boiler stops and restarts toward of end of heat cycle.

[lclark]

it is a w/m wtgo4 w/riello40 f5 burner.after a call for heat when the returns get warm,it shuts down and restarts within seconds{it does the purge}at first thought the thermostat and or the honeywell L8124A.but now am wondering maybe the riello?runtime 20 to40 mins if cold.by then the thermo is satisfied,house is warm and i wonder should it do that?

[jadnashua]

Some heating systems have a maximum run-time...if the thermostat is still calling for heat when that time has elapsed, it will shut down, and (there may be a delay) restart to finish the work of heating the house. This could be entirely normal. It could also be something overheated, or some other fault, and the system safety circuits shut it down. You'd have to read the functional description of the system to determine which.

[david_griffin]

it is a w/m wtgo4 w/riello40 f5 burner.after a call for heat when the returns get warm,it shuts down and restarts within seconds{it does the purge}at first thought the thermostat and or the honeywell L8124A.but now am wondering maybe the riello?runtime 20 to40 mins if cold.by then the thermo is satisfied,house is warm and i wonder should it do that?

The fault can be everywhere. You have to determine step by step what is going on. Get multimeter and check- maybe only burner itself gets crazy, maybe it starts without the command from the furnace.

[Tom Sawyer]

How does that happen? What is he supposed to check with the multimeter? When you say "everywhere" do you really mean everywhere?

[jadnashua]

A modern boiler has all sorts of safety and functional control logic; often, some of it controlled by a computer. Without reading the manual, you won't know if what is happening is entirely normal, or if not, why it is shutting down and restarting. Often, the thing will have error or status codes. You need to read AND understand. Then, and only then, can you start to diagnose if it is a problem, and then, where it is.

[Tom Sawyer]

Normally Ja, I agree with you but he has a weil Mclain CI boiler with old style analog controls. There are a whole bunch of things that could be causing the problem from to wide a delta T swing, improperly set limits, improperly set aquastat, not enough fire, the list goes on. Without being there and running diagnostics we can play this game all day. The Riello burner is probably not the cause though. It gets it's signal from the aquastat. Unlike Beckett and Carlin burners the Riello uses a line voltage primary control.