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Adding Baseboard to Existing Loop

Hi all,
I’m in the middle of a small renovation of my family room. I’d like to add some baseboard on the cold side of the room. Lots of questions below.

Background: It appears that the previous owner removed a section of baseboard that was piped through the slab before adding a fireplace (which I since removed). They never added a new section to compensate. 2016 I got a Lockinvar KHN085 installed by a local company. During planning I did my own heat loss calculation and noted that my family room was under-radiated by about 5 feet. Not a surprise as it has been a bit chilly in this room for the past 10 years. Fast-forward to today – I have an opportunity to add some baseboard to the cold side of the room as part of my reno. Room is on a slab, front and back walls are exterior and one wall is shared with the insulated garage.

What makes this a bit more difficult is that my family room is on a slab. I am also replacing the patio door with something a bit taller which will take up most of the stud space under the header not leaving any space on this wall to route pipe. The tile is not being redone, so trenching a pipe isn't an option.

System: Lochinvar KHN 085, 2 zones piped in series (1st Floor, 2nd Floor), slant fin baseboards, Taco 007 circulator used for the zones. I have the ODR set to run almost non-stop all winter. Very conformable in the house other than the area I am trying to deal with.

My proposed solution: My thought was to add the baseboard to zone 1 between the powder room (next to my family room) and the rest of the family room. See poorly drawn picture below (not to scale in the slightest). I would remove the elbow exiting the powder room and pipe straight out into the stud bay in the family room. I’d pipe up the stud into the ceiling, follow the joist bay to the other side, then back down the stud to the baseboard location. I’d pipe the return the same way, connecting back into the existing pipe headed to the rest of the family room.

With the additional 5 feet of baseboard, I’d be just under the 67’ threshold for the zone. As mentioned previously, I’d also be matching my heat loss per my calculations. My math was correct for the rest of the house.

Lots of questions.
1. I’d be adding ~60 feet of piping and a few more elbows. I assume this won’t be a problem for the circulator pump?
2. Any issues with going in the ceiling with this piping run? This configuration would lead some water being trapped in the baseboard if I would ever need to drain the loop. Should I be installing a drain valve next to the baseboard to drain if needed?
3. I’d like to use Pex (would use PAP). Do the copper to Pex adaptors present any flow issues that I should be worried about?
Looking for input on my plan. Any input on better methods or pointing out something I missed would be greatly appreciated.

Thanks all!


  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,531
    edited November 2020
    The 67 FT of radiation is based on 3/4" copper with approx 4 GPM flow. And that is based on an average Baseboard output of about 550 BTU per foot.

    By using a Pex Product with a minimum inside diameter of at least 3/4" you should be able to move 4 GPM with little or no noise. ( Noise is the main reason for the low flow rate).

    The Pump Head will need to be addressed. Pump Head is the ability of the pump to overcome the resistance to flow created by the piping system. Since you are adding over 60 ft of piping, you are adding more resistance. The rule of thumb for measuring pump head is

    line 2 is to allow for the friction loss of the normal amount of fittings. By using PEX and some of those radius brackets you will avoid a bunch of 90° elbows and that will help.

    Now compare that to your pump curve and you will have your answer.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,531
    Now, let's say the PAP you choose has an inside diameter that is slightly less than 3/4", You may need to increase the Pump Head to compensate for the smaller pipe diameter. You still want to try for 4 GPM thru the smaller tubing, but a stronger pump will accomplish that.

    You can even get 4 GPM to move thru 1/2" diameter tubing. The problem becomes the noise of water rushing thru the pipe. If you design correctly in the beginning, you don't need to re-engineer the system after the sheetrock is done.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • hot_rod
    hot_rod Member Posts: 21,844
    Another thought would be a recessed hydronic coil kit like this. This would avoid going up and over the door, have adjustable output, and draining would not be an issue.
    Put a thermostat on the blower and you also have a separate zone.
    may want to pipe a bit of an adjustable bypass to assure the fin tube gets adequate flow, most of these are 1/2".
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,531
    edited November 2020
    hot_rod said:

    Another thought would be a recessed hydronic coil kit like this. This would avoid going up and over the door, have adjustable output, and draining would not be an issue..

    That's what I like about you, BOB. You are always thinking "inside the box"

    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
    EBEBRATT-Ed Member Posts: 15,307
    With that much baseboard on the loop I would run a larger supply 1" and split the loop in half and run two returns. Add on rooms are exposed on more walls than a typical house. A split loop will reduce the pump head.

    Also running 1 loop will have the water temp cool off by the time it heats the last section of baseboard splitting the loop will operate better.

  • BoilerQuest
    BoilerQuest Member Posts: 17
    Makes sense. I appreciate the detailed explanation. So in my case, adding 60 feet of pipe, I’d be adding 3.6 head-ft of resistance to my zone 1. The Taco 007 Curve @ 4GPM says I have ~9.5 head-ft available. So is my extension going to put me over? Who knows - I never measured the actual piping and I know the installer didn’t.
    So, this morning I was able to measure my zone 1 length (thanks to my basement drop ceiling). Measuring from outlet to inlet of my circ. pump I measured 186 feet of piping (piping and baseboard total). Using the pump head formula, I get 11.16 head-feet for my current system. So I am currently past capacity or on the edge of my current pump. I understand this is an estimate, but does this sound right? If it’s this close, why didn’t the installers bother measuring or looking at these runs prior to selecting the pump? I’m not complaining as my system works well, just curious.

