Low temp. hydronic heat emitters

[chuck172]

I'm just curious here, wondering if anyone is thinking of replacing fin-tube radiation with low temp radiators?

 

[heaterman]

I'm just curious here, wondering if anyone is thinking of replacing fin-tube radiation with low temp radiators?

If they are not they should be. Low temp emitters like a radiant floor, wall or ceiling and of course panel rads really increase the flexibility of a persons system. Locking yourself into something that works only in a narrow 30-40* operating range is only utilizing half of your wood load.

Nothing like the feel of a rad sitting there at 120-130* gently warming the room.

 

[peakbagger]

It all comes down to how quick you want the house to respond to temperature changes and how much wall or floor space you have. If you drop the temp of the supply water, you need more surface area and that radiation need to be unobstructed Baseboard radiation evolved as it was cheaper to build and install than cast iron and the smaller radiators and boilers take up less room than cast iron units. Radiant floor heat was around in the past and there are many failed examples of how copper tubes in a concrete slab was not a great idea, especially when the slab was uninsulated and the concretre was poorly placed on marginal soils. It wasnt until the development of the barrier PEX, by the Europeans in a response to the switch to low temp district heating that radiant got a start in the US. Once HVAC folks figured out how to get people to be willing to pay a price premium to install radiant over baseboard, radiant is now the preferred setup. From a builders point of view, baseboard is still the cheapest and quickest to install with the least space impact, therefore unless the clients are willing to pay a premium that is what they are going to install.

Arguably, for the typical home where the residents are gone during the day and can do nighttime setback, a faster response system, like high temp baseboards is the way to go as the heat can be set back for 12 to 16 hours per day which reduces the heating cost. On the other hand most radiant is installed in newer energy efficient construction so the setback concept may not save as much oil as the house loses less heat during setbback periods. The trade off is that floor based radiant generally allows a lower overall room temp than baseboard as the heat is less stratified.

For a wood burner with water storage, radiant is a no brainer as it maximizes the amount of usable heat that can be stored in a given volume of water which means a longer time between firing and a longer more efficient burn when the wood boiler is run. For a modern oil boiler with no storage which is essentially at full efficiency when it turns on, its a bit harder to justify due to the up front premium (which has dropped as the price of copper has risen).

 

[chuck172]

"For a wood burner with water storage, radiant is a no brainer as it maximizes the amount of usable heat that can be stored in a given volume of water which means a longer time between firing and a longer more efficient burn when the wood boiler is run. "

O.K., So how can I chip away at gradually replacing or adding low temp emitters.?
How about the expensive radiators like these:

http://www.econicres.com/low_temperature_radiators.php

 

[peakbagger]

Before you start replacing radiators, you really should get a hold of heating design program (like the slant fin one) and determine how many BTUs per room you need. In theory that was done long ago when your original system was designed but in reality, I expect that it was just done to the "rule of thumb". Once you know what you need per room start shopping for elements that have enough ratings to meet the BTU requirements.

As for how to feed the new radiation, I expect you need to start setting up seperate low temp zones. Radiant is not my thing but the little I know is that there are a couple of ways of operating the radiant loop at a lower temp, I have seen a setup for one off loops that uses a manaul thermostatic valve to keep the loop to a setpoint, but on larger systems, they use a injection pump and some electronics to maintain the loop temps for multiple loops.

 

[flyingcow]

The low temp rads do have me curious. I have staple up radiant in my kitchen flr. Love it.(hindsights 20-20, should have done an in floor radiant,in the subfloor, in the whole house) Plan on doing it under my living room flr, but I might consider putting low temps rads in. Just starting to look into them.
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I have baseboard in all my rooms. It is nice to have the baseboard for the quick heat. Especially when the wood boiler is pushing 195 thru the baseboard. BUT common sense tells me to put in radiant and keep everything an even temp. This should make my whole system perform better with less fires. Am i on the right thought process? Is this the same direction of your comments Heaterman?

 

[lawandorder]

THis is a good thread to have, Since installing the Tarm I have had problems gettting high heat output through the baseboard. Our greatroom has lots of glass, west exposure with lots of wind so winter time with the nightime temps going below zero I have noticed that some of the lower temps from storage is not enough to keep up overnight. I have begun looking to maybe replacing the baseboard with Runtal's lower temp baseboard and am exploring other avenues for heat especially with the bigger rooms. Not sure where to go from here. Do I consider radiator type heating or work on replacing the baseboard with low-temp designed. One question I have is wether it will be worth it. Will i get more heat out of newer baseboard???? Anyone having similar problems or solutions???

 

[kabbott]

Interesting thread. I have fin-tube and can maintain room temp on all but the coldest days with a water temp in the 130ish range. This allows me
to run my tank down to the upper 130's minimum. The second floor of my home will be in floor radiant since the subfloor needs to be replaced, I
have been considering Warmboard as it seems to offer some of the lowest usable water temps.

I have considered staple up for the first floor.
I have a few cast iron radiators, fairly large 4-5 feet long, would these allow water temps as low/lower than staple up?
What is the usable range for old cast iron radiators?

