Primary Loop Pushing Past Flow Checks

Tony_23

Those 1st three are grabbing all the FLOW, not all the HEAT. That's why the return is so hot. You can only get just so much flow thru a given size pipe.

The IFC doesn't restrict as much as you think. Try a 3 speed IFC. Those 007's could be pulling 10-15 gpm EACH. You only need 5-7 gpm each MAX.

Saggs

Got a large hot water system heating a small grocery store. Front half of store is heated w/ Modines and baseboard.Heating pipes are 1 1/2" black running 50ft with a connected loop or return running back to the boiler. All Modines are on the 1st floor, piping in basement. Each has it's own circ w/ IFC on the supply piping w/ the return running into the return piping adjacent to the supply line. I put a 007 on the primary loop to send hot water thru the loop anytime one unit calls. Problem is, anytime somthing calls for heat and activates the "primary" circ, it causes ghosting up thru all the Modine loops and soon everything is heating. I thought connecting the end of the black iron runs and making it a loop would solve this? Do I need to have all takeoffs done a "closely spaced tees"? and both on the same piece of piping? Any Thoughts? Maybe a smaller primary pump?

hot_rod

grab a book

on primary secondary piping. it doesn't sound like that is what you built? If you just connected the ends of a S&R piping WITHOUT the use of closely spaced tees, you don't have a P/S piping.

Dan has a stack of books, available here, to show how to properly build a P/s loop.

Modern Hydronics is another great book.

Search the archives at PMmag.com Siggy has dozens of articles available on P/S piping.

It needs to be designed and built correctly, to work correctly.

hot rod

Saggs

Hot Rod, I've piped a bunch of condensing gas units in primary/secondary and yes, did use the closley spaced tees for that application. We're trying to make an existing situation work and kinda wanted to avoid repiping all the returns. PITA due to all being in black iron. Do you see the closely spaced tees as the only option here? I do have a couple of Dan's books but was of course looking for a "quick, easy answer"...

Tony_23

No easy way

Even checks on the returns may not do it.
If you want P/S you must have closely-spaced tees.

Since you have a circ on each run-out, and only a 007 on the primary loop, why not go back to a S&R setup ? Seperate the supply and return, can the primary 007, and let each zone circ do it's thing. I bet it'd work

hot_rod

I agree with Tony

why didn't it work in the original layout? Maybe the long runs were un-insulated.

If you have flow, and temperature you move heat.

Saggs

We changed the original layout of S&R because at the very end of the 60ft "manifold" is a run of 3/4" BB and a 30K AHU w/ a hot water coil in it. These 2 smaller runs never got the flow or heat thru them to operate properly. Originally there was a 007 primary circ but it still wanted to push thru all the zones and flood them with heat when not needed. That was the reason we looped the S&R together, was to give the flow a place to go when all zones wern't calling. Once we looped the S&R together and added the 007 pusher it worked great. except the ghosting issue. I do appreciate the comments you've given me here.

hot_rod

I remember your first post

a few weeks back. that piping arrangement is not un-common or un-workable. Small zones at the end of 60' of run are possible.

There seems to be two issues. unwanted fllow through heaters and lack of flow at the end?

Check valves, or even zone valves should provide of flow check ability to stop the overheating. And that distance of piping is not beyond the capacity of a typical small wet rotor circ.

We do radiant systems with several thousands of feet of tube and they flow and heat properly. Some are zoned with valves, some with zone cics. it very possible to get 100% shut off of flow to emitters.

Something else must be going on with this job. Any way to get another set of eyes on it? Maybe someone has pipe a cross over bridge between the S&R that is prevent flow to the end of the loop? Any balance valves on the system to keep all the various flow requirements in order?

hr

Saggs

HR, I don't believe there are any "crossover" pipes other than the large supply and return pipes that go up to the modines. There are no balance valves anywhere in the system other than the BV webstone flanges and a 1 1/2" BV on the return line back to the boiler. Installing typical flow checks may be difficult as most of the piping is vertical thru the floor and black iron. I know I could put in zone valves but that is pricey. As I stated earlier, the main reson for the piping "upgrades" was to get better flow to the baseboard and the hot water coil at the end of the run. It acted as if the big modines were stealing the heat or flow from the smaller zones at the end of the piping. This was also b4 the 007 pusher pump was installed.

Tony_23

Sizes

What BTU rating on the Modines? What head loss thru them ? Maybe the circs for them are too large. In lieu of sizing them perfectly, try some 3 speed circs and start on LOW. I see 3 speed circs unnecessarily on high all the time, just as much as too large single speeds. You could be grabbing all 22-25 gpm pipe capacity before it ever gets to the end.

jp_2

oo7 placement

if you move the 007 in the point of its load, won't the headloss be confined to the load and not the whole system. that is, I'm assuming you have the 007 by those other branch circuits.

i'm assuming the 'cold' circuits had too much headloss thus no heat.

Saggs

There are 3 modines in the supply line b4 the other 2 smaller zones . They are about 75k, 75k, and 50k, btu. I'm running 007 w/ IFC's on all the zones. The IFC has a fair amount of restriction to them as is. Do you think I'm pulling all the heat out b4 it can get to the end of the run? After I looped the end of the S&R togther and added to 007 pusher pump, even with all modines and BB running, the return water was still rippin' hot coming back to the boiler, so I'm assuming I hadn't exhausted all the heat by then. Placement of the 007 circ on the supply line is about 5ft from boiler and about 35ft from next closest takeoff(modine) on the supply run. Maybe I could draw up somthing and try to get it posted.

EMC PLUMBING

007 ifc

i have had many of the same problems using the 007 ifc pump the flow control built in to the pump does not seem to work,i have stop using the ifc pumps and use a regular seperate flow control and have never had a problem since, i went throught this a few times,started using a seperate flow control or even the b&G iso-flow check flanges and they worked good to no flow where it wasnt wanted. Thats just my own experiance with the 007 ifc.I can bet if you use seperate flow control after the pumps it will work just fine. hope everything works out,those ifc pumps have driven me crazy for years,not any more.
good luck.
Eddie

E R

reverse flow with GV4 on a monoflo system

Installed Weil McClain GV-4 on an existing monoflo system.
Seems to be circulating in reverse. Return piping gets hot immediately and baseboard also gets hot in reverse order. Piping is correct and pump is in correct direction.System is 1-1/4" main supply with 3/4" and 1/2" risers to Cast Iron baseboard. Help!

Saggs

Thx again for the input. Does anyone know how many gpm the 3 spds put out on low? Eddie, will those B&G iso-flanges bolt right in where a webstone flange is now? If they are a swap out deal that would be an easy way to go.

Unknown

EDR

You may want to start another thread for your question as it may get missed in here.

Couderay

New thread

Start a new thread, much better responses.

jp_2

drawing

yep, i think a drawing would be useful here.

EMC PLUMBING

yeah take off the olds ones and you can swap out the flanges they come in sweat or ips

dave_21

can you draw a diagram or explain how you looped the primary together and what size you looped together.if this was s and r doesn`t the main reduce in size as units are taken off,so just wondering where you joined it togrther.