Closely Spaced Tees and spacing

mikel

I am (once again) upgading my boiler system for my radiant floor home. I intend to use the Taco RMB-1 to feed my secondary loop. (5 radiant zones in thin slabs each being pumped by Super Brutes 3 spds) My first question is should the secondary loop actually BE a loop? Taco's literature shows basic schematics. Or should it be like send and return manifold (sized about 1.5")

I am thinking a secondary low temp loop with closely spaced tees is the best way to go so that all the zones will get a good chance of getting equal BTUs. I have a 1.5 inch copper manifold here with twelve 3/4 stubs spaced 4 inches apart. Would this work as my closely spaced tees for all 5 zones? (one extra for expansion) Leaving it intact from the factory would save a lot of sweating and chances for leaks.

Do the closely spaced tees for each zone need to be spaced apart from each other? Like a buffer zone so that they don't cause turbulence? Or will this work as intended as long as the check valves are all doing their job on the load zones? Did I explain that clearly? I can post a drawing if anyone needs to see what I am talking about.

I am familiar with closely spaced tees, have all the great plumbing books, but I have yet to see anything that answers this question.

Thanks in advance for any insight.

Weezbo

the RMB is an injection system,

are your intentions to run sub panels off the system side of the RMB ? hence the need for lots of circulators?

i think you would want first supply last return or just build your own injection loops and sub systems ...

the injection side of the RMB would be your limiter, the system side has a pump of its own.... you could cascade temps off the system side of the RMB or balance each zone to the longest zone for single temp...

Brad White_120

Tee Spacing

It seems you are using the RMB to get the temperature you want from a cast iron conventional boiler; that you are not using a ModCon?

If I understand your piping arrangement correctly, you would be using the manifold as a series of closely spaced tees.

You do understand that these are "in-series" and that downstream outlets will be diluted and cooler than there upstream neighbors. If this is the case, the zones requiring hotter water naturally want to be first in line. They will have decaying temperatures as you run down the line.

The key then becomes predicting what temperature you will get at any particular point; are the upstream zones calling and if not will the downstream zones overheat? Those kinds of things.

Another thing about using this arrangement- closely spaced tees require a certain amount of straight pipe upstream and downstream. An elbow or another tee too close will cause turbulence and have an effect on tee outflow. I suggest 5-7 main diameters minimum, so this means you may have to plug intermediate branches. This may stump your plan.

To assure constant incoming temperatures to each zone, I would cut the manifold and face the ports towards each other much like a ladder. Into these branches and to connect them to the opposing branch, solder in closely spaced tees plus any balancing and isolation valves. It is off of these tees you will run to your zones.

See the diagram PDF attached. Each branch will have it's own temperature although it is a tad "circulator intesive". Maybe I do not grasp the entirety of your concept but I wanted to illustrate some concerns to be aware of.

mikel

Re: Tee spacing

Thanks for the great insight and pipe layout. That seems a lot nicer to control each zone and always have the right about of btu in the right place.

Would you suggest I use fewer pumps? Maybe one Super Brute (since I already have those) and zone valves? The RMB has a pump on the outlet but I don't think it would have near enough head to deal with it. Adding another pump in series would be good, no? Unless it mess with the primary loop. I want to protect the boiler at all costs. The entire house is radiant. (3/4" pex in 1.5"-2" gypcrete) and each zone is about 400 feet of tubing)

Maybe perhaps using prebuilt manifolds with balancing valves like the one I have attached? With valve actuators to control the call for heat from each zone? Would your schematic still work for me without the zone pump after the close tees on the crossover pipes(ladder rungs)? My plumber's knickname is leaky joe so the fewer sweat connections I have to resweat the better. (I live in the sticks and have one of the few radiant houses for miles)

I am using a Trinity t200 boiler. It is combi unit but I don't us the domestic heat exchanger. I have a 50 gal indirect that runs in priority mode. I am thinking of using the RMB to control reset on the boiler and for protection. It seems to have a lot more control than the Trinity's Sentry 2100. I like the min low temp loop setting the RMB has.

