hydronic radiant heat system: short cycling problem

[Larry Gagnon]

We are recent owners of a 1900sq ft home built on two levels that has hydronic radiant floor heating on both levels, embedded in concrete floors. The system runs with a natural gas fired Viessmann Vitogas 50 cast-iron atmospheric boiler and a Tekmar 360 digital mixing control with associated pumps and sensors. We have only been in this home less than one year so it is our first experience with high mass radiant floor heating this winter. (Our winter is southern Vnacouver Island, temperatures normally above freezing at their coldest and now getting up to about 8 deg C during the day).

Before I call in the experts I wonder if there are any on this newsgroup who might give me some advice on our system. The boiler seems to me to be cycling too often. During the night the boiler will fire for about 3 minutes every 8 minutes, sometimes even more frequently. This seems to me to be very rapid cycling given that the water in the radiant floor pipes is unlikely to be cooling down that rapidly??

Is this sort of cycling of the boiler normal? If not, what adjustments can be made to the mixing control to reduce the on-off cycle without affecting system efficiency?

Any ideas greatly appreciated.

Larry Gagnon

[m Ransley]

Your thermostat should have a setting for temp swing , or an anticipator, look at its manual and adjust it to more variance in temperature

[m Ransley]

You are loosing a high % of efficiency and increasing component wear on short cycling. It is not fully warm after 3 minutes, I would think once every hour or 2 is best The floors hold alot of heat . experiment with your stat and look into how the pump operates

[HeatMan]

Take your questions to The Wall.

Buy a brick while you're at it...