OUTDOOR RESET CONTROLS WITH STEAM

Boilerpro

I've been using tekmar controls since I started in the hot water/ steam heat business 7 years ago. Have yet to have one fail. Had one back room temp unit recently, and maybe a second, out of the box but once installed and running not a single problem. Tekmar is really cutting into the traditional control companies' market (Honeywell, Johnson, etc.). IMO they offer far better control capability with far better reliability in most applications.

Boilerpro

GUY

USING OUTDOOR RESET CONTROLS WITH A STEAM BOILER

DOES ANYBODY HAVE COMMMENTS ON THE USE OF AN OUTDOOR RESET CONTROL WITH A SINGLE ZONE STEAM SYSTEM?

MY PLUMBER HAS SUGGESTED USING A TEKMAR CONTROLS 269 WITH AN 071 FLOW LINE SENSOR.

I AM REPLACING BOILERS IN TWO ROWHOUSE APARTMENT BUILDINGS IN BOSTON.

ONE HOUSE IS 4 APARTMENTS ON 4 FLOORS (850 SQFT EACH) PLUS BASEMENT, THE OTHER BUILDING IS 5 APARTMENTS ON 5 HEATED FLOORS (950 SQFT EACH) PLUS BASEMENT.

THE BOILERS WILL BE A BURNHAM IN-7 (SMALLER BUILDING) AND IN-8 (LARGER BUILDING).

I AM A BIT WARY OF THE BENEFITS ( COMFORT AND FUEL SAVINGS) TO BE HAD VS THE $1500 EACH INSTALLED COST AND POSSIBLY GREATED CONTROL MAINTENANCE.

ANY COMMENTS WOULD BE APPRECIATED.

THANKS,

GUY

George Carey

tekmar steam boiler control

Guy,

I work for the tekmar rep here in Boston. These controls have been installed in several apartment bldgs./condominium bldgs. throughout the the metro-Boston area with positive results. One of the features the tekmar 269 has is the ability to install indoor sensors. This indoor feedback provides helpful information to the control so it can make better decisions regarding the boiler's on/off cycles. If you want, you can email me and we can discuss further.

George

ChrisL

Steam Controls

Using outdoor temps to set the duty cycle on a steam system is the best way of preventing wide swings in temps. The downside on most controls that do steam is that they don't take into account room temp. Without this info, the control can't adjust for windy days, sunny days, leaving the door open for a long time, etc.. I've never used the Tekmar control, but it looks pretty good. They do integrate an indoor sensor. The weakness I see is that the temp sensor will only shut down the boiler. If the temp is below where you want it, and the control curve is already satisfied, the boiler will not fire. If the boiler is firing to satisfy the control curve, and the room sensor hits the temp setting and shuts the boiler down, there still will be an overshoot in temp as there is no anticipatory circuit. So not perfect, but better than most. You might also look into www.esicontrols.com They have a steam controller that's a step up from the Tekmar...overkill for a residence, but well suited for a larger apartment building.

Chris L

GUY

BOILERPRO,

WHAT DO YOU THINK OF CHRIS L.'S COMMENTS REGARDING THE NEED FOR ROOM TEMP INPUT?

GUY

jalcoplumb_3

Room temp input...

In my opinion is not needed. This is a multi-family dwelling. The temp sensor will be in a unit that might not heat as well as others or the person could leave the window/door open all day. I am for providing the right amount of heat for the building based on the outside temp.

If you want to ensure you don't over heat the space you should use TRV's in conjunction with a heating control like the Tekmar unit or a Heat-Timer unit.

The cost for the units can be high. What were your other options? Most of the units have a warm weather shutdown feature. Your energy use will be consistent and should be better than what a thermostat could offer.

There is very little maintenance on these units.

Good Luck,
Joe Landree
J.A.L. Co. Plumbing & Heating

To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"

ChrisL

room sensors

I agree with Joe in that a room sensor can result in misreadings if someone has a window open, possibly resulting in an overshoot in temp in the other apartments.

However, how will a control that does not use a room sensor compensate for a windy day? I see 4-6 degree differences in wind exposed apartments. How about a sunny day?

The esi controls unit I mentiond has the best approach. It can run a room sensor in each apartment, and then take an average of all of the apartments. It will drop the highest and lowest temp, so that the control won't be fooled by an open window, or someone cooking a roast.

So, in conclusion, consider your building....do the apartments all have the same outside exposures, number of windows, etc.. Is the building well insulated, good windows? If the apartments are very similar, the tekmar unit should do the job. If not, consider the esi control,
and think this through thoroughly, as there is nothing worse than having to go every week to adjust the control.

