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# Confusing setup

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Member Posts: 45
Hi everyone,

I’m trying to figure out how we could optimize a poorly performing hydronic system at one of the buildings I just started to take care of.

Ive got a hot water Weil McLain LGB 6-23 with a 3 inch supply that branches off into two 1.5 inch circuits. Each circuit serves one half of the building. A 2400-50 pump circulates both circuits.

Now here comes my confusion.

Isn’t this pump undersized for a 3 inch supply or is the 3 inch way oversized for the heating demand?

The pump is dead and I can’t figure out whether or not I should replace the pump, or put two smaller pumps on each circuits supply.

«1

• Member Posts: 1,046
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The path to figuring out which pump is the correct pump starts with a load calculation. After that you factor in your piping and pressure drop from everything between the pump and including the emitter. That will give you a flowrate and head loss number. This will be how you size the pump.

Or you could start more simply. Prior to the pump failing, were the spaces heated appropriately?
• Member Posts: 23,282
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Pump size is related to pipe size only in that a bigger pipe means less resistance to flow.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
• Member Posts: 9,637
edited October 2022
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Note that the area of 2 x 1.5" pipes is far less than the area of a 1 x 3" pipe. That 3" pipe could likely be a 2" pipe.

You know the circulator doesn't need to be any larger than what is needed to move the output of the boiler and likely quite a bit less as the boiler is probably oversized. like @GGross said, calculating your load is the textbook way to figure it out.
• Member Posts: 4,002
edited October 2022
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That looks like a fairly new pump. How do you know it's dead?

8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

Two btu per sq ft for degree difference for a slab
• Member Posts: 45
edited October 2022
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GGross said:
The path to figuring out which pump is the correct pump starts with a load calculation. After that you factor in your piping and pressure drop from everything between the pump and including the emitter. That will give you a flowrate and head loss number. This will be how you size the pump. Or you could start more simply. Prior to the pump failing, were the spaces heated appropriately?
Unfortunately one of the cases where some on the top floor were opening their windows and some on the bottom floor were freezing. Seriously unbalanced distribution of heat from what I gather after speaking to some of the tenants.

Air is also a problem. The super told me that he has to bleed VERY often each heating season on one side of the building (60-70 times a year).

That looks like a fairly new pump. How do you know it's dead? Your -50 pump has the highest head rating in the 2400 series. Does the building have radiators? Fan Coils? Radiant?
I’ve been told that the pump was installed with the boiler 2-3 years ago. But it was supposedly running every minute of every day throughout the year. Even without calls for heat. It’s now making the loudest possible noise that you can hear on the top floor. Similar grinding noise to that of a non oiled up Bell and Gosset pump.

• Member Posts: 9,637
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It is pumping out of the air scoop so it can pull air in that automatic air vent especially if there are zone valves in the system. If there are zone valves some strategy is needed to either have the circulator adapt or have a pressure bypass so it doesn't deadhead the circulator when all zone valves are off. It likely needs the valves on one of the 2 loops partially closed to balance the system. I have serious doubts about if anyone did any math on anything that is happening in the boiler room.
• Member Posts: 45
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mattmia2 said:
It is pumping out of the air scoop so it can pull air in that automatic air vent especially if there are zone valves in the system. If there are zone valves some strategy is needed to either have the circulator adapt or have a pressure bypass so it doesn't deadhead the circulator when all zone valves are off. It likely needs the valves on one of the 2 loops partially closed to balance the system. I have serious doubts about if anyone did any math on anything that is happening in the boiler room.
This is what I told the owner but he didn’t seem to understand why the zone valves are a problem.

I was thinking of plugging the air scoop and installing two spirotherms one on each of the 1.5in supplies, after the circulator.
• Member Posts: 7,834
edited October 2022
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I was thinking of plugging the air scoop and installing two spirotherms one on each of the 1.5in supplies, after the circulator.
You want the Spiro-vent to be located on the inlet side of the pump. That has the lowest pressure in the entire system. That will also be the location where the maximum amount of dissolved air will become microbubbles. The Spirotherm vent is designed to make those microbubbles crash into each other to become larger, more buoyant bubbles so they float to the top of the vent.

