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Signaturestat with a mind of its own...

... and for better control (or so I thought), I bought a signaturestat and hooked it up to the humidification and AC systems. I also went through the trouble of installing and enabling the outdoor sensor, which not only gives an accurate exterior temp reading, but which also is supposed to enable a dewpoint-controlled humdification scheme.

Trouble is, the stat seems to like coming on whether the indoor humidity is below the set humidity threshold or not. Let's say I set the humidistat to 30% and the indoor RH is 43%. It would still come on from time to time, until I set the dewpoint to -15% as suggested by the manual (some windows were fogging up). Now for my control question:

Assuming the signaturestat is operating normally, why would it come on with Precision RH/DP enabled when the interior RH is exceeding the minimum RH set? Was it the dewpoint control with warm exterior temperatures that prodded the controller into adding more humidity than it otherwise would have?


  • Weezbo
    Weezbo Member Posts: 6,232
    Constantin,not to take you away from your current endeavour,....

    earlier you mentioned something about the radon abatement system you had installed,since then my other computer crashed twice and i have no means to revisit that post,....however did you install a fan in the attic? what type of control are you using for it? any issues?
  • Techman
    Techman Member Posts: 2,144

    Hi Constantin,Possibly a draft from behind the stat,either up or down the wall,with unconditioned air?Is the stat stuck in the default settings?
  • Constantin
    Constantin Member Posts: 3,796
    Hi Weezbo!

    Well, as you may recall, we had potentially huge radon issues here. Lots of radon in the soil (multiple neighbors with evac systems), a 9' thick clay layer around the house foundation, etc. conspiring to drive radon levels inside the house higher. In the old house, this was not a problem, since the old girl had more than one air change an hour...

    I started by laying a perforated pipe grid that penetrated into all sub-slab areas (i.e. at the height of the footers). The running footings we had in the interior had solid pipes cast into them to facilitate the radon system. The "tubs" between the footings were then filled with 3/4" aggregate (about 12" high). The idea being that the radon could permeate via the crushed stone to the pipes for pickup and evacuation.

    On top of that came the slab insulation, followed by the 6 mil polyethelene (taped) which acts as a vapor barrier also. All penetrations have expansion joints around them (lolly columns, the basement sewage ejector, etc.) and silicone sealant on top to keep the permeation low. The Radon pipe (4") transitioned to a solid long-sweep 90° before exiting the floor slab in the basement utility room.

    I then had the plumbers run a 4" stack into the attic, glued schedule 40 PVC, as if they were making a sanitation stack. Up there, I capped the thing with a rubber test plug, awaiting the test results from the basement. But before we tested, I applied a concrete sealer to the floor, which is also supposed to keep radon out.

    If the radon levels in the basement had been elevated, my first step would have been to cut a hole into the roof and vent the radon system out passively. If the results had still come back positive, I would have resorted to using a fan. Turns out, our insulation job did the trick... no radon remediation was needed inside the home. That was a good thing too...

    ... as the plumbing inspector ordered us to abandon the radon pipe! Yep, if it's not black with "RADON" written in yellow type on it, then some bonehead might conceivably try to tie a waste stack into it at some point in the future. I guess my permanent marker all over the risers did not count. Oh well.

    On the other hand, I now have a riser that I could conceivably use for other things, like running wire into the attic. The radon pipe stub still sticks out of the floor in the basement and is sealed with a rubber cap + lots of silicone.

    The radon levels in collection tubing are so high that when I tested them for fun, the lab called me up to warn me to stay out of that area. But with a rubber cap and the sealing work I did plus all the air movement that a utility room has, the radon levels are well below the action-levels.

    Make sense?
  • Constantin
    Constantin Member Posts: 3,796
    that's the thing...

    What I do know is that the RH and the temperatures measured are correct. The controller would indicate 43% RH, have a humidifiy setting of 30%, a dewpoint adjustment of -5%, but still come on!

