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boiler hi-lo cutoff control question

Steve Zerby
Steve Zerby Member Posts: 3

I was referred here by someone over at Fine Homebuilding's forum.

I've got a weil-mclean boiler with a tankless coil that is disconnected. The boiler still is operated by the hi-lo cut in switch for the tankless, which means that there is a max temp burner cut-out setting and a minimum temp cut-in setting.

When the boiler is turned on, it will keep the water at the min. temp setting. Since I don't need to keep the water hot for the tankless coil, is there anything wrong with turning the minimum cut-in setting as low as it will go? Would it be better to change the control to a cold-start control, or is there some benefit to keeping the water in the boiler at about 120 even when not calling for heat?

Also, I just burned up my second circulator in about 10 years. Is that normal? It's one of two Taco 007 circulators, each on their own zone. The zone that has had the circulators fail on it both times consists of two toe-kick heaters and about 15 feet of baseboard.




  • Leo_17
    Leo_17 Member Posts: 9
    Low Limit


    I service oil burners daily. If your Weil Mclain is an older one 66 or 68 series unless it makes hot water with an indirect I would keep the Low Limit at 120 or else it will clog up over the summer. If you are hard pressed on turning it off for the summer get it cleaned in May to save you money and the tech aggravation. Weil Mclains of this era and a Peerless JOT boiler are the worst for cold starts and being turned off for months at a time. Remember I have nothing to gain by the little extra oil you may use I am only speaking from the perspective of a tech who often has to deal with messes.

  • FredH
    FredH Member Posts: 18
    Boiler Wiring Question

    Just bought house

    Here is what I know

    1964 American Standard Arcoliner  wideback with General fittings tankless (estimated  original cap 5GPM) 164,000BTU/hr Becket burner

    Hi Limit Detroit Lubricator (Breaks burner line voltage on temp) Set at 185 Deg (Coasts up to 200+ ) Closes at approx 160 Deg

    3 taco 007 circulators with 3 American Standard relays with terminals for TT and SS(stack switch is non existing but looks like they are wired and jumped)

    3 luxon programable thermostats (new to replace old Honewell mercury round)

    I assume thermostat controls circulators only but not sure.

    Here is confusion.

    SPDT American Standard aquastat in tankless well is wired  NC(normaly closed)

    back to TT on burner relay (however, it is always closed, I am assumining it is malfunctioning.) it is wired in parallel with wires going back to circulator relays but not sure why. I think that it is just a complex (cobbled) way to jump TT on burner relay. Possibly an attempt to disconect circulator  and fire burner on low temp but not sure how. Not sure when NC opens( above or below adjustable setting)

    On back is White Rogers 11d31-1 spdt wired to close on rise to break line voltage to circulators. Adjustable differential is set to as close to 0 as possible

    If not set to 120Deg, circulators will not turn on and boiler will hang a few degrees above 160 deg on hi lim switch.

    Is it normal to have such a differential from top (temp/pressure guage and lolim sensor? It seems like a rather primitive way to control.

    Is boiler just bouncing between differential on hilim switch.

    what about thermal shock?  Should of cracked a long time ago.

     30 deg outside with all 3 circulators calling for heat, boiler  drops  to 130degs and  I still have hot water for shower. Tankless does have 30 gal aqua boost with its own circulator and separate aquastat.

    heating approx 3000 sq/ft (1000 perzone) Have not updated insulation yet.

    any advice/insight   

     would Intellicon HW+ help  save $ or just lower differential on hilim? Would circulators ever turn on?
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