The key is to have enough water pressure on the system so the inlet does not drop below the point at witch the pump will cause the hot water to flash into steam and cause cavitation. This is easily done by pumping away from the point of no pressure change (PONPC). That is why you pump away from the expansion tank. That is one of the reasons that many attach the expansion tank to the bottom port of the Spirotherm vent. In your case I might select the bottom of the old air scoop, because it is common to both circulator pumps.

Properly designed system will actually remove air from those far away zones using the sound laws of physics like:
Boyle's law and Henry's law on the properties of air diluted in water. Currently the system must be set up to add air by design. Some designed that so thaw the laws of physics work against you system.

Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
• Member Posts: 973
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In regards to the circulator, what do you mean by "dead". what model # is the circulator?

• Member Posts: 45
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I was thinking of plugging the air scoop and installing two spirotherms one on each of the 1.5in supplies, after the circulator.
You want the Spiro-vent to be located on the inlet side of the pump. That has the lowest pressure in the entire system. That will also be the location where the maximum amount of dissolved air will become microbubbles. The Spirotherm vent is designed to make those microbubbles crash into each other to become larger, more buoyant bubbles so they float to the top of the vent.

The key is to have enough water pressure on the system so the inlet does not drop below the point at witch the pump will cause the hot water to flash into steam and cause cavitation. This is easily done by pumping away from the point of no pressure change (PONPC). That is why you pump away from the expansion tank. That is one of the reasons that many attach the expansion tank to the bottom port of the Spirotherm vent. In your case I might select the bottom of the old air scoop, because it is common to both circulator pumps.

Properly designed system will actually remove air from those far away zones using the sound laws of physics like:
Boyle's law and Henry's law on the properties of air diluted in water. Currently the system must be set up to add air by design. Some designed that so thaw the laws of physics work against you system.

this is awesome. going to do it tomorrow. I'll take pics of the inside of that pump when i change it out. I'm sure it'll be a real treat
• Member Posts: 45
edited October 2022
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pedmec said:

In regards to the circulator, what do you mean by "dead". what model # is the circulator?

Hey its ZXM101050A. Also when i say dead, i mean that its making the most godawful grinding noise and a few apartments didnt get good heat over the weekend when we had it running (even after bleeding for hours)
• Member Posts: 5,834
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What type of air control, compression or diaphragm tank? If compression tank, then remove all air eliminators and plug the ports. It still might need another round or two of bleeding the baseboards.
And I'm not certain on this, but the smaller Taco circulators can mount motor up only if boiler pressure kept at 20 psi or above. Not sure of the specs on that circulator.
The 1.5 in. pipes aren't perimeter loops and each zone with zone valve a branch circuit? The manifolds end at some point?
If perimeter loops, then constant circulation shouldn't be an issue. If the circulator is dead heading, then some relays and control wiring are in order. Does that circulator need a motor starter?

• Member Posts: 22,131
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What type and where is the expansion tank connected? A diaphragm type tank connected to the bottom of that air purgers creates the PONPC and you should not see a negative pressure there,,air would not enter

The best air removal us at the hottest point in the piping, at the boiler, an auto vent up high would be next best, the lowest pressure.

With unknown piping the best pump would be an ECM that you can adjust the gpm and head, Grundfos Magna, etc, it would modulate based on zone valves opening and closing and never over pump the system

with ferrous metals in the system I’d install a combination air/dirt/ and magnetic separator where that scoop purger is A DiscalDirtMag for example
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream
• Member Posts: 45
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HVACNUT said:

What type of air control, compression or diaphragm tank? If compression tank, then remove all air eliminators and plug the ports. It still might need another round or two of bleeding the baseboards.
And I'm not certain on this, but the smaller Taco circulators can mount motor up only if boiler pressure kept at 20 psi or above. Not sure of the specs on that circulator.
The 1.5 in. pipes aren't perimeter loops and each zone with zone valve a branch circuit? The manifolds end at some point?
If perimeter loops, then constant circulation shouldn't be an issue. If the circulator is dead heading, then some relays and control wiring are in order. Does that circulator need a motor starter?

Hey its a diaphragm extrol tank.

I was thinking the same when i saw the taco mounted up like that but i wasnt 100% positive.

Yes those are perimeter loops and no it doesnt need a motor starter.

