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Basement single series loop; convert to direct return or ?

I am at my wit's end here. I've been crash-coursing for the last month on how I can get a little bit more granular control in my basement.

- Sq-ft is around 1100sq/ft for that level.
- Climate zone 6
- It is a single series loop of varying baseboard fin-tube lengths with 3/4" piping.
- Some bleeders on baseboard, other bleeders at 90-degree elbows on vertical risers of the loop. (some are leaking)
- Level is unfinished and open.
- Boiler is a Slant-Fin S-90 EDP.
- Pump for that zone is a Taco 007 on the return side of the boiler.
- Other level is heated by elements in the ceiling fed by a header and a B&G nrf22 - water temp is reduced with a mixing valve. ( I do not want to mess with this at the moment)

I'd like to implement some level of control using TRVs. From what I'm hearing these are nice for matching load, and coupled with a smart thermostat with remote sensors, would minimize electrical work with electronic valving. The only drawback I can see is the TRV can't be set-back at night or when there are no occupants in the house.

Initially I was excited to see some 3-way bypass TRVs. I figured the series was sized so elements down the line accounted for lost water temperature anyway so at design load, all TRVs open, the elements could still heat their areas. I was unable to find these 3-way TRVs. I did see a "bypass" set-up in baseboard (using copper tees and piping) to bypass the TRV and element with the TRV closed, but I never saw a confirmation of this working due to flow and pressure conditions.

Then I happened upon direct and reverse return designs. I've read that direct returns can work well with TRV and proportional pressure pumps. Reverse return has some balancing benefits.

I am not averse to doing some re-piping. I'd like to minimize expenditures on new things like a manifold and pex runs or convert to manifold zoning. I will if I have to, but if one of these other designs can work, I want to start there.

Any advice is appreciated. I am definitely willing to throw money at a heating person to do calcs or consult or quote and that is my next avenue if it looks like this is the direction I can take.

Thank you.


  • ch4man
    ch4man Member Posts: 296
    are you finishing off and or zoning the basement? it sounds as though its a wide open unfinished room. does it not heat well now?

    is the system zoned now as it is or does the basement heat when the second floor calls for heat, how many thermostats do you have currently
  • homegamer5000
    homegamer5000 Member Posts: 3
    Each floor has its own thermostat that calls for heat in its own zone. The house is a rectangle so the footprints are the same for both floors. The supply for the basement is a 3/4 tee off of the boiler hot side straight to the fin-tubes. The first level's supply goes to a mixing valve that runs to its pump and up to the header. The return side of the first floor zone comes back to a header with what I believe to be manual balancing valves.

    The basement has rooms heated by fin-tube elements. The largest being the "living room" where the thermostat is. I am doing some remodeling (basement is pretty much all open) and mostly following the same layout with improvements and I wanted to get this sorted before continuing. I want the rooms to have some amount of adjustment for comfort and to make it more robust to accommodate improvements down the road.

    This system as it stands is at minimum 20 years old. I am not worried about age per se, but perhaps in 10-20 years it will be time get a better boiler or something. On top of this, the bleeders are leaking and I do not want to finish the space with leaky bleeders.

  • homegamer5000
    homegamer5000 Member Posts: 3

    I guess I just want to know if it's feasible with my current boiler to do this. I don't want to cause it to short-cycle. I do want to make the system robust for future upgrades to more efficient equipment.

    Thank you.