Moving from series loop finned baseboard to parallel cast iron - how to pipe?

weekendguy

Hatterasguy said:

So, you have to ask yourself a question: What did the $1K (presumably contracted out) expenditure buy you at the end of the day?

@Hatterasguy

I thought if I ended up having to use a different approach to getting a decent delta T on the long zones because of delay, etc I could do so without affecting the way the smaller zones work. Plus I have on my shelf an 007, 0010, 0011VDT, 0014VDT so I figured one of those could be put to use. Yes, it would require some rework of the manifolds so some cost there. But I see your point. I can table this for now.

Also, with the Runtal rads (UF-3) they only use 1/2" fittings which is weird to me since they claim such higher output. Would I therefore need to pipe them parallel to the series loop and allow some water to bypass for the rest of the zone? Manual bypass or some kind of magic diverter device?

I think I'll call Runtal to better understand.

weekendguy

@Hatterasguy - I spoke to Runtal and they recommended a monoflo tee as a bypass. I have never used them but I will learn how they work. Thanks.

Brewbeer

With your overlength zones, piping them in series with the existing run could be problematic. Consider piping them on the same zone in parallel with the baseboard. Connect to the existing supply and return piping in the boiler room and throttle the flow to them with valves.

Are you still planning to split the long loops in half?

weekendguy

@Hatterasguy @Brewbeer The Runtal sections each come with an air vent.

One way to solve the flow issue would be to split the zone in half (thanks for the reminder Brew) since that half way point is just past the Runtal BB. That would make the Runtal the end or the beginning of the half zone (depends on flow direction). I would prefer to only have one zone valve opening to control flow to both halves but I could bump it up to 1" if that makes sense easier than adding another 3/4". The addition of the mid-point return line would be almost completely additive such that I could try the bypass only first to see if that works. Perhaps switch to a 1x3/4 diverter rather than 3/4x1/2 to reduce loss? Would that help? The 0013 pushes that long zone somewhat acceptably at 70% speed so I don't think it's a foregone conclusion that the downstream radiation will starve with just a bypass. If it does then the mid-point return could be added. That would be much less pipe to run than piping the full run in parallel but again even that could be added on to if the Runtal needs a full separate parallel loop. Maybe I should run a hot 1" P/S loop out away from the boiler, move the zone valves so they can control flow closer to the actual zones. That would reduce loss, no?

I think boiler decision first anyway. I'm not wild about knocking down the primary zone with sub 20F weather. :-)

Thank you both for your ideas and advice.

weekendguy

@Hatterasguy Is there some advantage to using larger monoflo tees? Less loss? Or does that just divert less to the CI BB?

weekendguy

@Hatterasguy @Brewbeer

Son of a #$%^%! I realize we're now full circle - we're back to the original title of my post so many years ago:

Moving from series loop finned baseboard to parallel cast iron - how to pipe?

:

weekendguy

@Hatterasguy Well, ok if you want to get technical but the current discussion has the same topic about how to replace finned baseboard with CI BB.

And it was 40K.

Paul48

Isn't the rated output of CI base and fin-tube the same, or very close?

weekendguy

@Hatterasguy @Paul48 I'm still trying to figure out how to pipe this. I can't get a clear picture. I'll have to call Runtal again on Monday.

Paul48

OK....I thought you were talking about cast iron.

weekendguy

@paul48 It's steel and "compatible with cast iron". I'm actually not sure how it's made but it's much higher output than finned BB.

Paul48

Or cast iron, from my recollection. I remember being quite surprised that cast wasn't higher output. What it does do, is hold the heat.

Paul48

Let me play the Devil's advocate..........If the Runtals have clearly defined flow requirements to achieve those outputs.....how do you guaranty those flows with monoflow tees?

weekendguy

@Hatterasguy Thank you for that link - it was very helpful. I also know Santa is bringing me some of Dan's books this year. :-)

@paul48 I don't know. That's what I meant earlier - if I try to just piggyback onto the existing loop (option #1) using the Runtal specifically, how many feet of horizontal emitter can I make into one loop ( one one monoflo tee)? I'm sure I don't need to pipe every 6 ft section through the floor to its own tee (that would add lots of loss to the loop anyway) but the reverse problem is not enough flow through the RUntal. I'm going to call them Monday - I find their literature to be sketchy.

Here is an option (#2). If I split the big loop in the center, that's right in the middle of the 40' Runtal section. I could feed both sides from the convection tubing first and each half loop would end with 20' of Runtal. They would both return through a common 1" return making the piping doable. They would still need to be bypassed I guess - could I use adjustable tees and tweak the amount of flow they get? I know they make pricey thermostatic valves but I'm thinking a one time setup situation might be adequate.

With a little more work (#3), I could take @Brewbeer 's suggestion and pipe the runtal separately. That would involve running a straight line to bypass the runtal completely, and then a S and R line to the Runtal. The advantage of this option is the possiblity of treating like a separate zone with its own control if needed. COnsidering how open the house is, that's probably not needed or even advised.

I'm thinking #2 might be the best compromise of effort/$ vs benefit. But I need your thoughts on my tee/valve questions.

Thanks all.

Paul48

There is a way to calculate flow through the monoflow tee. It's beyond me though. Taco? provides a formula for calculating the flow. I know I've seen it. You might be able to compensate for the downstream section by running 2 monoflow tees on it and creating more flow. If you can find it, you can handle the math.

Brewbeer

If you use option 2 with the panels after the baseboard, you could split each 3/4 line into two 1/2 inch branches and run one of these through the panel before joining them back at the common return to get flow through the panel.

weekendguy

@Brewbeer So that's the same as using a monoflo tee except (a) use a standard 3/4 x 1/2 x 1/2 tee (actually 2 of these) and (b) run the bypass with 1/2 instead of 3/4? So that is kind of the same net effect except it just about splits the flow 50/50 instead of whatever percentage a monoflo uses. Or is there another feature?

@paul48 I actually looked at Taco's literature. Unfortunately the flow calculations can only be looked up in a graph that stops at an effective length of 160ft. Mine is about double that.

I'm thinking some variation on Brewbeer's suggestion and maybe add a balancing valve to adjust flow through the panels. I still need to figure out how many feet of panel can be teed off the main line in one run. I'll see what Runtal says when I call.

I have time for this decision - I still need to (1) get flue lined, then (2) select a boiler installer. Then of course I need to select another installer when the first one quits because I keep telling him what I want him to do. :-)

weekendguy

@Hatterasguy Thanks for the analysis. Are you suggesting that I series pipe all 20 ft of Runtal on one tee for each half loop? Rather than breaking it up with 10 ft per tee or something like that? Also what about BB's suggestion of using (2) 1/2" lines? With possible adjustable diverter? I'd rather not have to drain and refill the zone again so whatever is reasonable to do up front I'm all for it. Many thanks. WEG

weekendguy

@Hatterasguy Thanks. Sorry to be thick but just to clarify.... when you refer to "bypass loop" do you mean the runtal loop itself bypassed from the main or do you mean the main loop which is bypassing the runtal? I see it used both ways. WEG