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High limit aquastat for radiant floors?

i know alot of guys do not use manual reset hi limits on there radiant systems but i myself do espically if it's a high temp staple up job for me it is cheap insurance that some other service tech does not turn the mixing control or manual mixing valve higher then the floor or wood will handle .i personally know of 2 jobs where in fact this had happened and the HO was pissed the installation co blamed the service company and it went back and forth ,radiant install company ate it and re did the radiant and the floor but still never added a manual hi limit funny huh even funnier is that they install these sysytems and leave no service info ,layout and or system temps and better yet do not service any of these systems they install and still never install a manual reset hi limit i quess they like to pay hi preimuns on there insurance .manaul reset hi limits are a smart extra to CYA against dial and knob turners peace and good luck clammy

Comments

  • Howie_6
    Howie_6 Member Posts: 8
    Installing Vitodens mixing valve control

    The manual says that a high-limit aquastat after the mixing valve is strongly recommended. Do you do this as a general practice to protect the floors (and the feet)? Is there anything better or an alternative to the honeywell strap on aquastat?

    Thanks,

    Howie
  • Paul Pollets
    Paul Pollets Member Posts: 3,656
    Viessmann mixing valves....

    ...have their own #2 sensor installed upstream of the pump. This sensor comes with the mixing valve motor and actuator. An additional aquastat is not needed. You'll want to look at the Viessmann schematic, which shows the proper wiring and controls.

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  • Howie_6
    Howie_6 Member Posts: 8
    I've installed that sensor... but

    Thanks Paul.... The installation manual states that a separate aquastat is recommended. I think that their logic would turn the pump off if the mixing valve motor failed and the temp got too high, but that doesn't explain what the manual says. Are they imagining some worst case scenario? Is the manual just incorrect and not up to date? I'm not home right now, but I can get the page number and scan it if you'd like.

    (Also, did you mean downstream of the pump? or did you mean the optional return sensor?)

    I'd be just as happy to be told it's really unnecessary, but I'm just trying to follow the instructions.

    Howie
  • Paul Pollets
    Paul Pollets Member Posts: 3,656
    #2 sensor

    the sensor mounts 18-24" from the pump outlet. we've never used an aquastat on the mixing valve piping. Why? The boiler has redundant controls for safety. We do pipe in a low water cutoff at the safety header,per code. Some jurisdictions require a manual reset high limit. We've demonstrated the Vitodens to the local inspectors and can trip out the boiler on high limit, than reset it. It does have a manual reset switch, which satifies the Seattle boiler inspectors.

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