New Boiler_Short cycling issue

Kevin Varga

I have installed a new boiler(oil, hot water) and I am experiancing periods of short cycling of the boiler. The house is at the set temp, the thermostats have had their anticipator settings adjusted. The system uses Honeywell T 87 thermostats and Taco zone valves. Any thoughts would be helpful

John Abbott

Could we....

have more information please. how many zones? How much load on each? Which taco zone valves? what size boiler? Total load connectected to system?

John

[Deleted User]

maybe you have to many zones

and no buffer tank to give the boiler something to chew on.

sootmonkey

hey

what type of aquastat? does it have a differantial setting?

c-rex

you don't

think the boiler is too big? This can happen........

Kevin Varga

more info

The boiler is a burnham V-84 (107,000 BTU/HR). Boiler has the standard Honeywell boiler control L8148 set at 190 degrees. I do not believe there is a setable diff on this.

Kevin

Unknown

Kevin

First off, be sure that the heat anticipators on the T87 thermostats are set to the proper setting for the Taco zone valves. If they are the 570 series zone valves this would pretty much be all the way down on the scale to 0.9 to 1.2 amps.

Second, while the boiler burner is running, watch the temperature on the gauge and see if it is fluctuating approximately 15°F from the high limit down to the cut-in point. This control would normally be set for a 180°F high limit. If the boiler were maintaining temperature for an immersion tankless heater, it would be set for 190°F or higher.

Third, what time period are you considering to be short cycling. Is this several seconds, minutes? Was this a replacement boiler with preexisting zone valves? More information would help pinpoint the root of the symptoms.

Glenn Stanton

Burnham Hydronics

Kevin Varga

Thanks for the help. The circulator comes on (I can
hear as I have vibration transmission issue)then the
boiler prepurges and the runs for one to two minutes
and shuts down with the circulator shutting down
within seconds. The zone valves are Taco 570's.
Currently there are 3 zones running having
responsibility for 1100 sq ft of floor space. We are
in the middle of a renovation. The completed project
will be close to 3000 sq ft. The previous boiler was
an Essex dual fuel boiler of 130,000 BTU capacity
although my original heat calc was for 110,000 for the
3000 sq ft. This was calc with room set temp at 68
degrees and outdoor temp at -15. Thanks for your
thoughts.

Kevin Varga

Wayco Wayne

Sounds like

anticipation problems to me. I have put an ampmeter that reads snall amps in line with the heating circuit that has a Taco zone valve. I can see why it would play havoc with a heat anticipator for a Honeywell T87F. The zone valve pulls different amps during different times of it's operation, and at times it rests and doesn't pull any amps. Long story short, do what Glenn said and set the anticipator all the way down, or change to an electronic tstat that uses PI controlling for it's anticipation. I like the Danfoss RET model tstats, but I'm sure Honeywell has a brand that uses similar technology. WW

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Robert O'Connor_3

If the circulator

is shutting down as well as the burner, then the short cycling is being caused by your external call for heat or thermostats and zone valves. Check those heat anticipators and/or the operation of the zone valves. Hope this helps.

Glenn