October 21, 20178 yr My gas-fired boiler (hydronic hot water heat), no AC, has been controlled with a simple two-wire thermostat, connected to R & G connections on the boiler transformer. The transformer connections available are R, G, C, W, and Y. I tried connecting C to 24V COM, R to 24RG, and W to W1. No luck. Any suggestions? Edited October 21, 20178 yr by Pg3t
October 21, 20178 yr Transformers have only two connections, do you mean the control panel at the boiler?
October 23, 20178 yr Author I'm thinking that my boiler may have a multiple winding transformer (also known as a multi-coil, or multi-winding transformer). But maybe that aspect is mute. Let me say it this way: My boiler has R, G, C, W, and Y connections available.
October 23, 20178 yr You need at least 3 wires for heat only, R (24VAC in), C (24VAC return) and W (heat). G is used for fan, but in a single mode system (e.g., heat only), that's not always needed, that is, it's taken care of automatically by the control board. Y is for cooling which you don't have so you can ignore it. Sometime a 2-wire cable actually has a third wire. Strip back the outer layer of the cable a bit (if you have one).
October 23, 20178 yr I'm not aware of any thermostat wire that's not copper.I certainly wouldn't use bailing wire. Sent from my Nexus 6P using Tapatalk
October 23, 20178 yr I certainly wouldn't use bailing wire. Sent from my Nexus 6P using Tapatalk That's baleful.
October 23, 20178 yr Author Well... I tried R (24VAC in), C (24VAC return) and W (heat) with no luck. Both of my attempts lit up the display on the Insteon thermostat, but didn't ignite the burners. When I opened the access cover and checked the wiring for the simple 2-wire thermostat, the connections were to G and R. I know that G is typically for the fan, but maybe a gas boiler is different for some odd reason. I attached a photo of the transformer and a photo of the schematic. Any ideas?
October 23, 20178 yr It appears that R and C are in their usual role to provide power to the thermostat and that G is the connection for heat (W).
October 24, 20178 yr Author Success! Here is what worked: C to 24V COM R to 24RH G to W1 Thanks to everyone who contributed, balelessly. Edited October 24, 20178 yr by Pg3t
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