MonoFlow & Pump Help

Bostopa

Hi all…back on after a few years.

So, have a B&G monoflo system with convectors…2nd floor get warm not bad first floor better…one loop for 1st & 2nd floor one pump and its a Grundfos 3 speed 15-58 pump.

So, on 2nd floor removed convenctor and installed a B&G Thermoflo Balancer wanted to see what the flow was. And what did I see…sero reading on the Thermoflo. The left side of pipe is getting hot as is the right side. Ok, so maybe the Thermoflo is stuck…removed it went to the facet put water throw it and it's working.

So, is the 15-58 pump just to small a pump for a monoflo system?

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Jamie Hall

Chances are its fine. Monoflow systems are absurdly sensitive to flow restrictions, and the water is probably just saying that that's more restriction than I like and bypassing…

Bostopa

Thanks Jamie,

But that answer doesnt really make a lot of sense to me…the 2nd floor is a bit colder, monoflo's have greater restriction and the gauge should show some kind of flow and shows zero. That does not imply fine to me.

I assume there needs to be a larger pump installed versus the existing 15-58

delcrossv

One pump for both floors? Zoned or all together?

The ones I've seen usually have B&G 100's on them. Low head, but high volume.

LRCCBJ

A monoflo system suffers from a relatively huge pressure drop at every diverter tee. The real question is whether they piped the system with 1" with either 3/4" or 1/2" takeoffs for the rads or whether they piped it in 3/4" with 1/2" takeoffs?

I can tell you from experience that the latter setup will never offer a sufficient flow rate with any of the Taco 00 pumps. I installed a Taco 011 and the system still cannot get below a DT of 27F. The Cv is just too great from the sum of six monoflo tees and the resulting flow rate is too low. The last two rads on the loop have severely diminished performance.

Bostopa

Hi DelcrossV…a few years back it did have a 100 on it…it was suggested to put a smaller 15-58 in there. But I still have the 100 and it was in real good shap…maybe I put that in there as a test. And yes one pump both floors its one loop.

LRCCBJ…so it's 11/4" main line comming off boiler goes down the middle of basement when it reaches farthest wall it branches off left and right to 1" lines. Each of those lines has the diverter tees which are 1" and the convectors are 1/2" going to them. So, each convenctor has a 1" monflo tee and the 1/2" pipe goes right to the convenctor. They are all like that.

Bostopa

Also in looking seems to me the 15-58 & B&G 100 have basically they same pump curve

LRCCBJ

https://forum.heatinghelp.com/discussion/comment/1814777#Comment_1814777

That's a good start. Now check the DT of the system after the first floor rads have fully warmed up. Also, how many diverter T's are you utilizing and what's the total length of the one loop? You could be marginal with the 15-58.

One additional question:

You have two branches with the 1" lines. Do you have an issue with ONE of those two branches versus an issue with BOTH of the two branches for the second floor? Water is going to take the branch of least resistance and this generally means you need a valve to "balance" the two branches if you wish to have equal flow in each.

EdTheHeaterMan

https://forum.heatinghelp.com/discussion/comment/1814750#Comment_1814750

Are you sure that is a zero? It looks to me like it may be at 0.5 GPM or even 0.4 GPM. That would be sending about 4000 to 5000 BTUs to that particular radiator. But the thermoFlow balancer only has increments that go down to 2 GPM. So how can you be sure it is actually at zero, and not at 0.4 GPM?

EdTheHeaterMan

https://forum.heatinghelp.com/discussion/comment/1814922#Comment_1814922

Not Exactly…

Here are both pump curves one over the other so you can see that there are portions at the higher GPM the B&G still has a significant amount of head while the Grundfos drops off. And that may be part of your problem with balance.

The Old B&G 100 has a much flatter curve. So if you are moving over 150,000 BTU of heat from that boiler to the system, you may not have enough GPM. Inversely, If you are only moving 60,000 BTUs you have too much head at high speed on that pump, you may need to drop to medium speed to get the balance you need. But if you are at 100,000 BTUs you are at about the same head and flow rate as the B&G100.

delcrossv

@EdTheHeaterMan Yep.

Swap back to the B&G and see what happens.

Bostopa

Hi all finally found some time to get back to the heating system.

So swapped out the 15-58 to the B&G 100 and founf no difference. As a matter of fact the thermoflo balance I installed in line to one of the convectors on the second floor now shows…like basically zero (0) flow.

LRCCBJ

No surprise there.

The 15-58 can deal with a head of 15' at 4 GPM.

The B&G MAXIMUM head is only 8'

Switching to it was a non-starter in the first place.

The monoflo system has significantly more resistance than either of these pumps can provide.

delcrossv

Despite what the meter says, did the second floor heat better or worse?

