Anyone using flow switch to control/manage peristaltic pump?

[lalittle]

Does anyone have any information on using a flow switch to help automate a peristaltic pump on an attached spa/pool? I want the peristaltic pump to operate whenever the the pool is circulating, but I do NOT want it to run when I switch the flow over to the spa. Even if I put the injection point down stream of the return valve (on the pool side of the flow), I won't want the peristaltic constantly injecting chlorine into the pipe when the spa is running. Simply hooking the injector pump to the main pump timer would require me to always remember to separately switch the peristaltic pump off when using the spa, and back on again when I'm finished so that it runs on the next pool pump cycle. Even though I would probably not forget to do this, I don't trust that others will remember, and I'd like to keep things more automated.

My thinking was that I could still put the peristaltic pump on the main timer, but that I could ALSO attach it to a flow switch on the pool side of the return flow. This way, the main pump would have to be on AND the flow would have to be on the pool side for the peristaltic to work.

The problem is that I don't know much about flow switches other than knowing that they are used for things like SWCGs and heaters. I found some on the web, but it would be helpful to get some direct feedback from others who have done this sort of thing.

I'm not sure about some of the specs, and I'm not clear about certain details, like if the flow switch needs to go downstream of the injection point (i.e. if the flow switch would be effected by the higher chlorine levels.) On my system, it would solve some hookup issues if I could put the switch AFTER the injection point, but intuition tells me that this might damage the switch over time.

Thanks,

Larry

 

[Bama Rambler]

Re: Anyone using flow switch to control/manage peristaltic p

If you get a stainless steel or plastic coated magnetic pickup switch you'll be fine to put it wherever you want.

 

[lalittle]

Re: Anyone using flow switch to control/manage peristaltic p

If you get a stainless steel or plastic coated magnetic pickup switch you'll be fine to put it wherever you want.

I'm rather overwhelmed by the number of different types of flow switches, and am finding it difficult to figure out which ones would work in my application. I'm finding that the specs on a lot of these switches don't cover all my questions. Some, for example, don't clearly state whether or not they work in higher concentrations of chlorine. I'm also not sure what pressure spec I'd need, what flow activation rate I'd want, or if it's a problem to use a low flow rate switch in a much higher flow rate pipe.

For example, in my setup, I have some capped connections where a booster pump (for a pressure side cleaner) was removed. It's simply a narrow line (1" I believe) that T's off the pool side return, and feeds to return jet in the pool (which of course is not currently active since the connections are capped off.) I'm planning on reconnecting it straight through in order to put a little flow to this extra return jet, and then using a "slot" eyeball jet to direct flow along the pool wall in order to induce circulation at that point. My goal is to get a rotational circulation going in order to get better skimming. I've already put these slotted jets on the other return jets, but this extra one will really help a dead spot.

My thinking is that since the connections are already accessible on the equipment deck (they're capped), it would be easy to install a flow switch here (i.e. no cutting into existing pipe needed.) My question, however, concerns the flow rate of this section of the line. I'll need to keep the flow rate very low in order to keep my other jets and poolskim working, but I have no idea how much actual flow it will end up being. Should I just get a switch designed for low flow rates (0.5 gpm, for example)? If I end up using substantially higher flow rates, will that be a problem for a switch designed for lower flow?

I checked Dwyer (as per your other post), but I still find myself asking a myriad of questions like this. Some of the Dwyer switches list "applications," but many don't, and of the paddle switches on their site, none were all plastic, which I "thought" was what I wanted for this. Dwyer did have a "shuttle" type flow switch that lists both "pools" and "chlorinators" as applications, but I'm still not clear if this means that it can take the much higher chlorine levels immediately downstream of the injection point. Also, this unit creates a 90 degree turn in the flow, but it seems like an "inline" switch might be more appropriate (although I'm not sure if thats really an issue for this situation.)

Thanks again for all the help here,

Larry

PS. On a side note, are there any issues with using the slotted eyeball jets on my returns in order to get rotational circulation? It adds some back pressure to the system, but it really helps to induce circulation, and the reduced flow from the other jets puts more force into the poolskim.

Also, would it be fine to use flexible PVC when adding the flow switch? The current connections are at some funny angles, so flexible PVC would make the installation easier.

 

[Bama Rambler]

Re: Anyone using flow switch to control/manage peristaltic p

The Dwyer V8 flow switch would be compatable.

If the piping is routed so that the vane sits in the flow, then the vane switches will work. You don't need to worry about the flow rate as very low flow will actuate the switch.

The slotted eyeballs will be fine to use.

 

[lalittle]

Re: Anyone using flow switch to control/manage peristaltic p

The Dwyer V8 flow switch would be compatable.

If the piping is routed so that the vane sits in the flow, then the vane switches will work. You don't need to worry about the flow rate as very low flow will actuate the switch.

Thanks again for the all the advice on this.

According to the specs on the Dwyer V8, it takes in the neighborhood of 10GPM to activate the switch. This changes depending on pipe size (and vane length), but it's close to this in the pipes sizes I'd be using. I'm pretty certain that this is well above the flow rate of the single return jet line that I was hoping to use (i.e. the one that already has capped, threaded ends available.) Once I limit the flow to this return (in order to keep flow to the other returns high enough) I don't think I'll be anywhere near 10gpm. I would think I'd need to be closer to the 1GPM range (or less) in order to be safe, and none of the Dwyer vane switches go below about 5GPM in a 1 inch pipe.

I'm still looking, so I'll report back on what I find.

Thanks,

Larry

 

[Bama Rambler]

Re: Anyone using flow switch to control/manage peristaltic p

With a trimable vane switch in a 1" pipe, all you have to do is trim the vane so that it barely misses the opposite pipe wall and it won't take nearly 10 gpm to set the switch. However if you think you have to have a switch that will sense at 1gpm then your best bet is a thermal dispersion model. They'll get down to .02 FPS which equals about ½ GPM in a 1" pipe.