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Recirc Line

I have a new Lochinvar WHN-199 combined with a new Squire 67 gallon indirect water heater.  The Squire has a 1/2” recirc line, which is run with a Taco 006-BT4 pump (installed 10+ years ago).  This Taco pump is controlled by an Intermatic switch programmed to cycle on during priority times, depending on the day of the week.  Now that I can monitor the temperature of the Squire tank via the Lochinvar controller, it is clear that when the recirc line is flowing that the loss of BTU’s is relatively substantial.  Might there be a more efficient pump to use on the recirc line, in place of the Taco, which would provide a lower/slower flow, while not compromising the objective of having hot water available throughout the house when needed?  My thought is that a new pump on the recirc line will save both NG, due to less cycling, and electricity.


  • SWEI
    SWEI Member Posts: 7,356
    Changing the pump

    will save a bit on electrical costs and reduce noise.  By moving less water across the loop, you will reduce the ∆T and therefor the average temp of the loop, which should reduce fuel use by a small amount.  If you want more savings, consider insulating the loop (or replacing existing insulation with a with higher R-value) and optimizing the pump run times using either occupancy sensors or triggering on light switches.  If your schedule is relatively predictable, you might look at the SmartPlus learning pumps Taco is offering.  No direct experience with those yet.
  • heatpro02920
    heatpro02920 Member Posts: 991
    I like the grundfos pumps

    The tacos look good too..

    With Recirc systems, there are a few things I try to do when I install them to make them as efficient as possible..

    First the less time you run them the better, so I install a timer and aquastat, install the a-stat as far from the heater and close to the last fixture as possible {harder to do if you use an all in one pump}...

    make the recirc loop hold as little water as possible, small lines with a straight path

    Insulate all the DHW lines as well as you can, I run insulated pex and then run them in a separate bay {near heating piping if possible} and insulate them bays {new construction of course}..

    and run the recirc line at the lowest comfortable temperature...

    The ideal systems have occupancy controls, so when someone is in the bathroom or approaching a kitchen sink the unit starts, then only circs until that fixture has hot water waiting...

    Some day there will be faucets available that automatically do this and stop the pump when it is warm, but until then light, power, and motion sensors can be used, while timers and a-stats help, to me I just hate spending money on DHW. I can not wait for the day when DHW is handled with point of use heaters, just run cold lines and the heaters are built into all the fixtures...
  • icesailor
    icesailor Member Posts: 7,265

    Let me understand this. You replaced your old (probably oil) boiler with a Lochinvar 199,000 BTU boiler that had some sort of a Taco 006BT 10 year old circulator. How many BTU's was the old boiler? Was a proper heat loss done for the building? Unless you have one large hacienda, it sounds like it is way oversized. An oversized boiler which you mentioned will not have the same turn down ratio that a properly sized boiler will give you.

    But, they reconnected the old recirc line. And you are trying to save a slight amount of money by replacing the old circulator with another which will give you little if any savings.

    Those of us still living in the past, always put a Honeywell 4006A thermostat that would break on rise so when the return got hot, it stopped the circulator because the hot water was already back and there was no reason to run the recirculation circulator. If there is a clock timer that lets it run when no one is using water and just pumps water through the tank and back, THAT is un-efficient. The control scheme should be such that the boiler is on high fire when the circulator is on. You can heat an awful lot of potable water with 199,000 BTU's. In fact, 199,000 is a code limit for potable water heaters.

    You'll be stepping over $100.00 bills to pick up a possible hand full of dimes.
  • heatpro02920
    heatpro02920 Member Posts: 991
    You'll be stepping over $100.00 bills to pick up a possible hand full of dimes.

    depending on the size of your hand this could be profitable, key is to step in gum, then step on the $100 bill so it sticks to your shoe, then also pick up the handful of dimes.. Win Win...

    If his existing recirc pump is on its way out, noisy and inefficient, than changing it wouldn't be a terrible idea, I do see where you are going with this, unless his house is very loose and 5K+ sq ft he is most likely over sized on the heating side.

    As a pro this is nothing I am not used to seeing, I almost look forward to turning the basement corner of a 10 year old, 2050 sq ft, well insulated x6 construction, raised ranch and seeing the brand new Intrepid TR50 sitting there, this happened to me about 2 months ago, that slant fin tr50 will fire up to around 350K BTU's, and this houses heatloss is 60K TOPS... They pulled out a Burnham that was leaking and someone either had this monster sitting in their shop or was just asleep at the wheel, sad to say its not the most over sized appliance I have ever seen either... I replaced a pair of 700K BTU boilers in a small motel with a single 480K BTU unit, 5 years ago and to date it has never not kept up... One of the things that separates the good from the not so good in our business is the heat loss..
  • BostonGTR
    BostonGTR Member Posts: 18
    Recirc Line

    The pump on the recirc line is not making any noise; sounds like I'll just leave it in place.  The house is 6,000 sq ft.  The next smaller boiler from Lochinvar was the WHN155; which was undersized compared to the results from the heat loss study.  The controller settings have been tweaked for our house and as such the boiler is operating in the sweet spot; generating substantial savings over the oil boiler.
  • SWEI
    SWEI Member Posts: 7,356
    The heat loss calculation

    should probably be mandatory, but the devil would definitely be in the details as far as implementation.  This probably deserves its own post in the Codes forum.