Hydronic air heaters with tankless

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Active Member
Jun 28, 2015
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Are hydronic air heaters a fairly new thing, or are they more common in some areas than others?
I'm in Southern California, and was looking to replace my water heater with a Noritz Combi tankless, with the thought that it could then work together with a Lennox hydronic air heater.
But I'm not finding very good options when it comes to somebody that works on both Noritz tankless and Lennox HVAC. And little mention of hydronic setups in the area.
And the one potential I found had too many Yelp reviews that worried me.

Is there a reason hydronic air handlers with a tankless water heater don't make sense to use in this area?
If I get a standard Noritz tankless WH, is there a way in the future to get it working with a hydronic air handler?

Why do I want hydronic? I keep asking myself that as well.
I don't think it will save much in the way of $$$'s.
I like that it would drop down the number of 'combustion appliances' by one.
And it would seem to make the hydronic air handler less complex so less apt to need fixing in the future.
But maybe makes the water heater then more complex needing more attention.
Maybe it's all just a wash in the end?
If doing the radiant heating in tiles, then the Noritz Combi might make sense, but are there really any benefits to going that route for use with a hydronic air handler?



Nov 14, 2017
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Lafayette, CA
Hydronic heat is great in slabs-comfort-wise- but, it depends on square footage whether it is worth it as an air handler. Smaller sq. ft homes are viable but hardly worth it $ wise.
The Navien combi is a better product (IMHO).
Combi is a better choice from the outset. You don't want to convert later from a simple tankless, because you will have lost your investment in the WH when you buy the combi.
Solar PV with heat pump (electric for heat and A/C) is the real winner.
after 6 years, you will have paid for your system in savings (total electric bill for my northern CA home came to $18 over 12 months)


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Feb 22, 2011
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Warren, VT
They are more formally called Fan Coil Units. The coil is similar to a car radiator, where boiler water goes through the water side and a large fan blows air across the coil to distribute the heat through ducting, similar to an air handler fan in a furnace. They are useful where radiant heat is used in one part of a house and forced air is desired in another part.
You don't want to use a tankless water heater for heat, for many reasons, including lower efficiency, more expensive annual maintenance, etc.
Same goes for a combi-boiler, but not as bad. Combi boilers have to be able to provide heat at various rates and also be able to provide a lot of hot water on demand. In your area, a heat pump water heater would be your best investment for hot water, and cold climate heat pump(s) for heating and cooling.


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Jan 3, 2011
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Valley View, Texas
Personally, I think the tankless water heater is a fad. They crank up the current so high to get it to the heat they need and it costs more in the long run because they get build-up on the coils so fast from the water. If you have minerals in the water, it's a pain (and everyone does to some extent or the water tastes awful).

A larger, well insulated tank works better, heats slowly, does not build-up and can be used to provide hot water for a heater along with other methods like solar. However, solar can be a big mess too. And they only work when the sun shines. I used one to heat a swimming pool in Texas and it worked quite well, but it was a mess. Luckily I had a low sloped roof so it was not hard to work on it. And they have improved since then as well. But you can use these in addition to that heater that I mentioned. Just feed it in at the bottom and allow gravity to circulate it - works like a champ for low use times and saves a bundle. (have to have a check valve to force it to go the right way and keep it full. Only problem is that once it heats up the tank, it won't heat any more, and you do have to insulate them heavily or it is wasted.)

Get hot water heaters that have crapped out and tie them together in parallel so that they gravity feed and let them run separately. Lots of cobbling, but much cheaper. The pressure is low and a little antifreeze with sealant will keep it from leaking. I use this too heat my shop in the winter. (small shop)