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

[Marc_F_Hult <MFHult@xxxxxxxxxxxxxxxxxxxxx>]

Lighthouse,

You need to find out what you are buying. Single-pipe steam systems (steams
moves out a single pipe, condenses to water in the radiator, and flows back to
the boiler via the same pipe) are a whole lot different that hot water
systems. Do the radiators have a vent that allows air to escape when the heat
goes on? If so, is most likely steam (and I commiserate).


...Marc
Marc_F_Hult
www.ECOntrol.org

On 8 Dec 2006 07:28:15 -0800, "Lighthouse" <gruntledlark@xxxxxxxxx> wrote in
message  <1165591695.608049.295350@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>:

>i should clarify my situation a bit. i should note that this building
>isn't technically mine yet. it's scheduled to close in January. i'm
>trying to be proactive and doing a little homework. the boilers are
>relatively new--only about 6 years old. the radiators i *think* are on
>a single pipe system (the building is over 100 years old and probably
>had big-ass cast iron radiators originally). i really want to make the
>place much more comfortable as i plan to move my own father into one of
>the units. believe me, i don't plan to torment anyone. hahaha. there
>are 6 units altogether w/ 2 boilers. one boiler heats 3 units on one
>side of the building. the other boiler heats 3 units on the back side
>of the building. 3 floors--2 units per floor. uninsulated brick
>construction.
>
>the current tenants are relatively comfortable right now. the problem
>is that since ONE tenant controls the therm for 3 units, if he goes
>away for the weekend or something and the temp changes drastically...
>i'm sure you get the idea. obviously, the best solution would be to
>refit the system so that each unit can control its temp independently
>of the others. i will probably do that in about 2 years. i am in the
>process of buying this building right now. it is my first commercial
>building and i am putting ALL my cash on the line for the d/p'mt. i
>really can't afford to bring in a heating expert this year to install
>shunts, bypasses and thermostatically controlled valves. i'm looking
>for a low cost, low tech temp solution that works. I hope that makes
>the puzzle more clear. i appreciate all the views you guys are posting.
>
>
>
>
>
>Marc_F_Hult wrote:
>> To answer your last question first:
>>
>> One could/can use simple inexpensive, traditional Honeywell thermostats
that
>> have a bimetallic spring as the temperature sensor and a mercury (ugh :-(
tilt
>> switch as the switching mechanism. But these have a manual COOL-OFF-HEAT
>> setting in part because you can only set the dial to one temperature, not
two.
>> If there are inexpensive thermostats available that let you set two
>> temperatures (I dunno), that is, separate COOL ON and HEAT ON settings,
they
>> might be adapted to your use. Okay so far?
>>
>> Assuming that you have a thermostat arrangement (whether one or two
physical
>> units)  that complete two circuits with a Single-Pole, Single-Throw (SPST)
>> switches when the temperature is TOO COLD or TOO HOT (that is, "call for"
heat
>> or cool), you use this information to override the signal from your
>> conventionally installed 4th/7th thermostat which is the Tstat that
controls
>> the boiler most of the time.
>>
>> Assuming for the moment that your boiler control consists in a 24VAC
circuit
>> that needs to be completed with a SPST switch, and you have a conventional
>> thermostat with effectively a SPST switch like the Honeywell I describe in
the
>> first paragraph above,
>>
>> TstatTerm1 -- NC_TooHot_1 -+- NC_TooHot_2 -+- NC_TooHot_3 -+--- Boiler
>>                            |               |               |
>>                                                     NO_TooCold_1
>>                                                            |
>>                                                     NO_TooCold_2
>>                                                            |
>>                                                     NO_TooCold_3
>>                                                            |
>> TstatTerm2 ----------------+---------------+---------------+--- Boiler
>>
>> where NC_TooHot_x are the Normally Closed (NC) contacts of a relay and
>>       NO_TooCold_x are the Normally Open (NO) contacts of a relay.
>>
>> So any closure of any NC_TooHot switch will turn off (override) the boiler
>> unless any of the NO_TooCold-x switches are closed. One can modify the
>> override logic by (eg) moving the location of the NO_TooCold_x switches to
the
>> locations shown with the + .
>>
>> Note that the circuit diagram above shows the control signal to the boiler,
>> not the signal from each SPST switch in each thermostat to each relay coil,
>> Right?
>>
>> The relays themselves are powered by whatever voltage the relay coils that
you
>> choose should happen to need (12vdc, 24VAC etc). One wrinkle is that the
>> anticipator circuit in the conventional thermostats described are designed
for
>> 24VAC so you might avoid complications by using 24VAC throughout -- but
maybe
>> not, Depends on the thermostat chosen.
>>
>> HTH ... Marc
>> Marc_F_Hult
>> www.ECOntrol.org
>>
>> On 6 Dec 2006 20:14:47 -0800, "Lighthouse" <gruntledlark@xxxxxxxxx> wrote
in
>> message  <1165464887.275804.321050@xxxxxxxxxxxxxxxxxxxxxxxxxxx>:
>>
>> >Marc, this sounds pretty close to what i want to do. not the Aprilaire
>> >thing (way outta my budget), but the other. hope you don't mind helping
>> >me out w/ a few of the details. ok, conventional therms, cat5, serial
>> >wiring, parallel wiring. i'm down w/ all that. i'm not sure about the
>> >24V xformer and the relays. i'm assuming that both of those get
>> >installed in the boiler room along w/ my 7th therm. what kind of
>> >relays?  is the 24v xformr the kind used in doorbell circuits? how do
>> >those fit into the wiring scheme? is it possible for you to sketch this
>> >out for me?
>> >
>> >what would be the difference w/ using an AUTO therm instead? as for
>> >discouraging tampering w/ the settings i could possibly camo the therms
>> >inside the casing of a smoke alarm unit.
>> >
>> >thanks for the ideas!
>> >
>> >Marc_F_Hult wrote:
>> >>
>> >> 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