Removed baseboards, capped monoflo Tee. Questions

newtonkid88

Hi

My 1960s 2-story house has a single zone monoflo system. I want to separate the zones. New G115 Buderus Boiler. New Grundfos 15-85F/FC Circulator. Black steel pipe. 

The existing monoflo Ts stamped 1” x 1/2”. The 1/2” steel pipe inner diameter appears to be about the same size as 3/4” HePex ID.

I know I have to run a pipe between the “capped” Ts. Does that pipe have to have a bleeder screw/valve to bleed air?

I plan on keeping the 2nd floor on the monoflo system. And run the 1st floor in 3/4” HePex in a series circuit to keep it simple. The first floor is a relatively open floorplan so I’m okay with uneven heating elements.

I also plan on using one of the abandoned monoflo Ts to add a radiator on the 2nd floor. 

1) Does the “capped” Ts pipe need to have a bleeder screw/valve to bleed air?

2) Anything to know about using the abandoned Ts to add a radiator on the second floor? That is going to be a long(er) run.

Thank you

Jamie Hall

There does need to be a pipe between the two runs of the monoflow Ts. It should already be there. There does NOT have to be a pipe between the two legs of the Ts -- the pipes which formerly went to a radiator. Just cap them and leave it at that.

Adding a radiator in a new location may or may not work. The monoflow system is very sensitive to the head loss in the lines to a radiator and the radiator vs. the restriction in the Ts. If the new radiator and location has very nearly the same head loss as the removed radiator and piping, it may work well. Otherwise it may not work well -- or at all.

kcopp

Running a series loop on cast iron baseboard may not be your best option. The baseboard may have some significant balance issues. A manifold setup in the basement and running 1/2" hePex to each baseboard would be a better approach.
I also concur w/ Jamie that messing around w/ the mono flow arrangement could prove tricky and give you fits when you refill and try to operate....

newtonkid88

Jamie Hall said:

There does need to be a pipe between the two runs of the monoflow Ts. It should already be there. There does NOT have to be a pipe between the two legs of the Ts -- the pipes which formerly went to a radiator. Just cap them and leave it at that. Adding a radiator in a new location may or may not work. The monoflow system is very sensitive to the head loss in the lines to a radiator and the radiator vs. the restriction in the Ts. If the new radiator and location has very nearly the same head loss as the removed radiator and piping, it may work well. Otherwise it may not work well -- or at all.

Thank you.

I had 9 runs originally. 5 on 1st floor. 4 on 2nd floor. I am removing the 5 runs on the 1st floor and want to add 2 runs about 12 ft of radiator on the 2nd floor.

Am I allowed to have a trap between two radiators on the same run? Radiator, drop down between joists, and back up to another radiator? On the same monoflo run.

newtonkid88

kcopp said:

Running a series loop on cast iron baseboard may not be your best option. The baseboard may have some significant balance issues. A manifold setup in the basement and running 1/2" hePex to each baseboard would be a better approach. I also concur w/ Jamie that messing around w/ the mono flow arrangement could prove tricky and give you fits when you refill and try to operate....

I had, and am using new Slant Fin 30 or MP80, not cast iron radiator.

 Why 1/2” hePex? When the radiator tube is 3/4”?

I am okay with the uneven heat on the first floor because it’s a relatively open floor plan

thanks

EdTheHeaterMan

Since you are using copper tube w/alum fin baseboard, then you should be fine with a series loop. As long as you don't exceed the capacity of the pipe size. For example ,the rule of thumb for 3/4" copper is 40,000 BTUh can fit in that pipe size. Fine Line 30 is rated at 580 BTUh per foot @ 180°. so as long as you don't have more than about 70 ft of element on that loop, you should be fine. If you have more that 70 feet then you should divide it in 1/2 and make either 2 supply or 2 return in 3/4" then you can tee the two loops together with a 1"x3/4"x3/4" tee and home run a 1" to the boiler room.