The super told me that the zone valves are old and that they are constantly getting stuck closed. He is constantly having to open them so I think i want to cut the power to all of them and rely on the Heat Timer I purchased to provide comfortable to all apartments like I have at my other buildings. Believe it or not they work great and the tenants are all comfortable. I dont see the need in having my super constantly servicing them if we achieve balanced heat distribution and solve the air problem.
• Member Posts: 7,834
edited October 2022
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BMurrins said:

The super told me that the zone valves are old and that they are constantly getting stuck closed.

This is another reason for adding the air/dirt separator with magnet. It will reduce the amount of crap that is being pumped around that system and maybe collect some of it to keep it away from other mechanical parts like the pumps. That old pump location might be the best place for it if it will fit there.

Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
• Member Posts: 9,637
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Perhaps the air is just air that isn't getting removed effectively by the old style air scoop. The perimeter loop isn't going to purge the emitters very well, if there are emitters that weren't bled properly that air will keep moving around the system.
• Member Posts: 22,131
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And that high head circulator could be forcing open the zone valves. If you have high cv zone valves, some brands only close off 8 psi delta P

Doubtful, but if a high head circ is needed on that building
always select a low Cv zone valve. A 2 Cv zone valve Would have a 50 psi shut off
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream
• Member Posts: 9,637
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I'm still trying to decide if there is a way that circulator could cause enough delta p to pull air in the automatic vent if it is sufficiently misapplied or if will just increase velocity.

You can see the expansion tank if you look closely.
• Member Posts: 22,131
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mattmia2 said:
I'm still trying to decide if there is a way that circulator could cause enough delta p to pull air in the automatic vent if it is sufficiently misapplied or if will just increase velocity. You can see the expansion tank if you look closely.
If the PONPC is at or near that purger and the  and air vent I doubt you would see negative  pressure there. Assuming the system is properly pressurized? With low static pressure, other parts of the system could go sub atmospheric. That is where an auto vent out in the system piping could allow air ingress
If you could see or guesstimate the piping, you could predict where that could occur
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream
• Member Posts: 45
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Hey guys quick update. I did some research and it turns out that the pump is NOT a 2400 series pump. It’s a 122 1/4hp pump.

sorry for the confusion there
• Member Posts: 4,002
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BMurrins said:

Hey guys quick update. I did some research and it turns out that the pump is NOT a 2400 series pump. It’s a 122 1/4hp pump.

sorry for the confusion there

Are you sure? The Taco 122 is a 3-piece pump and doesn't look anything like that and you can't mount them vertically.

I wouldn't be surprised if you found nothing when you take that pump apart. Cavitation and air pockets can make a lot of noise.
8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

Two btu per sq ft for degree difference for a slab
• Member Posts: 234
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@bmurrins I believe you have our 2400 Series pump based on the ZXM number you supplied. You either have a -50 or -70. -50 flange to flange is 6 3/8" and the -70 is 8 1/2". The actual Taco part number can be found on the capacitor cover shown in the attachment.
• Member Posts: 973
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sounds to me like you cavitating the circulator. that air scoop has no chance of working and is probably working against you as its creating to much pressure drop at the suction side of the circulator. in line circulators require a straight piece of pipe before entering the suction side of the circulator. air scoops require a straight length of pipe too to allow for air to separate and float to the top as it enters the air scoop.
• Member Posts: 45
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Sorry everyone for getting the pumps confused! You’re right it’s a 2400! Got the model numbers mixed up while doing some google searches.

pedmec said:
sounds to me like you cavitating the circulator. that air scoop has no chance of working and is probably working against you as its creating to much pressure drop at the suction side of the circulator. in line circulators require a straight piece of pipe before entering the suction side of the circulator. air scoops require a straight length of pipe too to allow for air to separate and float to the top as it enters the air scoop.
Any ideas to efficiently resolve without destroying the owners budget?
• Member Posts: 4,002
edited October 2022
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Let’s try to figure out a system curve which will tell you the proper pump to use. Can you put some information together?

- Total feet of BB (baseboard).

- Manufacturer of the BB or a picture with the cover removed to show the heating element.
- A schematic of the piping to and from the boiler that shows length and size of piping.
- Show zone valves and any other pumps. Also, make and model numbers.
8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

Two btu per sq ft for degree difference for a slab
• Member Posts: 1,946
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If that circulator has not used up all of its nine lives yet? Turn it on its side so the motor is horizontal with the wiring box up and not in the vertical position it's in now.
( I'm not positive but I believe that the Taco company recommends a horizontal installation.}

Another thing you can do is install two of this type of Spirovent air separators (VDR-M series, See picture) on each of the two pictured copper lines. This Spirovent will eliminate all the air from your system as well as help remove any ferrous type material that may be circulating in the system.
Do that and then plug or cap the ports on the top of the green air scoop. Run a line from the bottom of the air scoop to a properly sized expansion tank.

