VFD tied directly to a Pressure Transducer

[LLSolutions]

Heres the situation; customer has what I would call a rather elaborate residential pool. 5 valves that control various water features; slide, deck jets, stair jets and such, these valves are all controlled by a hayward brand pool controller. The issue is getting the pressure to remain at correct levels. The Hayward controller only offers high and low speed, via a 2 speed pump or a matching vfd - their drive is only capable of offering 2 speeds. My idea was to put a pressure transducer in the return manifold that feeds all the jets and tie that directly to the 4-20ma input on a 3rd party VFD. The drive would still be enabled by the hayward controllers time of day schedule but at least it will self regulate when valve are opened and closed by the Hayward's wireless remote. Anyone ever attempted this before? Its seems similar to what high rises that don't use water towers do? Any successes or failures?

 

[Cow]

It sounds like it should work great.

 

[ptonsparky]

We do basically the same thing for wells. Sure should work with a pool. Bet the motors last longer too.

 

[mcclary's electrical]

Heres the situation; customer has what I would call a rather elaborate residential pool. 5 valves that control various water features; slide, deck jets, stair jets and such, these valves are all controlled by a hayward brand pool controller. The issue is getting the pressure to remain at correct levels. The Hayward controller only offers high and low speed, via a 2 speed pump or a matching vfd - their drive is only capable of offering 2 speeds. My idea was to put a pressure transducer in the return manifold that feeds all the jets and tie that directly to the 4-20ma input on a 3rd party VFD. The drive would still be enabled by the hayward controllers time of day schedule but at least it will self regulate when valve are opened and closed by the Hayward's wireless remote. Anyone ever attempted this before? Its seems similar to what high rises that don't use water towers do? Any successes or failures?

Under normal working conditions, it sounds like it would work fine, but a clogging filter is going to look the same to the transducer as someone turning valves off. It is not going to stay calibrated.

 

[LLSolutions]

Under normal working conditions, it sounds like it would work fine, but a clogging filter is going to look the same to the transducer as someone turning valves off. It is not going to stay calibrated.

Yea that was a thought, I had thought about using a wet differential pressure switch around the filter and just tying that through the enable point. I'm becoming less and less impressed with this Hayward Goldline system, they tout it as total automation but you're locked into their settings. If someone could just make a waterproof programable remote with a customizable display I'd rather write my own program on a PLC.

 

[Jraef]

Make sure you use a VFD that has a PID (or at least PI) controller built-in, otherwise it will just hunt all day long.

 

[dbuckley]

Make sure you use a VFD that has a PID (or at least PI) controller built-in, otherwise it will just hunt all day long.

Yeah, but the fountains will look great

Edited to add: you could probably sell the dancing fountains as an extra cost feature!

 

[LLSolutions]

Any one make an external PID module, Stand alone type, not like BMS or anything?

 

[don_resqcapt19]

There are a lot of stand alone process controllers that could be used for this application. You could look at omega.com, redlion.net and a number of other places.

 

[Jraef]

Some of the "smart relays" like the Siemens LOGO do PID control, plus they have other I/O to use too and they will do the timer function for you. One of those with an analog input will cost you under $150.00

But a lot of VFDs have PID built in now. Do you have a favorite brand? If not, I think the ABB ACS Series drives have the easiest PID control loop setup on the market.

 

[LLSolutions]

I was looking at Teco Drives and controllers from westinghouse, anyone have any good/bad experience?

 

[jcole]

What if you used a flow tranducer instead of a pressure transducer? This will help with filter issue.

Remember pumps dont produce pressure they produce flow. Resistance to flow produces pressure. Your controlling flow with the drive not resistance to flow.

You might get better control this way. Just a suggestion.

 

[ptonsparky]

Some pumps can produce very high pressures. A flow switch would need to be used in conjunction with some sort of pressure limiting device be it a simple pressure switch or pressure release valve.

 

[iwire]

What if you used a flow tranducer instead of a pressure transducer? This will help with filter issue.

Remember pumps dont produce pressure they produce flow. Resistance to flow produces pressure. Your controlling flow with the drive not resistance to flow.

You might get better control this way. Just a suggestion.

I don't think flow control is the way to go, where do you envision placing the flow transducer in relation to the pump or zones?

I would stick with pressure.

 

[Jraef]

If you use one of the higher level Teco drives, it would have PID built-in. But the cheapest ones like the FM50 and FM100 will not. I suggest the EV or higher, the N3 drive also has a "Sleep Function" for the PID loop which is nice to have on an application like this. It essentially puts the drive in standby mode if everything it OK for a long time, saves from cycling on and off a lot. Teco are decent drives, decent pricing.

 

[LLSolutions]

Thanks guys, I'm gonna go with the fm50 and just buy the separate controller, its about the same price as buying the EV but leaves room to expand the capability of the controls. I'll try and get some pictures up when i'm all done. 2-3 years max!