Veissman heat pump integration with electric heating

KuusamoMart

We have a Viessmann Vitocal 200 which heats our whole house; it is backed up by a 30kW electric boiler. Because we are close to the arctic circle, we experience temperatures below that at which the heat pump shuts down in protection mode.
We have a couple of issues with the system:
1. There is no room temperature sensor, the heat pump indoor unit is installed in a utility room that has no heating other than the pipework for the heating system. The heat pump tries to heat the room it's located in to the set temperature which results in the rest of the house getting too hot.
2. There doesn't appear to be any integration between the heat pump and the electric boiler; we would like it to be set up so that the electric boiler is only active when the heat pump goes into the protection mode. As it stands, we have to manually switch the electric boiler on and off when the temperature drops near the point that the heat pump shuts down. The electric boiler does appear to have a remote on /off control, but we have no idea how it needs to be connected to the Viessmann heat pump indoor unit.

I should mention that this setup was installed in a house we have just purchased and the installers left no details of how the system was configured.

hot_rod

I wonder that Viessmann doesn’t have a control function to make the transition. Have you looked through the control section of the manual?

KuusamoMart

I have located the relevant section and it does show control for an external heat source; it's not clear what sets the operating point so have to assume it uses the external heat source if it can't maintain the set temperature.
Regarding the room temperature setting, there is no mention of how room temperature is measured, despite having a setting for room temperature! I guess it's measure locally at the indoor unit which is useless in our installation. There is a connector for a room temperature sensor, but the manual refers to it being used only for cooling mode; I will probably just enable the sensor and wire a sensor to the controller and see what it does!

hot_rod

There are a few ways to combine the two sources. A 3 way valve that selects one or the other based on only outdoor temperature. We make a product called Caleffi HybridCal for that application
I think one of the US HP manufactures control lets the HP run and somehow supplements it with a backup boiler or other heater. Basically keeping the COP up.

Viessmann is usually pretty up to speed with high tech controls to maximize their products. Get together with a knowledgable Viessmann rep, it must be a common question.

KuusamoMart

The Viessmann heat pump supports an external heat source and doesn't require a mixer as it can handle water up to 70C on its secondary circuit.
I have tried contacting Viessmann but haven't had any response as yet; I will try the office in this country to see if they are any more responsive, I had held back due to language issues but I guess there is nothing to loose!

hot_rod

Dig deep at their website, they may have some control essays. Sometimes you need an installer login to get the heavy technical docs. Best bet is to befriend a tech support or knowledgable Viessmann installer. Is there a Viessmann chat room out on the www? That could be a good place to engage someone with
experience with that product.

The German ISH show is coming up, hundreds of Viessmann people attend, take a trip to Frankfurt this March, maybe get a factory tour and meet the design team and, programmers🤓

Or go with an aftermarket or homebuilt switchover control.
It can be as simple as a temperature control with a sensor on a north facing wall. When COP drops below 1 based on the output HP charts, switch to another fuel source