Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Boiler Protection

This is a budget job. What is the easiest way to protect a cast iron (Peerless) boiler from low return water temperatures. Three zones are BB; another three zones are slab-on-grade radiant. Primary-secondary piping.

I don't want to use an ESBE thermic bypass valve since I've had problems with them and want to try something other than Siggy's double thermostatic valve method.

Viessmann Vitogas will turn off the primary pump if return water temperatures are below a certain temperature.

Any thoughts?

<A HREF="http://www.heatinghelp.com/getListed.cfm?id=53&Step=30">To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"</A>


  • hr
    hr Member Posts: 6,106
    Those are the two

    simplest, and least expensive, ways to offer some protection. Personally I don't worry about return protection on low mass systems like baseboard. Hundreds of thousands of them running fine without return protection.

    It's the high mass systems that can present prolonged, and damaging, cold returns. Someone, maybe Siggy, mentioned that IF the radiant load is less than 1/4 of the boiler output, the return protection issue is much less severe.

    A simple, simple method would have a setpoint control at the boiler return, that would just drop off the radiant pump if temperatures fall too low. Much like the Viessmann system, except it would allow the boiler to continue to supply BB loads and merely pulse the heat to the slab.

    VS injection mixing with a Grundfos MixiMiser is a fairly inexpensive way to get your radiant mix temperature, boiler protection, and even outdoor reset (on the radiant zone) for a few hundred bucks. Since you are already P/S piping :) Still one of my all time favorites mix methods.

    hot rod

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • Boilerpro_3
    Boilerpro_3 Member Posts: 1,231
    Say, what problems have you had with the ESBE thermix?

    I stay away from the 1 inch, since they don't flow very well. You definitely have to keep your delta tee tight since the 140F return model doesn't open fully until 160F, so supply is already at 180 with 20F delta tee. Also, you really need to have your air seperator on the boiler loop and always pump P/S so when the valve is in bypass mode, you still get full flow to the system to keep it properly balanced.

  • ESBE

    didn't work and allowed the boiler to see low water temperatures.

    That's a good idea, hot rod; aquastat on the primary piping, normally closed, break on temperature drop and set it at 140°. Sound right?

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • zeb_3
    zeb_3 Member Posts: 104

    For inexpensive boiler protection I install a 1/2" by-pass from the supply to the return, throttling it w/ a valve manually.
  • DaveGateway
    DaveGateway Member Posts: 568
    Cycle the pump

    I've had tremendous success with cycling the low temp pump with an aquastat. The Penn/Johnson A419 digital is an inexpensive remote sense temp controller that I've also used for slab sensing. On an existing mix temp system it is a control option that provides boiler protection without intrusive repipe. The wide diff. allows a long cycle for even the lowest mass of boilers to 'recoup' as long as it's piped P/S.

    Sorry BP, I have always been into thermic valves but it seems I have to grab my suppliers by the throat and DEMAND them.Default sent me the electric way......
  • DaveGateway
    DaveGateway Member Posts: 568
    Manual Bypass

    Unless you are going to be there for every "cold slab" start up, which includes the stat turned off for a day, you cannot gaurantee boiler protection with system or boiler bypass piping strategies.
  • Alan , like Zeb says

    we use a simple bypass between the supply to the return if it's needed . To keep it inexpensive , what about installing a reverse acting aquastat in the return pipe to shut off the zones if the water temp get too low ? What model Peerless is it ?
  • hr
    hr Member Posts: 6,106
    A bypass alone

    will not assure adequate boiler return protection, as it has no way of knowing what the return temperature is, and no way to respond.

    It's "thermaly challanged"

    It certainly helps a bit and is standard equipment on all small residential Raypak copper tube boilers. But go a step further for protection of you customers investment :)

    It's become more critical with high mass low temperature emitters and smaller boiler hx and capacity.

    Click on the link below for some other ideas from the Burnham folks.

    hot rod


    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • Mike Kraft_2
    Mike Kraft_2 Member Posts: 398

    Wheels turned me on to this,Tekmar 260.Gives boiler protection as an injection loop.I bid a job that a gravity system was trashed.The first and second floors were piped in series loop to allow zoning:(.I also was showing this to Noel for his opinion.(its a Slant-Fin boiler)He liked it but felt a bypas was also a good idea.I tend to lean towards the control with the sensors.This home has all cast rads.Needless to say it doesnt work to well.The chimney was unlined and all the plaster fell off as the flue gas was a tad bit moist.


    It may have a bit more than you want but seems like it may help.

  • hydronicsmike
    hydronicsmike Member Posts: 855

    ...You must have been thinking of a 360 (Floating Action) or 361 (Variable Speed Injection) Control that will use a motorized Mixing Device for Boiler Protection. The 260 is a Boiler Control. It can maintain a Boiler minimum, but if you truly need to protect a Boiler from low Return Temperatures, you must use a motorized Mixing Device (or use a Thermostatic Valve in the Boiler Return like our friend BoilerPro does it).

    I hope this makes sense.
    Best Regards,

  • Mike Kraft_2
    Mike Kraft_2 Member Posts: 398

    The 260 wont allow the boiler to be protected from low water return?I interpreted it as giving the boiler pump priority for minimum temp on demand......no?

This discussion has been closed.