I had a new natural gas direct power vent hot water tank installed to work with my infloor radiant heating system. On my old one it was hard to tell the temp due to it being a 18 year old tank with a dial type. This one is light controlled, I had it set a 120 but bumped it up to 125 this evening. My understanding is the floor temp for the system is around 110-115. Just wondering if the HWT temp should be around that or a little higher. No kids in the house so me and the wife are aware of being careful turning on showers etc. Very small house, one level 1080 sq feet. Thanks for any info.

Are you saying that your potable water and hydronic heat use the same water heater? They should be zoned differently if installed properly. Can you elaborate... perhaps some pictures?

In my area, we cannot have heater to operate floor heating and potable water plumbed together. I would first check with Installation Instructions to make sure your heater is designed to operate both heating systems

Milo

Assuming an "open system", then that means the hot water will feed through the radiant heat first and then get delivered to the domestic fixture(s) after that. This suggests that you would want a higher temperature than 125F going out to the radiant heat to start as heat will be lost, and depending on the square footage of radiant heat, the heat loss could be great or very little. I would play around a bit here. Obviously, you need to start with temperature that results in an approximately 120F delivery of hot water to fixtures. My guess is that you will need to make adjustments to this in the Soring/Summer.

This is not allowed to be done in my area, but I've read up on it a bit...

Back to you.

Mark

06honda,
Extreme caution is required when combining domestic hot water & space heating in an open system. Legionella bacteria can grow & multiply in open systems that operate under 135 °F.. .