Recommendations for modern control of multi-zone steam system in a church building

Tom_134

Friends,

I am a volunteer who has inherited a church building (17K sq ft) with steam heat and seven zone-valve controlled regions controlled by seven different thermostats. After reading Dan's books, I am soliciting your considered recommendations on how to INCREMENTALLY replace the current six programmable thermostats with a more modern environment, allowing remote monitoring and adjustment (I don't live at the church!).

The boilers (installed 2000) will not run until outside air is 50F or less. At that temperature, the boilers come on and are cycled to maintain between 1 and 2 psi. The seven zones open to their radiators when heat is called for and eventually close when satisfied. Other than outside air, there is no thermostatic control of the boilers themselves - they just run in case heat is needed.

I have two aspirations.

• First, certain thermostats are in "historical" locations which are no longer relevant - and which I wish to replace with EIMs and wireless sensors located in "relevant" locations. I might even want multiple sensor locations within a single zone. However, I am concerned that the environment may not be so simple that I could comfortably use home products. For example, one zone is controlled by a White-Rodgers 1F94-71 thermostat wired to the zone valve over a three-wire control arrangement (see attachment from the installation manual) attaching a wire to terminal SIX. Clearly, I need a solution that can handle such an interface. Strangely, other zones use two-wire links.
  
• My second aspiration is that I want to be able to monitor, manage and collect history on the calls for heat in each zone. With seven zones, I fear that I will need seven EIM-sensor pairs, but still want the history collected somehow. I also want to be able to manage the heating environment over the Internet (we have connectivity in the church).
  

I would appreciate hearing suggestions for anyone and everyone on this matter. I'd like to start by replacing zones one-by-one as funds become available while preserving some sort of monitoring and management unity. I know this is a lot to ask for, but it appears that the market place is maturing quickly. My major concern is that I get the right equipment to deal with the three-wire control arrangement and then extend its reach over time.
Thanks in advance for your help.
-- Tom Board

Steamhead

First thing to do is rewire the controls so the boilers don't run unless something is calling for heat. There is no reason for boilers to maintain pressure like that- modern boilers produce steam quickly enough that there's little if any time lag between the initial call for heat and the boilers' delivering steam.

We did this in a church in Baltimore with six zones, and their gas consumption dropped by 35% in milder weather. The project was rather extensive since the zone valves didn't have end switches- we had to completely re-do the cabinet where the relays were installed. But I think it paid for itself in a year.

Do this first, then you'll have more money for other upgrades.

nicholas bonham-carter

Is your desire with all this zoning to achieve comfort, or economy? If you are controlling the system by zones, then I would see if the boiler can be fired high and low on pressure, so that fuel is not wasted by the short-cycling which must inevitably occur when only one zone is calling for heat. I would ditch the outside temperature override, and only have the boilers be fired when needed.
As far as controls are concerned, the Ecobee3 thermostat offers Internet connectivity, as well as multiple wireless sensor capability. The sensors are only to be used for a short range (45 feet) from the main thermostat, which is a great drawback, but may work for you.
One piece of advice for you is to make this system as simple as possible, so that another person without your technical abilities can also step in and manage the system in your absence.--NBC

Tom_134

Steamhead and NBC,
Thanks for your replies.

It is clear that the intent of all this zoning was economy - one zone controls a single room and another controls only three, because those rooms would likely be occupied sometime other than Sunday each week. Other zones control vertical stacks of rooms (over two or even three levels). This original wisdom has become a liability as the use of rooms has changed over the 90 years since the original construction. Now I have spaces used all week (e.g. a nursery school) for which heat is controlled by a thermostat in an empty conference room. Rather than pay to relocate any thermostats, I'd like to go wireless.

Internet access is a convenience factor - I'd like to be able to turn up the heat in the Sanctuary for a Saturday wedding without being present at the building. I'd also like the peace-of-mind of seeing the temperatures during a "polar vortex" while I am on vacation (somewhere warm, I hope).

Both of you commented on the boilers running much of the time. They are currently controlled to start-up when their output pressure drops below 1 psi at the header, and to shut-off when that same pressure reaches 2 psi (approx). When there is no call for heat, I observe this to occur about every hour with maybe five minutes of firing. Originally, there was an additional timer-based switch that defeated this cycling overnight by disabling the boilers completely (did I mention economy?) I guess that during those periods the church simply had no heat at all! That timer broke before my time and I have chosen to not repair it.

Steamhead's suggested that we tie a "call for heat" to firing the boilers rather than cycle them like this. Would starting from a cold boiler and creating steam at each call be that much less fuel? Steamhead mentions 35% savings.

Neither of you commented on my "SIX" wire connection White-Rodgers thermostat. Can you give me any clues on how more mainstream thermostat vendors (like Honeywell) code leads for my zone valve control application? When the current thermostat breaks, I will need a replacement.

Thanks again for your help. I am most interested in the wireless thermostat market for solutions at this time, but I appreciate any advice on this "specialized environment."

-- Tom

SWEI

A bunch of thermostats with each having its own EIM is not how I would look to manage this. You would be far better served by a control system that uses temperature sensors in your designated thermostat locations. They usually look like thermostats, but allow the control system to see actual temperatures instead of just a switch closure. With that information, decisions can be made as conditions are changing (based on trends, instead of waiting until after they have occurred.) Where is this church located?

Tom_134

Our church is located in north suburbs of Chicago.

Steamhead

Looks to me like terminal 6 might be a "common" wire that allows 24 volts to power the thermostat. I'd need to see a circuit diagram of the zone valve itself to be sure. If I'm right, it's basically a 2-wire thermostat switching circuit.

You can use an ordinary 2-wire thermostat to operate any zone valve by having it operate a relay whose switching pattern (for example, SPDT which is the same as Honeywell's Series 20) matches the zone valve's requirements.

But I'd make the zone valves control the boiler first.

nicholas bonham-carter

Can you give us details on the boilers (make, model, steam ratings), along with some pictures please.
You can ditch the outside temperature sensor, as said. Steam in a pipe at 2 psi, will not keep pressure when the burner cuts off. In fact quite the opposite, as a vacuum develops. Unless there is some sort of timing device in the burner circuit, there will be a constant on-off-on of aproximately 5 minutes each.
Therefore firing in response to a call for heat from on of the zones will stop this wasted fuel.
Now for the real money-saver-the two boilers can be stage-fired on pressure, with a vaporstat. On a call for heat from any one of the zones, both boilers will fire, and when a pressure of 6 ounces is attained, the lag boiler will cut out, leaving the lead boiler to maintain the steam. When additional zones open up, and the pressure drops, then once again the lag boiler will fire, enabling the system to maintain its pressure, which should still be less than a pound (assuming regular radiators). This is where the real economy will come in.
Boilerpwro, AKA Dave Bunnel, the steam whisperer is in Chicago, as is Abracadabra, and could make this work for you, or you can do it yourself.--NBC

JUGHNE

Pictures would confirm that there are actually 2 separate boilers rather than one large boiler with 2 separate burners & flues; which looks a lot like two units.
Visited a church with that setup and first glance is deceiving.