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Buderus Panel Rads - Do I NEED a Pressure Accuated Bypass Valve?

LegendsCreek
LegendsCreek Member Posts: 61
edited February 2016 in Oil Heating
Hi Everyone. I am hoping for some quick advice on a set up I am doing in my guest house.

I am replacing a zone on a oil forced water boiler with all Buderus panel rads. I had a zone in my home changed to these last year and I love them.

My question is: I am doing 3 rads, bedroom, bathroom and livingroom. I am doing a 2 pipe direct return. I am installing 3 thermostats onto the rads so each room can be directly controlled. There is also a wall thermostat that we will be using. Buderus says I need to install a pressure actuated bypass valve between supply and return. I don't know why, but I was going to purchase it and then saw that it's $215. That is expensive. Do I really need the valve? If so, are there cheaper ones? OR, can I just replace the pump on the boiler for this particular zone? I read that newer pumps are much more energy efficient, and they take away the need for this bypass valve. If so, what kind of pump should I get? The pumps on the boiler now are at least 40 years old and should probably be replaced anyway.

Thanks in advance for any advice.

Comments

  • SWEI
    SWEI Member Posts: 7,356
    How many pumps are currently in the system? Can you post a photo of the pump(s) and surrounding piping, hopefully to include the boiler?

    You should be able to replace the existing pump with a modern ECM circulator and dispense with the PBV altogether. The system will run more efficiently and quieter as a result.
  • LegendsCreek
    LegendsCreek Member Posts: 61
    Thanks for the reply. Please see the attached photos. 1 of the 2 pumps that heat the building, and 1 with the boiler. I would much rather replace the whole pump than to buy a PBV.

  • SWEI
    SWEI Member Posts: 7,356
    I see two circulator pumps in the second photo. Does this boiler also heat your domestic hot water?

    The boiler and the pumps are both well past their wear dates. The corrosion and rust are not good signs. Do you have natural gas available in the area?
  • LegendsCreek
    LegendsCreek Member Posts: 61
    There are 2 pumps, correct. It does not heat the hot water anymore, I capped it off and we heat with electric tankless. There is no gas in our area.
  • SWEI
    SWEI Member Posts: 7,356
    I can't find a catalog reference, but I believe the boiler probably dates from the mid-late 1960s. It somewhat desperately needs a trained set of eyes on it before you start replacing parts. Where are you located?
  • LegendsCreek
    LegendsCreek Member Posts: 61
    edited February 2016
    I am in RI. I have had the boiler serviced already. It's working fine but will need to be replaced in the next few years.

    Do you think I need the bypass valve for the Buderus rads, or can I replace the pump that supplies the zone I am working on so avoid using a bypass valve?
  • LegendsCreek
    LegendsCreek Member Posts: 61
    I forgot to mention, the boiler looks like it's in rough shape because it sat in the boiler room for 14 years without being used and a roof leak, so it got rusty. They serviced it (reputable company I use for all 4 of my boilers), and it's working great though I need to replace is in a few years.
  • SWEI
    SWEI Member Posts: 7,356
    Do you get your electricity from National Grid? If so, I believe there is a rebate on ECM circs that should reduce the cost of a modern ECM variable speed circ to about that of a conventional wet-rotor circ.

    What kind of emitters are in the house? How big is the house and roughly what kind of envelope (insulation, windows, etc.)?

    Can you post a photo of the pressure tank and auto-fill device? I'd like to see if we can verify a couple of things here.
  • LegendsCreek
    LegendsCreek Member Posts: 61
    I am not sure how to answer any of your questions about emitters, envelopes or any of that. Electric is from National Grid so I will check for rebates. Can I switch to any ECM pump for this zone to avoid having to use the pressure bypass valve, or only to a specific pump? What should I look for when buying the pump to make sure I don't need to use the PBV?
  • SWEI
    SWEI Member Posts: 7,356
    A variable speed ECM circ will not need a pressure bypass. It slows its flow based on either the difference in pressure (from zone valves opening and closing) or the difference between supply and return water temperature. For a single zone, I would suggest the Taco VT2218, which is the model that works off of temperature difference. You should be certain the system is clean (inside) before you install one of these new pumps. They have very strong magnets in them that will attract rust particles and foul up the works. We can help you through that process if you post more photos.

    https://www.nationalgridus.com/media/pdfs/resi-ways-to-save/ri_hehe.pdf says the rebates apply only to gas heating customers, though I believe most of the supply houses back there are giving an instant rebate on the circs right at the counter.
  • SWEI
    SWEI Member Posts: 7,356
    Envelope refers the type of construction and the condition of walls, doors, windows, attic, etc. That and the square footage of the house will help us understand the heat requirements, which can factor in to pump sizing. I doubt there will be a problem, but it's always good to have as much info as possible when attempting to advise on a system we can not see in person.
  • SWEI
    SWEI Member Posts: 7,356
    Forgot to ask if you are planning on using TRVs with those panel radiators? If so, a ΔP pump design (like a Grundfos Alpha or the Taco VR1816) would probably be a better fit.
  • LegendsCreek
    LegendsCreek Member Posts: 61
    By TRV, do you mean the thermostat dial that goes on the radiator? If so, then yes I am using them.