Chris

George Carey

indoor sensors

The tekmar 269 has the capability of taking up to (2) indoor sensors which basically are resistors. By wiring these (resistors) sensors in parallel/series you can install several sensors in the building as long the number of sensors is squared so that they are wired both in series with each other as well as in parallel with each other. For example, you can wire 4 sensors in parallel/series back to one of the sensor inputs. Instead of 4 you could wire 9 or 16. As long as the sensors are in parallel and series with each other. The control will average the temperature of all these sensors to determine what the indoor temperature is. Of course, we are talking about a steam system where distribution, air venting, steam trap operation, etc. all affect the comfort level in the building. A simple cycle-timing control can't improve a bad steam system. But it can improve the issue of where to put the one thermostat, who controls it?, how accurate is it?,etc...

GUY

Chris,

The buildings are 140 (approx) year old attached, brick row houses. There is one apartment per floor, each with the same front and rear exposures and window locations.

The front of the buildings face roughly West, south-west and gets good afternoon light and warmth in the front. The rear of the buildings gets much less intense morning light, and is also partially shaded from mid afternoon due to the proximity of buildings to the rear. The onlydifference between the apartments is the height above grade. The apartments on the 3rd, 4th and 5th floor get more intense afternoon sun in the front rooms than the ground and second floor apartments get

As much of the 5 unit building is original, the front and rear wall "insulation" in the lower four (out of five) apartments is 12" of brick plus 3/4" of horse-hair plaster. The top floor apartment has been gutted and well re-built with lots of insulation in the ceiling and front and rear walls.

The windows are being rebuilt or replaced with single glazed wood sash plus good quality modern storm windows.

The rear two rooms of the middle floor apartment (#3) are the only abberant cold spots which I have been trying to work through.

Wind is a factor in Boston. It can be extremely windy here (interesting fact: Boston has more wind than chicago.) and infiltration and heat loss due to wind could be significant.

ChrisL

Steam control

Mary,

You have sort of a similar situation to what I face. I have 2 buildings in different locations. Both built about 1920's, similar construction to yours. One is an 11 unit, the other 13 unit. During the heating season, I get a call atleast every week. The systems in both buildings are in good shape, newer boilers, and I am running Tour and Andersson controllers in both. (these units have outdoor reset, and integrate a room sensor). The major source of my problems is getting a dependable reading from the room sensor.

Apartment heating is a different ballgame than a single family home, in that you are trying to heat each apartment properly, but are handicapped in that you have to heat the whole building, and can't compensate for different apartment needs. This was not a problem when they built these buildings, since fuel or coal was very cheap, so they would just err on the high side. If it got too hot, the tenant could close the radiator valve, or open a window. Furthermore, people expect more accuracy and reliability in heating than they did back then.

So getting back to my point, I frequently get a call for heat. I go to the building, and check the room sensor on the control display. It reads 70. I then go to the apartment that is cold and it reads 66. Well it turns out that the people in the 70 degree apartment were baking cookies today, so the controller thinks everything is ok. Meanwhile, the other 10 apartments are 66 and cold.

In this situation, a controller like a Heat timer, or Tekmar will be ok, since it only uses outside temps to set run time.

The failing though will be on a windy day. As I mentioned in a previous message, in my buildings, its not unusual to see a 6 to 8 degree difference in temps from a wind exposed apartment and one that is sheltered. Your building has similar construction, so a windy day will result in a very different requirement than a non windy day. It is here that a more refined controller is needed to compensate. Only the ESI control I mentioned will solve this problem. Tekmar has a great product line, but their steam controller is unable to compensate for wind. This might not be a problem on a tight newer building, but can result in a lot of calls over the season in an older building.

I am curious what you were running in the past? Was it doing the job well?

Chris

GUY

I have been using t-stats in each building

Chris,

Actually, It is Guy writing from my wife Mary's business e-mail address.

I have been using an Enerstat thermostat, carefully placed in the ground floor apartment, in the larger building, and a Danfoss TP75 thermostat (which I generally like) in our apartment in the smaller building. Due to the location in the smaller building, we do experience the "cookie factor" ( ie cooking as a heat source throwing the thermostat off), but as it is in our apartment, I am able to compensate.

My most effective way to combat calls about the heat is to use the set-back features to force the boiler on. We still get temp swingsand overshoot , though. I know that a modern boiler vs. the big snowmen that we have now, and almost anything controlling it will bring heat more quickly, but it would be nice to make the buildings as comfortable and efficient as we can reasonably afford.

Thanks for your comments.

Guy