Mixing radiant with baseboard

edbdfish

I have baseboard heat on 3/4 line. I'm doing some renovation and have an opportunity to add a bit of radiant heat to the bathroom floor from underneath in between joists. I don't need to heat the whole bathroom just take the chill off the floor. I bought metal fins that attach to PEX and they only make them for 1/2". Now I have 1/2" PEX that I want to add to an existing 3/4" zone. It's maybe 50' of PEX. I thought that maybe I could just add a loop of 3/4 line so that it doesn't restrict the flow. I installed it but the PEX isn't heating up. I guess the water is bypassing the loop. Does that makes sense that it would do that? I'm now thinking my only option is to let the water pass through the PEX which would restrict 3/4 down to 1/2. Or is there some other alternative? I know this isn't the way your supposed to do this but I'm just trying to see if something would work on the situation that I'm in. I can't add another zone here just for radiant.

Thanks

edbdfish

I didn't use monoflow tees, would that resolve it?

Ironman

What method of piping was employed in the original system? More info is needed.

edbdfish

The 3/4 is copper.

STEVEusaPA

A monoflow tee may help but it may create a different problem. Too much flow is not good either.

Ironman

Is the system piped monoflo, series loop, direct return, reverse return?

edbdfish

Based on diagrams I can find this one seems the closest resembling to what I think I have. https://www.radiantcompany.com/wp-content/uploads/closedboilerschem.gif

4 zone manifold going from boiler and coming back to another 4 manifold.

edbdfish

Which I guess makes it a series loop, right?

edbdfish

Just to restate. I have a series loop system. One of the zones runs to a room + bathroom which contains around 24ft of baseboard total. I'm trying to add about 50' 1/2" pex with ultra-fin plates in the middle of that zone.

1. If I let the 3/4" restrict to 1/2" and then back to 3/4", would the baseboards beyond the 1/2" take a noticeable hit, or should it be fine?
2. I could use monoflow tees instead, but was reading how having a long run from the monoflow could make it hard to purge. Being that this would be in-floor, I won't have access to any extra bleeding valves, or in-the-middle ball valves to aid me with a purge.

Should I just try restricting down to 1/2" and see if I notice a hit in temperature? I'd rather keep it simpler if monoflows could potentially create problems after I close the walls. Or should restricting down to 1/2" be avoided at all cost?

Ironman

I cannot recommend that you try it. Best case scenario, the floor will give you about 750 btus. That's really not gonna do much. And, it will only produce heat when the BBs are heating.

It situations like yours, we typically recommend using an electric radiant floor mat. Its thermostat will allow you to control it as an individual zone based on air or floor temp and program it to stay off when you want. You'll also have a much better btu output.

edbdfish

I thought that electric heat pads are meant for under-tile, and wouldn't work under joists. I guess maybe there are some for that, I'll take a look.

But if I were to try going the hydronic path, any thoughts on the restriction vs monoflow scenario ?

Thanks!