Short Cycling Boiler...

Lou Miller

I just had a new Crown CT-5 oil fired boiler (Riello burner) and indirect water heater installed. The house is divided into 4 zones and a 5th zone (it's actually the 6th zone which is priority) is used for the water heater. The water heater works perfectly. I'm having problems with the boiler short cycling with the 4 zones used for heat though. We're using a Taco zone valve control (ZVC 406), Taco zone valves, and Honeywell T87F (tradeline) thermostats. The installers set the anticipators on the therms at 1.2 if that has anything to do with it. I have tried altering the anticipators but it hasn't changed a thing.

Basically, what's happening is when we're just trying to keep a consistent temp (not altering the therms) the boiler starts up, runs for about 10-15 seconds and shuts off. We have the bolier water temp set at 170. A combination of it being mild, and fairly low heat loss in the house, has kept the boiler from running freqently. This means the boiler water temp usually drops down to around 120-130 since it doesn't run much. What happens is that I'll see the yellow thermostat light come on at the ZVC. It takes about a minute or so, then the red zone valve light will come on. The burner kicks in, then a few sceonds later the bolier starts to run. It runs for no more than 10 seconds before shutting off. It shuts off so fast that I can't possibly see how this is working properly. The one zone frequently calls for heat, but shuts off before the zone valve even opens. It only does this while maintaining the temp. I turn the heat down considerably when I go to work. When I get home, I turn the therms back up to normal temps and everything works perfectly until the therms are satisfied initially. When it's time for them to call for heat again is when the problems start.

The above is everything that I KNOW is happening. Another thing that seems to be happening is the thermostats are reading a different temp than what the room actually is. I don't have anything to back this up with other than my body's reaction to the temp in the room. My wife and I have always kept the heat around 66 degrees and have been comfortable. There's times when the thermostats read 68 and it feels really cold. Maybe this is in our heads only, but it sure seems to be reality. There's other times that the temps read 68 and it feels like 78. The thermostats were installed properly. The installers went around and checked them again to make sure they were level, and I did the same as well. They are all perfectly level just incase anyone thinks that may be the problem. When we bring the temps in the house back up to normal after having them lowered during the workday, the house feels really warm when it reaches 66. After a while of maintaining that temp, it starts to feel really cold and we usually have to bum them up to 68. Even then it starts to feel cold a couple of hours later. We even had them set at 70 one night. they read 70, but our bodies (at least in our minds anyway) were freezing. The installers say that nothing is wrong since the thermostats are being satisfied. My body says another thing.

Some other issues are that the thermostats seem to be acting strange. I've got one that when set to 66 causes the boiler to run until it hits 70 at the therm. Another is the exact opposite. You have to set the temp at 70 in order to get it to reach 66 before shutting off. One seems to be very accurate and the fourth is off by a degree, but it seems to vary whether its off higher or lower. Again, they are all perfectly level.

Could all of my issues just simply be a matter of bad thermostats? Somehow, I have to think there's more to it than that. I specified I wanted Honeywell Therms just because I didn't want any issues. Could the problems be inside the Taco unit? The water heater could not work any better than it does though. No short cycling whatsoever when the water heater zone calls for heat.

Any comments or suggestions would be greatly appreciated.

Paul Mitchell_2

Problem

What type of Taco zone valves?

Lou Miller

> What type of Taco zone valves?



On the side of the valve, there's a 571. I assume, that's the model number. Other than that, I have no idea.

Oh, I probably should mentioned above that we're using baseboard heat. 3 zones are cast iron, and 1 is copper fin tube.

Paul Mitchell_2

Tricky

Usually the heat anticipator is set to what it is operating. You are using the zone control board. So you would have to check the amp draw at the T-stat. If you were hooked to a valve directly the setting would be .9
Maybe you are getting some sort of feed back to the board causing this short cycle problem. Also if the heat anticipator is not set correctly it will cause trouble. I would assume the installer checked. Honestly if you have a problem you should continue to work with the installer. The old standard T87F is not Mr. accurate...new or not. They can be up to 3 degrees off.

Lou Miller

Then it might not be a bad idea to just go ahead an replace the thermostats on my own??? The installer says that everything is working the way it should. I don't agree. It'll cost me about an hour of my time and around $130 to install 4 new thermostats. I'm not saying I'm going to do this for sure yet, but what's the downside of me replacing them? I don't really care about spending a little more money at this point.

If the T87F's are not the way to go, then what is? I didn't want to bother with digital thermostats because the wiring isn't there for it. Besides, our schedules are so whacky that we could never program them properly anyway. It's a lot easier for the last person out the door to turn them down and the first person home to turn them up.

Mike T., Swampeast MO

Anything different about the zone that calls frequently?

