Omnistat 2 RC1000 Heat Runtime

[Jrock]

Hello,

My RC1000 has been acting oddly since it started getting cold. It is set at "Heat Only" so it has only been used for the "Fan" mode for a while. Anyway, Lets say for example, it is 65 degrees in the house. I set the heat to 67 and it comes on as normal. It will run for a while then shutdown before it reaches the desired temperature. It will then immediately restart again and continue in this cycle until the desired temperature is reached.. It does this sometimes even when it needs to make a 1 degree increase in temperature.

Before this season it has been working fine for over a year. It did stop communicating with my HAI panel earlier this year but it was because the port was bad on my OIIe. The board was still under warranty so I paid the difference to upgrade to the OPII.

Any help would be appreciated.

 

[tmbrown97]

First thing I'd check might be voltage drop - have you been around the display to see if it acts like it's losing power, or what it does during this?

 

[Jrock]

One time I turned up the heat at the thermostat and noticed a few minutes had gone by and the heat had still not come on. So I go back to the thermostat and the arrow is randomly flickering like crazy. I tried adjusting the temp but the heat wont come on. So I disconnected and reconnected it from the wall to reset it and I have not had that particular issue since.

I just turned the heat up. I will keep an eye on the thermostat to see how it acts during its cycles.

 

[Jrock]

I watched the thermostat and logged the heating activity.

1:06pm

Temp: 68​

Turn heat up to 70​

1:25pm

Temp: 69​

Furnace turns off then immediately back on​

1:38pm

Temp: 70​

Off and on again​

1:50pm

Temp: 71​

Off on again​

So it seems to be cycling at every degree change. The Omnistat will be two years old in April I believe. It is connected to a OmniPro II. I verified all settings on the thermostat. All communication seems to be working fine. It sees the outside temp and I can control it from all my devices (Except my Blackberry phone or Playbook ).

Any suggestions?

 

[Desert_AIP]

Have you changed any of the default settings in the anticipation logic?
heat minimum on/off, EEC settings, heat anticipator?

e.g.

Heat Minimum On:
The number of minutes the thermostat forces the heat to remain on before turning off.
Raising this number will increase the total time the heating system is on (saving energy), but
may allow the temperature to drift farther from the setpoint (decreasing comfort). When
combined with Heat Minimum Off, cycles per hours can be obtained by using the following
calculation: 60 / (Heat Minimum On + Heat Minimum off). The default time is 6 minutes.
Heat Minimum Off:
The number of minutes the thermostat forces the heat to remain off before starting again.
Raising this number will increase the total time that the heating system is off (saving energy),
but may allow the temperature to drift farther from the setpoint (decreasing comfort). When
combined with Heat Minimum On, cycles per hours can be obtained by using the following
calculation: 60 / (Heat Minimum On + Heat Minimum off). The default time is 6 minutes.

 

[Jrock]

Have you changed any of the default settings in the anticipation logic?
heat minimum on/off, EEC settings, heat anticipator?

e.g.

Heat Minimum On:
The number of minutes the thermostat forces the heat to remain on before turning off.
Raising this number will increase the total time the heating system is on (saving energy), but
may allow the temperature to drift farther from the setpoint (decreasing comfort). When
combined with Heat Minimum Off, cycles per hours can be obtained by using the following
calculation: 60 / (Heat Minimum On + Heat Minimum off). The default time is 6 minutes.
Heat Minimum Off:
The number of minutes the thermostat forces the heat to remain off before starting again.
Raising this number will increase the total time that the heating system is off (saving energy),
but may allow the temperature to drift farther from the setpoint (decreasing comfort). When
combined with Heat Minimum On, cycles per hours can be obtained by using the following
calculation: 60 / (Heat Minimum On + Heat Minimum off). The default time is 6 minutes.

Thanks for your reply...

This is the first thing I thought of when I started noticing the issue. I never changed any of those settings, but I did go in and review them and everything is still set at the default settings.

However, the settings you mentioned are minimum on/off settings. The issue I am having is the system is not running long enough. I also considered the heat anticipator being the issue, but the system is starting right back up again so its not like it thinks it is close enough to the desired in temperature.

 

[Desert_AIP]

Not running long enough may be the minimum on time. Once it goes on it should not turn off before the minimum on time is reached

I clipped those as examples as the doc entries for the EEC parameters and anticipator control are longer.

What type of system are you controlling? Heat pump?
Are you sure it is the thermostat shutting down the system and not an internal safety shutting down because of a low compressor pressure or something similar?

 

[Jrock]

The system is running way more than the minimum on. I believe the default minimum is around 6 minutes. Its forced air natural gas.

 

[tmbrown97]

I had a normal gas system in a previous rental - should've been a 2-zone, but it wasn't... so had to adjust the dampers in the attic twice/year. If I restricted the upstairs too much it triggered a safety that caused similar behavior to what you describe.

The only real way to know if it's the tstat is to measure the voltages to see if it's keeping the relay closed, opening it for a moment, losing power completely, etc.

Might be worth paying for a service call to check the system out too...

 

[Jrock]

Thanks for your input. I have a service contract on my furnace and water heater with my utility company. I don't think they charge for service calls.

During Hurricane Irene a tree fell on my house so I shut off the main gas line without shutting off the emergency switch on the furnace. Not sure if that matters or not. The heat was not being used at that point so I do not know if it was working properly.

Ill check the voltage on and if all seems good Ill definitely call for service.

 

[tmbrown97]

I don't think you need to do anything special when your gas cuts off... I had work done on my gas main a couple months ago - I had to relight the fireplace and hot water heater, but the furnace uses an electronic ignition system so I didn't have to touch it.

 

[Jrock]

My furnace has an electronic ignition too. I didn't know until I was trying to figure out how to light it when I turned the gas back on.

 

[Jrock]

So I ended up working out a deal with the contractor who is repairing the damage to my house from Hurricane Irene...

A tree fell on the house and came through the roof at various points and hit the chimney. Instead of having him rebuild the chimney from the ground up (which is much more expensive than I thought) they completely removed the chimney and installed a new energy efficient furnace and hot water heater and added central air to my house.

Everything was installed today and seems to be working flawlessly! I guess it wasn't the tstat after all. It was kinda warm out today so the system was only run to test but so far so good!

Thanks again for all your replies and suggestions.