Upgrading the system

JasonA

Hello,

I have been lurking for awhile, getting an education and preparing to make a few changes to upgrade the existing heating system in my house. Here is a general description of the existing system and components and attached is the proposed upgrades to this existing system.

3-Story Brick Row House, approximately 2,100 SF living space.

100K BTU Natural Draft, Cast Iron, HW Boiler

3-Zone HW

Cast Iron baseboard, panel convector and UC fan coil units

Zone One is a mix of CI baseboard and the panel radiator (towel warmer) – piped in series

Zone Two is a mix of CI baseboard and two FC units – piped in series

Zone Three is all CI baseboard – piped in series

One B&G circulator piped on the return side. 24V zone valves with end switches.

No controls other than the packaged aquastat that came with the boiler. Aquastat set at 180 degrees



Current Issues:

1. Zone One does not keep the current keep the current room warm, a marble floor coupled with the CI baseboard enclosed in under a bookcase is the likely problem.

2. Zone Two – The CI baseboard is at the end of the series and does not get warm enough where the heat is needed most.

3. Zone Three – the last CI baseboard element has to be blead on a nearly daily basis.



The attached layout shows the proposed changes highlighting the following:

1. Moving the pump to the “pumping away” location and replacing the existing scoop air eliminator with a Spirovent

2. Breaking Zone Two in two. Putting the CI baseboard on one series loop and the fan coils on another and piping the fan coils with diverter tees.

3. Zone One gets the biggest change, adding a 3-way mixing valve, circulator and radiant floor loop and piping the radiant floor and the panel radiator (towel warmer) together at the new lower temperature. The radiant floor/towel warmer to be controlled by a Tekmar D- 510A two stage heating thermostat with slab sensor. The first stage would be the floor/towel warmer and if required the second stage would kick in the CI baseboard (IHL-3)

4. Adding a Tekmar D-260 outdoor reset controller to modulate the boiler temperature.



Your thoughts would be greatly appreciated. Am I missing anything? Is this complete overkill? Are there any gross errors in my thinking and or the piping layout?



Thanks



Jason

Tim_Hodgson

At what temperatures

do the fan coil motors turn on and off?

Good Luck,

Tim 

JasonA

Kick Space fan coils

They have a built in low limit that is supposed to come on at about 110 degrees. Good point, I assume the set back control must have a min temperature set point.

Ironman

Piping Corrections

There are at least two corrections to make. They are indicated by the green lines that the Taco Flo Pro program produced. The program will change the line colors to red or pink when the piping is correct.



1. The fan coils will receive no flow unless you use mono flo Tee's (not recommended) or secondary circs on each.



2. The return from the manifolds needs to be connected at the same point as the cold (return) port from the mixing valve. In other words, the valve's return line cannot connect to the common return line, but must connect to the return branch coming from the manifolds.



I have to go out the door for now, but will review your control strategy later.

JasonA

Where are the monoflo T's?

I made the corrections to the floor loop but I am still getting a green line from the Taco program so I guess there is still a problem?



I can't find the symbol for monoflo or venturi tees in the program - the only option available is Twin Tees which are for Primary/Secondary systems.



Thanks for your help

Ironman

Try This...

Put a manual balancing valve between the supply and return Tee of each AHU.



You also need to tap the supply Tee for the radiant floor loop up stream of the main circ, not down stream. In other words, put it between the air separator and the main circ.

JasonA

Green lines

Made the changes and still getting the green lines. Is it all just semantics here?



Regarding the Kickspace fan coil units. What is the preferred way to pipe these units? I have access to split them off of the existing CI baseboard loop but I do not have access to run each of them independent of each other.



Is the flocheck in the correct location?



How does the proposed control package look?



Thanks again.



Jason

STEVEusaPA

for starters....

I would remove the balancing valves between the tees to the fan coils.  Depending on how the heat load is being distributed in that loop, you could leave them in series with the baseboard, putting them before the CI or after, depending upon what you need for temperature.  But in that case, you're asking alot of your circulator. You're going to definately have to make sure you calculate & pick the right one.  As far as the green lines go, I can't redraw my home system on this software and get it to 'work'.  I don't know if it's because I'm only using the trial version.  I would like to purchase the full version, but if I can't make it work on an already designed system, I don't want to trust it.  I also dont think the flow check in the radiant zone is in the right spot, but I would defer to the amazing Ironman for his thoughts.

