# Adding Low Temp Radiators



## Pologuy9906 (Dec 16, 2014)

Has anyone taken the plunge on adding low temp radiators? I have a Flex Fuel 30kw with 900 gallons of storage. I came across this site last year.

http://www.hydronicalternatives.com/Products/Radiators.aspx

I think switching from standard baseboard to the wall hung units could extend the time between burns. Any help would be appreciated.


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## Bad LP (Dec 16, 2014)

I'm going to be watching this as I have been thinking the same thing for one of my rooms.


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## Pologuy9906 (Dec 16, 2014)

The way I figured it, these allow you to operate in the 130° range. You could oversize the radiator for the room maximizing heat output. You can also control each unit seperately. Don'tknow how it works but very interested in what this forum thinks. Couldn't have made it through my oil or wood installs without this site.


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## Clarkbug (Dec 16, 2014)

If you size the radiators for low temp water and put individual controls on them, you can definitely extend the time between burns.  It also means you will be burning longer and with more wood when you do burn, so take that into account.

Low temp emitters are the way to go with storage.


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## timberr (Dec 16, 2014)

I did and it made a big difference. Before the switch I would come home after 12 hrs (during the dead of winter) and my 500 gal. was down 140* and the house was cold and the boiler would struggle to get ahead (my system the boiler heats storage, storage heats the house). At this point my backup boiler (propane) would be kicking in. I replaced my existing baseboard with Slant Fin LTR 40; I replaced foot for foot and the house has been very comfortable. I also use a Tekmar 260 control and use the Setback feature (boiler reset to some) I have been very happy with the results. Storage lasts, I never seem to have a problem staying a head. With temps in the 30* I do one burn/day.


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## maple1 (Dec 16, 2014)

I want to add some old-fashioned cast iron rads in a couple of places here, at the ends of my baseboard zones. Haven't been able to convince the other occupants on the idea yet though.

They would no doubt let you use water that isn't as hot, and should extend your times between burns. But whether it's enough extra time to let you skip a day here & there as often as you would like to would be up for guess.

I have been going longer on storage just by letting my baseboard circulate for longer, after swapping in an Alpha pump & lowering aquastat settings a bit. My first year I was making a fire on when top of storage got below 150, more or less. Now I don't worry about it until the house starts cooling - so far this year, that's been when storage has gotten down to 120-130 on top. It'll be a bit sooner as it gets colder - but it's paying off I think on the other end as I'm not putting in that extra half load or so at the end of the burn to drive my storage up to fully loaded. So on top of some cast rads, I would still like to have more storage too - but still haven't figured out how to do it with the space I have. I need me a new garage to unload my basement some...


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## maple1 (Dec 16, 2014)

On the panel rads linked above with the incorporated TRVs - can you series them together on one single zone, or do they each need to be on their own zone/circuit? I couldn't tell exactly from the brochure I was looking at. I was thinking no, but also don't know what blind stops & all the other tappings/fittings on them are for.


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## Pologuy9906 (Dec 16, 2014)

I'm no plumber but after completing the install of the gaser, I'm up for the challenge. I have a fairly big family room with cathedral ceilings and Windows. It's always the coldest room in the house.


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## Karl_northwind (Dec 16, 2014)

maple1 said:


> On the panel rads linked above with the incorporated TRVs - can you series them together on one single zone, or do they each need to be on their own zone/circuit? I couldn't tell exactly from the brochure I was looking at. I was thinking no, but also don't know what blind stops & all the other tappings/fittings on them are for.


you can do several things.  I have installed panel rads in series, parallel, used the extra tappings to put 2 radiators in sort of a series/parallel setup (2 12"x72" radiators, with a TRV and hot in on the right side, the 2 end tappings between them to parallel the top and bottom headers, and return out the bottom of the far side for parallel flow.) 

we did a house/barn last year that has an effecta 60 KW, 2000 gal storage, and the customer reported that in 10 deg weather the house temp dropped when the storage temp got to 115F at the top.   all that and the heat distribution for the house (including 130' underground pipe) all runs on a grundfos alpha using between 9 and 40 watts) 

they are absolutely my preferred retrofit technology.  hands down.


