zoned or not zoned?? thermostatic control of multiple spaces

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.

Reply to
Lighthouse
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You could install a single thermostat in the boiler room and run remote temperature probes to the three apartments. Set the temperature from the utility room triggering the boiler on the lowest remote temperature being sensed.

Reply to
Robert L Bass

Robert thanks, but i'm not sure ~how~ to do that. what kind of remote temperature probes do i use? can you point me to an example? would i be able to see the temperatures of the probes in the boiler room? not crucial, but nice to have. i'd like to know if the lowest temperature is 50 degrees or 70 degrees.

Robert L Bass wrote:

emperature probes to the three apartments. Set the

ote temperature being sensed.

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Reply to
Lighthouse

I'll have to ask tech support at my thermoistat supplier. I'll try to get an answer tomorrow unles someone else chimes in first.

Reply to
Robert L Bass

If it's hot water heated how about you call a local HVAC contractor?

It might be better to spend a little more money and setup actual zones. That way if you put different thermostats in different units you'll have a chance to actually control how each one is heated. It's rather pointless to have multiple temperature sensors if there's not actually a way to control zones.

That and an HVAC contractor might also be able to help with the specifics of a rented dwelling. There may be some ways to have the central controller be able to limit things (like tenant's cranking it up to 85, etc).

It shouldn't be all that expensive to have someone look at the setup and suggest how to put zones on it.

-Bill Kearney

Reply to
Bill Kearney

you're probably right Bill, but there's this part of me that loves to cobble stuff together that works just as well or better than a commercial product. thanks but i hope to gather more "tinkerer's" advice here.

Bill Kearney wrote:

Reply to
Lighthouse

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

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Reply to
Marc_F_Hult

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:

Reply to
Lighthouse

Realizing the problems with the electrical code and possible insurance risks, right?

Honestly, for rental units you're asking for trouble with dumb ideas like that. Likewise, cobbling together some sort of hack, and tormenting your tenants in the process, really doesn't seem like a good idea.

When I suggested a contractor it was intended to avoid various problems like that. Installations that follow code, professional time spent in/out of the tenant space, avoiding risks to existing boiler gear, etc.

-Bill Kearney

Reply to
Bill Kearney

don't know how this would be "tormenting" my tenants. it's not like i'm going to have them wear panties on their heads while i install this. i'm not installing high voltage security fencing in the living units. i'm looking to replace an existing thermostat. i won't do anything unless i understand it completely. that's why i asked for some additional clarification. i used to build, test, and operate nuclear power plants so i'm pretty confident that i can wire up a few thermostats w/o blowing anything up.

Bill Kearney wrote:

Reply to
Lighthouse

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

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Reply to
Marc_F_Hult

That's how I read this at first, too, untill I went back and re-read the first post. Curently, there is a single thermostat in a tenant space controlling the temperature for all three. "Lighthouse" is trying to install something more equitable.

I would put in a damper system, in this case. This will give your tennants the maximum amount of control in each of their spaces, without having to install a seperate air handler for each. Install an electric damper in the ducts leading to each apartment. The damper will be triggered in parallel (probably via a 12v relay) with the boiler. Each tennant now has his own thermostat which he can set to any temperatre he pleases. If the boiler/blower is running, his duct will simply open when the room is too cold. If it's not running, it will start up, open his duct, and warm the place up.

Anyone who lives with someone else knows that different people have vastly different temperature prefernces, and a few degrees either way can be intolerably uncomfortable for some people. So this is a big deal, to me.

Electric dampers can be had on Ebay for around $80.

As for a maximum temperature setting, you could always just put some stop screws or rivits in a conventional lever thermostat or put wireless temp probes in the apartments with stiff contractual penalties if anyone lets their apartments get too hot or too cold (expensive/freezing pipes).

Reply to
E. Lee Dickinson

thanks for the idea Lee, but the system is hot water. as far as i know there are no controls on hte indivdual baseboard radiators.

