Vitodens Installation Underway

Larry_10

Our Vitodens (8-32) is up and running. Very smooth startup. So far the domestic hot water side is working, and by the end of next week our space heating will be on-line if all goes according to plan. I'll post some pictures after it's complete.

It was also nice to see that I can do some of the fancy stuff I had hoped to do down the line. An alarm connection appears very simple. The other one is a bit tricky. I wanted my automation/security system to signal the Vitodens to go into the "reduced room temp" mode. This way setting the alarm to "away", "home" or "vacation" could automate setting the correct heating curve (except domestic hot water production would still have to be manually set when going on vacation). At first glance it doesn't seem like the Vitodens can do this as coding address OC8 when set to 000 only allows you switch between "timer program" and "continuous heating". The trick is to set the timer program so it's in setback 100% of the time so you are then switching between normal heating (contact closed on X4 terminals 1,2) and setback (contact open).

I do have one dumb question. Right now the control is setup for hot water priority (address 003:001). Exactly what happens if you set this to work without priority (address 003:000)? Does domestic hot water production then wait until space heating is satisfied (essentially a space heating priority mode)? The reason I ask is our hydro-air handlers may not like having their hot water supply turned off in the middle of a cycle. If domestic hot water is being produced, the air handler is smart enough to wait until it's coils are hot before starting it's blower. I'm just not sure what will happen if the AHer loses supply hot water mid cycle. FWIW, we had to go with a 79 gallon Vitocell because of a dump load. 99.99% of the time we can easily wait for more hot water to be produced.

Mark Eatherton1

I think...

you could run out of DHW if you disable DHW priority. THe boiler will keep both pumps running, and the water temperatures will be dillute to both loads. I don't think your air handler will care if the water supply temp drops mid cycle. It should just shut off the fan, waiting for hot water to arrive again. Under most scenarios, the room will not lose a whole lot of temperature before the FCU comes back on again.

One thing for sure, you can change the coding and test it to see what happens, and if you don't like it, switch back!

ME