    I cranked the dewpoint adjuster "up" to -15% and now the thing is quiet. Good thing too - the RH upstairs spiked in the mid-50's but is now coming down at 3% per day. Needless to say, I found the manual less than informative when it comes to explaining how the precision/depoint setting is supposed to work.
  • Weezbo
    Weezbo Member Posts: 6,232
    Very Thank You Constantin. *~/:)

    i did not know that the radon pipe had to have yellow markings...i can see the use of a big yellow highlighter in my future :)like i do not have enough to do already :)

    sorry for sniveling :)

    my buddy will think that i have been consulting my crystal ball again when i choose to inform him of the new and ever enthralling code upgrade we need to make :) rubber hat and ,rubber gloves and a scuba suit Were in :)makes sense.

    we did essentially the same with the only difference that ABS is plentiful and pvc difficult to find...the pipe with the holes in it you cast in the crete sounds like a slightly better idea ,than ,the after the fact way we roll it in a crawl space. .... under a slab we are not far off in that we use the tuff coat, or whatever that super strong radon stuff is, and the tube installed under everything with sealed joints everywhere ... we run the pipe together and bang it out to the garage ...(no glue on the fitting...then run it back down from the roof ,to that point....if we dint need it, we cap it. if we do ,we glue it together and put the fan and control in the trusses and thankfully that isn't my job:) when it was 35 below we got news to go get it done...poor Brek dashed of to connect everything...Brrr...man its chilly out there...

    thought i'd share that ... did you also have to seal the shower or bath tubs?

    all these details undermine all our effort when one of them is left out...the S Ejector is all sealed and taped with expansion joints means that there are fixtures in the basement , right ? we have some floor drains in one place we did ,however, the radon abatement was not part of my deal ...i need to check the bath tub next i return to the job....just to make sure all is sealed.

    I know how much this century technology elevates your spirits ..so, today young Shawn finished the "Profile"
    installation...the Caleffi BZU and BLR ,touch screen programmer, and internet connect...everything was reading 69.9 :) The Caleffi controller is a beautiful thing. the set point sensors behave like they are made of stone...until you walk past one of them then they change a tenth of a degree :) it is beautiful to behold *~/:)

    maybe i post a pic sometime...for you :) i really wanted to use the Profile from Caleffi with the three Viessman for superior control...my buddy went some other direction on me and is thinking some thermostat lash up to smartsource or something :( it is discouraging at times...the smart source thing has surv,smoke and fire,mag sensors ,window door motion...and a room sensor in conjunction with the t stat ...maybe it is ok so i just shut up and go with it....the Caleffi control does that and more ...maybe i should just keep my word and say nothing...man i like that controller:)

    i am not worthy to enter under your roof....you really take lots of effort and right thinking to do things. back to the question you had, my friend Wayne,may have an answer for you. it is my intention to pick his brain the next we meet :)

    best of Luck with the controller and sensors..and thank you for mentioning the yellow markings on the pipe...it may be that few people have noticed that in the fine print.

    is warm today ...maybe 14 above! stay warm and in your comfort zone...*~/:)


    i just thought of something...

    Wisdom and associates here in Alaska have had many hours of fine thinking on the very subject of your question... i could not find the www addy however i did find an invensys pupblication ...Pneumatic Controls forHVAC ...Fundamentals of Pneumatic Controls... maybe it is a good read from what i remmeber :) seems there are mechanical ways to recalibrate this and that .... ? maybe?
  • Constantin
    Constantin Member Posts: 3,796
    Hi Weezbo!

    Remember, we live in the people's republic of Cambridge, not all "code-required" things are actually required by code, as the local FD found out. Every radon remediation system I have seen pictures of used regular white PVC pipe. I can't think of a good reason not to. Marking the pipe for Radon is easy enough.

    Any homeowner building a new home or gutting an old one in an at-risk area should seriously consider having the infrastructure put in... it's so inexpensive compared to trying to do it after the fact. I am a big fan also of doing it in stages, i.e. not bothering with an active system until all other avenues have been tried - one less thing to babysit. Using the concrete sealer is easy enough, as is a passive stack.

    Oh, and if you do happen to come to the East Coast, I'd be honored to have you here. Jack's been here, others have too, Wallies of the world unite!
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