How to wire a boiler

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Old 12-14-10, 11:50 AM
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How to wire a boiler

Im a electrician helper. My cousin is a plumber so he does alot of boilers. I was helping him intstall one and he had to hire a electrician to wire it becuase im not familiar with ow voltage at all.

Can some 1 please explain to me the circuit inside the boiler. Lets say its a 120 v gas fired boiler that controls a few base board radiators. The things that needed to be wired were, thermostat,aqua stat,low water cut off, and a gas vent damper.


If some 1 can take some time to explain how to wire these things id reallly appriciate it. thanks
 
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Old 12-14-10, 12:02 PM
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I don't think we could cover all the bases over the internet. If you download the installation manual for the boiler model in question, it should give you a control schematic, etc.
 
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Old 12-14-10, 02:08 PM
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I just want a decent explanation, ex.. The thermostat kicks on when below a certian temp...signals to the relay... the relay is connected to this this n this...(low water cut off, aqua stat, damper vent.. something where i have a good understanding from the stat kick on dwn to the boiler firing back to the stat shuting off. I cant find any decent explanations in google.
 
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Old 12-14-10, 03:43 PM
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I'll give it a try.

First, let's start with the boiler. The most BASIC setup will will be ONE ZONE, ONE THERMOSTAT, ONE PUMP. And of course the gas or oil combustion device.

The AQUASTAT is what controls this stuff.

In the basic aquastat, there is a 24VAC transformer, a DOUBLE POLE relay, and a water temperature bulb in the boiler that controls the HIGH LIMIT for the water temp.

The thermostat connects to (usually) the T T terminals. The thermostat MAKES contact when the room temp falls below setpoint.

When the thermostat closes, it energizes the RELAY in the aquastat.

One pole of the relay sends 120VAC to the CIRCULATOR PUMP, (usually terminals C1 and C2). This voltage will remain as long as the thermostat is still calling for heat.

The other pole of the relay can send 120VAC to an OIL burner, (and some gas valves are 120VAC, but not the modern ones really, mostly old stuff), OR in the case of a low voltage gas valve, it will send 24 VAC to that valve. (usually terminals B1 and B2)

Inside the aquastat, the HIGH LIMIT control will cut off the burner if the water reaches that temperature setpoint, typically 180F. If the thermostat is still calling for heat and the boiler cools to around 165-170, the burner will fire again and heat to 180 again. This cycle will repeat as long as the thermostat calls.

When the thermostat satisfies, the burner and the circulator will shut down.

That's about as basic as aquastats get...
 
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Old 12-14-10, 04:19 PM
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LWCO and VENT DAMPER

These are basically 'accessories'... add-ons...

Either could be wired into the LV or the HV circuits.

The DAMPER is 'usually' wired into the LV circuit and is in SERIES with the voltage to the gas valve or oil burner. There are 'proving switches' in the damper control that will not allow the burner to fire until the damper is PROVEN to be OPEN. Most modern boilers have connectors for these to plug directly into the aquastat or ignition control devices.

The LWCO is a Low Water Cut Off device that will not allow the boiler to fire if it senses there isn't enough water in the system. They can be wired a number of ways... sometimes the device will cut the 120VAC to the whole boiler, sometimes will only prevent the burner from firing, but it's best to cut off the circulator pump as well... you don't want to run those dry.

Questions? anyone? Buehler? Buehler?
 
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Old 12-14-10, 04:33 PM
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Originally Posted by NJ Trooper View Post
Questions? anyone? Buehler? Buehler?
This forum is so boring that my head is resting on my desk, my eyes are nearly closed, my mouth is part way open, and I am drooling.

[me too Mike! me too! - NJT]
 

Last edited by NJT; 12-14-10 at 05:10 PM.
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Old 12-14-10, 04:37 PM
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Thaks alot for ur reply. Im preety sure my cousin told me theres a internal aqua stat in the boiler. Is that the 1 ur talking about?The way ur explaining it is that the aqua stat is temp controler with a relay , transformer and bulb all in 1 piece? The one I was talking about is a external aqua stat that gets wired in...

Im sorry if I sound dumb , I wanna learn this. I know once I learn it il look back and say what a stupid question, but its hard when I really know nothing about it.. Il post a url of the stat im talking about. http://customer.honeywell.com/techli...0s/60-2104.pdf


l4006a aquastat
 

Last edited by NJT; 12-14-10 at 05:11 PM.
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Old 12-14-10, 05:16 PM
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No apologies! The quest for knowledge is a noble cause.

Yes, talking about a BASIC system. The main control would be an aquastat connected to the boiler.

Without knowing the specifics of the installation you were working on, it's impossible to guess what the 4006 is to be used for. One possibility is a secondary high limit ... a 'fail-safe' in case the main one takes a dump.

BTW, aquastat - one word.
 
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