Raise the pipes?


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Old 08-23-10, 03:25 PM
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Raise the pipes?

I have a 1" iron pipe loop around my basement with monoflow tees tapped up to baseboards with 1/2" copper. 1 side is monoflow, the other side is a basic tee.
I am going to be finishing the basement and need to raise the pipes.
I am thinking of going to a 3/4" Pex pipe, and getting those Raven 3/4 x 3/4 x 1/2 monoflow tees and replacing what I have with the pex. This way I can mount the pex up in the rafters away from headspace. In my mind I am replacing with what I have with the same thing, just going from a 1" main loop to a 3/4" loop.

I have attached photos of what my baseboards look like, and what my heating system looks like.

Is what im thinking correct? will this work? is there a better way?

low pipes!


Monoflow tee


Boiler / Heating system (on-demand, no hot water tank)


Baseboards




Thank you to everyone for your help.
 
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Old 08-23-10, 04:10 PM
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In my mind I am replacing with what I have with the same thing, just going from a 1" main loop to a 3/4" loop.
But it's not the same thing... you said it yourself! You want to cut down the size of the main loop from 1" to 3/4" ... and that right there is going to limit the allowable flow through the system, and the amount of BTU that you can extract from that flow.

Put another way, you can get about 40,000 BTU from the flow in a 3/4" loop, and have the water return to the boiler about 20 cooler than it entered the loop. With 1" pipe, you are talking about 100,000 BTU with the same 'delta T' (temp change).

Depending on how many heat emitters you have on the loop, you could very well upset the balance of the system and end up with some rooms to hot and some to cool...

Why not stay with 1" ?
 
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Old 08-23-10, 04:36 PM
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Thanks for the reply. I could go 1" but I can't find pex 1" monoflow tees. Pex is probably the only way I can get these pipes out of the way.
 
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Old 08-23-10, 04:44 PM
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I would seriously consider using 3/4 inch PEX and a manifold system and doing away with both the main loop and the Monoflo fittings. You could re-use the existing Monoflow tees with 1-1/4 inch PEX. Remember that PEX has a slightly smaller inside diameter than does steel pipe or copper.
 
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Old 08-23-10, 06:29 PM
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How would I connect 1-1/4 pex to 1" iron female thread?
 
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Old 08-24-10, 09:40 AM
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I like the idea of using the existing monoflow tees as suggested by furd.

What do you think of using 1" PEX and buying a bunch of 1 x 1 threaded couplers to connect to my existing monoflow tees?

Cash-Acme U140 - Cash-Acme - 1" x 1" Pipe to Male Pipe Thread Connector

This way i need to buy 36 connectors and about 100' of 1" pex....
(9 baseboards x 2 sides x 2 ends per side = 36 female threaded ends)

Will this work?

Thank you!
 
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Old 08-24-10, 03:39 PM
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Before we go too much further here, I wanted to throw this out just so you don't make a mistake and use the wrong tubing...

Are you aware that the PEX tubing used for heating systems is not the same as for potable water? There needs to be an "Oxygen Barrier" built into tubing for heating systems. I would think that if you go ahead with this project, you would want to use ' Pex-Al-Pex ' which is PEX tubing with an aluminum layer 'sandwiched' in the walls of the tubing. It's purpose is to prevent oxygen from migrating into the system (which it would do with standard potable tubing).

Furd also mentioned that PEX tubing has a slightly smaller I.D. than iron or copper of the same size... so he may well be correct that you would want to use 1-1/4" tubing... don't know that for sure, but it's something else you need to determine.

Don't think that getting that piping apart is going to be easy! It's not, you will need some serious wrenches, and some serious manpower to muscle all those connections apart. Given that, it's also possible that some of the existing fittings may become damaged in the process.

Not trying to discourage, just wanting to prepare you for what you might encounter in the process...
 
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Old 08-24-10, 03:44 PM
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One more little bit... 1" or 1-1/4" PEX is a lot more rigid than you might think... and if it 'kinks' during the install process, you need to cut the kink out and use a coupler, or replace the section of tubing.

Watch the bending radius also, there are limits... so in addition to the $300 bucks worth of sharkbites, you might have to plan on some elbows and other fittings... and don't forget you will need fittings to terminate back at the boiler.
 
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Old 08-24-10, 03:49 PM
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Do also think about Furd's other suggestion of doing away with the monoflo fittings.

His idea of using supply and return manifolds at the boiler, and running 9 pairs of 1/2" tubing out to each convector cabinet (which is what it appears that you have, not 'baseboard') has merit. Even though you may need more tubing, it may end up being cheaper than the 1" or 1-1/4" that you are thinking about. The fittings will certainly be cheaper, and 1/2" tubing is a LOT easier to work with than the big stuff...
 
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Old 08-26-10, 10:52 AM
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I researched it and your right... 18 1/2 pex to copper fittings for each convector cabinet and 2 10 port manifolds would be cheaper and a better design then what i have now.

basically, I put 1 manifold at the supply and 1 at the return and run a line from each to every convector cabinet?

thanks,
Mike
 
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Old 08-26-10, 03:24 PM
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Again I will strongly urge you to go one size larger when using PEX. If you cannot find 3/4 inch PEX to 1/2 inch copper adapters then use bell reducers at the convector cabinet connections.
 
