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Boggled Blower
TR3driver   9/11/2013 2:00:35 PM
Watch out for those sleeve bearings.  Unlike ball bearings, which get noisy before they fail (and so give warning that they are about to fail); sleeve bearings tend to silently bind.  I predict that some frosty night, you'll find the blower moving in slow motion (or totally stopped) and the sail switch won't enable the burner.

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Re: Design for Obsolesence, PART 2
SONOFFARMER   8/30/2013 9:31:57 PM
Actually, the new refrigerant evaporator coil (R 410a) will funciton with the old condensing unit (R 22) THe controls are relatively simple circuits in Air Only systems and nothing an average McGiver could not figure out if they are on a heatpump system. The down side of attempting to to save the condensing unit is that it is the shorter lived component 9 out of 10 times. If both units were made at around the same time, by the same people, and you got the life expentency out of the piece that should have died last, it is a good time to change out to the non-obsolete refrigerant; R22 is scheduled to be gone in less than 10 years anyway.


Moral of the story: Look at the silver lining.

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Re: IT was DFM, at least partly
btlbcc   8/28/2013 6:20:59 PM
Ken E., yes, that was pretty much the problem with the original blower.  Actually, it should be possible, with proper material selection and anti-seize compund, but I suspect that would rather seriously (and negatively) impact the cost/price.

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bobjengr   8/24/2013 1:16:01 PM
 Very good post Brooks.  Aftermarket "kits" represent to me a real-world problem and deserve as much attention from engineering management and design teams as do original equipment.  I have had more pains from replacement parts than I ever had with OE assemblies.  I retired from a major appliance manufacturer and "kit" design seemed to be the projects given to coops and temporary engineers.  Those with the least experience were given subassemblies that made the greatest profit for the company.  Your experience is not that uncommon.  Again, good post.

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Re: Transient Protection
wbswenberg   8/23/2013 7:22:48 PM
How did my power transient comment get over here?

My across the street neighbor I believe is the 1st one in the neighborhood with a furnace problem.  He call and the tech replaced the controller board.  Next time he asked me.  I explained the basics from working on older furnaces when I was a teenager.  It would fire but not blow.  Since it was high efficiency it also has a combustion blower and it was working.    

We jumpered the blower and it worked.  So that left the temperature sensor. That was also high voltage and we jumpered around it and the furnace worked.  Then I told him my problem of finding the replacement.  He got online and had the right one within an hour.

So when my furnace quit I guessed the same problem but no.  I check the code at the control board was flashing.  It indicated the combustion blower.  I noticed a lot of sand - ash around the blower. I vacuumed it out. I jumped it and it worked.  And power was being provided when the burner was on.  I'm in test engineering and have fixed a lot of equipment.  The 1st thing I do is make a show of blessing the equipment and then checking the fuses.  

And I kid around with the laying on of hands followed by good trouble shooing.  And thinking.    On a lark I flicked the blower with my finger.  The blower started and the furnace fired.  It has been working ever since.  And now you know why I'm LORD of test equipment.  

Ken E.
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Re: IT was DFM, at least partly
Ken E.   8/23/2013 4:30:52 PM
Apparently after these have been running with combustion heat on the blower for awhile, you can't get them apart anyhow, so doesn't matter what they did with shaft or materials.

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Design for Obsolesence
Critic   8/23/2013 3:51:55 PM
This story reminds me of a couple of fiascos I have experienced. 

1. I installed laminate flooring in my kitchen and adjoining areas.  I purchased about 10% extra flooring in case I needed to replace some in the future.  Sure enough, we experienced not one, but two minor floods, which required replacement of relatively small sections of flooring.  The second time, I did not quite have enough planks to finish the job, so I had to move some damaged flooring to the inside of a closet where it wouldn't be visible to the casual observer.

It would seem that it would be simple enough to go back to the store where I bought the flooring and get more.  Nope, it just doesn't work that way.  In what seems like every 2 - 3 years, manufacturers change flooring patterns, colors, and plank widths so you cannot purchase replacement planks.  If you want to repair your floor, you have to replace all of the flooring if you want it to match.

Always buy plenty of extra flooring, tile, whatever material you think you might need one day.  It may not be available anymore when you need it!

2. The refrigerant evaporator coil in my central A/C air handler developed perforations after about 10 years of service, and needed to be replaced.  A replacement was (you guessed it) no longer available.  So, you either have a new coil custom fabricated at great expense, or you replace the entire air handler.  But, wait, there's a catch... the new air handler would not be compatible with the old outside unit (different refrigerant, control configuration, etc.).  So the entire system gets replaced!

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Re: IT was DFM, at least partly
btlbcc   8/23/2013 1:44:44 PM
William K.,

Oh, I understand why they did it.  I just think it's piss-poor design.  And as for the price increasing, I'd have to say in defense of DFM, etc., that yes, some companies will increase the price in such a situation and some will hold or reduce it.  Corporate morality or something like that...

I'm sure that (as I originally started out to do) the intent of the industry (generally, not necessarily the specific manufacturer) is that people should replace the entire blower rather than bother to repair it.  Okay, I understand that.  But when an after-market replacement that the supplier says is an exact replacement isn't, it's a bit annoying.

And of course there's the spare part price business - handling a single spare part through vending and warehousing, etc. tends to increase the cost multiple times the original cost to the OEM.  There's the story of an early VW dealer who, to prove that parts for this foreign car were readily available, built an entire VW beetle out of spare parts.  He calculated that the car cost him $20K, at a time when a brand new VW cost $1600.


William K.
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IT was DFM, at least partly
William K.   8/22/2013 4:56:17 PM
This is an interesting posting. But I would point out that elimination of the flat on the shaft not only reduced the cost of the motor. but it also reduced the assembly time and effort by removing the need to align the setscrew with the flat on the shaft. Also, the shaft material could be a softer steel since the setscrew had to displace some metal when it was tightened. So the only real cost of the assembly change was increasing the torque setting on the driver for the setscrew. Generally, when the DFM crew gets going here is no consideration given to th fact that eventually there may be a need to repair the system. The result is that you find crimps and welds in place of screws and bolts, and while the manufacturing cost goes down the selling price goes up.

User Rank
Re: it's annoying
patb2009   8/22/2013 4:54:26 PM
sometimes just some furnace tape and a couple of sheet metal screws works too.

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