Anticipator Adjustment / Air Vents / Gas Bill

sweetlou

I am getting completely different opinions on what the anticipator needs to be set at. I have a steam heating system. The boiler is probably about 45-50 yrs old. I have an old honeywell round thermostat. One site (pg 10) <a href="http://www.gogeisel.com/geiselonline/support/Honeywell/CT87A_B_J.pdf">http://www.gogeisel.com/geiselonline/support/Honeywell/CT87A_B_J.pdf</a> recommends the highest setting for steam (1.2). Another site: <a href="http://www.inspect-ny.com/heat/Thermostats6.htm  ">http://www.inspect-ny.com/heat/Thermostats6.htm  </a> says "The heat anticipator on the thermostat should be set to match the

requirement & electrical characteristics of the particular heating

or air conditioning control circuit that it is switching on and off. Based on that input I would set it at .2. (Almost the complete opposite!) I keep the temp about 65 when were home (weeknights and weekends) and 59-60 degrees when were gone or while sleeping. My gas bills during the winter months (in Michigan) are in the $400-$500 range and this seems way too high.



Also,  I installed varivalve air vents so I could close the air vents in rooms I seldom use or decrease in rooms that get too hot (kitchen). I read somewhere that your actually better off leaving them all open (if trying to reduce gas bills). This goes against advice I received. Please set me straight on the air vent matter and the differing information on the anticipator setting. Thank You.

DavidK_2

I'm no expert,

but I also have one of the old round thermostats. My understanding is that the "anticipator" should be set so that the house gets up to temperature quickly, but does not overshoot the desired temperature. FWIW I run mine at about .5 - seems to be a good compromise - the furnace does not cycle too frequently, but at the same time it does not overshoot the set temperature.



There is probably a better way to set this, I did it by trial and error. I'm curious if there is a better way of doing this.

sweetlou

Pictures of my heating system

I've attached 2 sets of pictures. Which should I be using to set the anticipator?

Unknown

Vents & TRVs

Hi - I don't have much experience with anticipators. However if it were me, I'd follow the instructions give in the link you provided

http://www.gogeisel.com/geiselonline/support/Honeywell/CT87A_B_J.pdf 

as that is the Honeywell data sheet for that model instrument. There is another way of adjusting them that I know of but since I haven't experience doing it I don't feel I'm competent to give advice on that. Maybe some else with experience with these can help you. As David mentioned, the idea of an anticipator is to use the "coasting" of the steam system sort of the same thing as driving up to a stop sign. You take you foot off the gas and the car coasts up to the stop.  If you took you foot off the gas just when you reached the stop you obviously run right through the intersection. On your steam system the idea is to have the burner shut off and the coast to the set heat on the thermostat. This cutting off early shortens the time the burner is running and saves fuel.  I think I'd start with the recommended settings and as David said, adjust them as necessary. Monitoring  the time and  temperature to see how long is needs to make the temperature change will tell you a lot about your system and which way you need to change the settings. It's a good idea to time and chart your system's regular operation so when you make a change you know whether it improves the system or not.



If you don't already have a it I would suggest you get a copy of "WeGot Steam Heat" which is available on this site.

http://www.heatinghelp.com/products/Books/5/61/We-Got-Steam-Heat-A-Homeowners-Guide-to-Peaceful-Coexistence

It's written for the homeowner, easy reading, humorous,. and in a few evenings you'll know far more about you heating system. My copy has paid for itself many times over.



Radiator Vents-  Your heating system is controlled by the setting on your thermostat.

The thermostat measures the temperature of the room in which it is located. If the rest of the house is freezing but the room where the thermostat is located has reached the set temperature on the thermostat, the thermostat turns the heating system off. Conversely if the rest of the house is hot and the room where the thermostat is located is cold,  the heating system will continue to run. So you can see that opening or closing the radiator vents don't effect the system unless of course it is the room where the thermostat is located.  What one tries to doe is  "balance" the venting of the radiators so the whole house heats evenly in the shortest amount of time. The Varivents maybe causing you more harm than good as they are probably contibuting to your overheating. You can control over heating by using a smaller capacity vent on a radiator or better still, using a TRV.



