Hydronic baseboard and radiant floor pex from the same thermostat?

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Old 03-31-14, 12:52 PM
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Hydronic baseboard and radiant floor pex from the same thermostat?

I have an existing hydronic baseboard system in my house. Some rooms have a several baseboards providing sufficient heat and some only a couple, creating cooler spots. I'd like to supplement these rooms with radiant pex between my floor joists, since I have access from my basement. I can't install more baseboards b/c the rooms lacking heat have no more walls to install them on.

Since I'm not creating new zones with my radiant floor, I want to make sure I'd be able to wire the main boiler pump and the pex loop pump to start/stop with the same thermostat calls for heat.

I'm assuming I can, so if so, is there anything special I need to be on the lookout or account for?
 
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Old 03-31-14, 01:23 PM
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I would probably start out by doing a room by room heat loss estimate to try and get a handle on how much heat emitter is required in each room.

You would have a better handle on why the cooler rooms were deficient, and an idea of how much radiant you might need to add in order to balance the heating... after all, you don't want to add TOO MUCH and tip the scale the other way, do you?

Yes, all kinds of controls are available to run multiple pumps, that's the easy part actually.

Look for an article (Google it) by John Siegenthaler entitled " A Little Floor Warming Please "
 
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Old 03-31-14, 02:23 PM
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Thanks Trooper

I do plan to put some numbers together, but wanted to make sure I could do what I wanted first without having to zone it out with separate thermostats.

It's obvious by looking at the rooms why some are deficient in heat... for instance my kitchen has only about 8 feet of baseboard compared to my dining room that has closer to 20 feet. My kitchen also has more windows, more exterior walls and an exterior door. So while tipping the scales the other way will be possible, it will be an uphill battle to do so. Truth is in the numbers though, to your point.

I have seen the article you referenced from other topic threads and am getting familiar with it.

Are there any specific controls or reference material you recommend for my multi-pump plan?

Thanks!
 
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Old 03-31-14, 02:45 PM
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Are there any specific controls or reference material you recommend for my multi-pump plan?
Nothing specific at this stage of the game.

I think you understand, since you've looked at that article, the basic concepts of radiant floor heat. That you need to mix the temperature down, and obviously that you need another pump.

How is the system currently configured? Single zone? One pump runs all? Or do you now have multiple zones?
 
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Old 03-31-14, 07:08 PM
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I'm currently a single zone system. You and some other members helped me, several months ago, start putting together my plan for a zoned system. I'll be converting this spring/summer, when the season changes (though in the midwest, i'm not sure that will happen this year!). I'll be moving to a 2 or 3 zone at that time. This winter really highlighted the difference in heat between my rooms, so I've decided to add the pex floor system as well.

I have an Armstrong pump on my system now which is only a few years old and in good working order, so I'm going to stick with it and use zone valves when I convert to my zoned system.

My pex loop will have the mixing valve and dedicated pump. I plan to build my supply/return manifolds with some extra connections, in case I want to expand the pex system in the future, which is likely.

What I'm still wrapping my head around is the mixing valve... I completely understand the concept and why its necessary, I'm just trying to understand exactly how its installed and the proper piping. Any model I look at the instructions seem reasonable... Mixing valve installed before the supply manifold with boiler water in to the Hot, return manifold water to the cold (which is T'd to the boiler return) and the mixed water going to the supply manifold. Then I watch a This Old House video with Richard Thretheway (whom I tend to think he knows what he's doing), where he pipes the mixing valve slightly different. He pipes it more on the back side of the return. It looks as though the return water is piped to the Hot on the valve and the cold is piped directly to the boiler return. It seems the Mixed side of the valve is recirculated from the return. Boiler water is mixed with the valve mix water. I'm probably bungling up this description, so if you haven't seen already... How to Install Radiant Heat | Video | This Old House (about 2:15 in to the video).
Is this an alternative way to pipe it or the proper way and I'm taking the product instruction diagrams too literal?
 
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Old 03-31-14, 07:11 PM
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FYI it would be far easier to remove the element and install high output stuff in the colder rooms..

Save a ton of money and labor...

Work smarter not harder I was always taught...
 
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Old 03-31-14, 07:17 PM
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You've got my attention with "work smarter, not harder"... What are the high output alternatives you're referring to?
 
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Old 03-31-14, 07:51 PM
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baseboard typically produces 550 btus per ft at 180f water temp.

So if I have a room that will only fit 10ft of baseboard. That baseboard will produce 5500btu of heat.. But say that room has lots on windows and I calculate that I need more btus in that room.

So you install high output baseboard,,,

Here on page 4 you see the ratings for standard bb. You see at 4gpm @ 180f is rated for 610 btu per ft.. ( Older baseboard is typically 550 btu per ft)

http://www.slantfin.com/images/stori...ne30_30_10.pdf

Here is the HO stuff. It will fit in the same covers I believe.. Measure your existing elements fins..

Page 3. The H1 or H3 element.

http://www.slantfin.com/images/stori...ak80_80_10.pdf

So you see now at 180f you can have 840 btus per ft. So now that 10ft or wall space with HO element will produce 8400 btu instead of 5500. 2900 btu more.. Thats huge IMO..

But your best to do a heat loss of each room to see what btu's you really need... They have multi packs too with dual or triple elements...
 
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Old 04-01-14, 05:28 AM
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Then there's the "Smith" high output stuff... personally not too crazy about the aesthetics of the cabinet, but it certainly does have high output ratings.

Smith Environmental Hydronic Baseboard Heaters - Heating Edge Hydronic
 
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Old 04-01-14, 07:52 AM
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Another thought since you have basement access from below is to go with some type of floor mount fan coil (not saying this is a better alternative to what has been suggested). Just another option. Last summer, I added a floor mount fan coil to my living room that was way under radiated and it is now very comfortable. It wasn't super expensive and was a relatively easy DIY project.

Here's a link. Turbonics Inc., Specialists in Hydronic Heating Solutions.
 
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Old 04-01-14, 09:05 AM
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That's not a bad idea at all! If you can set it up so that the discharge blows up and into the existing baseboard you'll get increased output from that as well...
 
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Old 04-01-14, 11:01 AM
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I have added underfloor Pex to a fintube baseboard system and got them to seamlessly work together off of a single pump and t-stat. That said... Maybe we should back way up?

First things first...

Have you done a room by room heatloss calculation?

If so, do you have enough baseboard in each room to cover the heatloss?

Not sure what kind of heating system it is. If its a non-condensing boiler and you have the minimum lengths of baseboards to cover each room's heat loss, maybe a simpler and better approach is just to reduce the output of those in the warmest rooms to balance it all off? If you have sufficient radiation to cover each room's heatloss maybe all you need is a roll of aluminum foil? Wrap part of the fintubes in the warmer rooms to limit their output. For $2 you might resolve it completely.
 
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