Hi, we're in the process of building a home right now in Toronto. We have a basement walk-out which has a concrete slab with radiant already roughed-in. Main & second floor will be forced air. We're having a hard time understand the "best" (simple, long-term economic) solution available. It would be ideal to have a single heat source for both the radiant as well as the forced air; additionally, if we could somehow heat on-demand potable water at the same time using the same system, even better. We don't want a huge hot water tank. We've heard suggestions on a single system with an air-handler and direct or in-direct sources of heat to provide all of the above, but we don't know how it all ties together. Obviously, we'd need AC in the mix as well. Are there any generally recommended approaches for accomplishing this? Any feedback is welcome, thanks! Dave

When you say you don't want a huge hot water tank, are you OK with a normal size hot water tank?

Have you done a heat load calculation ("manual J"), or had someone do one for you? That's the first step to allow you to make an informed decision.

There is of course a whole bunch of ways to do this. I agree that you need to determine your house needs thru a heat loss analysis to determine equipment needs. As for the heating, you could incorporate a fan-coil unit(radiator) into the forced air furnace transfering heat to the air from the same hot water that heats the hydronic floor. That is how the outside wood boiler folks integrate them into existing forced air systems. That same hot water could heat an indirect domestic water tank.

How come you are not using radiant for all the heat? Then you could use a smaller ducted AC system, incorporated with air exchange ventilation...

I have a hydro-air zone as well as radiator & radiant zones sipping off a "reverse indirect" 48 gallon buffer tank maintained at 130F. The potable water is heated only as it flows through the internal coils on the buffer tank. As it happens I'm using a cheap Takagi for "boiler" serving the buffer, but an appropriately size mod-con boiler would work as-well or better. There is an AC coil in the hydro-air air handler as well.

A more elegant solution my kludge would be a hydro-air handler & radiant served by an HTP Versa Hydro or Versa Flame:

http://www.htproducts.com/versaflame.html

http://www.htproducts.com/versahydro.html

It's been around awhile now with a good track record:

https://www.youtube.com/watch?v=LrtkY4SKNUo

https://www.youtube.com/watch?v=yk3DAL4RchY

If you want to do it completely un-buffered (no tank) it's often possible, but takes a lot of design expertise to get right.

Even the smallest Versa has more than enough hot water and heating capacity for most homes. If you're filling a monster spa or something you'd have to go with a big 'un though.

I would suggest that running a condensing heat source all winter in a cold climate at DHW temp for all heat demands is less ideal in concept at least than running something more akin to slab radiant temps.

You can size hydroair coils for temps as low as any radiant system. one temp, very low temp, separate DHW heat plant or indirect. I'm kind of infatuated with the new UFT boilers from HTP... hard to shake a stick at a 10 to 1 turndown with an 8k min modulation... all that plus a firetube heat exchanger. Pretty sweet stuff.

Rob- have you installed many of the UFTs yet?

Just last week I just recommended the smallest UFT to a friend in CT who was having a hard time finding local contractors willing to install anything even remotely appropriately sized for his ~30K heat load (derived via fuel-use on his failing oil-boiler.) Even crummy on-line IBR type load calculators were coming up with loads in the-mid-40s. His "best case" contractor flat-out refused to quote down-sizing his recommended & quoted Weil-McLain ECO-110 to the ECO-70, despite the fact that the min-fire output of the -110 is fully 2/3 the design temp heat load, and above the mid-winter average heat load. (Way to lose a contract, turkey!)

The UFT is currently on the "A-list" as the replacement boiler for whenever the $250 Takagi craps out. (I think I got my money's worth out of it, eh? ;-) )

Wow it's hard to beat $250, well done

We are just starting to work with the UFT, so no, we don't have a lot installed yet. Based on the other firetube model's track record though, and the fact that I'm pretty sure either HTP is ripping off the by all accounts excellent IBC version (or there is some sharing going on... must be...) I'm expecting good things.

I can't ignore an 8k min mod though... we're definitely going to be giving this one a good run.

It does get tiresome fighting the "bigger is better" crowd... luckily I've stopped getting funny looks from our guys when I specify a small boiler!! Keep fighting the good fight, sir.

Posted By Dana1 on 13 Oct 2015 04:09 PM
the min-fire output of the -110 is fully 2/3 the design temp heat load, and above the mid-winter average heat load. (Way to lose a contract, turkey!)

If only it were true that contractors lost most jobs that way, instead of the one-in-a-thousand that gets reviewed by a knowledgeable engineer.

This particular contractor lost the job despite having an interested buyer asking him to simply down-size the boiler.

I guess he never got the memo about the customer always being right, or maybe the pickin's are too easy for hydronic contractors in central CT?

To tell somebody that you won't even quote what the customer specifically asks for is just bad business.

Even if the contractor thinks the customer is wrong, it's OK to just ask them to sign a waiver absolving them of responsibility if the boiler turned out to be unable to keep up with the load or something. I signed one of those to get a contractor to install what I wanted (the $250 Takagi) rather than what the contractor recommended, and guess what happened!? The contractor GOT THE JOB! They were paid well for the work, and brought onto two other projects after the fact (and would again.)

Some contractors you can work with, others...

...well...