If the circulator is truly dead then repair or replace it and install it horizontally with the wiring box in the up position.

Doing this should help to optimize this system quite nicely.
• Member Posts: 45
edited October 2022
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Intplm. said:

If that circulator has not used up all of its nine lives yet? Turn it on its side so the motor is horizontal with the wiring box up and not in the vertical position it's in now.
( I'm not positive but I believe that the Taco company recommends a horizontal installation.}

Another thing you can do is install two of this type of Spirovent air separators (VDR-M series, See picture) on each of the two pictured copper lines. This Spirovent will eliminate all the air from your system as well as help remove any ferrous type material that may be circulating in the system.
Do that and then plug or cap the ports on the top of the green air scoop. Run a line from the bottom of the air scoop to a properly sized expansion tank.

If the circulator is truly dead then repair or replace it and install it horizontally with the wiring box in the up position.

Doing this should help to optimize this system quite nicely.

-------

I wanted to install Spirovents but figured that the purpose would be defeated putting these AFTER the pump.

I also wanted to do away with the air scoop but with that humungous 3 inch pipe, my air elimination options are limited being that I'd be WAY over budget with a 3 inch spirovent Sr.

I wish that pipe was two inches but I like to dream haha
• Member Posts: 45
edited October 2022
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Let’s try to figure out a system curve which will tell you the proper pump to use. Can you put some information together?

- Total feet of BB (baseboard).

- Manufacturer of the BB or a picture with the cover removed to show the heating element.
- A schematic of the piping to and from the boiler that shows length and size of piping.
- Show zone valves and any other pumps. Also, make and model numbers.
I dont have a picture of the radiators but theyre standard 3/4 copper pipe baseboards with aluminum fins.
I did the math this morning and I figure around 350-400k btus. Rounding up, around 25ft of head. At 20 degree rise, 40-45 gpm.
• Member Posts: 9,637
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You could reduce it to 2" and use a 2" microbubble air separator. That 3" is much larger than it needs to be for the flow that can flow thought 2 x 1.5" pipes. You could also use 2 smaller circulators on the 1.5" and put the separators before the circulators. I would recommend figuring out what circulator you really need for this system however.
• Member Posts: 45
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mattmia2 said:

You could reduce it to 2" and use a 2" microbubble air separator. That 3" is much larger than it needs to be for the flow that can flow thought 2 x 1.5" pipes. You could also use 2 smaller circulators on the 1.5" and put the separators before the circulators. I would recommend figuring out what circulator you really need for this system however.

I like the idea of changing it to two inches. Itd really give me more options with air elimination.
I've also had the idea of putting two smaller pumps on each supply but if I change to two inches, I'd put only one pump after the spirotherm
• Member Posts: 7,834
edited October 2022
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I believe this is what you are thinking of doing. The existing pump may still be good and you can get 2" flanges that will fit that pump.
If you do the math and find that pump is too large, then you can get a proper size pump.

Zone valves closing will cause a problem no matter what pump you select, then you need to add a differential bypass valve in order to have the system operate properly with closed valves.
Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
• Member Posts: 973
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Can you double check the complete model # of the circulator. It will matter as there are different heads and gpm to each circulator in the 2400 series of circulators. Looks at least a minimum 2400-65 or 2400-70 (switches from a 2-bolt flange to a 4 bolt flange @ the 2400-65) which is really big as far as flow rate would be concerned. unless they mongrolled the circulator and just switched out the motor with impeller. all the specs from taco show 2400-50 as 2 bolt pattern. i also might have missed an older spec.

• Member Posts: 45
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pedmec said:
Can you double check the complete model # of the circulator. It will matter as there are different heads and gpm to each circulator in the 2400 series of circulators. Looks at least a minimum 2400-65 or 2400-70 (switches from a 2-bolt flange to a 4 bolt flange @ the 2400-65) which is really big as far as flow rate would be concerned. unless they mongrolled the circulator and just switched out the motor with impeller. all the specs from taco show 2400-50 as 2 bolt pattern. i also might have missed an older spec.
Sure I’ll head over there tomorrow and double check.

