Mastiffman
New Member
Posts:3
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| 30 Mar 2008 06:40 PM |
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Hello everyone. This is my first post. Have been visiting for years. Learned a lot.
Built a SIP home in the UP of MI. This was our first winter in the house and it is all we expected. Our energy costs have gone way down.
Installed radiant floor heat using a Takagi JR. Used PEX tubing in a staple-up to the subfloor. The floor surface is ceramic tile throughout. Insulated underneath over a 4' crawl space. 2 zones-bed and baths with an 8' ceiling and a great room with vaulted ceiling.
The thermostats are set at the factory with a 1° differential. Would it save energy to set them at the max 3° diff. ?
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NRT.Rob
Veteran Member
Posts:1741
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| 02 Apr 2008 09:29 PM |
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how big are the zones? |
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| Rockport Mechanical<br>RockportMechanical.com |
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Mastiffman
New Member
Posts:3
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| 16 Apr 2008 05:02 PM |
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My answer must have gotten lost in cyberspace. The great room with vaulted ceiling is about 660sq.ft. The two bedrooms and baths with 8' ceiling is about 400sq.ft. |
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NRT.Rob
Veteran Member
Posts:1741
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| 16 Apr 2008 05:05 PM |
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you need a buffer tank, IMHO. |
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| Rockport Mechanical<br>RockportMechanical.com |
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Mastiffman
New Member
Posts:3
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| 18 Apr 2008 05:59 PM |
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What does a buffer tank do? I'm not having trouble keeping the house warm, just trying to optimize for energy savings. |
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NRT.Rob
Veteran Member
Posts:1741
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| 19 Apr 2008 02:17 PM |
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the buffer tank (just a passive tank piped into the system) makes the unit run for a bit on a heat demand and then shut off for a bit before it turns back on, by bufferring the heat demand with added water mass (in the buffer tank).
The same way raising your tstat spread would cause longer run times. But this has a real effect. Given that your heat source is really not built to run this way (low delta-T across the heater), the buffer tank should help it out a bit.
If you did this, AND went to the 3 deg differential, the takagi would probably be happiest. |
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| Rockport Mechanical<br>RockportMechanical.com |
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PanelCrafters
Advanced Member
Posts:680
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| 19 Apr 2008 03:27 PM |
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Posted By NRT.Rob on 04/19/2008 2:17 PM
the buffer tank (just a passive tank piped into the system) makes the unit run for a bit on a heat demand and then shut off for a bit before it turns back on, by bufferring the heat demand with added water mass (in the buffer tank).
The same way raising your tstat spread would cause longer run times. But this has a real effect. Given that your heat source is really not built to run this way (low delta-T across the heater), the buffer tank should help it out a bit. Rob, How does this work? I assume that the buffer tank is connected to the boiler(whatever the heat source) output and that the zones are fed from it. Is that correct? So, I assume that water is used from the buffer while the boiler is coming up to temp? Can you explain the process a little more? Thanks! |
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| ....jc<br>If you're not building with OSB SIPS(or ICF's), why are you building? |
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NRT.Rob
Veteran Member
Posts:1741
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| 19 Apr 2008 03:35 PM |
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Not exactly; you have the piping idea correct (typically). However, imagine a cold buffer tank; it requires a number of BTUs to heat it up to the point where it can satisfy the zone demands. That is the "buffer", rather than having a low-mass heat source jack up its own temperature really fast and shut down (as it might with small low mass zones, especially ones with poor conductivity), it must first heat the tank. this provides a store of BTUs for the zones as well.
works best with a reset control so you can leverage the buffer tank for every series of demands (pull out heat without asking the heat source to fire, cool down the tank as far as practical, and then turn on the heat source again to charge it back up).
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| Rockport Mechanical<br>RockportMechanical.com |
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jmagill
Basic Member
Posts:374
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| 19 Apr 2008 05:37 PM |
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Rob, we have the exact same setup, except ours is pex in concrete. I would assume that the concrete is "our" buffer mass.
And in wording that some of us "not industry people" can maybe understand a bit easier, it lets the Takgai not work in many short cycles but more in longer cycles less often?
Is that correct?
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NRT.Rob
Veteran Member
Posts:1741
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| 19 Apr 2008 08:54 PM |
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Usually I'm a little better at cutting the jargon. Less, longer cycles, yes.
Slab has some buffer capacity built in, yes. whether that's good, bad or indifferent is different for everyone, but i were forced at gunpoint to use an ODWH instead of a mod/con or a tank water heater for a radiant system, I would want to run it on a single, larger slab zone if possible. |
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