Install Hydronic Kickspace heater in the baseboard loop or "scoop T" side loop?

Jells

I'm installing 2 BM TWIN-FLO III baseboard heaters with 1/2" pipe on a 3/4 loop of ~160' with just baseboard powered by a Taco 007. Here's the install manual: https://s3.amazonaws.com/s3.supplyhouse.com/product_files/KickstartInstall1.pdf

Should I use the scoop T side branch method or just put them in the loop? What will the CV of the 1/2" units in the loop do? The manual doesn't help much "They are essentially small unit heaters, and will work on one or two pipe systems, or in a series loop where pressure and temperature drop can be tolerated". Ever since noticing how tiny the actual port in a Honeywell zone valve is, I've been dubious about resistance concerns in loops.

Ironman

Don't reduce the size of the loop by putting the toe kick in series. That port in the zone valve is only 1/2" in length, not several feet.

You need to create a separate branch for each toe kick.

Jells

But then surely I can use the scoop T off the loop as the mfr recommends? A branch for each is not practical in this retrofit to add more emitter.

Some of this CV stuff is just not intuitive to me, a 3/16 valve port seems more resistance than 10' of 1/2" pipe.

Ironman

Jells said:

But then surely I can use the scoop T off the loop as the mfr recommends? A branch for each is not practical in this retrofit to add more emitter.

IDK what you're trying to convey, but the second sentence above contradicts the first.

Doing it like the directions show IS creating a branch for each heater.

If you don't understand cv, then I would advise that you follow the manufacturer's drawing instead of trying to figure out how it's factored.

Jells

Sorry Bob, I thought you meant a branch off a manifold at the heater, not the scoop loop off the main loop. Terminology is always a **** when you get out of your field of expertise! I remember being 21 and asking at the plumbing supplier for an elbow with male on one side and female on the other. Dude looked at me with contempt and said "you mean a STREET ELBOW?"

Jells

Here's another odd piece of this job that perhaps someone can explain to me: the instructions say if the unit is bottom fed it only needs a scoop T at the return, but if not, it needs them at both ends of the side loop. Why would orientation make a difference in this kind of closed flowing system? Shouldn't gravity pulling down on the down side create suction balancing gravity resisting on the up side?

Easy enough just to use both no matter what, It seems impossible it can hurt, just cost a couple bucks more.

Solid_Fuel_Man

It's commonly referred to as a mon-o-flo T, or technically a venturi T, as monoflo is a Bell&Gosset trade mark.

One venturi T is generally adequate, they are referring to if the heater is below the line as it's harder to push hot water downward so another venturi T helps. Same rule was used by the dead men who installed monoflo systems, one T if radiation above the main loop, and two if radiation below such as a heated basement with loop in the ceiling.

Jells

Thanks. Is there a downside to playing it safe and using 2 whatever? Seems a small cost in a big picture.

Ironman

No, 2 Tees are fine.

EBEBRATT-Ed

If the heater are below the main use 2 venturi tees. If above the main use one tee on the return.

I am a little concerned with your "160' hot water loop" How much finned element is on that loop? Your only allowed about 68' of 3/4 finned element on a 3/4 loop. Is this a series loop system?

Jells

Ed, there's only about 24' finned in the 450 sq ft apt, hence why I'm adding the 2 kickspace units to add emission, @140 it just wasn't putting out enough BTUs for the extreme cold we were getting.

What's a riot is how pissed the tenant was that I had grabbed a fan of hers and put it on the baseboard to increase throughput, when that is all this unit basically is, a fan on finned pipe. Some people are more interested in playing the victim than actually getting their problem solved!

Harvey Ramer

There is a better way than using monoflow tees. They make purge air difficult and often add unnecessary pressure drop.

Use regular tees and install a circuit setter between the 2 tees. For initial air purge, the circuit setter can be fully closed. Once that is done, the circuit setter may be slowly closed until the delta-t across the kickspace heater reaches 20°, or what ever you desire.
This method may be slightly more expensive but the improved functionality is worth it, to me anyway.

