Question About Silencer Spa Blower

[Fins]

Does anybody know if it's possible to add a speed controller to slow down a Silencer spa blower? Ours is a 1.5 HP model and it puts out too much air. Causes water to bubble out of the spa. I tried the trick of drilling a 1/4" hole in the blower discharge but it makes way too much noise. Seems like it should be possible to slow down the blower. I would prefer to not replace it if possible.

Thanks in advance for any ideas.

 

[jblizzle]

Have you tried just to not use the blower? A properly designed spa should not always need a blower. You might want to try taking the blower off to remove its restriction and see if the spa works well without it installed at all.

I also feel like I have seen posted that you could restrict the flow by putting a valve on the pipe. Although I do not recall if that adds too much stress to the blower motor.

 

[Fins]

Our spa has next to no pressure without the blower on. Past few pools did not need a blower to have plenty of pressure. With this one, you can barely see any disturbance on the surface of the water until the blower is turned on. Once the blower is turned on, it goes into turbo mode. Pool builder has been no help and says its normal for the type of venturi tee jets we have. I'm ordering the next size down jets to see if they make any difference. Currently have 8 Waterway 7/16" venturi tees. Going to replace the 7/16" jets with 1/4" jets to see if that helps a little.

 

[mas985]

Our spa has next to no pressure without the blower on.

Have you tried the spa with the blower removed from the air pipe. Just having it off is not enough. You must remove it from the air pipe because it adds air restriction when off.

Going to replace the 7/16" jets with 1/4" jets to see if that helps a little.

That is a huge change. But it won't change the amount of air from the blower. That is completely independent of the spa jet orifice size. The spa jet size determines the amount of water pressure that the jet exerts.

 

[Fins]

Tried removing the blower entirely last night and it made no difference. The spa has extremely low water pressure without the blower on. My guess is that the 8 - 7/16" jets require more flow than my single pump can provide at spa pressure. Looks like from Waterway's literature, the 7/16" jets flow around 16 GPM at spa pressure if my memory serves me correctly. The 1/4" jets only require around 9 GPM. All piping is 2".

Ive never had a spa that required a blower to make water pressure so this is a new one for me. The PB just shrugged it off as a non-issue and said that's why you have a blower.

 

[jblizzle]

The blower does not add water pressure it just adds air to the flow and agitates the stream.

 

[JoyfulNoise]

What size pump is driving your pool/spa?

16GPM/head x 8 heads = 128GPM

That's A LOT of flow even for the largest pool pump on the market. If your filter is too small then it will limit the flow as well.

[EDIT]

Never mind, I see your pump specs in your signature.

Perhaps the heat pump is limiting the flow rate more than the cartridge filter?

[END EDIT]

 

[mas985]

The blower does not add water pressure it just adds air to the flow and agitates the stream.

+1


But are you getting any air out of the jets without the blower installed? What size air pipe did they use?

7/16" jets usually require around 20 GPM per jet for strong jets while 3/8" is around 15 GPM and 1/4" is 10 GPM per jet. If you are going through the filter and heater before the jets, then 1/4" jets are probably the right size. 8 7/16" jets should have had two loops and two pumps.

Is the second pump for just the jets? What size pipe did they use for the jets?

 

[Fins]

Thanks for the feedback. Not sure I can explain it any differently other than to say with the spa empty, when I return through the jets only, the water sprays about half way across the spa. When I turn on the blower, the water sprays almost completely horizontally across the spa with hardly any drop until it hits the wall opposite the jet. I understand that the blower is not increasing the static pressure of the water however it sure seems to be increasing the velocity pressure and therefore the total pressure of the flow is incrementally increased as well. I don't really know why but that's what's happening. If you put your hand in front of the jet without the blower on, it feels about like a garden hose with no nozzle on it. When you turn the blower on, the water jet feels like it wants to drill a hole in your hand.

I am getting zero air out of the jets with the blower and blower check valve removed from the riser tube. The riser tube for the blower is 2". I am not certain what happens to the air line once the it heads underground. The equipment pad is 23' from the spa. Filter is clean. In both pool and spa mode, all water goes through both the filter and the heater before heading to the spa or pool.

I only have one pump. Flows the pool and a few small water features normally and changes to 100% spa when put into spa mode. 2 separate drains in spa and 2" piping start to finish. Pump suction strainer basket is clean.

I'm going to order the 1/4" jets tonight and see how that works.

 

[mas985]

The air mixing with the water is making the water lighter and less dense so for a given force the velocity will increase since force is related to both velocity and mass through momentum. The water air mixture also exhibits slightly less head loss through the jet opening. So while the velocity of the water increased, the mass decreased but the net force of the water should be about the same although the air blower does add some force to the equation but air is 800 times less dense than water and if the blower puts out 122 cu-ft/min, the equivalent flow of water creating the same force is about 1 GPM so it is pretty much insignificant. However, water mixed with air does feel different than water alone even though the force may be nearly the same because of the pulsating effect.

 

[Fins]

So - are 1/4" jets the right answer?

I was amazed today by how sensitive the air flow is to orifice size on the directional nozzles. With 3/4" diameter nozzles, there is too much air and water will bubble out of the spa directly above nozzles. I replaced the 3/4" nozzles with 3/8" nozzles and I get no air at all. Nothing. I took a uni-bit and drilled out the nozzles to be roughly 7/16" and I get a nice bubble action without dumping water out of the spa.

Would have made life a lot simpler if the PB would have just set this up correctly to begin with. Didn't realize it was my responsibility to commission the pool.

 

[mas985]

Are you talking about the eyeballs (exterior fitting) or the jet nozzles? Most venturi tees can only take up to 7/16". 3/4" are huge for nozzles. More like an eyeball.

 

[Fins]

Are you talking about the eyeballs (exterior fitting) or the jet nozzles? Most venturi tees can only take up to 7/16". 3/4" are huge for nozzles. More like an eyeball.

By orifice size on the directional nozzles, I am referring to the eyeballs.

The venturi tees currently have 7/16" jets installed in them (8) and is what I think is causing my low water pressure challenge.

The size of of the eyeball opening has a dramatic effect on the volume of air from the blower. The blower must have a seriously steep fan curve. A small change in static results in a huge change in volume. I was very surprised to see that with 3/8" eyeballs, I got no air and the blower promptly overheated. Drilled out to 7/16" and the air volume is about right although I did have to drill a 1/4" hole in the blower riser tube to keep the blower from overheating. These blowers should be offered with speed controllers for tuning. Seems like it should be a pretty simple and handy option.

Thanks for for the advice. I really appreciate it.

 

[mas985]

Ok, I think I understand what you are saying now. The 1/4" jet nozzles may help and you may not need the blower anymore. The higher exit velocity of the 1/4" might be enough to run without the blower but I can't be sure.

Just curious, when you run the spa jets now, what is the filter pressure at?

 

[Fins]

Installed the 1/4" jets in the venturi tees yesterday and it made a huge difference. For the first time since this pool was built, the jets are pulling air without the aid of the blower and we're almost getting enough agitation of the water where the blower is not always needed. The PB added two additional jets to the spa and used the same pump and piping as was originally designed for the 6 jet spa. I know he meant well but I'm pretty sure he doesn't understand the impact of that decision. Oh well. It's good enough at this point.

Still wish there was a way to vary the speed of the blower. Seems like a simple rheostat would be a simple and handy feature to dial in the amount of aeration.