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## maple1 (Dec 16, 2014)

I was under the understanding from past reading that a panel rad with its own TRV would function like it's own zone, and the TRV would function like a zone valve - i.e., if the TRV was satisfied, there would be no flow through/beyond that rad that could go to on to another panel rad/TRV plumbed in series with it. (And subsequently, that would mean each panel rad/TRV combo would need plumbed individually as its own zone). So I was incorrect in that thinking? Cool if so - there are getting to be so many things I would do over differently if starting from scratch with a new build. Even more things to think about retrofitting too.


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## Clarkbug (Dec 16, 2014)

maple1 said:


> I was under the understanding from past reading that a panel rad with its own TRV would function like it's own zone, and the TRV would function like a zone valve - i.e., if the TRV was satisfied, there would be no flow through/beyond that rad that could go to on to another panel rad/TRV plumbed in series with it. (And subsequently, that would mean each panel rad/TRV combo would need plumbed individually as its own zone). So I was incorrect in that thinking? Cool if so - there are getting to be so many things I would do over differently if starting from scratch with a new build. Even more things to think about retrofitting too.



They do make a fitting that has a bypass in it to feed downstream units, so you can do that if refitting fin tube.  Not sure of the drops or flow that you can move, but its an option.  

Manifold and each unit on its own run is the best for comfort, but not ideal in a retrofit.

I'm still jealous of Floydian's setup.  Its darn slick.


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## arbutus (Dec 16, 2014)

I have one Buderus model 22 panel radiator in each room on the second story of my house - three bedrooms, two bathrooms.
Each radiator has a TRV so each room can be set to its own temperature (max room temperature is limited by water temperature)
All radiators are plumbed in parallel with a manifold.  A single GF Alpha pump is blissfully pumping away.

This works perfectly with low temperature water ... minimum water temperature is 70F, needed when outdoor temperatures drop below 50F.  Maximum water temperature is 140 or so at negative 20F.

Buderus publishes the curves and formulas for heat output with reduced temperature water in their design manual.

If you have a good handle on heat loss you can match up min water temp, max water temp, outdoor design temp, and radiator size, and ensure adequate heat delivery.  If you do not have a good heat loss estimate, good luck.


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## arbutus (Dec 16, 2014)

Pologuy9906 said:


> The way I figured it, these allow you to operate in the 130° range. You could oversize the radiator for the room maximizing heat output. You can also control each unit seperately. Don'tknow how it works but very interested in what this forum thinks. Couldn't have made it through my oil or wood installs without this site.


 

Walking by one of my large panel rads I can start to feel radiant heat on the back of my hand when the water is about 90F (or outdoor temp is about 30F).
Put your hand a foot or so in front of one on a cold night when the water is 130F (-10F outdoor) and you can really feel it.


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## arbutus (Dec 16, 2014)

Pologuy, I have the type 22 radiator listed in the link.
23 ⅝’’ 59’’ 4” 11964 $*533.55*

Prices were significantly less than this at the local plumbing and hvac supply place.  IIRC prices were higher at supplyhouse.com.



All this was installed as a retrofit, replacing electric baseboard.


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## Pologuy9906 (Dec 16, 2014)

Send me some pictures.


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## Bad LP (Dec 16, 2014)

With a mixed house using FHW base and RFH these look the perfect addition to a pressurized storage system.


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## Jeff S (Dec 16, 2014)

I installed cast iron radiators about 5 years ago and use 110-120* for my heating, last year when we had -20* outside temps for a couple of weeks I did run my Rads at 130*.I love using these temps because you can sit on the radiators without burning yourself.


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## Pologuy9906 (Dec 16, 2014)

So what are some reliable brands?


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## Bob Rohr (Dec 16, 2014)

maple1 said:


> On the panel rads linked above with the incorporated TRVs - can you series them together on one single zone, or do they each need to be on their own zone/circuit? I couldn't tell exactly from the brochure I was looking at. I was thinking no, but also don't know what blind stops & all the other tappings/fittings on them are for.




Panel rads often connect with "H" valves.  You can get a version with an adjustable bypass built in.  Remember temperature drop as you flow thru series rads.  Typically 2 or 3 in series is max, each could also have a TRV temperature control.

You can add setback TRVs and now WiFi TRVs are available.


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## Pologuy9906 (Dec 17, 2014)

I'll start with doing the heat loss calc for each room. That will give me the BTU output @180°F AWT.


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## woodsmaster (Dec 17, 2014)

Clarkbug said:


> They do make a fitting that has a bypass in it to feed downstream units, so you can do that if refitting fin tube.  Not sure of the drops or flow that you can move, but its an option.
> 
> Manifold and each unit on its own run is the best for comfort, but not ideal in a retrofit.
> 
> I'm still jealous of Floydian's setup.  Its darn slick.



