Central vacuum recommendations?

[Hatsuwr]

Last week, just after reaching 50 years, the rotor burned out on my NuTone CV350. I'm not sure I want to spend $250+ on a replacement motor. I'll try rewinding it at some point, and will keep an eye out for units that are being scrapped to pull a rotor from, but even if it gets fixed it will probably be relegated to garage use.

So, I'm looking for a replacement. My main priority is performance, although I'm not sure how I would balance CFM and suction - leaning towards giving more weight to CFM right now. Bottom-emptying is much preferred, although I can work around that if there's enough to justify it.

I'm not at all concerned about noise or cleanliness of exhaust air, since it will be installed in my utility room and exhaust will be routed outside. I haven't read much about cyclonic systems yet, but it seems like they might be a good fit to eliminate the cost of bag changed and maybe have a smaller impact on performance as it becomes loaded.

Here is a spreadsheet I threw together for MD, Cyclovac, and Flo-Master (also has the info for my old NuTone). Let me know if you'd like to see any other brands or more points of comparison here:


The Cyclovac 725 Hybrid is at the top of my list right now. It seems to be the best value among the mid-to-high performance models (as far as air watts per dollar). It can be operated with or without bags. One strange thing is that it's air watts rating is 6% lower than the A700tv2, despite having a 2% higher CFM rating and <1% lower water lift rating.

 

[cheesewonton]

Last week, just after reaching 50 years, the rotor burned out on my NuTone CV350. I'm not sure I want to spend $250+ on a replacement motor. I'll try rewinding it at some point, and will keep an eye out for units that are being scrapped to pull a rotor from, but even if it gets fixed it will probably be relegated to garage use.

So, I'm looking for a replacement. My main priority is performance, although I'm not sure how I would balance CFM and suction - leaning towards giving more weight to CFM right now. Bottom-emptying is much preferred, although I can work around that if there's enough to justify it.

I'm not at all concerned about noise or cleanliness of exhaust air, since it will be installed in my utility room and exhaust will be routed outside. I haven't read much about cyclonic systems yet, but it seems like they might be a good fit to eliminate the cost of bag changed and maybe have a smaller impact on performance as it becomes loaded.

Here is a spreadsheet I threw together for MD, Cyclovac, and Flo-Master (also has the info for my old NuTone). Let me know if you'd like to see any other brands or more points of comparison here:


The Cyclovac 725 Hybrid is at the top of my list right now. It seems to be the best value among the mid-to-high performance models (as far as air watts per dollar). It can be operated with or without bags. One strange thing is that it's air watts rating is 6% lower than the A700tv2, despite having a 2% higher CFM rating and <1% lower water lift rating.

Air Watts are an instantaneous measure of vacuum motor power. As the size of the orifice changes airflow and suction values change. Thus for each orifice size there is an associated air watt value. Each motor will have a combination of airflow and suction at a certain orifice size that yields the maximum air watt value. It may be that A700tv2 manages to achieve that combination of airflow and suction that yields a higher max air watt value than the 725 can achieve. Remember it requires both suction and airflow working together to achieve air watts.

 

[Hatsuwr]

Air Watts are an instantaneous measure of vacuum motor power. As the size of the orifice changes airflow and suction values change. Thus for each orifice size there is an associated air watt value. Each motor will have a combination of airflow and suction at a certain orifice size that yields the maximum air watt value. It may be that A700tv2 manages to achieve that combination of airflow and suction that yields a higher max air watt value than the 725 can achieve. Remember it requires both suction and airflow working together to achieve air watts.

Would be nice if they posted the air flow vs water lift curves!

 

[cheesewonton]

If you have the model number of the motor you can usually find them on the Bison-Ametek website.

https://www.bisonametek.com/product...696&utm_content=312471696&utm_source=hs_email

 

[Hatsuwr]

If you have the model number of the motor you can usually find them on the Bison-Ametek website.

https://www.bisonametek.com/products/find-a-product?utm_campaign=2024 New Website Launch&utm_medium=email&_hsmi=312471696&utm_content=312471696&utm_source=hs_email

Yea Ametek is good about that, just gotta get MD, Cyclovac, and Flo-Master on board!

Speaking of Ametek though, I was able to find the rotor, it's part #215330. Best price I've found so far is about $125 with shipping... Not too bad.

Alternatively, I also found that there are a great many motors that seem to be more or less drop in replacements for mine, and with better performance. These range in price from $200-$400. I didn't want to just replace the whole motor with an identical one when it was only the rotor at fault, but replacing with an upgraded one doesn't seem like a bad idea.

Here's what I've narrowed the list of potential motors to:



And here are their air flow vs suction curves:

 

[panasonicvac]

The CycloVac you're thinking of is a good option. They do offer an extended 25 year warranty.

 

[Hatsuwr]

The CycloVac you're thinking of is a good option. They do offer an extended 25 year warranty.

I just discovered today that I can probably fit an 8.4" motor into my old vacuum. I would probably need a little adaptor that I can 3D print since the bottom of the 8.4" ones have a sort of cone shape instead of being flat like my 115334.

The 122501-00 seems to be what is used in the A715h and DB8000, and I'm debating seeing if I can make one of them work.

 

[ultralux88]

My personal opinion would be the MD M715h. Being honest though, I am an MD dealer. But its extremely powerful, and my experience is that the support bag design does lead to better airflow, which is why I prefer the MD, FloMaster, and SilentMaster lines of theirs where the bag is in the top of the unit held in the outer cloth bag.

 

[Hatsuwr]

My personal opinion would be the MD M715h. Being honest though, I am an MD dealer. But its extremely powerful, and my experience is that the support bag design does lead to better airflow, which is why I prefer the MD, FloMaster, and SilentMaster lines of theirs where the bag is in the top of the unit held in the outer cloth bag.

I decided to go ahead and get the bigger motor (the same one used in the M715h if I'm not mistaken). Waiting to hear back from a cheaper retailer on Monday, and will hopefully have it within a week.

I'm curious how the performance will compare. I have a good quality vacuum gauge to measure no flow vacuum pressure. I imagine that will be lower that on newer vacuums just because of random small leaks everywhere than I have yet to seal up. I'm not sure how I would measure CFM... I have a cheap anemometer, but I'd have to build some sort of expansion adapter to decrease the velocity quite a bit. I doubt that would be accurate enough to even be worth it though.

 

[cheesewonton]

I decided to go ahead and get the bigger motor (the same one used in the M715h if I'm not mistaken). Waiting to hear back from a cheaper retailer on Monday, and will hopefully have it within a week.

I'm curious how the performance will compare. I have a good quality vacuum gauge to measure no flow vacuum pressure. I imagine that will be lower that on newer vacuums just because of random small leaks everywhere than I have yet to seal up. I'm not sure how I would measure CFM... I have a cheap anemometer, but I'd have to build some sort of expansion adapter to decrease the velocity quite a bit. I doubt that would be accurate enough to even be worth it though.

Use the anemometer to measure airspeed at the center of the hose connection. No duct. Move the anemometer around until you get the highest airspeed reading. Calculate the area of the hose opening in cubic feet. It will be small, on the order of 0.006 something to 0.008 something square feet. Go out four decimal places. Multiply the airspeed by the area in cubic feet then multiply that by 0.8. That last factor is a rule of thumb factor used for calculating turbulent airflow since, if you could measure airspeed all across the diameter of the opening you would find airspeed at the center is much higher than airspeed at the outside of the hole. The air along the sides of the tubing doesn't flow as fast due to friction.