Am I short cycling?

jlo1029

Hello

Thanks everyone who responded to my earlier post. I now have a working sight glass AND LWCO AND the book! So much to learn.

I have noticed that when it's not very cold out, my boiler will run for about 3.5 minutes out of every 10-15.

The house is warm and I have working main vents.

Is this normal? Or a sign of a problem?

My thermostat is a honeywell digital wifi.. but the wifi doesn't work because it's not compatible with my router.
Model is TH8320WF . I've read stuff about setting it up for steam but it went right over my head!

Thanks!

Jamie Hall

Somewhere buried in the menus of that thermostat there is a setting for system type and cycle rate. It's all in the manual, if you have it (or here: http://www.honeywellmanual.com/honeywell-th8320wf1029-user-manual-pdf/). You're looking for system type (option 17) 5 (Heat only) and then Heating Cycle Rate (option 0240) 1 (Gas/Oil steam or gravity system).

That should fix the problem.

jlo1029

Thank you!! I changed 0240 to 1 (it was on 6). So now I should have 1 cycle per hour instead of 6, correct?

Jamie Hall

jlo1029 said:

Thank you!! I changed 0240 to 1 (it was on 6). So now I should have 1 cycle per hour instead of 6, correct?

That's the theory...

mikeg2015

Sometimes 1 may result in too wide of temp swings. If the system ran about 3 out of 15 minutes and swung lets say 0.5F, then it would in theory run approx. 12 every 60 minutes and swing 2F. Or more likely overshot by 3F, then drop by 1 F before cycling on again. To me, that’s too wide of a swing.

You might try “2” first and see how that is. It should run approx. 6 minute out of 30 in the conditions above. Which I’d consider acceptable compromise.

1 I think works better with higher mass systems like hit water and radiant floor heat that warm up and cool off slower. Steam has a lot of mass, but far, far less stored energy that hot water.

Iron is more dense, but stored 1/10th the energy per lb that’s water. So a 1 8lb gallon of water can store the same energy as 80lbs of iron. So a hot water radiator stores probably almost 2x the energy as steam. Steam runs hotter, but a hot water radiator heats all of the iron and water completely.

EBEBRATT-Ed

3.5 min burner on time is a little on the short side. Starting and stopping puts wear and tear on the burner, run time does not. I would like to see a burner run time of 5 min minimum if possible. It's a compromise between comfort and short cycling.

nicholas bonham-carter

It sounds like the thermostat setup may need some work, as the CPH setting probably allows only one long burn per hour.
Remember that the thermostat cannot compensate for an unbalanced system, with inadequate main venting.—NBC