Coverting single zone from monoflow to two pipe

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Al S

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I have a single zone heated ranch feeding convectors through monoflow tees. I want to remove the copper 1 1/4 monflow trunk and replace with PEX. I realize I need to upsize to 1 1/2 for the Uponor and get PEX monoflow tees.

Does it not make more sense to switch to a two pipe direct return system?
 

Fitter30

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If the monoflow is working correctly wouldn't change it. Two pipe - pipe it reverse return and add a globe valve one size smaller than fin tube pipe size for flow control. Why do you want to change out the copper?
 

Paulypfunk

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With monoflow tees you would sometimes have the problem of the first heaters on the piping run being hot, and the subsequent heaters getting cooler and cooler, so sizing of the trunk is important to insure you have enough BTUs to go around. On the other hand, I like the simplicity of a monoflow diverter tee. If it ain’t broke don’t fix it unless you have other reasons for switching out the copper.
 

Al S

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If the monoflow is working correctly wouldn't change it. Two pipe - pipe it reverse return and add a globe valve one size smaller than fin tube pipe size for flow control. Why do you want to change out the copper?
Hi and thanks for responding. I want to change out the copper because I want to also change from semi-recessed convector to high output baseboard or even panel radiators. As a matter of context, the monoflow tees are all on the supply side first. The last convector on the run never really warmed up as much as the rest though there may be issues with slight clogging etc. The 1 1/4 copper extends below the faces of the basement joists and I feel the PEX allows me some ease of tucking things away higher. Also, and correct me if I'm wrong, panel rads work better in a two pipe solution direct or reverse return. If I go with monoflow using PEX, don't I need to upsize to 1 1/2 to make up for the ID?
 

Fitter30

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1.25" copper 1 .25" id max flow 16.3 gpm
1.25" pex 1 .069" id max flow 11.2 gpm
1.5" pex 1 .263" id max flow 1 5.6 gpm
 

Al S

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1.25" copper 1 .25" id max flow 16.3 gpm
1.25" pex 1 .069" id max flow 11.2 gpm
1.5" pex 1 .263" id max flow 1 5.6 gpm
Thanks for the valuable reference information. Is the above information more relevant if a monoflow layout is used? I am aware I need to upsize to keep as close to the current flow as I have. If the layout becomes a serial loop or separate supply and return loop feeding high output baseboard or panel rads, don't the size requirement needs can be smaller than that of a monoflow?

Thanks in advance
 

Fitter30

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Thanks for the valuable reference information. Is the above information more relevant if a monoflow layout is used? I am aware I need to upsize to keep as close to the current flow as I have. If the layout becomes a serial loop or separate supply and return loop feeding high output baseboard or panel rads, don't the size requirement needs can be smaller than that of a monoflow?

Thanks in advance
Changing system design isn't just throwing pipe up look at this article. Are you going to still have one large zone or muilti. This is from the article.
First you have to identify the radiator and then measure the dimensions and count the sections. Dan Holohan wrote a book called “EDR (Every Darn Radiator).” This book is very helpful to identify the radiators, and it gives their “equivalent direct radiation” outputs. That’s how they used to measure the outputs of these radiators in the old days.

https://www.phcppros.com/articles/7804-when-old-tech-meets-new-tech
 

Al S

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Changing system design isn't just throwing pipe up look at this article. This is in the article
First you have to identify the radiator and then measure the dimensions and count the sections. Dan Holohan wrote a book called “EDR (Every Darn Radiator).” This book is very helpful to identify the radiators, and it gives their “equivalent direct radiation” outputs. That’s how they used to measure the outputs of these radiators in the old days.

https://www.phcppros.com/articles/7804-when-old-tech-meets-new-tech

I agree 100%. This will be done once, which is why I am researching and seeking the advice of those who know. I don't think what I am looking to do is far outside the realm of what home owners seek to do to make changes in older designs.
I so appreciate the reference and perhaps this will shed some light. Thanks much.
 
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