Adding Low Temp Radiators

[Pologuy9906]

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.

(broken link removed to 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.

 

[Bad LP]

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

 

[Pologuy9906]

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.

 

[Clarkbug]

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.

 

[timberr]

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.

 

[maple1]

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...

 

[maple1]

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.

 

[Pologuy9906]

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.

 

[Karl_northwind]

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.

 

[maple1]

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.

 

[Clarkbug]

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.

 

[arbutus]

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.

 

[arbutus]

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.

 

[arbutus]

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.

 

[Pologuy9906]

Send me some pictures.

 

[Bad LP]

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

 

[Jeff S]

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.

 

[Pologuy9906]

So what are some reliable brands?

 

[Bob Rohr]

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.

 

[Pologuy9906]

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

 

[woodsmaster]

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...

 

[arbutus]

^ 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.

 

[woodsmaster]

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.

 

[maple1]

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.

 

[woodsmaster]

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.