Different heat emitters--like fin baseboard compared to radiators/convectors/cast iron baseboard in the other zones?

Unusual amount of glass area?

High exposure (like 3 outside walls)?

When we bring the temps in the house back up to normal after having them lowered during the workday, the house feels really warm when it reaches 66. After a while of maintaining that temp, it starts to feel really cold and we usually have to bum them up to 68. Even then it starts to feel cold a couple of hours later. We even had them set at 70 one night. they read 70, but our bodies (at least in our minds anyway) were freezing.

That's a classic definition of "cold 70". You're getting the air warm when you recover from setback, but the objects and surfaces in the space are still cool. Trying to counter this by raising the temp (say for one night) will only make you even less comfortable than if you keep things at your "normal" comfort point and use less daytime setback.

Lou Miller

Different??? No, not really. Basically, the house is a rancher. We have three zones for the main level of the house. All of these zones are heated by cast iron baseboard. The other zone is for the basement and that is heated by copper fin tube. The way the house is constructed, the basement zone might as well be in another house all together. It has no bearing (IMO anyway) on the rest of the house. It probably runs the least of the three since it's mostly underground (and it's being heated by the boiler itself to an extent).

When we installed the new system, there wasn't enough time in the day to get all of the zones going. So, they got the basement zone and water heater done that day. We thought we could crank the temps up in the basement and have some of that heat go through the floor and help the main level. Not a chance. We might have seen a 1 degree rise in temps, if that. We had the other zones running the next day, so it was only one cold night.

The three zones on the main level are all pretty much the same. With the exception of a large window in the living room, all of the rooms in the zones have your pretty standard size windows.

None of the rooms, except for the basement, have exposure to any more than 2 exterior walls.

I'm not really sure what else to add here, but nothing seems out of the norm, to me anyway.

kev

wiring

Is it possible that the thermostats are not wired to the correct piping? The thermostat in the living room may be controlling a bedroom etc. That and what seems to be a wiring problem at the taco control.

Paul Mitchell_2

No

Chance of them all being a problem is slim to none and a waste. Honeywell makes some great new digital t-stats that are non-programmable and can be set for heat only. 5000 series. You should be able to use these with the control box. I agree with one post maybe the wires are mixed up for the zones...Maybe your old t-stat was so off that it was really 73 in the room when you thought it was 68. The T87 is inaccurate and the thermometer on it is useless. I have seen them perpetually on 70...etc.

ThermalJake

Does setting back each day really help anything? I always thought that setting back should be reserved for when one goes on an extended weekend or full week away. I think that I remember timing the boiler during a 24 hour period of maintaining temps, and then again when set back and recovered. We found that the boiler ran LONGER (++GPH fuel) during the 24 hours that we set back.
Maybe others have some thoughts about this.
Jake

Marty_3

t'stat to valve

As kf stated, make absolutely sure that the t'stats are wired to the correct corresponding zone valve. Set all the stats as far back as they'll go. Then set one zone up to say 68* and ascertain that the corersponding baseboard heats up. If so, set it back and go to the next one until you've been thru all the zones. If that checks out, then I would take a hard look at the control panel.

Monte

Are your thermostats located on a wall where heat or cold might be able to move into the wall cavity behind them? Also, do you have any thermometers you could place in the rooms in the vacinity of the thermostats?

Lou Miller

Paul

I'll take a look at 5000 series stats. Based on having the T87 stats for a little while now, I'd have to agree with you about the thermometer on them being worthless. Most of the time, my body disagrees with what they are reading. The thing is though, I always thought of them as the "old reliable". They've been around forever, and are in millions of homes. I've never heard of anyone complaining about them before. I am inclined to agree with you in this case though.

I'm sure I can get the installer to come back and fool with it if I get on him enough. At this point though, since he believes that everything is fine, I think I'm just better off taking a stab at fixing it myself. Besides, the guys did an awesome job on the install, charged me a great price, and did more work than they originally said they would. If I can fix it by simply swapping out the stats, then I'll get on him to come back.

Lou Miller

Jake

I dunno if it makes any difference or not. It's just something I've always done. I'd be curious to see what others have to say on this too. Maybe I'll try both over a period of time and see if there's any difference in oil consumption. It's kind of hard to compare apples to apples though with the varying temps outside. The weather in PA has been wierd, to say the least, this year. One day it's in the single digits, then a week later it's around 60. Go figure...

Lou Miller

Monte

No, the stats are all located on interior walls. All of the holes we drilled for the wiring were filled with spray foam to keep any air from getting there. I guess there's always a chance, but I seriously doubt it.

Lou Miller

KF and Marty

Thanks for the input, but I've been through everything at least 100 times now. I'm positive that the wiring is done correctly.