TRVs - This stands for Thermostatic Radiator Valves,   There are several types of TRV and for a one pipe steam system (which I assume you have) you have to have a TRV that is specifically designed for a one pipe steam system. A onepipe TRV has to have a vacuum breaker.



TRVs won't heat a room but they will stop it from getting too hot. I use them to close off  the part of the house I don't use in the winter.



How they work - The TRV is installed between your radiator and the radiator vent.

When the room temperature is below the setting on the TRV the air in the radiator passes theough the TRV and out the radiator vent When steam reaches the radiator vent it closes.  At this point the whole setup operates just like the TRV wasn't there.



When the rooming temperature reaches the temperatur setting on the TRV, the TRV closes and doesn't allow air or steam to pass through to the radiator vent. On the next steam cycle when the boiler shuts off the vacuum breaker on the TRV opens and allows air to fill the radiator. When the boiler starts again since the TRV valve is closed air can't escape from thje radiator and therefore steam can't enter the radiator. The radiator cools causing the rooms to cool. When the temperature of the room drops below the set temperature on the TRV the valve opens and air is allowed to again escape.  The temperature range settings on TRV is from 43 F to 83F. In the winter I close of rooms in my house by setting the TRV in that room to the lowest  (43 degree) setting. This stops the room from freezing and saves fuel.  TRVs aren't exactly cheap so you may just want to use them on the rooms where you are having the biggest overheating problem. That's about it for TRVs. I attached a Danfoss TRV sheet. The vacuum breaker in the Danfoss is internal. With Danfoss you have to supply the (straight ) radiator  vent.



You might also want to take a look at your main vents as having good main venting means the radiators heat faster. Faster heating means less time the burner is operating which means a saving in fuel. since we are talking about burners, have you had your boiler's  burner cleaned & serviced lately?  This is a good idea to have done as a burner tech has combustion measuring equipment and can make sure you burner is properly adjusted for the most economical fuel settings.

 I might mention all I've said is covered in more detail by "We Got Steam Heat". I know I keep pitching this book but I know how helpful it was to me so I know it will be helpful to others.

- Rod

Jamie Hall

In principle...

the anticipator is set by the current draw of whatever the thermostat is connected to.  In amps.  Which assumes that you know what that is -- which you usually don't.



In practice, the trial and error method probably works as well as any.  The objective of the excercise is to set the anticipator so the thermostat turns the system off at the right time so that the residual heat just brings the space up to temperature.  Right.  Obviously, this works only under one set of conditions... so the best thing to do is to set it so that the temperature comes up nicely, and doesn't overshoot enough to annoy you...



Unfortunately, the anticipator setting won't affect your gas bills much.  But without knowing what kind of space, and how large, you are heating, any comment I might make on how high or low the gas bill is would be pure guesswork.

sweetlou

more

Thanks for the feedback guys. I should mention that the house is about 2300 sq ft and is a 1 story house

DavidK_2

heating bill

Your heating bill is determined by weather, boiler efficiency, and house efficiency (and of course, the cost of fuel). 

There is probably not much you can do about boiler efficiency, except to keep the burners clean.

House effeciency is determined by air infiltration, and heat conduction. If your's is a typical older steam heated house, it probably leaks alot, and doesn't have much insulation. I actually like a house that leaks a little (otherwise I'd have to install an air to air heat exchanger). But adding insulation is always a good thing.

How much insulation do you have in your attic?

sweetlou

Insulation

I'm going to add insulation to the attic. Currently its at 3 inches...I believe I need 16 to get it to R-49. The subfloor over the ventilated crawlspace is not insulated. Probably add some there as well. Still confused about the big differences (.23 vs 1.2) in recommended anticipator settings. It seems if it is short cycling it would waste fuel.

Unknown

Anticipator

Thinking of it as driving on a road up and over a steep ridge. On the way up the hill you have your foot pushed heavily on the gas. As you get close to the top you take you foot off the gas and coast over the top of the ridge. Your brain is the "anticipator". If it anticipates too early you make an (mental) adjustment so the next time you come up the ridge you hold your foot on the gas a bit longer.  You can adjust your thermostat the same way. If you don't make the temperature "ridge" adjust it so the burner stays on a a bit longer. If the temperature goes past the set temperature on the thermostat, just adjust the anticipator the other way.  You save fuel by cutting the burner off early and "coasting".



