wish we had AC.

I have actually asked the furnace guy to keep an eye out for a good deal on an AC unit, and if one can be found (scratch and dent, or gently used), we will likely splurge, and put it in at the same time as the furnace (as they can share venting, and the additional labour cost of doing them at the same time is minimal). Our bedroom at the top of the house, and gets quite hot throughout the day. AC definitely isn't a requirement here, but a luxury, but if we can get a unit for the right price, it will likely be worth it for our comfort (and that it will make our house more marketable, should we need to sell or rent it out in the future).
« Last Edit: January 14, 2013, 09:47:02 PM by Self-employed-swami »
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Skyn_Flynt

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Re: furnace repair or replace?
« Reply #13 on: January 14, 2013, 04:37:34 PM »
I'm seriously considering building my own house (or duplex) and just using wall unit A/C and infrared heaters. I'm not convinced HVAC is really necessary for a small space.

My first house was 1100 square feet, built in 1950. It had a gas furnace in the floor of a central room. When it came on, heat simply drifted through the house. Yeah the hallway got stuffy and one room was chilly (used a space heater to augment it) but it eliminated the complexity of HVAC which I kind of liked.

« Last Edit: January 14, 2013, 04:45:20 PM by Skyn_Flynt »

Skyn_Flynt

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Re: furnace repair or replace?
« Reply #14 on: January 20, 2013, 07:44:56 AM »
Looks like I invited the fates with that post. :-O The furnace won't come on.

Since I've already signed a lease for my next move (downsize) in March, I don't feel like fixing this right now. I'll just do it after moving, and write it off as part of the expense for converting this current house to a rental.

We get cold snaps here, but I have two electric space heaters and warm clothing. It's been a generally warm winter anyway this year, and I'd only been running the heat half of the nights. Just have a month and a half of this to deal with... I'll put up with it.
« Last Edit: January 20, 2013, 07:56:28 AM by Skyn_Flynt »

Self-employed-swami

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Re: furnace repair or replace?
« Reply #15 on: January 20, 2013, 07:52:54 AM »
Whoops~

I hope it stays warm until you move!
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Skyn_Flynt

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Re: furnace repair or replace?
« Reply #16 on: January 20, 2013, 07:59:45 AM »
What's funny to me is that although people on this forum pat their own backs about turning the heat off, .... (ooooh we are so "badass") ... it's how millions of Japanese normally live. They use small propane heaters, or an electric kotatsu table, sleep with water bottles. Central HVAC is considered too wasteful.
« Last Edit: January 20, 2013, 08:20:42 AM by Skyn_Flynt »

Another Reader

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Re: furnace repair or replace?
« Reply #17 on: January 20, 2013, 08:18:58 AM »
Hey Prettymuchfi:

Just got my first PG&E bill since the furnace replacement. It covers through January 14th, so some of the recent cold snap is in there. That should be offset by three days of no furnace, right? Nope. Instead of going down, the gas usage is UP by 30 percent per day. WTF??? This was supposed to be a more efficient furnace and I have kept the temperature lower than last year. If you can repair the Day and Night, do it. After this bill, I wish I had repaired mine.

Self-employed-swami

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Re: furnace repair or replace?
« Reply #18 on: January 20, 2013, 09:59:27 AM »
Oh no AR!

Could the install people have burned through a lot of gas, during the installation process?
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fchinita

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Re: furnace repair or replace?
« Reply #19 on: January 28, 2013, 01:42:46 PM »
If it is a sticky relay (and you have some soldering skills) you can take the board out to see the relay reference, order it and replace it yourself.

I replaced the relay in a dehumidifier which cost me 5, GE were trying to charge 50 for the whole control board!

Good luck fixing it.

StarswirlTheMustached

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Re: furnace repair or replace?
« Reply #20 on: January 28, 2013, 02:46:38 PM »
What's funny to me is that although people on this forum pat their own backs about turning the heat off, .... (ooooh we are so "badass") ... it's how millions of Japanese normally live. They use small propane heaters, or an electric kotatsu table, sleep with water bottles. Central HVAC is considered too wasteful.

They also don't really insulate. Central HVAC makes a lot more sense when the building isn't a sieve.
Being an island and having the climate moderated by the pacific ocean sure doesn't hurt, either.
Otaku be trollin'?

LadyM

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Re: furnace repair or replace?
« Reply #21 on: February 02, 2013, 06:17:36 PM »

The control board I was quoted $500 + labour to replace is available on Amazon for $45 and although it has quite a few wires, its all very low tech and easy to work on if you've ever done any assembly stuff before (e.g. building your own computer). Part: http://amazon.com/Fan-Blower-Control-ICM271-Electronics/dp/B000TMK310/, Photo of similar board to mine and thread: http://diychatroom.com/f17/bryant-carrier-relay-board-78018/.

We just replaced our control board and it was quite easy. The new control board was a little over $100, and we replaced the thermostat as well....we did the thermostat first because we thought it was the problem (our furnace and AC wouldn't come on when the thermostat said it was on). The furnace and older thermostat were installed in 2000, so relatively young.