Weezbo

those are some very sharp looking headders*~/:)

the deal is your cross over bridges give you same water temps the flow through the branches could be way higher than the RiMBy if you used them to feed sub systems. that is distribution if the available BTU meets the demand.

you would need pumps to do that off the close spaced t's as there would be nothing to circulate without them.the water would simply shoot past the bridge into the return of the system side of the RMB ...if you ran seperate zones off the mixing block with zone valves then you would likely need to acertain the applicabilities as it were.

the picture Brad gave you is different from the flow in the RMBies the crossover bridges picture is just an illustration of the (Bridge)component.

mikel

Switched to Watts Manifolds

After consulting with my local supplier, NYT and some great help on the wall I have come up with this configuration for my 16 year old radiant heating system. It is pump intensive, I know, but they are all small pumps except for the Grundfos 26-99 on the primary boiler loop. NYT reccommends it. (I had to replace the boiler heat exchanger because the orginal one took a dirt nap after on my 3 year old Trinity t200 from the OEM undersized internal pump and some extremely hard water conditions combined with the previous piping scheme)

Anyone know if I can mount A watts stainless steel manifold rotated like this? (rotated 90 degrees) or does it mess with the flow meters? Rotated fits in my install much smoother and doesn't make a mess with the pex trying to make so many turns in a tight space. I also want to keep the Radiant sends lower than the close tees in my primary loop to provide a thermal trap.

Brad White_9

Why Not

Mikel-

Nice drawing by the way.

Why not use a common circulator for your supply radiant manifold instead of all of the parallel ones? You can do individual control with power heads on the manifold ports, or just manually balance each circuit. Your pressures will be governed by your longest tubing run of course, so if the total flows are not much, might you may even get by with a single 15-58? Either way you will be running in series with the RMB so maybe loop that (your original question, I think.)

EDIT: Oh, the manifold orientation? Venting is the issue I see. I would mount them vent-up. If purged properly though, and if the system is clean of particulates, I do not see an issue with them in any orientation.

Where are you located? I have a spare 26-99 that was over-powering a radiant manifold for a few years until I replaced it with a 15-58. It is yours if you want it. Orange is cool. May be a good spare. Your call.

mikel

Sure, I will take you up on the 26-99. Send me an email with the price, etc.
I live about 50 miles south of Buffalo, NY

I originally was going to power the manifold with one pump and using actuators on the manifold, but we were concerned about what a larger head pump would do if only one zone was running. they do make a pressure differential bypass for the 1" Watts manifold but not for the 1-1/2 inch. whichi is what I am usuing. I could plumb in my own but space is limited. I also had the super brutes already to go. I too like the less is better approach but at this stage I will try this arrangement and see how it does.

Thanks for the input on the orientation. I will have purging on the high point of the low temp just after the RMB (which also have small vent) so the purge on the manifold won't be needed as much.

Thanks again.

Brad White_9

Your approach makes sense, Mikel

What you might do ILO a bona-fide bypass is if you have a spare port, crack one a bit. The only thing I do not like about that kind of arrangement is that it goes toward quenching the condensing feature.

I will give you the 26-99; just cover the shipping costs. I will e-mail you off line.

Brad

mikel

Plan B... it never ends.

Brad, I got to thinking, I have a 100,000 btu plate heat exchanger sitting unused in the Trinity boiler. What if I put that into the secondary loop and let the RMB pump it's heat into that? Sensor in the radiant loop side. And that would isolate the pex from the mod/condensor and solve the pump in a series problem. Will it work?
Think I am losing too many Btu's in this deal? Creating flow problems with the 3/4" exchanger size? I have modified my drawing to illustrate the idea.

Did you get my email info with our shipping number? If not check your spam folder.