E. Lee Dick>

Reply to
Lighthouse

What is "intolerable" depends on the circumstances ...

As a perennially broke grad student with wife and kids, I was caretaker of a century-old, uninsulated, brick apartment building in Minnesota (three-story, three entrances/addresses, 19 units) that was heated by a *single* steam boiler using a single-pipe system with no useable valves.

It had _no_ thermostat. Control was via a manually adjusted timer with which I could turn the boiler ON or OFF for any given 15-minute interval during 24 hours. So most nights after the weather report, I'd trundle down to the boiler room to set each of the 96 little levers on the rotary dial of the timer, turning more on if I guessed it would get colder and fewer if it was predicted to get warmer -- typically with more set to ON during night and early morning than afternoon.

'Course this was itself a fabulous improvement over the original when the control consisted in shoveling and banking more or less coal ...

There was no way that all the tenants could be "satisfied". But nobody froze.

The owner lived in a basement apartment next to the boiler -- He was always too hot (unless he was in jail ...) and I lived on the very far end of the building -- six units and three entrances away -- and the building temperature was 'best' if I was cold. Cycling the heat quickly so that the owner didn't get too hot meant that the far end never received any heat at all because the steam never arrived although the pipes clanked and the air vented from the radiators.

We've gotten spoiled ;-) ... (and yes, it *was* much colder then, even in Minnesota.

... Marc Marc_F_Hult

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Reply to
Marc_F_Hult

Lighthouse has specified twice that he needs to control a _boiler_. Typically that means radiators/baseboard heat without forced air. (But not always -- I have a boiler-heated forced air system).

With a boiler + radiator (not forced air), none of the suggestions/options you suggest would apply but absent more concrete info, we are jist guessing.

... Marc Marc_F_Hult

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Reply to
Marc_F_Hult

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

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Reply to
Marc_F_Hult

In reading the first post, boiler didn't make me think it was a forced air setup.

Seems I was correct.

There is the big question of how the water pipes are laid out. If there's any chance of controlling the actual water flow it'd allow much more efficient control. But if it's an older residence chopped up into multiple units that's unlikely. So you're back to Marc's idea of using relays and high/low thresholds.

Another idea to consider is flow control on the radiators themselves. Again, what sort of water system this uses has great impact on what's possible/practical/safe. All of which is probabyl well outside the realm of this particular newsgroup. I'd point you over to alt.hvac but that's a cesspool (much like another one know to regulars around here).

Here's a thought, got a contractor supply place nearby? One that specifically handles HVAC parts? Present the question to someone there and see what range of solutions they come up with.

-Bill Kearney

Reply to
Bill Kearney

:scratches head: How on earth did I do that, and even write 'boiler' a number of times in my post? The extent of my experience with hot water heat is the in-floor radiant at my parent's house, and one time sitting on a radiator and startling myself.

Now that I am free from any expectation of an intelligent post on the subject, I will pontificate.

Solenoid valves in place of duct dampers? That would assume the apartment systems are in parallel instead of series. Not likely, as Bill mentioned, in a retrofit.

If they're curently in series, could a shunt to bypass the radiators be possible? I doubt that unless they're ground floor with exposed basement.

What about just putting the thermostats in series? This would be the most energy effecient -- coldest-set thermostat wins.

Reply to
E. Lee Dickinson

Some folks might (or might not) consider that torment. We'll leave that to other newsgroups. Now, I have to go burn out my eyes for even thinking of that picture...

Oh yeah, that's confidence inspiring... (I'm kidding, of course)

Torment only from the perspective of putting something in place, rigging it up so to speak, and have it end up being a pain in the ass to use, or that it took forever to get "working". Tenants are a pain in the ass, but then so are a lot of landlords. It's often best to use contractors in-between. But hey, that's just a suggestion.

-Bill Kearney

Reply to
Bill Kearney

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:

Reply to
Lighthouse

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