Newbie vent question

[TWarren]

I received a new kiln as a gift...Olympic 1414HE.  Firing box is about 1.4 cu ft.  Vent kits are REALLY pricey, so I'm putting one together.  I have a question about the blower motor.  The Orton vent kit (recommended for this kiln by the manufacturer) comes with a 73 cfm motor.  The Skutt kit comes with a 140cfm motor.  Does any one have an opinion on which blower motor might do the job?  Thanks in advance.

[Hulk]

i) Motor well protected from corrosive kiln atmosphere
ii) Adjustable plenum

If you are considering moving your vent setup to a larger kiln in future, choosing a "stronger" fan for your 1.4 cubic foot kiln may make sense*.

I bought an inexpensive inline 100 cfm motor for my setup. It's strong enough to pull a stream of superheated atmosphere from my 7 cubic foot kiln and is still working fine after a few dozen bisque and glaze firings. When it fails, I'll look at replacements that do not have the motor hanging in the vent stream! Although the superheated and no doubt rather corrosive stream of kiln atmosphere is mixed with ambient air in the plenum (the box fitted against the kiln), it is still corrosive enough to wear away unprotected and/or susceptible materials...
 

*the stronger the fan pulls, the greater/larger the ambient port in the plenum "should" be?
I'm saying yes.
An adjustable ambient port (aka "bypass" port) in the plenum allows for ...adjustment!
A stronger fan allows for more dilution of kiln atmosphere and sizing up in future.

Added: Reasonable trade off between suitability, quiet, long-lasting, price, likely looking at well over a hundred US dollars.

Added II: This might be a starting point
Jabsco 35115-7020
Searching that ^ string will generate related hits. Note the flange specs.
Max inlet and ambient temps, ah, that might be a red flag.

Added III: Jabsco 35515-0010 max inlet temp is higher, 130°F

Added IV: both Jabsco models, above, turn a fan in the vent stream, however, the motor does not. The commercial solutions I see use similar fans...

When my cheap inline freezes up, I'll be shopping!

Edited October 19, 2023 by Hulk
quality fan motors aren't cheap!

[Bill Kielb]

3 hours ago, TWarren said:

Does any one have an opinion on which blower motor might do the job?  Thanks in advance.

What is super important on ANY of these designs is the mixing manifold which allows much more room air and only a TINY amount of kiln air. So much of a mix of room and kiln air as to keep the discharge airstream 120 - 130 degrees or less even with the kiln at top operating temperature. When I measured a conventional operating system I found the combined exhaust was 7CFM per kiln in a two kiln 140 cfm system.. So the 140 cfm capacity was really used up in maintaining the proper suction pressure with a true flow of 1/10th or less of the rated airflow.

you can use an inline fan, but designing to ensure the fan does not overheat is a must. Inline fans need to cool themselves with the airstream.  The video below is an example of doing this in a hybrid fashion where an economical off the shelf long life (super quiet) inline blower is used to provide above kiln exhaust and still have enough power to run the downdraft system as it was designed. So almost all room air from above the kiln which means the inline blower will always see mostly near room temperature air and a small amount of kiln air still mixed with room air using the old mixing manifold design.

https://youtu.be/etpa2Pc9Hug?feature=shared

So this does answer your question to the extent prox 70 Cfm per kiln is plenty and most manufactured fans come with self cooling motors so wasting the horsepower to maintain suction so to speak (only prox 7cfm of airflow) is easiest and probably more goof proof from an overheating standpoint. The hybrid system in the video just takes the wasted horsepower if you will, and puts it to use moving air.

Edited October 19, 2023 by Bill Kielb