Replacing Bearing in Zehnder Fan
Trevor_Lambert
| Posted in Mechanicals on
Has anyone replaced the bearing in one of the fans in their Zehnder CA550 and can tell me which part number to order?
One of the fans is starting to make noises intermittently, and I’d rather replace a $20 bearing than replace the whole fan for something like $500. Seems rather wasteful as well.
Maybe the bearing will have a part number on it, but I’d rather have it in hand to avoid removing and reinstalling the fan an extra time.
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Replies
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Have you had a look yet?
It has been my experience that the more compact a motor is the less likely the bearing will be replaceable.
Adding some oil can’t hurt.
Walta
I don't know where I'd add oil. I'm pretty sure it's a sealed bearing. I replaced one in the past under warranty, and from what I recall the bearing isn't even visible on the assembled fan.
One strategy to consider is to order a new fan, swap the new fan in, and then have the old one on your bench to take your time figuring out the process and the part needed. Then you'll have a fan with a new bearing ready to swap in the next time there's an issue.
How old it? I'm wondering how soon I need to start worrying about mine.
It's about 5 years old. The sound went away, and hasn't been back for a few months now.
Uh oh, mine is also about 5 years old. I wonder if there's a way we can collaborate on figuring this out. I live in NH, on the Vermont border in case we happen to be nearby.
I have sometimes been successful oiling “sealed” and “non-serviceable” bearings by using something like mystery oil dribbled (sparingly) on the shaft near the bearing while turning the shaft by hand at an upward angle. The oil will wick into the bearing this way and buy you some time. Note that this only works with sleeve and sintered bearings, not ball bearings.
For ball bearings, if you can get the cover off, a little spray can applied white lithium grease usually works pretty well. If you can get the bearing out completely, clean it with automotive brake cleaner (which is very useful stuff, albeit fairly nasty) first to decrease it before you apply new grease. You need to work the new grease in between the balls with this type of bearing, so slowly turning it by hand while greasing helps here too.
Regardless of the type of bearing, if at all possible, clean it before lubricating it. Dirt in any bearing will shorten its life.
Bill
The bearings for the Zehnder Q350 fan motors are 608Z's...there are two of them. I just replaced a set in my Q350 and fitted 608ZZ bearings...slightly specc'ed up versions of the 608Z.
After six years the exhaust blower on my ERV started squeaking. The replacement part was ~$700, which is silly as the whole unit is about a $1k, so I decided to take chance and replace the bearings.
The good news is the EBM motors used in the ERV are very well designed, not simple but very doable. It uses the same 608z bearings. You do have to take a lot of it apart to do it though:
-remove the blower unit from the shroud
-remove the overmolded wires/connector from the back of the motor
-remove the rear motor cover plate
-take out the control PCB (slides right off the motor pins)
-remove the plastic dust cup over the bearings
-remove the snap ring on the shaft and slide the stator housing right off
-with a drift punch gently tap out the bearings, they come out very easily
Reverse to assemble. Don't forget the dust cap like me, I had to assembly the motor twice.
A couple of things to watch. DO NOT TRY TO TAKE THE BLOWER WHEEL OFF THE MOTOR. Removing the blower wheel is not needed to access the bearings. At least on mine, the blower wheel is clamped on with screws, if removed, it would be very hard to get it back and in balance. Again, since it is clamped, it is possible to tilt it slightly, take care on how the bower is supported during disassembly and don't put load on it.
The fact that the blower wheel was clamped on came handy as my unit always had a slight vibration, by pushing on it to tilt it slightly in different positions I managed to get most of it out. I think this bit of vibration is why the bearing failed early.
Now that I have done it once, this is a pretty simple repair. Now knowing how to do it, it would take longer to take the blower out of the ERV than to replace the bearings. The new bearings were $5.60 a pair plus about 2 hours of labor including removing and re-installing the blower, well ahead. Plus the new blower would have been a long lead, nor ERV or listening to a squealing bearing for 4 to 6 weeks would not have been fun.
So I ordered up some 608ZZ bearings, and set to work on replacing them today. Unfortunately, there are some significant differences between the CA550 I have and whatever model you have. The circuit board doesn't just slide out, there are a few things you need to do first. The bearings also cannot be freed with a drift punch, you need a 4", 3-jaw bearing puller to get the top one out, and the bottom one I actually haven't figured out how to remove yet. There wasn't much point, because I had discovered the bearings are different. The 608zz are 8x22x7mm, the ones in the CA550 are 10x26x8mm.