Glenn_3

Lou,

My suggestion; Get a honeywell T84001018 thermostat Yes its digital but has only 2 terminals for connecting your wires. Can't hook it up wrong. Doesn't need to be level to work right and no anticipator to worry about. In fact before you attach it to the wall, hook up wires and let it hang from them away from wall. Will work great with your Taco control panel.

Am willing to bet alot of your problems are with the anticipators in the T87s

A setting of 1.2 should cause overheating in all your zones.
With them being connected to your Taco panel,I would think a setting of .2 would be would give you a better control.

If you still have the instruction sheet that came with the control panel check it. I'm pretty sure it has the setting for the anticipator on it.


But try one T8400 and see if doesn't work better for you.

Weezbo

i read this post a bit....

my thought is disconnect the end switch from the boiler and then spin the two wires together go turn up all the t stats. you tell me what happens then. ok?

bill_51

oops.........

actually, if you set the heat anticipator to .2 and the zone valves actually draw .9 amps then you have a good chance of burning out the heat anticipator. i haven't really paid attention to what the heat anticipator is factory set at but i know it isn't 1.2(all the way to the left i believe) sounds to me like the guy who did the install didn't bother with checking the actual amp draw of the zone valves and just cranked up the anticipator so it wouldn't burn out by being set too low. if anything that may cause the space to overheat by a degree or two.....
now, the honeywell 1018 t-stats are fine but you have to do a bit of extra wiring, the taco zone valve will not allow the proper milliamps to come through it to power the stat, you need to connect the bleed resistor to the zone valve........if you don't do this then you will experience the stat blinking on and off while it is calling for the zone valve to open and you will also need to set the cycle rate for 3.....its all in the instruction booklet. the bleed resistor comes with the stat and has its own little instruction sheet for the various wiring. those are decent stats but you will need to do a bit extra to connect them
yeah, i've been dealing with honeywell wayyy too long

bill_51

oops.........

actually, if you set the heat anticipator to .2 and the zone valves actually draw .9 amps then you have a good chance of burning out the heat anticipator. i haven't really paid attention to what the heat anticipator is factory set at but i know it isn't 1.2(all the way to the left i believe) sounds to me like the guy who did the install didn't bother with checking the actual amp draw of the zone valves and just cranked up the anticipator so it wouldn't burn out by being set too low. if anything that may cause the space to overheat by a degree or two.....
now, the honeywell 1018 t-stats are fine but you have to do a bit of extra wiring, the taco zone valve will not allow the proper milliamps to come through it to power the stat, you need to connect the bleed resistor to the zone valve........if you don't do this then you will experience the stat blinking on and off while it is calling for the zone valve to open and you will also need to set the cycle rate for 3.....its all in the instruction booklet. the bleed resistor comes with the stat and has its own little instruction sheet for the various wiring. those are decent stats but you will need to do a bit extra to connect them
yeah, i've been dealing with honeywell wayyy too long

bill_51

oops again(this time mine)

reread the post i was responding to and realized that i said alomost the same thing glen did.........also the info was for being connected directly to the zone valve and not a control panel that controls the valves.......its too ealry for me to post anything i guess, i'll go back in my corner

EBEBRATT-Ed

Do what Weezbo says. This will help you troubleshoot the problem. Still sounds like a wiring or anticipator problem.
What is the high limit set for-is it shutting the burner down?? Is a limit control killing the power to the Yaco panel incorrectly??

Lou Miller

It's working good now.

Thanks again for all the responses everyone. I went out and got 4 CT500 stats and installed them. The CT500 was the only one they had, so I went with it. From what I can tell at Honeywell's site, it's basically the same stat as the others that were suggested (all digital manual). I couldn't see any difference in them (although I'm sure there are some very minor differences). I installed them Friday morning and now, Saturday afternoon, I've yet to see a single zone cause short cycling. The T87s that I removed were all reading 68 when I pulled them out. The CT500s all seemed to read 70 when first plugged in (I assume this is where the default is set from the factory), but quickly changed to 65. I also picked up a wireless remote thermometer so I could have something else to check the temps with to see how accurate the new stats are. All of my readings are within 1 degree of each other. So the new stats seems to be pretty accurate. Seems as though all the T87s were off by 3 degrees or so like someone mentioned above. I sett all the heat cycle rates at 3. The temp control default at c1. The house is as comfortable as can be now. Most of the zones run for around 3 minutes or so before shutting off.

I don't want to mock the T87s as a whole, but it sure seems like the ones I had were worthless. Now I can finally gloat about how much I like my new heating system

Thanks again everyone.

Lou Miller

> my thought is disconnect the end switch from the

> boiler and then spin the two wires together go

> turn up all the t stats. you tell me what happens

> then. ok?




I don't think I need to do this now. However, I'm curious as to what would have happened.

Weezbo

well?

whazzup ?