I’d also like you guys to know that this install wasn’t done by an HVAC contractor. PSEG (New Jersey Gas/electric company) did the install when the old owners converted from oil. No math was done by these guys and supposedly told the super “we just replaced what was here”. PSEG is partnered with Weil McLain so that explains the excessively large boiler. The old owners took no interest in the project and signed off on something they knew nothing about.

It took them over a year to close out their permits they failed inspection 6-7 times.
• Member Posts: 45
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I believe this is what you are thinking of doing. The existing pump may still be good and you can get 2" flanges that will fit that pump. If you do the math and find that pump is too large, then you can get a proper size pump. Zone valves closing will cause a problem no matter what pump you select, then you need to add a differential bypass valve in order to have the system operate properly with closed valves.
Thank you for taking the time to make this! This is what I wanted to do sans the bypass valve but I’ll be sure to install it.
• Member Posts: 7,834
edited October 2022
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The DBV is like a relief valve. If all the zones are open then the DBV is closed. If most of the zone valves are closed then the DBV will be mostly open. If this circulator pump is designed to be running 24/7 then when all the zone valves are closed in the summer, the DBV will by-pass 100% of the water. Most of the valves are designed on a 90° valve body. It took me a while to find that one and it is from Europe. You may need to find a different piping configuration to use what is available locally.

@hot_rod will know if Caleffi has a 1-1/2" or a 2" version you can special order

Or he will have an alternative that is cost efficient
Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
• Member Posts: 4,002
edited October 2022
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Without know the specifics, I'm going to use a rule of thumb (WAG) that Dan taught us to figure the pressure drop, i.e. 6 feet of head per 100 feet of pipe.

Let's say the supply is 100 feet and the return is 100 feet. That means 12 ft. of head. @BMurrins tell us that flow will be 40-45 gpm. That gives us all we need to size the pump.

Pump curves 8 and 9 will do the job and both of them are nice and flat and won't cause as much trouble as the one you have. If you decide on two pumps, one on each of the 1½" lines, you could go with less expensive wet rotor pumps like a Grundfos 26-99. Ideally, you could look into ΔP pumps that vary flow as a function of demand, saving electricity. Lots of options.

Caveat: As I said, the head calculation is a rule of thumb and not necessarily reliable. To dial it in, you'll need some hard numbers on lengths of pipe and pipe sizes.

8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

Two btu per sq ft for degree difference for a slab
• Member Posts: 22,131
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The expansion tank connection needs to be before the circulators, but no reason why the purger could not be after the circ

The 1-1/4 Caleffi 519 bypass can handle 45 gpm. Here is the info
https://s3.amazonaws.com/s3.supplyhouse.com/product_files/Caleffi-519700A-Product%20Overview.pdf

A delta P circ is a better solution if the pump needs to be replaced
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream
• Member Posts: 45
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pedmec said:
Can you double check the complete model # of the circulator. It will matter as there are different heads and gpm to each circulator in the 2400 series of circulators. Looks at least a minimum 2400-65 or 2400-70 (switches from a 2-bolt flange to a 4 bolt flange @ the 2400-65) which is really big as far as flow rate would be concerned. unless they mongrolled the circulator and just switched out the motor with impeller. all the specs from taco show 2400-50 as 2 bolt pattern. i also might have missed an older spec.
Hey I double checked it’s a 2400-70.
• Member Posts: 4,002
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"Confusing setup" I agree.
8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

Two btu per sq ft for degree difference for a slab
• Member Posts: 7,834
edited October 2022
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Based on this statement,
I dont have a picture of the radiators but theyre standard 3/4 copper pipe baseboards with aluminum fins.
I did the math this morning and I figure around 350-400k btus. Rounding up, around 25ft of head. At 20 degree rise, 40-45 gpm.
if it is true, then you have the correct circulator. The-70 will produce about 45 GPM at 22 ft Head.

I don't believe your math is accurate but it may be close. Read page 7 of this booklet for a better understanding of Head Pressure requirements and how to measure it more easily. http://media.blueridgecompany.com/documents/ZoningMadeEasy.pdf

EDIT: the last three paragraphs of page 4 has another need calculation about the relationship of the BTUh to Gallon Per Minute.
Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics