Air to Water Heat Pump (aka Hydronic Distribution of WBF heat)

[slowzuki]

To get the COP you are looking for, you need to keep the air circulating through the heat pump constantly at that level. If you try to capture all the heat out of it, your COP is going to fall to what the temp leaving the unit is at or close to it. Your either not going to heat your infloor well or your going to dump a lot of heat into your basement. You don't need to waste a bunch of money to find this out.

Get a heat load calc on your house
See if your heat pump can even produce that much heat, at a reasonable COP, off the COP vs temp chart, note the temp needed.
At that temp, calc the cfm needed to move the heat down there, less a heat exchange efficiency.
Check to see if your insert is even close to able to produce that amount of heat, remembering you can't capture anywhere close to 100% with a duct/fan setup.

I'm a real negative sort on this it sounds like but I'd rather see you put money and time into something more workable.

 

[bigburner]

the proposed system is crazy and would marginally work at best with no energy savings. Don't remove the cast iron rads, because you will never heat your house [in that climate] with under floor radiant, and under hardwood is the last place you want to put it. We will only install it as a warm floor system and will take no responsibility for floor issues. The insulation is the key, then add t-valve to rads, put a mix valve on return of boiler to keep it warm[above 140] if you find out that you can now live with lower water temps. put the inserts in the FP and enjoy them, ever carried 40 cords of wood up the stairs plus the mess.

Now if you are intent on doing something stupid here's my suggestion. you can move heat the easiest by using a refrigerant pump, this system doesn't change state it will just pump liquid [like 134a] put a heat exchanger where you have a heat source and where you have a load and bamb heat moves there.

 

[benjamin]

Dang, you guys make me look like I've been passing the peace pipe around with Craig a little too much.

I'd like to hear more about this DIY foam injection. What is your framing system in a house like that? Are you plugging the air space between the sheating and the brick? intentionally or accidentally?

 

[leejad]

Re: hydronic heat exchange and insurance, etc., there is a lot of lore on that. I'll find one of the best articles written that I read, send the link when I can. It basically seemed like asking for trouble, though, esp. as it is essentially adding a steam component to the non-steam systems (steam in event of a point of failure, right?) I let go of that thought, reluctantly, as did the industry in the US that used to produce such devices commercially.

benjamin, the foam should be stopped by the paper on the outside of the cladding, and should (that is should...) not plug the drainage plain at all. Watching thermal imager prices closely (I need one for sure), doing tests, ripping out small inspection sites on 2nd floor (no wainscoting), yadda to make sure something stupid doesn't happen. Don't want to screw up the designs of the old masters and get a whack of wood rot, etc.

bigburner, this is the first I have heard of radiant floor not being acceptable for our climate, and I have pretty bright friends who have done such retrofits here. Post-insulation, I'll get the heat load calc. on the house (as per slowsuzuki) and check it twice to ensure it is more than adequate even when no fire is burning in either insert, and on the coldest possible days. The issue with wood and moisture is something I'll pay very close attention to (I'm from a piano restoration background, I get it.)

now, before we get all worried... there is very little to the proposed method which is not already an anticipated part of this retrofit and upgrade. More expensive fans, a little more ducting, a little more thermo and systems control, really no big deal. If I wasn't already up to my elbows in the extensive retrofit, then perhaps doing this just for the sake of doing it would be a crazy and stupid. But as proposed, I'll get my great inserts, my Geyser (or equivalent), my upgraded systems... and hopefully an additional source of energy not normally anticipated to further reduce expenses and help pay for the whole shebang.

I will say that the admonishments are swaying my resolve on the heated floor vs. retrofit rads somewhat... those are methods I damned near pulled the pin on some time back. But we all know that there is greater flexibility regarding alternate energy in low temp. systems, and so far I don't know a way of gaining any advantage from alt. energy sources (be they solar, ground source, or... well, you know) using the old system.

If I am missing something (entirely bloody possible), please feel free to point out the obvious.

Alright.. back under the crawls space I go. You should see the in-floor heating... rads attached to underfloor, causing major bowing in the library floor. I kid you not. Now that is underfloor heating that even I don't approve of...