# Zone priority: Can only heat 1 zone at a time?



## josbrone01 (2 mo ago)

Hi, I am a home owner and have a question about HVAC zone priorities: 

A few years ago we installed a brand new Lochinvar Knight condensing high efficiency gas boiler (WHN110). Heat is distributed to 2 zones (upstairs and downstairs) using forced hot air. It also has a superstor water heater. The whole thing works great. But it uses a "Taco" priority relay to heat only one zone a time. When it was installed, the HVAC guy asked me which zone I wanted to prioritize. I didn't think much of it, and went with his suggestion of prioritizing the upstairs (where bedrooms are located). But now if both zones are cold, it will only heat the upstairs ... the downstairs will blow cold air (actually luke warm air). That is pretty annoying to blow cold air in the winter!

During yearly maintenance, I asked the technician about this, and they said I could turn OFF the taco relay with the flip of a switch. OK, problem solved, I guess. So now it heats both zones at the same time. But my questions are:

1. Why would you even install a priority relay? 
2. Is there some benefit to leaving the relay active, and only heating one zone at time? E.g. Am I ruining the efficiency or doing something bad by disabling the relay they installed? Is it maybe overloading the system?


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