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HVAC Forums => HVAC Help => Topic started by: can514 on November 05, 2019, 01:17:35 PM

Post by: can514 on November 05, 2019, 01:17:35 PM
Hi there, first time posting!

We have a single-stage heating boiler (hooked up to rads, no forced air nor fan) to be hooked up to an ecobee4 and need your expertise in connecting the HRV (VanEE)! There's only one zone and the existing boiler only has two wires coming to the thermostat - plan is to use the C/B from the HRV to power to the ecobee and possibly use the fan from the HRV to help with circulation.

HRV, to my knowledge, is only acting as an air exchanger / dehumidifier. There's R/Y/G/B from coming from the HRV to an independent control module which currently allows us to "set" a humidification level, control fan at max, min, or off.

How should they be wired to the ecobee?


P.S. There is a possibility that we'll add an A/C to the system NEXT year.
Post by: Admin on November 05, 2019, 05:36:38 PM
Does this boiler have a control board with a C terminal?

You can’t power the Ecobee using the HRV B and C terminals.

How exactly do you plan on adding an air conditioner to a boiler system when you don’t have a forced air system?  You likely have to go with a ductless air-conditioning system which has its own control and would not integrate with the Ecobee.

You likely have to buy an external transformer and maybe even an isolation relay to make this work.  I attached 2 diagrams below.  You would need at least four wires going from the boiler to the thermostat for the first diagram and 3 wires for the second.  I prefer the 4 wire method so no isolation relay is required.  RC, C, RH, W1.  A lot of people get fooled by this and don’t understand you have to power the Ecobee using the RC terminal and this has nothing to do air conditioning like most other thermostats.

If the existing HRV control is located near your existing thermostat you can steal the 4 HRV wires and fish them over to the thermostat.  The HRV would also have to be installed near the boiler.  I would first disconnect 2 of the wires from the HRV.  R and Y.  Now extend them over to the boiler where you would install an external transformer.  Connect these 2 wires to the transformer.  You can use these for the Ecobee RC and C connections.  Use the existing 2 thermostat wires for your RH and W1 Ecobee connections.  Now the HRV control wires G and B can be connected to the ecobee ACC terminals to control the HRV.

Post by: can514 on November 05, 2019, 06:35:29 PM
Thanks for the quick reply! I prefer the 4-wire setup as well. Yes, an A/C would be a ductless system linked and used only in the summer time - some systems are compatible with the ecobee; depending on which such as Mitsubishi and LG. (Actually trying to figure out if the Flair can somehow work into the ecobee.) The old facility doesn't have the means to put in a forced air system so we're trying to accommodate based on what's available and what can be added for most functionality.

This boiler doesn't have a C terminal - I've wired other boilers to the ecobee with an external transformer to RC and C before; figured it might be possible with the built-in 24V transformer in the VanEE 12LC HRV.

I had checked other posts and no one seems to have any idea what the R & Y from the HRV is for? I believe the R is an actual heating element as when the independent control turns on, the supply runs hot air - and I thought this may be used as an auxiliary heat on the ecobee. As for the Y, I'm guessing one of the two fan (i.e. max/min) settings.
Post by: Admin on November 05, 2019, 07:31:55 PM
The Y just powers the LED lights on various Vanee controls.  The R might have something to do with humidity control features.  The Ecobee only needs to connect to the B and G terminals.  I’ve never worked with that model of HRV.  It looks more like a commercial system but does show compatibility with the Bronze Wall Control, which only uses the B and G wires.  You’re basic wall control may have 4 wires but only 2 are required to run the HRV.  The dehumidistat features are questionable.  The HRV is an air exchanger, not a humidifier or dehumidifier.  It only happens to do those things under certain indoor and outdoor conditions.

I’m not sure if that HRV actually supplies 24V.  I would just worry the boiler operation and heat could be affected by the HRV should it stop working.

I would think the make up air heat is something that runs automatically within that HRV.  It’s not something the Ecobee can control. 
Post by: can514 on November 05, 2019, 08:57:00 PM
We actually have the basic wall control (#40210) from VanEE which is 4-wire - my assumptions were based on that. The plan with the ecobee is for main boiler + HRV (heat or not, we'll see how it works out). With the Basic Wall Control, everything is manual and we'd prefer remote control - if it doesn't work out, might just throw on a Platinum Wall Control, set & forget.

I double-checked the wiring of the 12LC and the standard 4-wire run on 12VDC - but there is a 24VAC connection on the main terminal. I'll measure and double-check before doing anything.