Kaos

You won't get this running with a high volume pump, you need a high head pump. That is either a 009, 011 or 013 depending on the BTU you need to move. You can also stack two 007e in series for smaller zones if you want something with lower power use.

Bostopa

Thanks everyone for the input.

Interestingly enough the upstairs (2nd floor) seems to be warmer now than first floor) the house is in Massachusetts and its been pretty cold the last couple days.

Then I took a Fluke meter with thermocouples and thats also what iyt looks like when I measure the temps. I need to re-verify again though. So this is going on with the B&G 100 installed.

Kaos, I also understand what you are saying. I guess couple questions for everyone. How do I know really which pump to buy? A 9, 11 or a 13?? Also is there a B&G equiuvalent to any of the suggested Taco which also has a 3 speed setting that gives me even more flexibility for adjustments…like say a NRF-36?

Again I appreciate everyones help!!

Kaos

Draw a quick napkin schematics of your system. Include boiler size and BTU output of each rad in the loop.

LRCCBJ

https://forum.heatinghelp.com/discussion/comment/1827004#Comment_1827004

………….and how many monoflo tees are utilized………….and the length of the run to and from the boiler!!!

AND whether the piping is 3/4 or 1". Massive difference!!

Bostopa

Had this from a few years back. there are convectors. Each convector comes off the monoflo with a 1/2" black iron pipe. I also have the old convectors BTU output that I found for each convector, I just didnt put it on the drawing. I also included the boilers rating plate as a pic.

Kaos

I'm assuming it is a single pump setup. That means you want 11GPM through your boiler so roughly 6 gpm through each loop.

At 6gmp 1" monoflow T is about 1.5' to 3' head so say 30' for the longer loop and 21' for the shorter loop.

One issue you'll have right off the batt is the two loops are not balanced. Hope there is a throttle valve somewhere to balance them out.

If you look at the taco pump curves, if you have any hope in hell of flowing about the right volume of water you need the 0013 and even that might be too small. Don't even think about multi speed as it simple there is nothing you can turn down.

EDIT: @LRCCBJ has it right, I was looking at a smaller T. 012 is the right pump

LRCCBJ

The sketch provides useful info.

I need to make a few assumptions:

1. The average output of the convectors is 5,000 BTUH at design. A conservative number on the high side.
2. The assumed DT is 20F.
3. The 13 convectors on the first floor need a flow rate of 6.5 GPM with an output of 65KBTU
4. The 9 convectors on the second floor need a flow rate of 4.5 GPM with an output of 45KBTU
5. The monoflo tees have a Cv of 14.5 (actually less but we will use it)

Therefore, the total flow rate through the boiler and through the 1.25 pipe is 11 GPM.

The monoflo tees downstairs provide a pressure drop of 8.3 feet.

The 1.25" pipe provides a pressure drop of 1.25 feet.

The roughly 70' of 1" pipe downstairs provides a pressure drop of 3 feet (actually less).

So, the total is 12.55 feet with a flow rate of 11 GPM.

The Taco 0012 would work fine.

However: You may need a balancing valve for the second floor at the point where the 1.25" meets the T for the 1". The second floor has less resistance than the first floor and it will steal flow from the first floor more than desired.

hot_rod

your boiler output is 97,000, so 9.7 gpm with a 20 delta design

Call it 10 gpm at 10’, right on the speed 3 of a 15-58 or equal

Here is the alpha 15/58

IMG_9193.jpeg

Bostopa

Evening all so Hot Rod your saing the 15-58 is fine versus getting a Taco 11 or 13 or even a 9?

Kaos

@LRCCBJ has the right info. You want a Taco 012 or UPS43-44.

hot_rod

by the numbers the 15-58 should work , but if it didn’t previously

Just know the larger pumps get $$, so get as close as you can

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Kaos

The 3 speed Taco 0013 is cheaper than either the Grundfos or the Taco 0012. On medium speed it is probably in the ballpark as well.

Monoflow setups with oversized boilers need big pumps, these are never cheap. You need to move a lot of GPM to maintain a reasonable delta across the boiler and you need a fair bit of head to push through all the T fittings. There is no way around it.

Bostopa

Yeah those pumps do get pricey but it is what it is.

Guess I'm curious the second floor does have heat coming through it…I'm just trying to understand by eleiminating the flow restiction will more heat get up there.

LRCCBJ

Guess I'm curious the second floor does have heat coming through it…I'm just trying to understand by eleiminating the flow restiction will more heat get up there.

Do me a favor and see if you can measure the temperature of the second floor radiator in the second floor front bedroom and the one in the second floor rear bedroom. Use an infrared gun.

Now measure the temperature in the kitchen and in the dining room with the infrared gun.

Be sure the boiler has been running for at least 30 minutes.

Report back with those four temperature readings.

Please also explain your mention of a "flow restriction"