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  1. #1
    Join Date
    Feb 2004
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    Where is air is clean
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    Question Weil Mclain ultra

    I'm having a conversion done from oil to gas in my home. HVAC guy is putting in a Weil Mclain ultra 155...I've seen the work the HVAC guys does and as a novice I can say it was VERY neat and impressive,,,It was at the house of the electrician that will be wiring up the boiler. That job had standard gas unit (not a mod con) with multiple zones radiant heat ect. and indirect DHW..The electrician was showing me the Tekmar unit that controls his whole unit saying that him and the HVAC guy never did a Weil Mclain MON CON yet but that I would have the Control unit. They both have over 25 yrs in the business.
    My question is the Weil Mclain spec's show the the control board is built -in and handles all controls,, and that when adding zones you just have to use a relay to each zone pump,,I'll have 3 heating zones and 1 indirect for DHW..Will a Tekmar be necessary??

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    67,875
    Unless you heating zones all need different water temps. you don't need a tekmar.

    Just a zone panal with to turn the zone circs on and off, and an end switch to tell the Ultra a heat zone is calling. The Ultra's control will handle the water temp from there. It has its own outdoor reset built into it.

    Also, the Ultra has a seperate terminal set for the indirect, that over rides outdoor reset when it gets a call for domestic hot water, so that it will increase water temp to heat up the indirect quicker.
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  3. #3
    Join Date
    Nov 2008
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    12

    Confused ???Mclain Ultra thermostat wiring ???

    What is this "end switch" that cues the Ultra boiler? I don't have one.
    I have 2 secondary zone pumps. Right now they are controlled only by the room thermostat through two seperate relays. The boiler is always maintaining its parameters due to the jumper across the low voltage #5 and #6 terminals on the Ultra.
    Should I have the pumps wired to the Ultra terminal with this "end switch" so the boiler can shutoff with the thermostat?

    Great website we have here!
    Last edited by ultra105; 11-12-2008 at 05:37 AM. Reason: please make this clear to me

  4. #4
    Join Date
    Jan 2004
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    Lancaster PA
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    That goes into DIY, which is not allowed on thise site.

    Question is. Do your relays have end switches.

    An end switch, is a dry contact switch. Which is what hooks to the Ultra's heat terminals.
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  5. #5
    Join Date
    Nov 2008
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    12

    ultra 105 end switch

    The guy who installed my boiler had never installed an ultra before mine.
    I read the manual after he had finished and it brought up a few good questions.

    Is it bad to have my boiler thermostat always on, so when my zone pump thermostat kicks in , it crashes a bunch of cold water into the hot primary?

    Wouldn't it be better to let the whole boiler cool down when there is no call for heat?

    I am concerned about thermal shock and efficiency.

    If I can get the right answers here, I can have my HVAC guy come back out and wire it correctly!

  6. #6
    Join Date
    Jan 2004
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    Lancaster PA
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    67,875
    Quote Originally Posted by ultra105 View Post
    The guy who installed my boiler had never installed an ultra before mine.
    I read the manual after he had finished and it brought up a few good questions.

    Is it bad to have my boiler thermostat always on, so when my zone pump thermostat kicks in , it crashes a bunch of cold water into the hot primary?

    Haven't had one that had a problem with that. I have several on zoned systems, and that is a common occurance when one zone satisfies, and another calls shortly after.

    Wouldn't it be better to let the whole boiler cool down when there is no call for heat?

    Its a waste of fuel maintaining boiler temp 24/7.

    I am concerned about thermal shock and efficiency.

    If I can get the right answers here, I can have my HVAC guy come back out and wire it correctly!
    The outdoor sensor should be ran, so the Ultra can use its outdoor reset abilities.
    And the end switch of the circ relay/relays be wired to control when the boiler runs.

    Maintaining boiler water temp 24/7 lowers AFUE.

    The Ultra, will down fire itself if it gets too much cold water fed into it when its hot.
    The factory programing lowers firing rate, if temp rise exceeds 30F differencial. Which helps a little to protect agianst thermal shock damage.

    Its normal, for zoned systems to be at temp from satisfying a heating call from one zone, and then another zone calls, and the boiler has room temp water coming into it when it was already up to temp.
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  7. #7
    Join Date
    Nov 2008
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    ultra 105

    Good, so I won't worry about thermal shock so much anymore.

    I don't think my zone relays have an end switch, but I don't know.

    I will ask my contractor what he knows about it and see If he can hook it up better this time.

    I can see where I am wasting fuel keeping boiler hot 24/7

  8. #8
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    Jan 2004
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    If they don't have end switches.
    Bite the bullet, and have him install circ relays that do. Or a zone panel that does.
    It will be worth the money.
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  9. #9
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    Nov 2008
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    Zone circ relay with end switch

    Thank you so much for your time and expertise!
    You are a very helpful person and many people are grateful for you.

    After the guy installed my boiler, I felt like I couldn't critique his work/knowledge even though this was his first Ultra!

    I am hoping that with this forum's help, I can gain enough knowledge/confidence to go back to my installer and help him learn a new trick or two!


    I will get that outdoor temp sensor installed,
    I will get zone circ relays with end switches that wire to the boiler,
    I may need a bigger bladder tank than the one gallon I have.
    I haven't ran the boiler any hotter than 150 yet.

  10. #10
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    Jan 2004
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    Hopefully, your exagerating how small the expansion tank is.
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  11. #11
    Join Date
    Nov 2008
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    12

    expansion tank too small?

    Quote Originally Posted by beenthere View Post
    Hopefully, your exagerating how small the expansion tank is.
    NO, its only one gallon! And the guy left if pre charged at 40psi

    I had immediate problems after he left!

    I lowered the tank pressure to 14psi, but it is only one gallon!

    Should I have him install a 3 gallon to be safe, I do have a small house with only 12 radiators?

  12. #12
    Join Date
    Nov 2008
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    12
    Maybe my low pressure explains why the upper zone pump makes so much noise when running.

    It's at 15psi hot. I think he started it at 9psi cold.

  13. #13
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    Jan 2004
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    It sounds like he used a domestic water expansion tank, instead of a heating expansion tank.

    Standard small tank for heating is 15 gallon.
    12 PSIG factory precharge.
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