Boiler cycling time

Steve Ebels

Simply stick a 30 gallon elctric water heater (sans elements) in your primary loop. It would give the Burnham a little more to chew on when it fires. Longer burn cycles=better system efficiency.

Just an off the cuff thought.

BTW what was the heat loss of the house and what's the input of the boiler? Also are there, or is there one or two zones that call for heat most of the time? I was just looking at the sq ft and the number of zones........ Come out to an average of only 250 sq ft / zone. If only a couple of 'em are calling at a time it will fer sure short cycle. Any possibilty of tying some of the smaller zones on with a larger one to eliminate those demands for only 5-10,000 btu's?

jekmech

Boiler cycling time

A year and a half ago I installed a 3500 sq ft radiant floor heating system in a three story log home. PEX is in 4" concrete in the basement and in 1 1/2" gypcrete in the second two floors. The homeowner is more then satisfied with the level of comfort the system provides. Oil consumption has been average to in my opinion a bit high. Being rather new to low temp radiant floor systems I am concerned about the frequent cycling time of the boiler. The mechanicals consist of an oil fired Burnham V8 with with a Tiger Loop on the oil line and a Field's through the wall power vent. The boiler is piped primary secondary which feeds a supplemental hydro coil in the A/C ducting, an indirect water heater and three manifold loops which provide 14 individually controlled floor zones. The radiant floor controls include a Wirsbo ProMix with outdoor reset. While I realize that numerous variables will have an effect on a homes heat load and therefore the boilers output periodic checks have found the boilers cycle time to be 1 to 3 minutes on and an equal or just slightly longer off cycle under moderate to cold outdoor conditions. Am I worrying about nothing or should I be concerned about not having a longer cycling period. In a recent trade journal article what sounded like a somewhat similar problem was addressed. It was suggest that the circulators on the boiler and primary loops be put on a timer relay to allow the remaining BTU's in the boiler to continue to be circulated through the primary loop (where the temp sensor is located) thereby increasing the time between a call for heat. Does this make sense and is it worth the effort and expense? Any other thoughts and ideas would be appreciated.

bluenose_11

short cycling?

What is controlling the burner? Just the aquastat? I would say a one to three minute burner on time under moderate load may not be that bad,but the longer the better.What size is the burner nozzle?

Boilerpro

It sounds like..

you have a separate boiler control system. When using this setup there should be constant flow past the sensor whenever the system is in operation. The boiler's pump should be called on whenever there is a call for heat from the system. The burner should be controlled by the boiler control. Most better boiler controls have a separate contact for a system pump, and this is where the boiler pump should be connected. By wiring it this way, the system draws heat from the boiler whenever there is a call for heat and only when the stored heat is not enough will the burner be called on. If you don't hae this separate relay then it is best to let the boielr pump run continuously. This procduces much longer burn times.


Boilerpro

hr

Best to crunch some numbers

Start with the free heat loss calculator available to the left of the Heating Help page. It's not uncommon to see oversized equipment installed. If, in fact, the boiler is grossly oversized it will be hard to get it to run long steady cycles.

There are some "tricks" to help, but we need some more info on the heatloss of your building and the boiler output, to steer you.

hot rod

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