After working on computers or cars, this stuff is all very low tech.

Don't get me wrong. I wouldn't want to be diagnosing some strange fault, but at the price of these components, its possible to treat them as a black box and just replace the whole part -- which seems to be the most common suggestion for the control board (just replace it!). Except for the gas stuff - which I don't want to go near!

Low tech indeed. It's not rocket science, and we used our powers of diagnosis plus our old pal the internet to help confirm our suspicions. It didn't seem like too risky of a plan, especially when companies want to charge you $70 just to show up.

  • order a new control board (to fix the start-stop problem when the blower is done, probably from a sticky relay on the board)
  • replace the control board
  • remove the blower
  • rebalance and reinstall the blower

If that all goes well (yes, a big IF), my furnace should be good to go for another 10 years or so. For $50 and a few hours of my time learning a new skill.

You go! Replacing the board was easy for us, and it worked like a champ! I imagine you can tackle all that you listed above. Good luck!
"While money can't buy happiness, it certainly lets you choose your own form of misery." - Groucho Marx

prettymuchfi

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Re: furnace repair or replace?
« Reply #22 on: February 04, 2013, 08:53:03 AM »
Thanks for the many posts! Some quick responses and an update.

Re Japan: Yes, similar to Sydney Australia when I was growing up, though I understand its changed a little now with new construction. In the one or two cold months of the year, we'd all gather in the family room with the oil/electric heater and then head off to bed with a hot water bottle.

Re AR: new gas bill after new heater: Wow, that's really disappointing. Does the house feel generally warmer? The one thing that intrigued me about a new heater was the multi-speed options. Instead of "30 mins of heat followed by 60 mins of gradually cooling, repeat", I imagined that having half heat for much of that time would be comfortable in ways like: less hot/cold pockets in the house, less noise from the fan running full speed. Do you have pg&e with smart metering? You might be able to go online and compare before and after in the daily history they keep and get a better idea of what's going on.

Re new relay: I thought about that option. I decided against because: there are 2 relays and I wasn't sure which was which, there were a few capacitors on the board (perhaps used for timing?) and I was concerned that after almost 30 years they might be dried out. Easy enough to replace them too, but I find that sort of thing tends to snowball. Plus I remember pricing relays once before and they weren't cheap!

Re Skyn_Flint: Hope you're not freezing there!

So, on to the current status: In brief, I replaced the board about 5 days ago and its been working great (touch wood)!

Longer version: I found the board being resold at Amazon by multiple vendors and picked the cheapest for $55 and placed the order and waited. About a week later I got a phone call apologizing that the board was out of stock and did I want to cancel or wait. Doh. Eager to get it done, I found it locally for pickup at $85 + tax ... and went back to looking online. Found it again for $65 with shipping & no tax and ordered it.

The board arrived a week later and I was quite impressed. They re-engineered the original board beautifully for this purpose. Every connector was the same spade connector, and in the same place (except two were swapped) and well marked. The relays were replaced by (seemingly) solid state little black boxes, and most of the discrete circuitry was replaced by a single larger IC of some sort. Physically, its an identical size and the screw holes etc. all line up.

I restrained myself from just "going for it" and took the time to take a couple of pics of the existing board in place, drew a pencil diagram of all the wires, and then proceeded to pull them off one board and put them on the other, one by one. About 1/2 way through, I ran out of room for both boards and had to pull all the remaining connectors and remove the old board completely. The rest of the wires plugged in without problems. The screw connectors for the thermostat were slightly different (a terminal block vs individual screws on the board), but the order was the same and it was obvious.

The only tools I needed were a small hex nut driver (part of the cheap socket set I bought long ago for some other job), a screwdriver, and needle nose pliers. I used the hex nut screwdriver to remove some venting to give better access to the control box, and also the cover for the board. The pliers helped remove the automotive style spade connectors and the screwdriver for the 2 mounting screws and the thermostat wires. The whole job took ~45 mins, including the time to document beforehand.

So far, so good. The heater runs exactly the same, except without the fan stopping/starting 1-3 times at the end of each run.

Still to come: removing and balancing the blower. I was tempted to do it the same day, but decided it was best to reduce the number of variables and make sure that the new board was doing its job before throwing in messing around with the motor. I'll attempt the motor later this week. The hardest part there is removing more venting so I can get access to it and pull it out. Also, it looks like there is intentional clearance around the control board box so that I can leave it in place, but I won't know for sure until I try.

I'll keep you posted...

And I'm still royally pissed at the HVAC people who suggested $500 parts + labour to do this same job while all the while saying "this heater is so old, you'll just change out one part and another will fail". I reckon its just the opposite (sorry AR, but your experience was a crucial part of the nudge to try it myself). Put in a new heater with all its complexities and watch parts fail left right and center in about 10 years (as soon as its out of warranty). These older heaters are so simple, it can likely be repaired for many years to come. Especially when there are up-to-date replacements like the new control board available (and presumably similar advances with new blower motors, gas sensors etc).

Thanks again everyone for your encouragement and insights!