The problem with each unit on its own run is that if your plumbing is in a crawl space or an area you don't need to heat, you lose a lot of heat off the pipes. mine is set up that way and my crawl space probably stays over 70 degrees. that would be ok if it was a conditioned space because heat rises, but im sure i loose a lot of heat threw my uninsulated cinder block. If i were doing it again I would put 3 or 4 rads per run depending on size. I have the bypass things on mine so the water is always circulating and I'm sure that don't help with heat loss from the pipes either. If doing individual runs use a circulater that adjusts itself and don't use the bypass. One day I will change a few things on mine. Live and learn...


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## arbutus (Dec 17, 2014)

^ Good point.  The plumbing for my system is in a heated basement.
If you wanted radiators in parallel and had a place to put/disguise the lines, you could run larger diameter insulated pipes to a manifold within the heated space.


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## woodsmaster (Dec 17, 2014)

I will say it is the most comfortable, even, quiet heat I've ever had and I can run storage down to about 110 unless it's really cold out. If its really cold i can only go down to 125 or 130 but more rads would help with that.


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## maple1 (Dec 17, 2014)

timberr said:


> I did and it made a big difference. Before the switch I would come home after 12 hrs (during the dead of winter) and my 500 gal. was down 140* and the house was cold and the boiler would struggle to get ahead (my system the boiler heats storage, storage heats the house). At this point my backup boiler (propane) would be kicking in. I replaced my existing baseboard with Slant Fin LTR 40; I replaced foot for foot and the house has been very comfortable. I also use a Tekmar 260 control and use the Setback feature (boiler reset to some) I have been very happy with the results. Storage lasts, I never seem to have a problem staying a head. With temps in the 30* I do one burn/day.


 
Do you know how much more the LTR40 stuff costs compared to the 'regular' Slant Fin? Forget my 'regular' series # but think it has a 30 in it.


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## woodsmaster (Dec 17, 2014)

Another thing to consider when running low temps is if your heating your DHW recovery time will take longer and you may not be able to go lower than 130 if you use a lot of hot water.


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## Karl_northwind (Dec 17, 2014)

Pologuy9906 said:


> So what are some reliable brands?


we have and do use Pensotti, with good success.  Hydronic alternatives has also been recommended to me by those in the know.  on the east coast you will have lots of options.  Here in the Midwest, not so much. 

karl


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## Pologuy9906 (Dec 17, 2014)

I was on slant fins app doing a heat loss calc. I know my input was guestimating but the one room of concern came back with a 14,000 BTU @180°F. I currently have 36' of standard baseboard fins. The room is 22 x 15 and 20 ' cathedral ceilings. A fireplace, 75 sqrt of Windows a door that leads to an outside porch and freench doors which lead to my kitchen. This is the coldest room in the house. There has to be a better way than what I have. Outside temp is 44°F.


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## maple1 (Dec 17, 2014)

That's a huge room. Likely presents a heatload similar to a detached 2 car 2 storey garage. You'd likely have to load it right up with baseboard or rads. Can you load the windows with more glass or storms?


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## Clarkbug (Dec 17, 2014)

Pologuy, any chance of underfloor radiant?  If you can heat the floor and the furniture, without having to heat the open space, that could help the comfort in that room, and you can use the low temp water still.


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## Karl_northwind (Dec 17, 2014)

a combination of panel rads and in-floor would work really well in that big tall space.  heat the people and their feet with the floor, and the air and crank some real BTUs with the panel rads.   you can also use (depending on the water temps) the return water from the panel rad to do some in-floor heat delivery.  I have one system working that way and the customer LOVES it.  it's in the only(non bathroom)-non carpeted space in the house: the kitchen.  His wive is talking about having us com back and do the same thing in the bathroom floor as well.  this is a triangle tube 110, with a 38 gal buffer tank and 11 panel rads and a towel bar heater, replacing electric base boards.


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## arbutus (Dec 17, 2014)

I will add a +1 to the idea of heating the floor if possible.


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## Pologuy9906 (Dec 27, 2014)

Heating the floor is doable. My basement is open. I do have nails protruding down from the hardwood flooring. What's the best application for my scenario?


