Controlled residential ventilation during a major fire / Controlled residential ventilation on a summer night

Hello,

We want to install a central controlled residential ventilation system with heat recovery in the new building. I have a few questions about this:

1. Occasionally, traffic reports advise keeping windows and doors closed due to a large fire in district XY. How does this affect a controlled residential ventilation system? Can it then be switched off and completely sealed against outside air? Is the outside air actually analyzed in any way? Could someone (e.g., a burglar) intentionally introduce poisonous or anesthetic gases into the house through the supply air?

2. If, in summer, the nights are cooler but the house is still heated up from the day, I actually do not want to warm the supply air via the heat exchanger. In this case, can the exhaust air be routed past the heat exchanger?

I look forward to your answers and hope I have not caused any fear with the thought of gas poisoning from outside.

Best regards, Fokko

If your neighbor burns plastic in the chimney, you should also turn off the system. Poisonous gas is now rather the exception.

So someone (e.g. a burglar) could deliberately let poisonous gases or anesthetic gases into the house through the fresh air intake.

Forget your impressions that American television gives you. Reality looks different - unless you are in the focus of the state security, where the perpetrators wait a bit more patiently for their prey ;)

Regarding 1: A bit paranoid? Possible, but it actually happened to me once. Regarding 2: The system should have a heat recovery bypass, possibly also a ground heat exchanger.

Hello.

Here are my experiences:

1.) On our system, the supply air can be turned off. However, this is only possible if the chimney control in the system's control unit is deactivated. That means if you have a chimney, this would not be advisable, and possibly even dangerous.

2.) Yes, possible with bypass switching.

Normally, no sealing flap is included with ventilation systems of this size. Of course, such flaps exist, but they cost a bit. In larger devices, they are installed because heating/cooling coils are usually built in there, which are operated with water or glycol-water mixture. And in case of a heating shutdown during low outside temperatures, otherwise the water in the coils would freeze and consequently burst. (even though the fans are off, a certain mixing occurs).

How much the bypass circuit supports summer night cooling depends on the parameterization of the device. Since I myself work in the development of such systems at a manufacturer, I plan the following for myself: controlled residential ventilation with enthalpy heat exchanger and bypass (obviously), electric preheating coil to prevent icing, water reheating coil designed for the flow temperature of the underfloor heating. Additionally, the heat pump has the option to also operate as a cooling system and would then also cool via the reheating coil. The whole thing would naturally be a "DIY solution" that would be quite expensive for a regular customer.