As far as the capped off monoflow tees... if your system is set up with only one monoflow tee and one standard tee per radiator, you can increase the flow to the radiator on the second floor by using 2 monoflow tees on one radiator with the coned opening facing away from each other. But I don't believe that will be necessary. Do a little simple math on the existing 2nd floor loops. Measure the total equivalent length of one of the radiator loops to the second floor. Total straight pipe+total amount of elbows equivalent length+total amount of radiator+any valves equiv. length = X. As long as you don't exceed the measurements of the loops that work with your new pipe runs, then you should be fine. here is a chart for equiv. length I found on the web.


Sorry for using Algebra terms in the above. I never liked math in school. as a matter of fact, I was the kid who wrote "Hay Algebra! Forget about your X. She is not coming back! and I don't know Y" on the blackboard.

newtonkid88

EdTheHeaterMan said:

Since you are using copper tube w/alum fin baseboard, then you should be fine with a series loop. As long as you don't exceed the capacity of the pipe size. For example ,the rule of thumb for 3/4" copper is 40,000 BTUh can fit in that pipe size. Fine Line 30 is rated at 580 BTUh per foot @ 180°. so as long as you don't have more than about 70 ft of element on that loop, you should be fine. If you have more that 70 feet then you should divide it in 1/2 and make either 2 supply or 2 return in 3/4" then you can tee the two loops together with a 1"x3/4"x3/4" tee and home run a 1" to the boiler room. As far as the capped off monoflow tees... if your system is set up with only one monoflow tee and one standard tee per radiator, you can increase the flow to the radiator on the second floor by using 2 monoflow tees on one radiator with the coned opening facing away from each other. But I don't believe that will be necessary. Do a little simple math on the existing 2nd floor loops. Measure the total equivalent length of one of the radiator loops to the second floor. Total straight pipe+total amount of elbows equivalent length+total amount of radiator+any valves equiv. length = X. As long as you don't exceed the measurements of the loops that work with your new pipe runs, then you should be fine. here is a chart for equiv. length I found on the web. Sorry for using Algebra terms in the above. I never liked math in school. as a matter of fact, I was the kid who wrote "Hay Algebra! Forget about your X. She is not coming back! and I don't know Y" on the blackboard.

Thank you!

I will have exactly 55 feet of baseboard radiator element on the series loop. Any pipe that is not copper fin-tube will be 3/4” hePex.

I will do the math, thanks. 🤓.

The old (now scrapped) riser pipes were 1/2” black steel that converted to the old 3/4” copper fin-tube. Am I correct to say that 3/4” Uponor hePex has similar inner diameter as the old 1/2” black steel? I can visually see that are very similar but maybe I am missing something. 1/2” Pex is ALOT smaller than 1/2” black steel, ID.

hot_rod

Correct on the ID of pex. The insert type fittings also add some restriction, especially the thicker wall composite type. I like copper fittings for pex, they are the thinnest wall. Or the expansion type fittings, since you have an A pex..

DanHolohan

@Jamie Hall, B&G always recommended that the branches be connected, not capped. The pressure drop through the capped Monoflo tees can add a lot of unnecessary head to the pump. 

newtonkid88

DanHolohan said:

@Jamie Hall, B&G always recommended that the branches be connected, not capped. The pressure drop through the capped Monoflo tees can add a lot of unnecessary head to the pump. 

Does the connection pipe need to have a bleeder screw/vent? The old copper fintube radiators had a bleeder screw on the return end.

hot_rod

An EL chart showing the piping equivalent for diverter tees.

No harm in adding a bleeder ell especially if there are some ups and downs in the piping. Usually a fast purge and good microbubble air purger is adequate for excellent air removal.

DanHolohan

What HR said. Thanks. 

newtonkid88

hot_rod said:

An EL chart showing the piping equivalent for diverter tees. No harm in adding a bleeder ell especially if there are some ups and downs in the piping. Usually a fast purge and good microbubble air purger is adequate for excellent air removal.

When you say “ups and downs”, do you mean like a plumbing trap? One of the new radiator runs will have ups and downs to get through the new framing. Is that okay as long as there’s a bleeder at the radiator?

or were you only referring to the “abandoned”monoflo branch?

