Re: zoned or not zoned?? thermostatic control of multiple spaces

[Marc_F_Hult <MFHult@xxxxxxxxxxxxxxxxxxxxx>]

On 5 Dec 2006 16:57:06 -0800, "Lighthouse" <gruntledlark@xxxxxxxxx> wrote in
message  <1165366626.401890.76070@xxxxxxxxxxxxxxxxxxxxxxxxxxx>:

>I really wasn't sure how to title this msg. i have a building w/ 3 apts
>heated by a single boiler. currently there is one unit which maintains
>the thermostat.
>
>i would like to monitor the temp in each unit, but control the boiler
>from the utility room. oh yeah, and i don't want to pay for some fancy
>overpriced zoning system.
>
>it would be nice if i could do this w/ some type of wireless sensors--i
>see wireless thermometers always available for about $20 or so. it
>seems like there should be some way to modify these to do what i want.
>i don't know enough to be able to do this on my own, but i'm smart
>enough to follow instructions if anyone has some ideas.
>
>hard-wired isn't necessarily out of the question, but i have no idea
>how i might use 3 living area thermostats and set a control temp that
>may not match any of them.
>
>what i'm trying to avoid is having a single tenant freeze out or sweat
>out the other two. at the other extreme, i don't want the boiler
>responding to all three tenants setting their therms to 85 degrees.
>
>i'm hoping that by having temps reported from the 3 living areas to a
>"master" thermostat i can create some reasonable control. IOW, i need
>actual temp readings from the remote locations (rather than just on/off
>signals) so that a thermostat in an unheated basement can control the
>boiler. i hope that makes sense.
>
>any ideas? TIA.

I would do this with three (or four) communicating Aprilaire 8870
thermostats and Homeseer software running 24x7 on a low power dedicated PC.

But here's a solution that doesn't use a PC, is extremely reliable,
presumably inexpensive compared to your energy bill, could be installed
and(or) serviced by any competent HVAC serviceman, does not look out of the
ordinary to the occupants, could be incorporated as part of a future zoned
system, and requires no custom programming, PICs, soldering etc:

1) Install two inexpensive, conventional thermostats in each apartment in
no-tamper (fat chance! ;-) enclosures. Thermostat wire is OK but I suggest
using CAT-5.

2) You'll need 24VAC transformers and relays as well as the thermostats. You
might also find a low-cost  thermostat with an AUTO setting (not manual
Cool-Off-Heat as is conventional) that could replace each pair of
thermostats.

3) In each apartment, set one thermostat to COOL with the maximum tolerable
high temperature (say 76 F), and one to HEAT at the maximum tolerable low
temperature (say 66 F).

4) Install a seventh (!) thermostat in a centrally located ('average')
location that you can access.

5) Use each of the COOL outputs to energize a relay the controlled contacts
of which are wired in parallel fashion with the other two. This creates a
logical OR to force a TOO COLD OVERRIDE.

6) Use each of the three HEAT outputs to energize a relay the controlled
contacts of which are wired in parallel fashion with the other two. This
creates a logical OR to force a TOO HOT OVERRIDE.

7) Control the boiler with centrally located thermostat's output in series
with the TOO HOT OVERRIDE (TOO HOT opens circuit) and in parallel with the
TOO COLD OVERRIDE (TOO COLD completes circuit).

This creates a system in which the building w/should not exceed any of the
six independently set table TOO COLD OVERRIDE and TOO HOT ORERRIDE limits
and between those limits is controlled conventionally by the centrally
located thermostat.

As implied earlier, the fly in the ointment is the concept of a
"tamper-proof" thermostat enclosure.

... Marc
Marc_F_Hult
www.ECOntrol.org