Mixing under-floor radiant with wall panels okay?

josephny

Two years ago I installed an IBC SFC-199 boiler and hydronic pex floor heating (metal plates, under subfloor, between joists, insulation below). I did not know at that time that the floor has, in some locations, 2" thick of flooring, making the under-floor heat not work particularly well.

The house is old and has been enlarged in odd ways over the decades, so the basement is only underneath a portion of the first floor.

For the parts of the first floor (supported by concrete piers) not over the basement, I installed electric (pure resistive) wall hung heaters. Two years later and several of the heaters have failed -- and I wouldn't be surprised if more will fail.

I am in zone 5A (but it often feels like a 4 (;-).

So now I am thinking I need to add hydronic heat to those rooms that use electric (at least on the 1st floor -- I have no idea what I'll do for the 2nd and 3rd floors).

Can I just add several zones (and a controller) to the system (with with its own pump) for wall hung hydronic panels?

Is there a mix-and-match problem with 1 zone being under floor and another zone (or 3) being wall panels?

I'm concerned that the one zone I currently have has 4 circuits and approximately 800 linear feet of radiating tubing, while the new zones will be completely different.

Which leads me to my next question: How can I determines how many radiators to put on each circuit of the new zones?

Below is a layout of the house. The outer rooms in green are not over the basement.

The purple rectangles are my thoughts for 1 zone of panels.

Red for another zone of panels.

Brown for a 3rd zone.

Below is also a picture of my setup (I'm not a pro, as any pro could tell).

Thank you!

hot_rod

What temperature are you running to the radiant?
You can run up to 3 panels on a 1/2" circuit, generally. Depends on the size.

Any idea how much additional you need to add?

If so, use the output chart, at the temperature you can supply to see how much BTU/ hr they will add.

Maybe place another manifold at the boiler and run to the radiators.

If you want each radiator on its own TRV, consider a homerun. 1/2" pex to each radiator

josephny

hot_rod said:

What temperature are you running to the radiant?
You can run up to 3 panels on a 1/2" circuit, generally. Depends on the size.

Any idea how much additional you need to add?

If so, use the output chart, at the temperature you can supply to see how much BTU/ hr they will add.

Maybe place another manifold at the boiler and run to the radiators.

If you want each radiator on its own TRV, consider a homerun. 1/2" pex to each radiator

It has been a while since I set it, and I'm 100 miles away from the location, but I have a vague memory of 125'ish degrees F.

I don't know how much I need. But, I do know that in the month of January, the first floor electric heat used 3500 kWh of electricity. So, supplementing the radiant heat, if I understand correctly, the first floor alone required 12,000,000 btu in the month. Does that help?

I could put another manifold at the boiler, and I can run dedicated lines if needed. I like the idea of TRV, but I don't like the idea of users messing with them (I need to be the only mess'er).

Thanks.

hot_rod

Yep, either a best guesstimate, or an involved calculation. At least you have some data.

TRVs like any heating control can be locked at a not to exceed temperature.

If someone is motivated enough they will figure out how to override any thermostat. Drape a cold wet wash cloth over the control, for example.

I travel a bit, have stayed in hundreds of hotels. So I have some important tools along with me for comfort control. An Allen wrench to at least remove the window lock limiters.

Conifer745

I just got my system up and running using a similar combi boiler. We did under floor heating for the main floor stapled up through the joists and then radiant panels for our top floor, one in each bedroom, each with a TRV. The radiant panels are on their own zone with home-runs from each panel to a distribution manifold. The water is mixed to a lower temperature for the radiant floor zone, and we use an outdoor reset to adjust the boiler supply temp between 100 and 160 to promote condensing.  

  

With a mod-con boiler like ours the general advice on panels is to oversize them so they can accept a lower supply temp. Based on the #s you provided that works out to 16.7k BTU/hr, so maybe add a couple 12k panels to make up the difference. Or maybe you need more if the extra electric heat still wasn’t comfortable in January.

josephny

Thank you both for your help -- it has indeed been encouraging.

Unforunately, I can't honestly say I fully understand.

Sounds like if I add another manifold and pump and controller for the multiple zones, I should be able to add quite a few panels.

Sure would be easier to run 2 or 3 panels on a single loop.

Is there an easy/shortcut way to guestimate a design to add 4 or 5 circuits (thinking ahead to the 2nd floor) to the existing system?

HomerJSmith

Yes, you are correct. Wall hung steel radiators can be run with a lower temp and produce the same BTUs as a higher SWT temp if the panel is larger. The BTUs into the space are always going to be dependent on 3 factors. Supply Water Temp, flow, and the environment differential, that is, the environment temp and the panel SWT.

Are these panels to run in series with the baseboard or on their own circuit? If in series, I have always connected the panel with B&G Monoflo tees and used a thermostatic valve on the panel. If the panels are on their own circuit, I would go the manifold route.

josephny

HomerJSmith said:

Yes, you are correct. Wall hung steel radiators can be run with a lower temp and produce the same BTUs as a higher SWT temp if the panel is larger. The BTUs into the space are always going to be dependent on 3 factors. Supply Water Temp, flow, and the environment differential, that is, the environment temp and the panel SWT.

Are these panels to run in series with the baseboard or on their own circuit? If in series, I have always connected the panel with B&G Monoflo tees and used a thermostatic valve on the panel. If the panels are on their own circuit, I would go the manifold route.

That's great to hear.

There is no baseboard at all now. The only hydronic is between floor joists at the ceiling of the basement (which is only about half the footprint of the 1st floor).

Do I understand correctly that I can run a few panels in series on a single loop of 1/2" pex? I assume that that single loop would be its own zone with its own pump?

What is confusing is wouldn't using Monoflo Tees create an array of panels in parallel on the same loop?

hot_rod

Panel radiators have small passage ways, so you are limited in how much flow which equates to heat out put you can move through them.

Here are the 3 piping options. The H valve is available with adjustable bypass in the one version. This allows you to balance flow so 3 radiators could have the same output.

In series, you drop temperature at each radiator and the last radiator has less heat output. That is generally why only three in a loop.

But since you are guessing as to how much additional heat you need in each room, we are all just speculating🤔

josephny

I hope it's okay to resurrect this old thread (I am the OP), as I'm ready (that is, I really need to do this NOW).

Could someone confirm that I can add a tee (in red) just before the 1 and only pump on my system and put a pump (green rectangle) and then manifold on the new output of that tee that feeds either baseboard or panels? And add a tee (in yellow) on the return line as shown below?

Thank you!

hot_rod

If the panel rads are sized large enough to use the same temperature as the radiant, just add on to the manifolds. You can extend some brands, or get a new 8 or 10 port version.

josephny

hot_rod: Thank you so much!

I know enough to know that there are many other considerations, one of which the water temp.

I was wondering if it would be smarter to raise the temp of the boiler and add a mixing valve to the under-floor manifold, or to use larger rads and keep the same temp. Or, meet in the middle?

By "meet in the middle" I mean raise the temp to (for example) 135 or 140. The reason why I thought this should/could be a consideration is because (unbeknownst to me at the time of install) the floors in most of the areas with the pex underneath have 2.5" of wood on top of them (several layers of flooring) and the amount of heat getting through is limited. (Yes, I have insulation underneath the pex).

Is a temp of 140 for a combination of under-floor and radiators (or panels) in my situation a reasonable approach?

If I understand correctly, that would eliminate the need for another pump or a mixing valve.

But, can I still have separately controlled zones if I do it this way?

Thank you very (very) much.

hot_rod

temperatures within 10- maybe 15° of one another would not need a mix down loop. So a panel rad with a 120 SWT requirement could be on the same loop as a radiant needing 105 SWT. in my opinion.

If you add a mix valve, you need another circulator for that mix down.

If you can, or need to run the radiant at 135 or more due to the floor build up, that helps with the sizing of the panel radiators. You need the spec on the panel radiators and ideally the load of the rooms you are putting them in.

If all rooms are on the same zone thermostat you could add a tee like you show for the panel rads.

Or add trvs to the panel rads for control and use a delta P circ instead of the fixed speed. The circ will respond to the TRVs opening and add the extra gpm.