Thanks

Jamie Hall

Interesting and fair enough, @DanHolohan . I didn't know about the B&G recommendation. I must admit that the hydraulic properties of monoflow systems have always fascinated me. Clear enough how they work and why -- that's not the problem. I've never actually tried to balance one, but I've always had the feeling that they must be absurdly sensitive to the actual in the field piping.

DanHolohan

They sure are, Jamie. When they were popular, we got daily calls at the rep from contractors who installed them without first sizing them. The cure often involved adding another circulator to the troubled branch circuit. It wasted a lot of electricity. 

hot_rod

newtonkid88 said:

hot_rod said:

An EL chart showing the piping equivalent for diverter tees.

No harm in adding a bleeder ell especially if there are some ups and downs in the piping. Usually a fast purge and good microbubble air purger is adequate for excellent air removal.

When you say “ups and downs”, do you mean like a plumbing trap? One of the new radiator runs will have ups and downs to get through the new framing. Is that okay as long as there’s a bleeder at the radiator?

or were you only referring to the “abandoned”monoflo branch?

Thanks

Yes, as you fill a system, a high point vent, either a bleeder, or an auto-vent will speed up the removal of "fill air". Air will also migrate to high points when the system is off in summer months, so that high vent is a seasonal start vent also, if the air in never 100% removed.

A microbubble type air purger is 97% efficient in getting all air out, every system should have one.

newtonkid88

hot_rod said:

Yes, as you fill a system, a high point vent, either a bleeder, or an auto-vent will speed up the removal of "fill air". Air will also migrate to high points when the system is off in summer months, so that high vent is a seasonal start vent also, if the air in never 100% removed. A microbubble type air purger is 97% efficient in getting all air out, every system should have one.

My system has one of these installed in the basement near the boiler, on the monoflo loop. I will still use bleeder valves on the radiators. Thanks

newtonkid88

EdTheHeaterMan said:

So, I took measurements of the longest run with most elbows. I will do the math soon. 

I noticed that the monoflo Tees are only on the return side. The supply side is a regular Tee with the letter U on it. The monoflo Tee is made by Taco.

kcopp

newtonkid88 said:

kcopp said:

Running a series loop on cast iron baseboard may not be your best option. The baseboard may have some significant balance issues. A manifold setup in the basement and running 1/2" hePex to each baseboard would be a better approach.
I also concur w/ Jamie that messing around w/ the mono flow arrangement could prove tricky and give you fits when you refill and try to operate....

I had, and am using new Slant Fin 30 or MP80, not cast iron radiator.

 Why 1/2” hePex? When the radiator tube is 3/4”?

I am okay with the uneven heat on the first floor because it’s a relatively open floor plan

thanks

Somehow I missed the new copper fin baseboard... thought you were just zoning

newtonkid88

Is this the correct location to put a high-point vent if I need to run a 180 return elbow? Or should it be at the other end of the return pipe without the 180 elbow. Monoflo.

hot_rod

does it drop down thru the floor at the other end of the return bend? If so, use a bleeder ell at the turn down. It probably an easier fitting to find😗

newtonkid88

hot_rod said:

does it drop down thru the floor at the other end of the return bend? If so, use a bleeder ell at the turn down. It probably an easier fitting to find😗

I havent decided yet if the other end will drop down or go through the wall studs yet.

If the fitting availability is not an issue, which vent location is best? Thanks

hot_rod

The very best is on the highest point in the system. or at the last fitting anywhere in the piping before it drops down.
I consider those baseboard ells as a one shot, initial fill purge point. Once the system is filled with adequate flow 2- 4 feet per second, all the air gets removed back at the Spirovent.

The more threaded fittings in the fin tube the more potential for leak points.

My son visited a job in Colorado with a chronic air problem. The building maintenance guy drilled a hole through the outside wall in every condo to vent the baseboard ells to the outside. He bleed them on a regular basis

The building got new boilers and a repipe with a Caleffi Hydro-Sep and the need for the jerry- rigged baseboard vents went away.

It's more about proper piping.. Pump away, use a good central air purger and sleep easy