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## CaptainK (Dec 27, 2014)

Pologuy9906 said:


> Heating the floor is doable. My basement is open. I do have nails protruding down from the hardwood flooring. What's the best application for my scenario?



Been there... done that... 

two options..

1. A hammer, bend them all over.

This tends not to work as well as one would expect so then there is option 2...

A ladder or better a Work Platform
a 90° grinder with a cutting disk
an old pair of coveralls (cotton or it melts)
a good face shield, (just safety glasses if you believe that chicks dig scars)
Advil.

be advised, cut nails... cut hard.. DAMHIK...


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## arbutus (Dec 28, 2014)

CaptainK said:


> Been there... done that...
> 
> two options..
> 
> ...




6' Ladder, angle grinder, goggles, baseball type cap, work gloves, work clothes (long sleeves).  I did 800 sq feet of them and it was tedious for a few evenings but not hard.
Four year old child to hear the noise, run down stairs, observe for a minute with a gaping mouth, and run back up to ask "Mama, why is Dad shooting sparks across the basement?"


ALSO, EARPLUGS


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## arbutus (Dec 28, 2014)

Pologuy9906 said:


> Send me some pictures.


Had a chance to take one of the radiator in the girls' bedroom.

Added one of the small rad in the bathroom (someday I'll finish the trim and cover plates).
Also added a couple of the retrofit underfloor.  In one of the pictures you can see the Thermofin panel angled to go around the soil pipe.

ETA, this was Buderus brand, but it looks awefully similar, including model number and size to the fraction of an inch of the one that you posted.  I'm not sure who manufactured it, but I think this panel is sold under several different brand names.


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## Bob Rohr (Dec 28, 2014)

Pologuy9906 said:


> Heating the floor is doable. My basement is open. I do have nails protruding down from the hardwood flooring. What's the best application for my scenario?




The best tool that I found was an air powered die grinder with a thin muffler cutting wheel.  It's much faster spinning compared to an angle grinder and takes less metal per cut.
You can get real close to the floor and the tool never gets hot to hold.

There are electric versions also.  Thin wheel, high rpm gets the job done quickly.  Also a hat for the sparks and a fire extinguisher near by.


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## Pologuy9906 (Jan 3, 2015)

What do you think about me switching the 20'+ section with 20feet of panel rads with the 22 series. It would bump me up to 20,510btus. Then I could add the trench system for the other 10 foot section of baseboard. Eliminate the remaining baseboard. 

Any thoughts or suggestions.


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## GS7 (Jan 3, 2015)

Bad LP said:


> I'm going to be watching this as I have been thinking the same thing for one of my rooms.



You and me too...Has anyone with forced air added low temp radiators to their system? I'm thinking the return line of the water to to air heat exchanger could be tapped into.


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## Seasoned Oak (Jan 3, 2015)

I have a lot of cast iron radiators. Thats all they used here at one time years ago. Can still be purchase new for about $100 a foot.


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## Pologuy9906 (Jan 3, 2015)

Appears to be more prevalent than I thought. I thought I was somewhat alone in this. These systems are phenomenal. Imagine dialing everything in with the right equipment.


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## Pologuy9906 (Jan 3, 2015)

After researching this further, it appears there are two major players in Europe. Quinn and Rettig. Myson, hydronic alt, pensotti, dianorm, purloined appear to be one of the two. If you look at the specs they're all pretty much the same. So I'm looking for bang for the buck. Runtal seems expensive in comparison. 

I think over sizing it it the way to go. If I'm able to plumb this to receive the return water from my other zones, that could be an added benefit. Haven't figured out the how yet. It looks as though going to a much larger configuration gives the room heat at higher temps as well as continued heating at lower temps. I could always add trenching or radiant if this isn't sufficient. Most Europeans with gassers use radiators.


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## Bob Rohr (Jan 3, 2015)

Pologuy9906 said:


> After researching this further, it appears there are two major players in Europe. Quinn and Rettig. Myson, hydronic alt, pensotti, dianorm, purloined appear to be one of the two. If you look at the specs they're all pretty much the same. So I'm looking for bang for the buck. Runtal seems expensive in comparison.
> 
> I think over sizing it it the way to go. If I'm able to plumb this to receive the return water from my other zones, that could be an added benefit. Haven't figured out the how yet. It looks as though going to a much larger configuration gives the room heat at higher temps as well as continued heating at lower temps. I could always add trenching or radiant if this isn't sufficient. Most Europeans with gassers use radiators.