 

[chuck172]

I think there is need for information on low temp emitters. Seems like our systems would function better with them.

 

[Jeff S]

I just installed some cast iron radiators this year,so far I have used these all the way down to 110* when it is 40* outside with good results.

After doing heat loss calculation for each room,I set out to find radiators that would heat the house to 70* when its 0* outside with 140ish* water.Using the EDR (Equivalent direct radiation)chart on the colonialsupply.com site I came up with these figures.
50 BTU per EDR @ 120*
100 BTU per EDR@ 145*
150 BTU per EDR @ 170*

I like easy numbers so I opted for the 100 BTU per EDR figure,for example a room that has a 3000 BTU heat loss at system design would require a radiator that was 30 EDR or close to it.I was lucky that a friend of mine just did a tear out on a very large old house and acquired several radiators,with a little arm twisting he agreed to part with enough of them to do my project.So far all has worked well, though we haven't got much colder than 30*.I will know more as the heating season progresses.

 

[heaterman]

Most standard panel rads develop their rated output at 180 with some being measured at 200*. The particular ones I sell are at 180 but when I design a system I simply find the size that hits the heat loss indicated and then go 25-30% larger. For example, in the house we just finished up today the master bedroom called for 4260 btu's @ design temp. Using the rated output from our particular manufacturer showed that a 12"H x 39"W would give about 4420. I went to their rating chart which shows all different temps and found that if I wanted to heat the room with 130* water I needed to go with a 12"H x 51"W. A 12 x 59 was even better, delivering what was needed all the way down to 120*. The cost of course is a little more for the larger rad, about $70 in this case but it's well worth it when you consider the flexibility it lends to a system. Just over size a standard PR and sit back and grin while it heats your room with 130* water
Another thing we do often when working with a system that is currently functioning and in place is to simply leave it alone and add a zone of panel rads that are placed strategically as possible throughout the house. You'd be amazed at the load only 3 or 4 PR's can take off an existing system and how much lower the water temp can be while still keeping things snuggly.

 

[Jeff S]

Yes, oversizing heat emitters is key to using lower water temps.

 

[Floydian]

I am currently renovating our house and will be installing an all new heating system. I'm putting in a gasifier + 1000 gal storage + panel radiators sized for 120* water. I have done heat loss calculations and crunched lots of numbers and this setup should get me one fire a day which is what I want.

Heaterman, what brand of PR do you deal with? Some of the brands I have looked at only give a multiplier factor that doesn't even go down to 120*. I have done some extrapolating with their numbers for sizing but I would feel better looking at a rating chart like you mentioned. Maybe you could PM me this info if that's more appropriate.

Thanks,
Noah

 

[kabbott]

Another thing we do often when working with a system that is currently functioning and in place is to simply leave it alone and add a zone of panel rads that are placed strategically as possible throughout the house. You'd be amazed at the load only 3 or 4 PR's can take off an existing system and how much lower the water temp can be while still keeping things snuggly.

This leads to my next question: with an existing fin tube system what are the pro's/con's of hooking up cast iron radiators in series with
the existing fin tube?
Any major problems with going this route? In my case it would save a lot of tubing/labor installing a new loop.

I would assume as long as the emitter-load ratio is kept reasonable it would be ok. In other words don't load up one room with low temp emitters
on the same loop as another room with high temp emitters, that would run you out when the water temp is higher.

 

[chuck172]

Please PM me or let us all know what brand PR's your using heaterman.

 

[heaterman]

Another thing we do often when working with a system that is currently functioning and in place is to simply leave it alone and add a zone of panel rads that are placed strategically as possible throughout the house. You'd be amazed at the load only 3 or 4 PR's can take off an existing system and how much lower the water temp can be while still keeping things snuggly.

This leads to my next question: with an existing fin tube system what are the pro's/con's of hooking up cast iron radiators in series with
the existing fin tube?
Any major problems with going this route? In my case it would save a lot of tubing/labor installing a new loop.

I would assume as long as the emitter-load ratio is kept reasonable it would be ok. In other words don't load up one room with low temp emitters
on the same loop as another room with high temp emitters, that would run you out when the water temp is higher.

Well...............when installing additional radiation of any kind in an already existing loop, the thing to keep in mind is how many btu's can the loop carry in the first place. That is based on flow capacity of the loop. The second thing is how far a person can drop the temp in that loop and still have some amount of usable heat at the end of it. In other words, it really doesn't offer a lot of benefit to install more radiation on a loop which may already have 50' of BB on it. Assuming a flow of 3gpmthe temp at the end of the BB will have dropped about 20-30*. If the starting point was 160-170 a person will only have around 130-140 to work with. If you have an oversized iron rad or panel rad you can get some usable heat from those temps. If you add more BB there won't be a lot of benefit.
You also have to consider whether the additional head put in place by the new emitter will upset the apple cart in relation to flow in other zones. I've seen instances where this has been done on zone valve systems using a single circ and watched the flow in the high load/head loop wuit when other, easier to pump zones open.