I insulated under my floors (stone walls- bare floor basement) and it made a big difference. The neat thing yabout insulation is you only pay for it once.  We did a section at a time, under the rooms we used the most first, rather than make it a big job.

- Rod

Magnehelic

Anticipator

Absolutely, the anticipator should be set at or close to the actual amp draw (or fraction of 1 amp if that's all it draws) of the device it is controlling.......HOWEVER most home owners don't have the instrumentation to read this.....so trial and error can and does work.  If the setting is too low, you will experience many many heat cycles to raise the temp in the house up to setpoint (like on for 5 minutes, off for 3) and it will KILL your heating bill.  If it is set too high, the boiler will run on after achieving or even overshooting the setpoint.  So.....as long as your boiler fires (best way to check this is when the house is 5 degrees or more too cool) and runs up to the setpoint without shutting off and restarting, and then also doesn't overshoot the setpoint, you are golden.  I have MANY MANY times (even just last week) come across boiler and forced air systems where the appliance would run 10 or more cycles before reaching setpoint becasue some thing or someone had shorted across the RW terminals on the t-stat for more than 15-30 seconds, and burnt out the anticipator (creating a parallel circuit for the electrons to flow with the resistor (variable resistor = anticipator) still in the circuit).

     all that being said, if you haven't notice multiple run cycles to get to setpoint, you need to look elsewhere for the cause of your high bills.

Hope this helps 8-)

don

DavidK_2

confused

I've read about setting the anticipator draw to the same setting as the amperage draw of the device being controlled.  But I don't understand why this works. Maybe it is just a good starting point so that the anticipator and other controls use about the same amount of current?



Why does my thermostat "anticipator" care if the gas valve draws 1 amp or .1 amp?



Isn't what really matters the thermal inertia of the heating system? When my thermostat shuts off my boiler the radiators are still nice and warm, and continue to heat the house.

I don't know how you measure this - a nice heavy cast iron radiator will retain alot of heat, a thin light radiator will retain less heat.



Can somebody explain this to me, or point me to an explanation?



I understand that an oil burner can be significantly less efficient if it short cycles, is this true for gas as well? Probably so, but perhaps less so?



Just looking to learn Thanks.

Jamie Hall

As Don aptly noted

The correct starting point for the anticipator setting is the current draw of the system.  The anticipator is just a little resistor/heater, and the clever folks who dreamed it up set it up so that, given an average system in an average installation on an average day, the anticipator will heat up the thermostat element in the thermostat just enough faster so that the thermostat will turn off at the right time to compensate for the thermal inertia in the rest of the system.



However... note the "average system in an average installation"!  It's a starting point.  If you have a high inertia system -- gravity hot water, steam with great big cast iron radiators, etc. -- you may have to tweak the anticipator to turn the thermostat off faster.  On the other hand, if it's a low inertia system -- say copper fin tube radiation, or scorched air -- you may have to tweak it the other way.  It's never going to be perfect.  My own preference is to have the system overshoot the set temperature just a bit under most conditions...

DavidK_2

My preference

My preference it to have little (if any) overshoot. Otherwise the house can feel cold while it is waiting to once again slightly overheat. The price you pay for this is that when it is very cold it can take a little longer to bring the house back up to temperature. I also now wonder if there is a price to be paid in more gas use. . .



I think bottom line is it really does not matter much unless you stress details - which is probably why the "rule of thumb" works just fine.



To the OP your gas valve seems to draw .5 amps (unless I misread it, the zoomed pictures do not seem to work well for me - I try to scroll, and they just pop back) so I'd start with .5 (or if you like (1.2 + .2)/2 =  .7) and go from there.



Anyway you go about it will be a compromise. On cold days it could take longer to heat the house, on moderate days the boiler could cycle too often. I suppose you could set the anticipator different on different days,  but that is too much work for me Now I'll have to match the "security check" - Damn spammers