pressure drop through flow switch

Boon

I'm putting the flow switch into my boiler piping. It's a 1" Taco IFS01. Neither the instruction sheet nor a Taco brochure show any pressure drop info. How is there no mentionable pressure drop with a wide paddle perpendicular to the flow? Once again, I think I'm missing something.

thanks

keyote

I think youre needing to think bernoulli venturi, the paddle might cause slight restriction and pressure drop but velocity increases and after the paddle pressure returns. why are you worried ? The more important concern with those things i've heard is them working at low flow, their adjustments, the angle used, their trimming properly or weakening from trimming, their not getting hung up on side or bottoming ou,t and worst is the paddles breaking off and wreaking havoc. some guys i know use a bigger tee and bushing.
I ordered my KHN should be here soon so im watching have you seen that using PP instead of pvs is better
https://www.taco-hvac.com/uploads/FileLibrary/100-8.2.pdf
https://www.taco-hvac.com/uploads/FileLibrary/102-023.pdf

Boon

Not worried. Curious.

Yeah. I'm having trouble getting polypro fittings and it seems no matter how I try to vent it I get stuck mixing plastic. This is definitely a topic of its own but I haven't given up to the point I'm ready to post about it.

SWEI

Read the fine print: all of the PP systems I have seen are listed as a system and do not allow connection to other piping materials. Centrotherm has a tremendous variety of options covering pretty much any situation we have encountered. What fittings are you having trouble finding?

We pipe the intakes using PVC, since there's no appreciable risk of chloride leaching there.

Boon

Yes, I'm planning PVC for the intake and I'm aware that I can't mix. I've accumulated a little of everything, unfortunately, chasing a solution.

What fittings are you having trouble finding?

I bought Duravent PolyPro stuff from Boston Heating and the appliance adapter apparently didn't come with its clamp; can't find the clamp only anywhere and couldn't get through to BHS for resolution, though they were responsive on another issue. I thought the appliance adapter (2PPS-ADL) came with the adapter [it does at other suppliers and in the PolyPro brochure] but apparently not at BHS. And I can't find the Duravent sidewall kit anywhere to terminate the PolyPro.

Duravent has an adapter for PolyPro to CPVC/PVC. I thought I might be able to use that to transition. The KHN manual says the first 7 equivalent feet must be CPVC or PolyPro, but the concentric kit is PVC,... made sense to me that I could run 7+ equivalent feet of PolyPro and then transition to PVC using their adapter and connect to the concentric kit. Something tells me that is crazy and I'm still pursuing an all-PolyPro solution.

Part of my problem is I'm not licensed and so I'm relying on any online suppliers I can find that have this stuff in stock, which are few. Places like Johnstone, RE Michel, etc won't sell to me. Even Ferguson, who says they'll sell to me, gives me attitude and wants me to go away.

BobC

I don't know if they have what you need but have you tried Watertown Plumbing, I used to get all manner of odd bits and pieces there when I ran a plant on Coolidge Ave.

If they don't have what you need odds are they know who will. They are willing to deal with anyone at the parts counter.

Bob

hot_rod

The tech sheet from the manufacturer should show the pressure drop. here is an example.

http://www.caleffi.com/sites/default/files/file/01052_15_na.pdf

Jamie Hall

And in any case -- the pressure drop will be small. Keep in mind that that paddle is pushed out of the way by the flow... it doesn't stay hanging down in there.

keyote

Boon i also saw a discussion on KHn here where a couple guys had the gas port casting crack so be careful.
What the deal with the flow switch are they protecting the boiler or pump because they seem to be way too insensitive to do much good about 4.5 gpm im almost never pumping that much

keyote

where is the flow switch mounted if needed? I got some 1- 1/4" male thread x 1" sweat copper adapters to go on the boilerS/R ports so i can put my webstone union/ valve/ reversible drains/ right on boiler first.is the flow switch a soviet republic of massachusettes thing or a KHN requirement

hot_rod

You need to be very careful when you use a flow switch in anything but a threaded pipe tee, or weld o let.

The paddle length will need to be calculated and adjusted, and in some cases the paddle will need to be trimmed narrower as it can rub inside a copper tube as the diameter and length of travel changes the clearances of the paddle.

Even a short, close nipple in a sweat tee and FIP adapter presents a challenge for flow switches, the paddle needs a full stroke to be able to activate and flex out of the flow path to keep that Cv as advertized.

The depth the switch screws into a assembled branch is critical, if the paddle bottoms out, you got nothing.

The paddles come marked for the tee they fit into, if you build your own tee and branch, the numbers may no longer be relevant.

I caution against a flowswitch at or near the suction side of a circ.

keyote

hot rod do i even need one? if it cant read below 4.5 gpm whats it helping with? a 0- 10 gpm digital output that could be plaugged int o the boiler control for informational purposes would be neat but theyre like thousands?

hot_rod

Why do you want a flow switch? the boiler has plenty of safeties, so that is not a good reason to add one. Does code dictate it?

Mainly they are used on low mass copper tube boilers in DHW applications. Immediate shutdown should a pump fail of flow drop below the boiler min. requirement.

same for chillers and other critical flow equipment that does not have adequate safety under the hood.

Know it is a wear item, and if I had a dollar for every one I have seen "jumped out" It is a misunderstood device for the average repairman.

keyote

I agree im worried it will disintegrate, i saw this thread of boons who has the same boiler Im getting and thought it might be required but couldn't figure out why. I have a feeling its a soviet republic of massachusetts proclamation. I think the boiler has all sorts of safetys for no/low flow

hot_rod

Agressive fluid and over-pumping can take a paddle out in 6 months time. I doubt, from what you have learned here that will happen.

You have operating temperature control, safety high limit, pressure switch, excessive ∆T shutdown, maybe a few others already on board.

Add it only if you are required to, that is why it has the optional wiring connection readily available.

keyote

well ill stop worrying about it i dont think NYS requires it, but if they do and someone forgot to attach the paddle who could say it didnt fall off hint hint boon

Boon

The KHN manual Pg 57 says, "A flow switch is used to guarantee flow through the boiler before allowing it to fire. The flow switch must be installed at the boiler outlet."

I felt the key phrase was "before allowing it to fire," which kinda comes before all of those other safety mechanisms that Bob mentioned. At least that is how I interpreted it.

keyote

thanks boon just finished piping mine still have to do vent and controls i left out the flow switch figure ill jump any wires to fool it if need be lol. just seemed like a lot goes wrong with them and ny doesnt require. hope it was right call. did get the supply sensor in and actually i ordered an second tridicator gauge that I put on return
Are you up and running yet

Boon

Mostly. My boiler and indirect are running but I still have radiators to connect.