JasonA

Piping the fan coil units

Doing a little research on this site would suggest that the simplest approach would be to put the two FC units on their own zone with their own circulator. It is going to be very tough to re-pipe these units with monoflo tees and/or squeeze in a 1/2" bypass (both FC units are now piped in a series loop and both are 1/2" loop type, non-manifold). I would leave them in the same series configuration and set up the flow to where I want the "hotter" unit to be.



The flow control valves were put in the drawing to try and convince the "program" that the design was correct. The intention was to show monoflo tees but they are not part of the "program" selections.

Ironman

Fan Coils

I would agree that the best approach would be to have the fan coils on their loop / circ. The "amazing" Ironman had missed your original description that these were toe kick heaters and I also assumed that you may not have been able to re-pipe them separately back to the boiler.



The green lines may still be showing on that loop because you would need a third flow control on the branch that splits to the rads to force flow back to the fan coils. Remember, water (like people) will always take the path of least resistance unless compelled to do otherwise. Splitting out the fan coils is the best solution.



I would also connect the towel warmer to the radiant manifold if you're going to supply it with the same temp water as the floor, but you may find that you want hotter water to it. In that case, you'd have to separate it from the radiant mixed loop. The radiant floor/joist symbol that you've selected may also be causing the green lines to show. It should be connected to the manifold or eliminated from the drawing



The green lines on the radiant loop are probably still there because of the orientation of the mixing valve. The center port is the mix port and should be connected to the circ inlet. Put the check valve on the discharge side of the circ or use one that has an internal check and you should be OK.

JasonA

Final Design

Still got some green lines but I believe the concept is correct.



Please take a final look and let me know if you think I have everything in the correct order.



As far as sizing the pump for the FC unit loop. I did the base calculations, based on the TACO formula and used 3 gpm as that gives me the highest output for the FC units. Looks like a 005-IFC fits the bill.



Thanks again.

Ironman

Looks Good

The 3 way valve that you selected is a control valve (CV), not a mixing valve. Replace it with a mixing valve (MV) and  the lines should turn the right color. The mixing valves are the icon with the green head, second from the left on my edition.







P.S.

 Some further considerations:



1. Boiler reset is a good thing, but you don't want the boiler below 140* (unless it's a Buderus) or you'll get condensation and rot the boiler and flue. Loop reset would allow lower temps but require more re-piping.



2. 100btu's looks a little heavy unless you have a very loose house. You should calculate what your heat loss is and determine what the load is on your smallest zone. If it's substantially less than the firing rate of the boiler (and it probably will be), then you should consider a buffer tank to prevent short cycling. Short cycling will shorten the life of the boiler substantially and result in lower efficiency.

JasonA

Loop reset

The boiler is 100K input - 83K output. It probably is on the large side - 25 years old so something more modern is on the horizon



Loop reset - so now I'm going primary/secondary? Isn't there a minimum boiler water temp setting on the reset control or is there another make/model ILO the Tekmar that does have one?



I see there can definitely be a low temp water problem on the radiant loop if it is the only zone in play. Would this be better piped with a 4-way mixing valve ILO of the 3-way?

Ironman

I Don't See That...

Improving boiler flow when most of the water is circulating in the radiant floor and bypassing the boiler (referring to a 4 way valve).



Regarding a buffer tank: If you use a 2 pipe tank, you won't need another pump or pri/sec. piping. Just pump through it. If you use a 4 pipe tank, you'll need an extra circ and the tank will be your hydraulic separator that creates pri/sec.



And yes, the Tekmar has an adjustable curve with minimum boiler temp as well as a boiler protection feature.

JasonA

Sizing the buffer tank

That statement regarding the low water temp on the radiant loop did not make much sense.



The radiant loop will probably run about 120 degrees (under floor staple up with heat transfer plates heating 1/2" thick marble on 1-1 1/2" mud base). If I use a 3-way valve won't the return temp to the boiler be less than 120 degrees if only the radiant loop is in play? If I use a 4-way valve I should be able to keep the boiler return temp above the danger zone for my non condensing boiler?



I'll do my homework on the buffer tank but how do I go about sizing the tank?



Thanks for all your help.