Heat anticipator again

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Old 12-08-07, 10:35 AM
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Heat anticipator again

My Honeywell stats have settings for 9, 6, 3, or 1 CPH. Electric, regular forced air, hi efficiency forced air and radiant, respectively. I am not happy with the cycling at 3 CPH for my high-efficiency furnace.

I want the furnace to stay on longer when heating up from the weekday temp of 60 to the evening temp of 68. For example, it will run for 20 minutes and get the temp to 63 degrees, then shut down, purge and turn back on twice more before the house gets to 68. This seems stupid. I'd rather have it run 12 minutes at low stage and the rest of the time at high stage until the call is satisfied.

If I want the cycles to be longer, should I set it to 1 for radiant heat or 6 for regular forced air?

Thanks.
 
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Old 12-08-07, 10:45 AM
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Maybe this link will help.
This is for Honeywell's Thermostat Wizard

http://yourhome.honeywell.com/yourho...rd/Wizard.aspx

It will even help you figure out the model of your thermostat if you don't know that info.

Hope this helps...
 
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Old 12-08-07, 11:02 AM
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Originally Posted by Pete OldNavy View Post
Maybe this link will help.
This is for Honeywell's Thermostat Wizard
Thanks, I've got the T8602D2000. Unfortunately their online help does not address heat anticipator settings, presumably since this is more often a dealer issue, and my stats are "tradeline" or whatever they call it, meaning they are sold only by dealers of one type, but not big boxes and so on.
 
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Old 12-08-07, 11:18 AM
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The closest item I could find on their site with directions:
http://customer.honeywell.com/techli...0s/69-1567.pdf

See also:
http://customer.honeywell.com/Honeyw...ACHEHINT=Guest
for all thermostats listed.
Good luck.
 
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Old 12-08-07, 11:28 AM
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I found this page that has both Installation and Owners manuals. Just look for T8600 that might cover the T8602.

http://www.airconnectweb.com/links.php#

I also cannot find anything on heat anticipator settings.
 
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Old 12-08-07, 06:37 PM
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Thanks Pete I really appreciate it.

Unfortunately I have all the installer and consumer documentation that the contractor left behind, covering all the various programming settings, but nowhere does it tell me how the CPH settings compare to analog heat anticipator.

It seems to me the type of question somebody who knows the biz could answer. I was thinking radiant at 1 CPH would be right, but then again radiant would probably take the longest for the heat to reach the stat.

On the other hand, 9 CPH doesn't sound right because it seems like that would mean it would cycle on and off every 6-7 minutes. So it would help if I knew some baseline info, like which way is up!

I googled CPH with Heat Anticipator and after my own old threads on the topic, I got this article which discusses CPH in some detail:

http://www.alainc.com/Articles/article7Ribble.html

But nobody seems to be able to tell me why my stat would be cycling the furnace OFF when the room temp is nowhere near the stat's set point. The brief discussion I had with my HVAC contractor was not illuminating.
 
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Old 12-08-07, 08:00 PM
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1 cph is continuous run. The reason they invented the anticipator was to 'anticipate' the heat rise that would happen after the thermostat stopped calling for heat. With no anticipator and cast iron radiators or an 800 lb converted coal furnace, the room temp could rise another 5-7 degrees after the thermostat was satisfied. The anticipator, when adjusted correctly, would stop the furnace just in time to allow the residual heat to just reach the setpoint. It was done with a heating element inside the thermostat and based on the current draw of the control that was connected to the thermostat, a starting point could be set for the adjustment. Most modern heating systems don't have anywhere near the mass of the old ones so there is usually much less residual heat to anticipate. If you want a longer run, set the cycle rate at 1 and if the room overheats, set it to 2. Work your way up until it works the way you want. Let us know if your experimentation leads to any interesting findings. Thanks.

Ken
 
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Old 12-08-07, 08:28 PM
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Originally Posted by KField View Post
If you want a longer run, set the cycle rate at 1 and if the room overheats, set it to 2. Work your way up until it works the way you want. Let us know if your experimentation leads to any interesting findings. Thanks.

Ken
Thanks. I will try 1 and see if it overshoots significantly. Unfortunately there is no 2 setting.
 
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Old 12-09-07, 05:13 AM
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Sorry about that. I was using the example to show the effect of cycling. I think the off time is only about 5 minutes. I will try to find out from honeywell how long the off cycle is between on cycles.

Ken
 
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Old 12-09-07, 05:24 AM
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What is the avg run time, down time and how may time an hour are you getting at 3?

How long have you had the t-stat?

What is the outdoor temps when you notice these short runs?

How big is the furnace (BTU?, and sq footage of the home?
 
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Old 12-09-07, 02:11 PM
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Originally Posted by Jay11J View Post
What is the avg run time, down time and how may time an hour are you getting at 3?

How long have you had the t-stat?

What is the outdoor temps when you notice these short runs?

How big is the furnace (BTU?, and sq footage of the home?
1. I'd say the run time is between 13-20 minutes. The zone controller tells the furnace to go to high stage at 12 minutes, and sometimes it just revs into high and then quits. Other times it will run for a while.

Down time is usually just enough for the purge cycle to run. That is, the stat stops calling, the furnace purges, and then the stat starts calling again within a few minutes. I often hear the stat relay click to stop the call for heat but I don't often pay attention to when it starts calling for heat again. I think the purge runs for about three minutes so I'd say five minutes maximum between the stat's stop and start calls.

