steam control system choices?

Al Letellier_9

I did a similar but much larger system a couple of years ago. We had a cronically overheated building, 100,000 square feet, 260 radiators, two pipe system, two large boilers (100% backup) and an overpressured system. Combining using TRV's, a good trap maintenance program, and a steam boiler cycling control (Heattimer), we cut the fuel consumption a whopping 68%......not all buildings are the same, but done right, a cycling control can save you a ton of money.

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nicholas bonham-carter

steam control system choices?

what are the advantages and disadvantages of using a thermostat vs. an outdoor sensor type of boiler control such as the tekmar 269? [1050000 btu gas on 1-pipe steam]
i wonder how the sensor knows when it is 32 f. [and sunny,rainy,VERY windy,etc.]
is there really enough improvement to offset the very large price difference?[tekmar=10 x visionpro]
is this improvement comfort or economy?
we have about 60 radiators on 3 floors and all areas are now reasonably well balanced temperature wise.
maybe in the shoulder times of spring and fall it might have a better control over gas usage.
any other options beyond those 2 apart having a boilerman in the basement shoveling coal on the fire when he sees the color of the gray sky through the basement windownbc

Brad White_185

ODR on Steam

The way such controls work in principle is to set the number of cycles per hour allowed, (actually and more accurately the on-time), keyed to outdoor air temperature.

(I am not certain if wind is a part of that but my HW-based Honeywell Centra control had that in 1985 so the technology is there. That part only goes to infiltration, really, not "wind chill" which is physiological to the human body.)

The "on-time" is established from burner start until a condensate return sensor near the boiler reaches temperature (usually 160-180F to denote full system warm-up). When it is colder outside it allows more on-time than when it is warmer outside. An indoor sensor (it may allow more than one, I am not sure), gives another facet to the control triangle.

To me, the 269 (and there is another steam control by Tekmar too), combined with TRV's on the radiators makes a nice combination for when you cannot agree on a single apartment to rule the roost. The TRV's would take care of your "sunny" question at least. The system especially with the indoor sensor, attempts to "Strike an Average" where a single thermostat alone will P.O. a majority.

I cannot speak to cost but have specified these on 3-family and larger apartments and the Owners stated better comfort and savings but I have no hard data on the latter, (comfort being subjective from a distance). This goes back some years, the features may be different now.

But for that BTU input and serving 60 radiators, I imagine the cost of the control is marginal in the scheme of things. Are the fuel bills outrageous even after "all good things steam" are done? To me this kind of control would be applied only after venting, pressure and insulation are put to bed. As you say, it works now. What more are you trying to achieve? If you have room for improvement, maybe this is it?

My $0.02

Brad

Long Beach Ed

We've Tried them All

Over the years in buildings we own, we've tried many different systems.

I have found that if you have an area that is representative the the entire heated space and not subject to stupidness like open windows, tampering, bright sunshine, etc, then a good quality indoor thermostat works best with a well balanced system.

Of course if the thermostat is put in the room above the boiler, the heat will turn off before the farthest radiator sees steam. Likewise, if the thermostat is put in a cold room at the end of the main, the people above the boiler will cook.

The key is to balancing the system so the place heats evenly. That means radiators properly sized to the rooms, compensating for glass area, properly vented, etc. It's uneven heating that causes the problems.

I've found the outdoor sensors do not compensate well for wind loss, solar gain, etc, and stupidly cycle the boiler on and off simply based on outdoor temperature. They don't understand loss curves and usually assume a straight line loss regardless of the construction, wind, etc.

That's my experience. I'd love to hear what others have found.

gerry gill

yes, i'd recommend the tekmar

steam control for any multifamily complex..but add the indoor sensor so that the control knows whats happening indoors and can compensate for the outdoor sensor..i like them better than thermostats for anything other than a house..

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Long Beach Ed

Our Problem

Our problem, it seems is that we never had a product with indoor feedback, like the Tekmar. That will tell the control "enough," if overheating occurs.

We also probably used them in buildings that were too small, being three to ten families.

Interesting comments, Gentlemen.

Maine Ken

Any control thoughts on staging twin boilers? I have two upcoming projects that are screaming for two littles vs. one big!! Not sure of how to accomplish this with steam.

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Steamhead (in transit)

How

did you split the boiler's capacities?

If you split them 75%-25% or so, you might be able to get away with a Vaporstat to drop the smaller one out when the pickup factor is satisfied and the pressure has risen to 2 ounces or so.

For more elaborate setups, Slant/Fin's Caravan controls are probably as good as any.

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Tim Kelley_3

R&D Steam boiler controller

You may want to look into this controller. It has indoor sensors placed strategically for input. It uses an outdoor sensor for warm weather shut down, and on some models it has a weather anticipation setting that adds to your temp setting in extreme weather, though I have found in well balanced and vented systems there is no need for this.
I have been using these systems for 13 years in 12 to 30 unit apartment buildings with great success. I did try a Tekmar 269 on one building, even with 2 indoor sensors, I had trouble keeping the heat down in the building. It may have been my lack of experience, and/or patience.
I use Tekmar controls exclusively on my water heated buildings, but I wouldn't trade my R&D's for anything.
Here is there website http://www.rdcontrolsystems.com/index.html

gerry gill

you could use one

tekmar to trigger two independant relays..the relays in turn fire the boilers..then as Steamhead said you could use vaporstats to control high and low fire..Steve Pajek has invented an electronic vaporstat thats on ''prototype test run''on his boilers at his house..we have two twin steamers tandomed together there..the factory vapostats have been rather dissappointing in their calabration as of late, and that kind of pissed off Steve, so he invented a better mouse trap.

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gerry gill

That looks like a nice control

thanks for the link Tim..i hadn't heard of that one and will have to investigate it furthur..

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Al Letellier_9

steam controls

Keen only one word for it....Heattimer.E-mail me direct if you need more info.
Al





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