    What happens when the friction loss exceeds the pump capability?

    Thanks. Yes, that was my first consideration after searching around the forum for a bit. I’m actually building a seat/coat closet on the area not tiled in my first pic. I could easily fit something like that in the lower seat cabinet and be right where I need to be to tap my supply piping. However, I was hoping to avoid another T-stat, a blower, etc. if I could. More pipe seemed simpler at the time. I’ll keep this in mind. Any recommendations I should look into along with the slant fin Kicker?

    Thanks for the input. I agree that would probably be a better set-up, but I hope to avoid doing this. I’m not unhappy/unconformable enough with the current config. to do this yet. BTW, this was not an add-on room. The house was build with this step-down family room. Sits on the same plane/slab as the garage. Makes all kinds of stuff difficult – plumbing, heating, electrical…
  • hot_rod
    hot_rod Member Posts: 21,844
    A forced convection heater would only operate when the main zone does, they do have on off and 2 or variable speed control to fine tune it somewhat.

    There are other brands available with different features and noise levels, I just grabbed that pic.

    My though was to avoid all the extra piping, especially in the outside wall and the high spot you are creating.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    EBEBRATT-Ed Member Posts: 15,307

    Unfortunately most installers don't know how to calculate feet of head
  • Handyman 242
    Handyman 242 Member Posts: 15
    We want to get more water (BTUs) to flow so we have to remove as many restrictions as possible. I would recommend the following; it looks as though the return header on the zone valves from your picture is 3/4" copper, i would increase it to 1". You should also change out the existing TACO 571-2 zone valve CV rating of 6) to a Taco Z075-C2 which has a CV rating of 10 (less restriction), you will save .7 ft. of head loss through the zone valve. I like Hot Rods suggestion of the fan coil unit in the wall, when installed them I used 3/4" x 1/2" monoflow tee to feed the unit. In this way you would still maintain full flow though the base board loop. It would not be a separate zone but will work in conjunction with the existing zone thermostat.
    PS Most installers don't know what a CV rating is either or how to calculate the pressure drop through a valve.
  • slade8200
    slade8200 Member Posts: 5
    If it helps, I just added a zone to my boiler for the upstairs room in the garage. The room is 25x27, and I had 16' of electric baseboard and the cost was just unbelievable. We have expensive electricity in NH compared to other parts of the country, about 16c/kwh. Anyways, I took that out and put in 40' of hot water baseboard. The boiler is in the basement, so I had to go 40' across the house, 10' thru the breezeway, 10' up going into the garage, do the loop, all the bends and stuff (extra 30 or so feet) and then go back. I have one of those Grundfos 15-58 3speed circulators. The heat is absolutely amazing up there now, heats very fast and costs so much less.

    I also put 14' more feet of baseboard on my 1st floor in the house. There is 69' of baseboard so they split it (went from the boiler to the opposite side of the house in a 1" black pipe, then up to the baseboards and back around the sides of the house in 2 loops to the boiler. I have a 14x14 sunroom I finished but didn't put heat in, so I added 14' of baseboard to that off one of the 1st floor loops... works perfectly fine. If you're a little over the 63 or 67' magic number (don't remember what it is), I would not go crazy doing plumbing to correct this, you won't notice a difference in heat just because the last couple feet of baseboard don't have the 180deg water or whatever.
  • mferrer
    mferrer Member Posts: 33
    Not sure if this product would help or of its availability, but it may be worth looking into.

    It has a higher btu output than fintube. Maybe you can squeeze in a unit on the one side of the room and eliminate that long run uou were planning. Just a thought.


  • BoilerQuest
    BoilerQuest Member Posts: 17
    Thanks everyone. I really appreciate the input and ideas and helping me understand this stuff. Got sidetracked with patio door selection, but I’m back now.

    After reading through the replies and similar threads on the subject, I think I’ve been convinced to use a fan coil heater on the right side of the room and abandon the idea of adding the 60+ feet of piping to my zone. This really simplifies the piping involved as the main runs right behind the exposed joist. Here is my updated plan – any and all input is greatly appreciated.

    Plan: Install a K42 Twin-Flo III Kick Space Heater (inside cabinet yet to be built). Use ¾”x1/2” Monoflow T’s, spaced ~18” apart into ½” copper as shown below. Use hose kit between the copper ends and the heater.

    Heater: https://www.supplyhouse.com/Beacon-Morris-K42-K42-Twin-Flo-III-Kick-Space-Heater

    Hose Kit: https://www.supplyhouse.com/Beacon-Morris-HK-10-Kick-Space-Heater-Hose-Kit-for-K42-K84-or-K120-Twin-Flo-III

    Monoflow T’s: https://www.supplyhouse.com/Bell-Gossett-108119-3-4-x-1-2-Copper-Red-Ring-Monoflo-Tee?gclid=CjwKCAiA7939BRBMEiwA-hX5Jw7bork9yHW5OaLCjpzbPN3DXDlHmqsjkeUJ6kyClmc5qc67YKqllBoCbPgQAvD_BwE

    1. Should I use one or two ¾”x1/2” monoflow T’s?
    2. Should I add a valve in the ½ piping to allow for flow adjustment?
    3. Does the ½” piping and coil fan unit after the T’s count against my zone 1 head-loss? Or is it just the monoflow T’s that count? How much loss are we talking?

    I’m hoping to get this done without having to change out circ. pumps, zone valves, etc. if at all possible.