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Old 08-26-10, 05:22 PM
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I currently have about 80 feet of 1" pipe in the loop. I am going to close to 400 feet of 1/2" pex for 18 runs. Still think I need 3/4?
 
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Old 08-26-10, 07:11 PM
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I didn't look up the I.D. numbers on the 1/2" PEX yet... so I'm speaking hypothetically...

1/2" copper is good for around 15K BTU. I would be VERY surprised if any one of your convectors is that much output. What is the LARGEST convector cabinet in your home?

I'm personally doubtful that feeding the convectors with 1/2" PEX would be a problem, but do check... Furd us usually 'on the money'...

Before you commit to this, I'd like to entice TOHeating to weigh in on this... TO, sound like a good idea to ditch the monoflo loop and 'home run' each of the convectors?
 
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Old 08-26-10, 07:27 PM
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Largest convector is 4 feet. Most are 2 and 3 foot.
 
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Old 08-26-10, 08:54 PM
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What is important is the total distance (supply and return) between the convectors and the manifold. If you can keep this distance to about 25-30 feet (or 12 to 15 feet from the manifold) you should have no problems at all. Even doubling this conservative figure to 50-60 feet total (25-30 feet from the manifolds) will probably be okay. You could also use 1/2 inch on the closer runs with 3/4 inch on those convectors that are farthest from the manifold but I suspect the cost differential between purchasing full coils vs. cut lengths may be a factor.

I'm not too familiar with variable speed pumps but using one may make my point moot.

Also, the primary benefit to a Monoflo system is that the pressure differential across the loop is more or less constant regardless of the use of zone valves in the branches to the convectors or radiators. Using the variable speed pump negates this advantage to the Monoflo system.
 
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Old 08-26-10, 08:57 PM
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Originally Posted by microbmen View Post
Largest convector is 4 feet. Most are 2 and 3 foot.
But don't forget that cabinet convectors have multiple lengths of finned tube so the heat output is many times greater than a standard finned tube convector of the same length. Because the finned tubes are short and in parallel the pressure drop across a cabinet convector will be lower than the equivalent length of finned tube baseboard convector.
 
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Old 08-27-10, 08:02 AM
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what do you think of this tubing?
Viega 11425 - Viega - ViegaPEX Barrier Coil - 1/2" Coil (300 ft)

It has the oxygen barrier and is compatible with sharkbite fittings. It would save me a ton of time if I can go sharkbite to all the existing 1/2 copper to each convertor cabinet.
 
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Old 08-27-10, 08:15 AM
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also... if we think this tubing works, I can do 2 of my longer runs with 3/4" and use 3/4 - 1/2 sharkbites at the copper runs up to the convectors....that should give my upstairs plenty of heat, since there will be about a 10' run of copper up the walls.
 
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Old 09-09-10, 08:39 AM
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Careful with using Sharkbite type fittings with Pex-AL-Pex. First the larger sizes just plain don't work, the tube ID/OD is different than standard Pex. Second, and this is the tricky part, there is some 1/2" Pex-AL-Pex which is dimensionally compatible with standard crimp and Sharkbite fittings. Happy day as one can use the good O2 barrier Pex without buying into the expensive Wirsbo tooling. The problem shows up when one uses a crimp fitting on one end of a run and a Sharkbite fitting on the other. The aluminum core is extruded with a simple overlap joint that leaves a very small void that is a possible leak path along the length of the tubing. The internal seal of the crimp combined with the external seal of the Sharkbite exposes the core to pressure and the possibility of leaking. Its going to be an extremely slow pinhole leak that looks like a bad crimp connection. You will make the connection over again a few times, checking and rechecking your crimps to no avail. You will then cut out the offending section and pressure test it in a large tub for a few hours finally figuring out the leak is coming from between the layers. You might even cut the opposite end of the run off and replace it with a crimp fitting just to verify your hypothesis... And finally You will swap back to the Sharkbite on the opposite end only to have the leak re-appear.

Pex-AL-Pex is a great product but be prepared to use the manufactures proprietary fittings.
 
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Old 09-09-10, 03:53 PM
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Interesting post Squeezer, thanks! and my bet is that you 'been there, done that" !
 
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Old 09-09-10, 08:07 PM
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Beer 4U2

My post may have been based on experience...
 
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Old 09-29-10, 07:14 AM
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I wanted to thank everyone for you help.... and of course I have a few more questions
First, my project worked. Each one of my convetor cabinets get nice and hot with the new system,
here are some pictures.




secondly, I installed manifolds with flow control and flow meters, so that I can perfectly balance the system. Once the system is balanced I am getting about .2 GPM per convector. I think this is enough, because like I said each convector is getting quite hot. Should I want to make the system more efficient or give off more heat, should I consider getting a different circulator? currently I have a Taco 007-F3.
Thoughts?

Thanks again, this community is great!

-Mike
 
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Old 09-29-10, 08:21 AM
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nice looking job there Beer 4U2
 
 

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