In-floor PEX to fin tube baseboard?

pug335

I'm currently remodeling my 8x8 upstairs bathroom, total gut down to studs and joists. Currently the loop/run is boiler to upstairs bathroom with 6' of 3/4" fin tube then to my son's adjacent room that has 8' of 3/4" fin tube and back to boiler. I would like to get rid of the fintube in the bathroom to add a little more floor space. My question is can I go 1/2" in-floor PEX in the bathroom to 3/4" fintube in my son's connecting room? I know there's probably a ton of variables and calculations to consider but would appreciate anyone's professional insight.

GroundUp

Your baseboard is going to require a much higher water temperature than the radiant, so you'd need to split them up- not able to run them in series and work properly, plus the radiant would kill the flow rate to the BB as well. Can you add a zone at the boiler with another circ and thermostatic mixing valve to serve the bathroom only? Perhaps something like a Runtal panel radiator might be more appealing

pug335

Thanks for the fast response. Yes, you confirmed my concerns going from radiant to BB. Well, didn't really want to get into adding zones & mixing valves unless absolutely necessary. The Runtal panels are a great idea, though pricey. If I did go Runtal panel, what size for a 8x8 room would you recommend? Would like as small as footprint as possible.

Zman

It depends on the heat loss of the space. How many surfaces of the room are exposed to the exterior? A towel bar heater might be a good space saving solution.

rick in Alaska

I did just that on a flip I did. I had a small piece of baseboard in a bathroom for part of the heat, but I also wanted the tile to be warm. I piped the baseboard, first in line from the boiler, then ran a few loops under the floor in a suspended configuration. It worked quite well!
Rick

HomerJSmith

Ya! The two temps are certainly different. You don't want the infloor so hot that you do the 'Two Step', a reference to the dance on the show "Dancing In The Bars" errrr. I mean, "Dancing With The Stars".

You have to temper the infloor to about 90 deg with a flow of about 1/2 gal min. A warm bathroom floor is really nice. The little woman will love you for it.

Why not, an electric under tile heating arrangement and use a towel bar heat source, too.

mikeg2015

I wonder if bare copper under the subfloor between the joists, no fins would work. Use 4 or 5 1/2” copper in parallel. Place radiant foil barrier insulation under it so your not heating the ceiling below.

Leon82

> @rick in Alaska said:
> I did just that on a flip I did. I had a small piece of baseboard in a bathroom for part of the heat, but I also wanted the tile to be warm. I piped the baseboard, first in line from the boiler, then ran a few loops under the floor in a suspended configuration. It worked quite well!
> Rick

I did that as well in mine. It works pretty good, obviously not as good as true in floor but the tile gets warm and it adds heat to the room. and as a bonus it was enough to run the boiler at 20% and not cycle due to it being a 2 bedroom zone. A 4 foot element in each joist bay. Made a small reverse return loop at the end of the run for the 3 rooms

pug335

Wow okay thanks, these are a lot great options/ideas but not sure which one would be optimal for my application? And unfortunately this is just the tip of the iceberg, I have other concerns with my system.

We just had a new Bosch mod-con boiler installed by techs that have very green knowledge of these type of boilers. Unfortunately this seems to be the norm in my area and many others unless you're a mechanical minded proactive homeowner that actually cares and wants things running as optimally as possible you're stuck with HE boiler running subpar levels. So yes, unfortunately I'm that frustrated homeowner now trying to figure out how to add proper sized heating to my bathroom, stop the boiler from damaging short cycling, and dial in a proper ODR curve for my system without my head exploding?

I had to beg the installer to add the ODR as he said it was old tech and not needed on these new modulating boilers? It wasn't until he called Bosch and they confirmed it will improve efficiency that he ordered and installed it. However it was just slapped in without any curve being set.

So thankful I found this forum! Would greatly appreciate any help/insight please! Willing to send pics, specs?

Leon82

Download a copy of the manual do you can figure out hoe set the odr curve.

pug335

Leon82, what size room and what diameter & length bare copper did you run between joists?

Leon82

> @pug335 said:
> Leon82, what size room and what diameter & length bare copper did you run between joists?

4x8 and I used 3/4 fin tube elements i found on Craigslist

pug335

Leon82, so you left the fins on and the floor didn't get too warm? Tile?

Leon82

> @pug335 said:
> Leon82, so you left the fins on and the floor didn't get too warm? Tile?

Yes the find are on. It doesn't get too hot. My water temp usually is under 140.

The main house is set to 69 and the bedroom goes to 67 at night and during the day and goes to 69 in the early morning and at night before bed. The floor is usually nice and warm when we use it. Not perfect but never ice cold

This is a picture of the loop. It's all 3/4 so there is no restriction

pug335

Okay thanks! I believe I need to add more fintube anyway which should help reduce short cycling so I may end up trying that? Thanks again!