what exactly is considered short cycling?

jim_14

do you mean the amount of times the boiler turns off and on after steam hits all the rads?

Is a 1 pipe steamer supposed to run a few minutes between cycles or less then a minute?

MIKE6

short cycle

When a boiler flame goes on and off before steam pressure or room temp is reached.An example would be a boiler with a surge problem.Water level in boiler dropping because of dirt or oil in the system,shutting off on low water cutoff and after 90 seconds comming back on.

G Lyons

Short cycling T8600 and White Rogers Zone Valves #1361

After installing a new Dunkirk boiler and using an isolation relay between the White Rogers #1361 Zone valves and the boiler control, I found that the T8600 thermostat would bring the boiler on via the Aux switch in the zone valve and the isolation relay, only to shut off again. Thanks to Honeywell and my local supplier, Applied Automation and Brian on the counter, It was determined that an isolation relay was also needed between the Thermostat and the zone valve. Seems the thermostat could'nt handle the xtra load of that zone valve and the isolation relay. This problem cost me a few houres. The zone valves and thermostats were preexisting. Any input from others would be good.

Joe_39

ok so

a boiler shutting down on steam pressure rather then room temp is ok?

Unknown

G Lyons

You have experienced the effects of the T8600 thermostats "power Robbing" feature. You probably only needed the isolating relay between the thermostat and the zone valve. The end switch on the WR # 1361 is a dry contact. The problem was not that the thermostat could not handle the load of Zone Valve and relay it is the "Power Stealing" feature that messed you up. Here is some information about those thermostats.

ADVANCED POWERSTEALING CIRCUITRY

“Powerstealing” thermostats have become increasingly popular with contractors as a thermostat, which is easy and economical to install. Honeywell's new thermostats with Advanced Powerstealing are now available in both programmable (T8000, T8700, T8600) and non- programmable (T8400) thermostat families.

"Powerstealing" electronic thermostats draw energy for operation from the heating and cooling equipment. They have several advantages over battery-powered or hardwired thermostats, while being compatible with virtually all-heating and cooling systems.

Unlike battery-powered thermostats, Honeywell's new powerstealing thermostats do not require batteries to operate and still provide program backup with electronic memory. Hardwired electronic thermostats draw a consistent source of power directly from the system transformer. Because they rely directly on the heating and cooling equipment for energy, these thermostats require an extra wire to supply 24 Vac to the thermostat. This is fairly simple to do in new construction applications, but relatively difficult in retrofit situations. Powerstealing models can be installed without costly extra wiring and are a good choice for most home heating and cooling systems.

Powerstealing thermostats continuously draw a small amount of current from the heating or cooling system to operate. When the thermostat is not calling for heat or cool, the thermostat "steals" enough power to operate by allowing a small amount of current to flow through it into the relay coil. While older powerstealing thermostats require 10 mA to 20 mA to function, the advanced powerstealing of Honeywell's thermostats require a mere 0.1 mA to 10 mA to operate. When the thermostat is calling for heat or cool, the advanced power stealing of the new thermostats require only 2.5 IDA to 25 mA to operate compared to older powerstealing thermostats that required 10 IDA to 120 mA for proper operation.

Although powerstealing thermostats are compatible with most home heating and cooling systems, they aren't appropriate for some applications, including millivolt (powerpile) systems, line voltage systems, Taco Zone Valves and other systems that open the load circuit for more than 0.5 seconds during an "ON" cycle. In most cases, though, Honeywell has a powerstealing thermostat just right for your applications. And with the part number 4074EYC, your Taco Zone Valve compatibility problems can be easily solved.

John Cockerill

Thanks Tim That was really helpful.

John Cockerill Exquisite Heat
www.Exqheat.com

John Cockerill

Thanks Tim That was really helpful.

John Cockerill Exquisite Heat
www.Exqheat.com

G Lyons

Thank you Tim re T8600

This is what I thought I had going. The White Rogers Zone valve #1361 has an energised augsilary switch, (I wished it had a dry end switch,) When the thermostat called for heat and the zone valve was opening, it then energised the isolating relay as well as the warp type aux switch, which takes power to accomplish as well. Causing the T8600 to open.. In any case the isolation relays I installed between the thermostat and zone valves did the trick. Some more input ??..