Learn/Troubleshoot Heating system

[Bob O]

I am looking to improve or repair my heating system.
Like other people I have shut off vents and closed doors in rooms that were not being used but reading a bit about negative/positive pressure I decided to open these back up even though I don’t think it made that much of a difference.
I have found some good duct leaks around my A coil and humidifier that I need to seal off, I am going to attempt to clean the A coil the best I can since I have never done that in the 6 years I have lived in this house.
Now for some questions:
What kind of temp. difference should I between my return air and the temp. before the A coil?
My return is 60 deg. F and right before the A coil is 120 deg F and after the coil is 110 deg F.
The temp. at the register is 90 deg. F
I do not stay in my house at night so I reduce the stat to hold at 50 deg F then bump it up when I get home in the morning until I go to work.
Any advice or help is appreciated.

Thanks,
Bob

[totaleclipse]

Any advice or help is appreciated.

Not trying to be a jerk, but the best advice I can give is to call an HVAC Pro. Even with just a cleaning, there are a lot of things that can get really messed up if not done correctly. While the tech is out, have him/her check the entire system for correct operation.

[rimek]

Maybe not turn it down to 50°, that's a lot of load to catch up, and the 60° return-brrr! What is your outside temp now?
turning off rooms only brings an unconditioned space into the picture with poor insulation to the conditioned space. The best things for you to do is to be sure the filter is good, and seriously consider having a pro come in- it can save you $$ and time in the long run, especially if you're running inefficiently, but you might try keeping setback within 8° to see if the plant can keep up with that.

[propmanage]

50 Degrees would take hours for everything to bring up an envelop ambient temperature. Your Unit must either stay on for ever or keep bagging on and off until the building warms up. When you have the service person come, ask them to put in a new controllable thermostat and ask them to set you up with a set back program designed for you location climate.

[Bob O]

Sorry it has been so long since I have been back. I do have a programmable stat it is a Honeywell CT3200.
I have the min. temp set at 60 and the max temp set to 65. I have had this stat for a while but I would manually set the temp lower so it wouldn’t run until below 50 good or bad that is what I did.
Now I am not touching it and letting it run. I am collecting runtime data off the furnace and will look at it in the morning.
I disconnected the humidifier sol., placed a 24VAC relay in its place, and have this wired into a small Microloix1100 controller collecting data and logging into RSView32.
It seems to cycle every 7 min. and runs for 1.5 min if that means anything.
I don’t have a problem calling a service tech but I would like to have an idea what’s going on first if you know what I mean.

Thanks,
Bob

[comfortdoc]

It's on for 1.5 mins, then off for 7 mins, then back on for 1.5 mins? Is that the burner or blower cycle?

[comfortdoc]

It's on for 1.5 mins, then off for 7 mins, then back on for 1.5 mins? Is that the burner or blower cycle?

The return temp is to low for the furnace to ever reach peak efficiency. You are likely not saving money on energy since the furnace is now oversized for the operating conditions.

[Bob O]

comfortdoc,
Thanks for your reply.

Yes that is correct.
I just check and it has cycled 66 times and has ran for 5167 seconds or 86 min. from 6:30 pm to 4:30 am.
At 8 pm the stat drop temp to 60 deg F and then the rum time dropped to about 65 sec. and would cycle about ever 9 min.

FYI - Right now is is 12 deg F outside. I have my windows in plastics and had about 18 inches of insulation blown in this last fall.

Does anything stand out to you as to what could be wrong or is this correct?

Edit...This is the on time of the blower. The burner would have been on longer then this.

Thanks,
Bob

[Bob O]

I meant to attempt this this past weekend but could the A coil be plugged?
I was going to clean it best I could without removing it until this spring.
Could it be heating up because of no air flow and then shut down cool off and then start back up?

Edit...I have access to the coil. The panels are screwed into place from when they installed this unit way back when.

Thanks Again,
Bob

[propmanage]

Push your thermostat up to 80 and see if it does the same thing. Is the thermostat making set point too fast (Do you have heat close to the thermostat location?)
Are you able to take temperature readings at your supply and return plenum at the unit?

It should not run like that

[propmanage]

well yes could be a lot of things can you get the temps comming and going from the unit.

[propmanage]

Even if the burner is shutting off on high limit protection the fan should keep running until all the BTU’s have been used up and then it gets below low temperature and shuts the fan off. If you’re sure the filter is good, fan is clean and you have checked the settings? You should have your unit checked out by a technician. Sounds like a limit control issue and would require a technician to see what type of set up you have so it can be tested. .

[Bob O]

The stat is in the empty living room on the South side of the house and all my registers are open.
Return air temp is about 62 - 64 and the air temp measured above the A coil is 130. [I think and the reason I say that is I am guessing by where the lines are exiting the supply duct.]

The filter is a new cheap fiberglass one from HD. I meant to clean all that this past weekend but never got to it.

Heading off to work but will check in while at work for any other ideas.

Thanks Again,
Bob

[propmanage]

Pull the filter and see how it runs

[Bob O]

I am at work so I can't pull the filter but I will assume it won't make a difference since it is new and no dirt on it but will pull it tonight and log more data.

Thanks Again,
Bob

[propmanage]

Run it with out the filter and see how it does

[htrguy]

With 9 min cycle times that is roughly 6 cycles per hour (cph). The cph can be set on your thermostat. I use as few as I can get on all installations. Usually it's 3 CPH or 4. 6 is too many.

[Bob O]

I call Honeywell yesterday [I think] and they said all this is taken care of in the tstat by dip switch settings.
I have them set to but will double check when I get home tonight.

Thanks,
Bob

[propmanage]

Had a friend call last year asking a similar question, they had picked up a new filter at HD one that was recommended from the store person. Unit was starving for air, had started to trouble shoot the whole system until he finally and proudly told me about how he replaced the filter on his own. (He had picked up a filter thinking it would be better) You probably don’t have that issue but if the unit runs longer with out the filter you may have some restrictions. Or you could just call in the tech.

[Bob O]

That $.56 filter is out for a while tonight when I get home.
I 'll try anything once.