 

[heaterman]

I deal with a very good friend, Paul Ross at Hydronic Alternatives. He imports directly from Euro Land and I've found the pricing to be better than most while quality is as good or better. One feature I like about those rads is the fact that their design allows one to reverse it on the wall meaning that it can be fed from either end. I can get them powder coated in any color imaginable. The charcoal colored units in the pics are actually a semi smooth finish with a bit of metal flake in them. Really sharp and very high in WAF.

I used Buderus for a while but had rust through problems on a couple jobs where I know there shouldn't have been any issues. Speaking with some other guys in the trade, more than a couple said the same thing.

If you go to www.hydronicalternatives.com and do a little searching you'll find the section on panel radiator technical data. This will have the derating factors for lower water temps. Just as an anecdotal note. I have found that the numbers seem to be on the conservative side for output. According to the charts and the heat loss on my drafty 110 year old house, there's no way I should be heating it with the amount of rads I have in place. It does heat however and last winter the highest water temp I observed in the Vitola was around 165 IIRC.

BTW, if you have particular questions about these please contact me via PM or hit the contact list at (broken link removed) I don't want to use up Craig's bandwidth taking personal questions about products I sell. That wouldn't be polite and my mom (79 on the 23rd) would get after me.

 

[lawandorder]

so what options are avaliable for low temp baseboard??????

 

[flyingcow]

Good point. Well said. but in my case I'm going to add "zones", whether I put staple up rad(which if I was ambitous i would tear up my subfloor and put in a type of warmboard system) or put in low temp heaters. either way, this is a very good thread!! i very much appreciate the input on this stuff, and heaterman is a good person to have on this subject. Hey where is Brownianheat(sp?) Haven't seen him? He seems like a good common sense kinda guy.

 

[flyingcow]

Heaterman.......stupid question. The big knob on the end....mixing valve? Able to adjust output without a T-stat?

 

[Como]

Probably a TRV.

There is nothing complicated about radiators, they are the norm elsewhere and come in thousands of styles.

They have their advantages and disadvantages.

One factor not mentioned is that you can keep the thermostat down and feel the same level of heat, also they are much more controllable.

I always assumed that forced air was popular in the US dues to large houses to hide the ductwork and cheap energy, together with the ability to include air con.

If you have a low heat demand radiant baseboard should be worth considering. I have never liked the finned variety, ascetics and they are a pain to clean as well as the other issues mentioned.

 

[heaterman]

Heaterman.......stupid question. The big knob on the end....mixing valve? Able to adjust output without a T-stat?

That is the "thermostat" my good man. A thermostatic radiator valve or TRV allows each radiator to be it's own zone when piped off a manifold system. (Or even in a series loop with the correct valve set underneath) This with no zone valves or other controls in place, just a circ, a manifold and a TRV for each rad and presto, one can have as many "zones" as you wish. The ultimate beauty to me from a comfort standpoint is that the heat output from a radiator equipped with a TRV is proportional to the heat demand in the room. These little jewels are not on/off control devices but instead modulate the flow in the rad based on the load in the space they are located in. Heating with rads is such a simple concept but yet so foreign to common notions about heating here in the US that people find it difficult to understand. It's by far the most common form of providing heat in Europe where, incidentally, fuel costs are far above ours and have been for years.

 

[chuck172]

Low temp. emitters would require less storage. Maybe our friend Hansson from Sweden will chime in. I wonder what type of radiators he uses. He has an extremely efficient heating system utilizing only about 500 gallons of storage.

 

[chuck172]

Heaterman,
" just a circ, a manifold and a TRV for each rad and presto, one can have as many “zones” as you wish."
Could you go into a bit more detail on how you add panel radiators to a system already using conventional fintube radiation?
Would they be on there own loop, with their own circulator?

 

[flyingcow]

Heaterman.......stupid question. The big knob on the end....mixing valve? Able to adjust output without a T-stat?

That is the "thermostat" my good man. A thermostatic radiator valve or TRV allows each radiator to be it's own zone when piped off a manifold system. (Or even in a series loop with the correct valve set underneath) This with no zone valves or other controls in place, just a circ, a manifold and a TRV for each rad and presto, one can have as many "zones" as you wish. The ultimate beauty to me from a comfort standpoint is that the heat output from a radiator equipped with a TRV is proportional to the heat demand in the room. These little jewels are not on/off control devices but instead modulate the flow in the rad based on the load in the space they are located in. Heating with rads is such a simple concept but yet so foreign to common notions about heating here in the US that people find it difficult to understand. It's by far the most common form of providing heat in Europe where, incidentally, fuel costs are far above ours and have been for years.

Thanks, don't get called a good man too often. Quite frankly, don't remember when the last time was.
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But seriously, this would be good fit to help out with a upstairs room that doesn't seem to have enough baseboard. Really no easy way to put in more. But, these rads are something i could install and easy to pull pex up thru a small chase way. Since i've already gota mainfold in for my staple up flor to tie into. Thank You very much. If these are a nice fit, i could see myself doing room by room. And as you stated before, utulizing my storage a whole hell of a lot better.