Here is a cheat sheet to show output change at different temperatures.  From Caleffi idronics 6, google that if you need more info.  Built around the Dianorm but they are all very similar in construction and output tables.  Easily found in the US  Dianorm, Pensotti, Buderus, Rental, Myson.  Steer clear of imports from PRC

  Probably hundreds of panel rad manufacturers in Europe from mild to wild.  I'd guess 80% of the heating in Europe is panel rads, most think it is radiant floors.  Even the centuries old castles you visit have panel rads retro fitted into them.


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## Pologuy9906 (Jan 3, 2015)

Thanks. So figuring I want have consistent water flow @ 180 but rather 160s the btu drop off. So over sizing would probably yield the consistent 70° heat in the room.


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## woodsmaster (Jan 4, 2015)

Pologuy9906 said:


> Thanks. So figuring I want have consistent water flow @ 180 but rather 160s the btu drop off. So over sizing would probably yield the consistent 70° heat in the room.



 Ideally you would have an outdoor reset so the water temps rise and lower with the outdoor temp.


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## woodsmaster (Jan 4, 2015)

With this weather in the mid 30's I've been running my storage down to under 100 degrees !! I just time my fires to when I will be needing DHW, because at 120 and lower I wouldn't have much DHW.


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## Bob Rohr (Jan 4, 2015)

Pologuy9906 said:


> Thanks. So figuring I want have consistent water flow @ 180 but rather 160s the btu drop off. So over sizing would probably yield the consistent 70° heat in the room.




Correct, keep in mind that graph is used with average water temperature, not the supply.  So if you are supplying 160 with a 20° temperature drop you have an average of 150.

Using that graph above 150- 70 air temperature =  80.  Run up to a .65 multiplier.  Take the radiator out put from the sheet times .65 and see what the output will be at reduced temperature.

Remember also if you put multiple radiators in series, you have a temperature drop at every one, the last in line seeing much lower temperature.  Generally 2 maybe 3 small rads in series.

It's all about the surface area, which is why radiant floors or ceilings running 90 temperatures need to cover the entire square footage of the room.

The plus with panel rads is the output is radiant and convection, so they do move some heat via air currents.


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## Pologuy9906 (Jan 4, 2015)

This was with my tanks starting out at 111°. Flue temps were consistent. This zone is the shortest. It's right above the boiler room. I'll do the panel rads and eventually pipe in some underfloor radiant as well. I measured again. I have a 22', 10' and 4' section of conventional baseboard. Replace the 22' with 20' of panel rads. Get rid of the 4' and replace the 10' with another 10'. That increases the btu output to 32,700 btus@ 180° then downward based on your previous calc. The water is being pushed by a big pump, taco 2400-20.


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## maple1 (Jan 4, 2015)

Do you need a big pump? I couldn't be happier with my alpha - it's the cats hiney for pumping multiple zones.


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## Pologuy9906 (Jan 4, 2015)

I have four zones and adding a fifth. I was running a 007 which I was told was insufficient if multiple zones were calling for heat. I thought of a variable speed but decided to add a third 2400-20. My thought was to have the velocity just in case all zones were calling. I thought the quicker the water flows the more consistent the temp would be. If the water dragged through the run it would cool quicker. Going through quicker would decrease the heat lose.


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## Pologuy9906 (Jan 12, 2015)

I'm back........after calling around and looking at the numbers, I'm sizing the panel rads at 150° supply. This will give me a consistent 67° heat and possibly higher when the supply is 170°. Now my major concern............which unit to buy. I've contacted a few places and so far hydronicalternatives has given a decent price. If anyone has used panel rads in their setups, please give the brand you used. I would GREATLY appreciate it. I want to drain down my system next week. It would be perfect to add the panels then.

Thanks again


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## arbutus (Jan 13, 2015)

Again, I used Buderus brand, unsure as to the actual manufacturer, and my local plumbing supply house was able to order them in far less expesive than everywhere else.  Prices were very significantly less than the list prices on the hydronic alternatives website.


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## woodsmaster (Jan 14, 2015)

I used Stelrad. They were a discontinued line that I bought from a guy on Craigslist. I'm not even sure there is a dealer for them in this country. I think any brand will do the job. Just a matter of the look that you want and the price you can afford. Some put out more btu than others, size for size, some are single panel single convector, some are double panel single convector and some are double panel double convector.


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