But first, you may want to measure your temp drop across the baseboard loop. You may not be getting enough flow through all that pipe. Simply swapping the pump for one with higher head might solve the problem as well.

Jells

Thanks Harvey, interesting idea, but I'm all set up for the monoflo! I also only just got a dual readout thermometer and haven't been there since to actually read the delta T. Given that it's a taco 007 with no current valves or constrictions other than 2 spring type checks on it, I would think the flow sufficient, but in fact I have no idea what the gpm is. It didn't seem worth pursuing as the 2 fan units are overspec by any calculation so I should have no problems even if they're left on low fan speed.

EBEBRATT-Ed

@jells, is their any reason your running 140 deg water?? Boosting the water temp will give you a bunch more output

Jells

It's heated by the hot water tank. I'm looking at better solutions for these tiny apartments, but that's what's in there now. Previously in the unit was a minitherm boiler and 30gal indirect, and it was awful. Noisy, high maintenance, and the added heat during the summer was bad for the tenant's comfort. Most standby losses from the DHW tank just goes up the flue.

I have 3 other units that are fine with this system, and this one has had no complaints from tenants for the 7 years it's been in. The only significant difference for this one is maybe 25' more outside wall exposure in the 12x46 space, the other side of the building is attached to a 25' deep neighbor. Attached rowhouses can be pretty efficient.

Big Ed_4

Hmm 140* water , What temperature does the fan kick in on ? I would add an couple of peanut bleeders on the unit just incase ..

Jells

Stock fan aquastat is 120, if it's a problem I can replace is with a lower temp one. Not sure what a "peanut bleeder" is, do you mean an air vent at the top of the side loop? One of the little 1/8" auto-bleeds is in the plan for the "up" loop and unnecessary for the down one.

Jells

Any idea if putting a spring type check valve between the 2 monoflo tees is an issue? Would the resistance cause a problem? It could cause the kind of resistance that Harvey suggested would work without the monoflo's, so I'm afraid too much will be a problem. I'm just tight for space and would have to relocate the valve.

Big Ed_4

No No No....

An simple diverter .... 3/4" loop , use two 3/4"x1/2"x1/2" tees ...1/2" riser and 1/2" radiator bypass .... The further the tee'''s or longer the bypass ??? Love pex. ..... Simple machine

engdriver

Fairly simple answer, if kick heater is on 2nd floor or higher, one monoflo (3/4"x3/4"x 1/2") on the return side(creating a venturi effect) reg tee on the supply. If first floor or basement use two monoflos ,facing opposite ( supply forcing water up,return creating venturi). On the side of the kick heater coil (the higher tube outlet) you solder a 1/2"X1/8"NPTX1/2" baseboard tee so the 1/8" NPT faces the front (you install a 1/8" coin valve here so you can remove the grill and use a screwdriver to bleed the unit) I use a large sponge under the bleeder to catch the water, when all the air is out close the coin valve and your good to go! Hope this helps-

Jells

Thanks @engdriver , but that was a year ago! All went well, then 3 months later the tenant complaining moved out anyway. So it goes...

SuperTech

I just read the whole thread not realising that it's a year old. How did you end up doing it? Did you use venturi tees or did you use the circuit setter?

Jells

Venturi's. The whole thing went smooth as silk, using PEX and a few Sharkbites I was able to do it quickly, and without doing any stinky soldering in the apartment, or even having to clear her crap out of the closet one of them backed on to.

coverer1

How did you do it with shark bites when you needed Venturi/monoflo tees?

Jells

In my workshop l soldered up the venturis into a single section of 3/4 inch pipe, properly spaced with plain pipe on either end, and then used SharkBites on either end to connect into where I cut the loop. I also did the soldering to prep the units to attach the pex in my workshop.

coverer1

Did you install air vents?

Jells

coverer1 said:

Did you install air vents?

Not sure what you mean. Bleed valves to clear the kickspace units? I think I said upthread, yes on the one above the line, no on the one below that would feed any air back into the WH system with an air vent.