I'd say 2-3 cycles per hour. I am not using the PID function, the intelligent setting, AIR I think they call it. For example if I want 68 deg. at 5 PM, the furnace starts at 5 PM, not at 3:30 PM to make sure the temp is 68 at 5:00. The reason for this is that I didn't want the furnace cranking up at 4:30 or 5:00 AM to get things heated up to 68 by 6 AM. I'd rather have it blasting on high stage at 6:15 in the bathroom than get the whole zone to 68 by 6 or 6:30 or whatever.

2. I have had one stat since fall 2000, and the other since December 2001. We didn't start using the second floor zone until March 2002, when we got the remodeling to a livable level. The zone controller is a MABS 2 EZ.

Below are all the stat settings and readings.


Option-1st floor-2nd floor-Description-Setting
2 0 0 Fan Conventional
4 3 3 Heat Cycle High Eff
12 0 0 Changeover Auto
13 1 1 AIR Conventional
14 0 0 Display Fahrenheit
16 1 1 Clock 24h
19 0 0 Heat Fan no extended
20 0 0 Cool Fan no extended
24 1 1 Outdoor Temp Sensor yes
30 3 3 Deadband 3 deg. F
34 90 90 Setpoint Heat, hi limit 90 F
35 45 45 Setpoint Cool, lo limit 45 F
37 0 0 Display Temp Actual


Info
71 010 091 Mfg. Date Jan 2000, Sep 2001
72 315 328 Software ID code
73 306 449 Software revision number
74 647 647 EEPROM ID code


3. The outside temps are usually low 20s and below; that's when the house gets down to 60 during the day. If it's around 30 or above, the house does not lose as much heat, usually bottoming at 64 or so.

4. The home is about 1800 sq. ft. The furnace is:

Trane
XV90
62K-93K BTU output
TUY100R9V4V3
 
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Old 12-09-07, 05:52 PM
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Holy cow.. I can see why you have the short run time.. A 100k on a 1,800 home... Unless you got a single pane glass, no insulation in the walls? Did they do a load calc on the home?

What is the model # on the zone board?
 
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Old 12-09-07, 05:57 PM
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Sorry, I saw the model when I re read the post..

I am not able to pull this info on line,... Does the board have W2 on it?
 
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Old 12-09-07, 06:02 PM
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Originally Posted by Jay11J View Post
Holy cow.. I can see why you have the short run time.. A 100k on a 1,800 home... Unless you got a single pane glass, no insulation in the walls? Did they do a load calc on the home?

What is the model # on the zone board?
I specified Manual J to be done and the contractor said it was, although now that I think of it I never got the printout. I had a lot of trouble with them although they resolved everything major. No insulation on the first floor, that's correct. Dense-pack cellulose to be added after Christmas. Single-pane windows ... well, we have storms, but the blower door test I think showed we weren't too far off.

What difference would all that make to the heating system controls? We're not hitting the high limit.

The zone controller is a MABS EZ-2. It sets the high stage and has a ZoneMAX ZMS. I can't recall that it or the furnace high limit has ever been tripped. And I can hear the stat relay clicking to stop the heat call.
 
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Old 12-09-07, 06:14 PM
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Originally Posted by Jay11J View Post
Does the board have W2 on it?
Yes. W2 is connected from the zone controller to the furnace board and it is set to go to high stage at 12 minutes.
 
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Old 12-09-07, 06:32 PM
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Originally Posted by ArgMeMatey View Post

What difference would all that make to the heating system controls? We're not hitting the high limit.
Your duct may be sized ok, so the air flow may be good, and may not see the high limit.


Yes. W2 is connected from the zone controller to the furnace board and it is set to go to high stage at 12 minutes.
Honestly, I would push the timer out further on the zone panel, I did find the manual at last, i would push the timer out 30 min. that way you have a longer 1st stage run.
 
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Old 12-09-07, 11:28 PM
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Originally Posted by Jay11J View Post

Honestly, I would push the timer out further on the zone panel, I did find the manual at last, i would push the timer out 30 min. that way you have a longer 1st stage run.
The problem is that then it will almost never go to high stage and the place stays cold far too long after the stat starts calling for heat - on the order of radiant heat. If I do that on AIR the furnace will crank up at 3 AM and wouldn't be at the set point for hours because it will keep shutting down. When the system was originally put in, the installers improperly wired it so it would never go to high stage, so it would cycle forever and never reach the set point in really cold weather. That was fixed on the punch list in about February 2001.

It's only from 7-8 AM or in very cold weather that both zones have overlapping or simultaneous calls for heat, therefore keeping the furnace on for longer. To the best of my knowledge the MABS does not have a heat anticipator circuit and since the stats are single stage, they do not know when the furnace is on high or low.

I really need to try the 1 CPH setting to see what difference that makes.
 
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Old 12-10-07, 05:10 AM
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Originally Posted by ArgMeMatey View Post
If I do that on AIR the furnace will crank up at 3 AM and wouldn't be at the set point for hours because it will keep shutting down.
That's not right.. That furnace should be staying on till you'v reach set point. Almost sounds like it's cycling on and off on limit or something...
 
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