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berniemac · Joined: 04 Feb 2003 Posts: 2

Hello,

I am trying to connect a Drayton Digistat 3 to my Ariston Eurocombi boiler.

My problem is that the stat output on the boiler has two wires, but the stat input requires 3!

Any ideas?

ChrisR · Posted: Mon Feb 24, 2003 12:08 am Post subject:

The third wire's an earth isn't it? Or maybe it's a Make-on-rise connection for air conditioning.
If it's a Neutral (which I'm pretty certain it isn't) the stat is unsuitable for the boiler because the hysteresis will be too much.
In other words just use the break-on-rise pair of contacts.

(Many a boiler has been bust by connecting wrong things to the thermostat inputs. This Ariston is better than most in that the designers thought about it- it won't WORK if you put mains in there, but it won't break either.)

AGILE · Posted: Tue Mar 04, 2003 10:31 am Post subject: Re: Thermostat problem

Most modern digital stats and programmable stats have three connections.

These are usually marked:-

C Common

NO Normally Open

NC Normally Closed

Most modern boilers have two wires which have to be connected together to bring the boiler on. When connecting to a stat with the connections as above the two terminals to be used are the C and the NO .

Earlier rotating knob stats are usually designed for 230 v operation and require a neutral connection. They are often NOT suitable for use with a modern boiler. If in doubt check, as a boiler can be damaged if 230 v is wrongly connected to the thermostat connections.

Tony Glazier

ChrisR · Posted: Wed Mar 05, 2003 6:25 am Post subject:

The Digistat terminals will not be marked NO/NC. You want the connections marked 1(common) and 3(Demand).