Aquahot coupler for combustion air fan drive

[jestal]

Our aquahot starting making serious bad noises and at 8 below and trying to leave for warmer climes desparate measures were employed.

Pulled the burner out of the aquahot and tore it apart as if I knew what I was doing. The turbine/fan that pushes combustion air into the burner is driven by an electric motor. The electric motor shaft has one of these couplers and the fan shaft has a matching coupler.

The bearings on the turbine fan had started to fail and the turbine was rubbing the housing and the coupler had cracked. Note the crack line in the coupler and the chipping around the D shaped drive hole.

I repacked the (bad) bearings with new grease and reassembled with some washer shims to get sufficient clearance to the housing for the turbine fan (compensating for the play in the bad bearings) and reassembled. The cracked coupler was reinforced with the high strength zip tie.

It ran great and quietly for 4 days intermittantly as required until we got to warm weather.

Parts arrived in the mail. Then I replaced the cracked coupler and a new bearing kit was added. Of course the wrong kit came and next day air missed the flight by two days...always excitement.

If you google 450D manual the pics clearly describe this assembly.

The bearings (and replacements) were china origin despite being very costly from Aquahot. Plan is to get US replacements when I can find them, clean and repack them with Krytox and install them to try and make the unit more bulletproof.

The tiewrapped coupler is my submission for jerry rig of the year for 2017

Note: the burner assembly is very straightforward to tear apart. Just mark all the assembly points for matching re-assembly. Nothing really difficult nor are special tools required other than a pair of smaller snap ring pliers for an internal snap ring. The burner is pretty elementary, basic and easy to work on. Don't be afraid of it.

[rag_ftw]

You get my jerry-rig vote but even better it worked! Good job, sir!

[brobox]

Al, Nice write up for us DIY'ers if we are backed against a wall like you were. What a shame that Aqua Hot which once had a good reputation has also gone Chinese parts that will self destruct when needed the most. What good are furnace parts that fail when it gets cold?

[Dr4Film]

Roger Berke handles Aqua-Hot parts but since he is an authorized Aqua-Hot service center the parts may be the same as what comes directly from Aqua-Hot. You would have to contact him to discuss.

Another place to obtain Aqua-Hot parts is from this company.

Bus Service, Inc. - Your diesel and bus parts supplier

Dr4Film ----- Richard

[hawgguy]

Brilliant! I recently had a similar failure with similar bad noise before Thanksgiving. I chickened out from the complete teardown and pulled the Webasto unit and sent it to Roger. Roger replaced the motor, bearings and plastic clutches. Excellent, speedy service. Sitting at 13 degrees this morning I am very happy to have a purring Aquahot.

[Gary.Jones]

Goog grief...... !!!!!! I thought that our problems were probably limited to kinked hoses (Entegra's fault), Bad pumps (AH's fault), and bad boiler fluid (Century's fault ?) and now we also have to worry about every damn plastic part in the unit also (made from China on a "who can make this piece for even less that then other guy?" basis..... You gotta be kidding !! Thank God some foreign manufacturer doesn't make cheap Wabasco burners and cheap diesel nozzles or we would have to worry about those more than we currently do....


Gary

[DebbieMH]

Very nice - Jestal! I hope to be parked next to you when anything happens to our Anthem!

[brobox]

I manufactured a plastic product for 18 years. There are so many grades of plastics it's unbelievable. There are plastics that are formulated for cold weather outdoor use. They are a few pennies more per pound, but our produce was an outdoor product with a 3 year guarantee and we didn't have failures. Our material was made by Monsanto, a USA company where we were insured of the same grade with each delivery. Chinese plastics is mostly re-grind and junk material.

[jestal]

Chuck is right. Given the correct plastic material for an application it can be a superior choice. This failure was not so much the plastic but the fact that the bearing failure allowed the air pump turbine to rub and stall the electric motor which then cracked the coupler from forcing the D shaped shaft to spin inside the hole. Several small pieces of the coupler from the hole also chipped out. The plastic coupler is almost certainly quieter than a metal one although for what the Aquahot parts cost I would expect to see to metal couplers with an elastomeric cushion between to run really quite and durably.

In any case the aquahot parts and chinese bearings look to have been "costed to death"

Bob, mine made exactly the same noise as you recorded. I just ran it longer in the cold trying to leave town and it finally rubbed the turbine so hard it stalled and quite pumping combustion air whereupon it started to puff diesel smoke rings. That's when I panicked and pulled the thing out and cobbled the repair.

That whole assembly looks like a grandfathered design that is likely never to change due to opening potential litigation. It has several opportunities for improvement otherwise! Just the better bearings will be a step up. From what I saw I would expect every aquahot to eventually have the same failure as the grease in the bearings dries up. The bearings are preloaded during assembly so the tolerance variation will change the preload and the expected life, also. Interestingly, the service manual instructions on spinning the turbine once disassembled did not demonstrate any problems! Only by manually preloading the shaft to one side did i determine that the turbine was rubbing and why. Experience is a great thing.....too bad you have to get so old to get enough!

Personally I consider a bearing kit and two spare couplers to be mandatory on-board spare parts along with a filter and nozzle for the future as they are the moving parts most likely to fail.

[757driver]

Amazing the ingenuity of some of the forum members, nice job Al.

[hawgguy]

I think those plastic clutches/couplers are meant to fail in a sacrificial way to protect other stuff.

[lowejug]

Great... I am with Gary... it's not very comforting knowing our Aqua systems apparently have gone from very well reliable heating system to this... can't believe all these problems people keep posting...

[Cruzer]

I've replaced them in the past but due to wear. Never seen one split. I know that Aqua-Hot has made some real dump moves recently regarding pumps and such but I think that the split coupler is a fluke. The burner is Webasto, a German company, and Aqua-Hot just puts them in rather than determining what goes into the motor assembly. Looks like the entire world is buying stuff from China.

[Gary.Jones]

Al:

Please provide the part numbers for the parts that you had fail on you. if you have a good purchase source (other than Roger Burke), please publish an approximate price (MSRP or discounted). Thanks

Gary