Is the circulator pump too powerful?

gardenman · May 13

Hi,

In a three story house with a basement, I have the following setup with a Weil-Mclain Series 4 EG/PEG-75 Boiler that has 5 zones with the following circulator pumps:

Zone 1 - First Floor Loop (2500 sq ft) - Bell & Gossett 1/12 H.P. 1725 RPM 115V 1.75 AMPS

Zone 2 - Second Floor Loop (1000 sq ft) - Taco Multi Speed 0015-MSF3-IFC

Zone 3 - Third Floor Loop (1000 sq ft)- Taco Multi Speed 0015-MSF3-IFC

Zone 4 - Sun Room Loop on the First Floor (500 sq ft on the same plane as Zone 1 but different loops and pipes) - Bell & Gossett 1/12 H.P. 1725 RPM 115V 1.75 AMPS

Zone 5 - Basement Loop (1000 sq ft) - Bell & Gossett NRF-22

The weird thing is that when Zone 4 calls for heat, it starts to also heat up the radiators on the Third Floor - Zone 3 but not any other zone. When Zone 3 calls for heat it does NOT heat up any other zone. When any of the other zones call for heat they do not heat up any other zone.

Noting that all of the water in each zone gets mixed in the tank, is it possible that Zone 4 pump is too strong and is able to overcome the whatever path of resistance there is in the third floor riser?

Any solutions? Check valve perhaps? If there is a good location.

Appreciate the help.

Best,

delcrossv · May 13

I suspect that a Flo Control (check) valve would solve this. I Imagine Zones 3 and 4 are next to each other?

Really, each zone should have it's own flow control valve.

EdTheHeaterMan · May 13

Has this always happened? …or is this something new?

There may be something called Ghost Flow happening as a result of the piping configuration of Zone 4 and Zone 3 with regards to gravith flow within the pipe. I might take a guess that Zone 3 has larger pipes than the other zones that show no problem. The larger pipe is more susceptible to Ghost Flow. Here is a description of Ghost Flow from an old book on Zoning Made Easy. Look on page 11. One Zone One Circulator

Screenshot 2025-05-13 at 10.31.18 AM.png

If it is not Ghost Flow, then we need some of the Photos of the boiler room to include the pump locations in reference to the boiler and the different Tee fitting locations for each zone takeoff. If this is a new problem then perhaps an existing Flow Control Valve is stuck. Have you had any boiler work done just before the problem presented? Like a replacement pump installed or a new zone added?

If this is a "always been there" problem, then there may be a piping design flaw.

Ironman · May 13

The Taco pump for the 3rd floor has an internal flow check which is stuck open or has some debris in it. It’s in (or should be) the discharge side of the pump. Fix that and your problem will be resolved.

Alan (California Radiant) Forbes · May 13

Without knowing more information, it looks like the pumps for zones 2,3 and 5 are too large and that you need some check valves to prevent ghost flow.

HydronicMike · May 13

Agree on the checking the check valves. But the only way to confirm circulator sizing is to do the math.

hot_rod · May 13

without proper check protection you can also get reverse flow through an un-powered circulator

EdTheHeaterMan · May 14

So … any Photos "Coming Soon to a Theater Near You" @gardenman?

gardenman · May 14

https://forum.heatinghelp.com/discussion/comment/1855534#Comment_1855534

Yes. The Ghost Flow concept described by folks makes sense.

Here's the setup at the header and on the returns. It's all 3/4 " pipe coming off the header and the return is all 3/4" except for Zone 1 which has a legacy 1" pipe feeding into the B&G pump. Just as a side, each zone has the radiators connected in series. Zone 1 which covers the biggest area has this also but the space is pretty wide open so it spreads out pretty evenly.

Thanks to everyone for taking the time to look and think about this. I do think the check valve either being stuck open or needing to be installed on Zone 3 at the very least will help this.

Any other thoughts please do let me know.

hot_rod · May 14

you can get an idea of ghost flow by touching the pipe a foot or so before those flo checks. If that zone has been off for some time, the pipes should not be warm.

Yes, all the zones need check or flo checks

Your whole system could probable operate fine with one pump and check valves, if you ever do a boiler upgrade or replacement

It looks like 7 circs in the second pic?

gardenman · May 15

https://forum.heatinghelp.com/discussion/comment/1855581#Comment_1855581

Thanks!

No, it's 5 circulator pumps. The red B&G's are the same pumps just from the other side of the mechanical room.

Agree on the check valves.

It's on old house (1930's) but it has 3 stories plus a basement and a sun room on a slab so there is a lot of variability. The initial thought was to use zone valves but this seemed a little more straightforward and mitigated risk if the single circulator pump failed. It was definitely more $ but seemed easier to manage.

PC7060 · May 15

wow, 5 B&G! I’d upgrade to ECM pumps and cut your power use by 90%. Gives you better control as well

Alan (California Radiant) Forbes · May 15

@gardenman has Flo-Checks on all his supplies. Check that the knurled knobs are fully unscrewed which should allow the weight inside the device to cover the valve seat, preventing ghost flow.

Failing that, you could be getting ghost flow via the returns, through the pumps. Although not common, laminar flow can circulate water through one pipe. Hot water up the middle, cooler water down the sides. Feel the pipes.