    The building is over insulated, new windows, 2 layers of plywood under the drywall, drop ceiling with attic above that is also very well insulated. It's a small buildings so I was hoping since there are only 2 zones I can use a less expensive pump.

    Would something like the Grundfos UPS15-58FC work well? I like the price being close to $100.

    Thanks again
  • That particular Grundfos pump is not an ECM pump. The UPS15-58FC has a selector switch: low-medium-high that you set once. ECM pumps have a brain; depending on the kind you choose, they will detect differences in pressure or temperature and come up with an ideal RPM to heat the emitter.

    Let's say that you set your thermostat to 68°, but you set your radiator thermostatic radiator valves (TRV's) to 60°. As the TRV's start to close as the rooms reach 60°, an ECM pump will detect either the increase in the pressure drop or the increase in temperature and reduce the speed of the circulator. Eventually, all the TRV's will fully close and the circulator will ramp down to the slowest speed. The setpoint on the thermostat has not been satisfied and is still telling the circulator to keep running, but the circulator knows to slow down.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour
  • GW
    GW Member Posts: 4,592
    Seems like the consensus is spend money on a good pump and save some money and skip the bypass valves.

    To anewer your original question, no they are not required.

    Before the ecm pumps got popular we would use the 1558 pump you referenced, but one rad would have no trv, the room where the "room sensor" was installed. That way the 1558 could not dead head.

    Gary
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • LegendsCreek
    LegendsCreek Member Posts: 61
    Great advice. I am learning a lot! I do have an unused bumblebee by taco that I was saving for my wood boiler install. Would that be a good pump for my situation?
  • Ironman
    Ironman Member Posts: 7,076
    You need to use a delta P circ like the Grundfos Alpha or the Taco VR1816. Either of those work of a pressure differential so that when all the TRVs close the circ basically stops. The BumbleBee won't work.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • LegendsCreek
    LegendsCreek Member Posts: 61
    Hi again everyone. I just installed the Grundfos Alpha (painless install), but I am wondering about which setting is appropriate for the buderus panel radiators (because I didn't install the pressure bypass valve). There is an "auto" setting on this pump that supposedly learns, should I keep it on Auto?

    Thanks!
  • Ironman
    Ironman Member Posts: 7,076
    Yes. And open the flow setters on the rads all the way. They're under where the TRVs mount. Check the rad instructions for details.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • LegendsCreek
    LegendsCreek Member Posts: 61
    Thanks a lot. I have it set on Auto, and I have the flow settings up all the way, but I still haven't been able to install the TRV because I can't get the damn things on (they aren't the same brand as the ones in my house and they won't install).
  • GW
    GW Member Posts: 4,592
    What's is not doing? I've never seen one not fit.

    Gary
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • bmwpowere36m3
    bmwpowere36m3 Member Posts: 512
    Using Danfoss TRVs? Should just snap in place... like these: http://www.supplyhouse.com/Danfoss-013G8250-Direct-Mount-Operator-5558000-p?gclid=CJLsqonfmMsCFYIqHwodUxkN5A

    That's what I'm using with my Buderus panels.
  • LegendsCreek
    LegendsCreek Member Posts: 61
    I used Danfoss on my last install and they went on fine. This time I am trying to use Caleffi, the link is: supplyhouse.com/Caleffi-200000-Thermostatic-Control-Head-with-Built-in-Sensor-45-82-F
  • hot_rod
    hot_rod Member Posts: 18,210
    Got a pic of the valve you are trying to install the TRV on?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • LegendsCreek
    LegendsCreek Member Posts: 61
    Sure, the buderus valve is below:
  • hot_rod
    hot_rod Member Posts: 18,210
    Here is what the Caleffi valve looks like, the TRV screws right onto it.

    For "convertible" shut off valve, that plastic adapter ring snaps into a groove to give you the correct thread for the TRV.

    It sure looks like that Buderus valve has a much taller head, I don't see the Caleffi TRV actuator adapting unless that top is change-able.

    I'm not a Buderus expert, someone here will know? It may require the Buderus TRV head?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • bmwpowere36m3
    bmwpowere36m3 Member Posts: 512
    Buderus listed TRVs are Danfoss units, like the one I posted. They don't thread-on, though Danfoss does sell a "convertor" for those style valve bodies.
    LegendsCreek