JSF, refresh periodically a component with ajax?

Poll is what you need to use

Poll component make ajax calls in a specified interval.

For example Primefaces Poll

<h:form id="form">    <h:outputText id="txt_count" value="#{counterBean.count}" />    <p:poll interval="3" listener="#{counterBean.increment}" update="txt_count" /></h:form>

Link to showcase Primefaces Ajax Poll

Pure JSF approach would be to use js timer that will invoke periodical document.getElementById('someFormId:idOfButton').click();

or jquery $("#someFormId\\:idOfButton").click();

while the button will look like this

<h:commandButton id="idOfButton">    <f:ajax render="txt_count"></f:ajax></h:commandButton>

something like this

setInterval(function(){$("idOfButton").click()},3000);

More about timer JavaScript Timing Events

In RichFaces there is a poll component as well. Here is a nice example they provide

<a4j:region>      <h:form>            <a4j:poll id="poll" interval="1000" enabled="#{userBean.pollEnabled}" reRender="poll,grid"/>      </h:form></a4j:region><h:form>      <h:panelGrid columns="2" width="80%" id="grid">           <h:panelGrid columns="1">                <h:outputText value="Polling Inactive" rendered="#{not userBean.pollEnabled}" />                <h:outputText value="Polling Active" rendered="#{userBean.pollEnabled}" />                <a4j:commandButton style="width:120px" id="control" value="#{userBean.pollEnabled?'Stop':'Start'} Polling" reRender="poll, grid">                       <a4j:actionparam name="polling" value="#{!userBean.pollEnabled}" assignTo="#{userBean.pollEnabled}"/>                </a4j:commandButton>          </h:panelGrid>          <h:outputText id="serverDate" style="font-size:16px" value="Server Date: #{userBean.date}"/>    </h:panelGrid></h:form>