Alternate means of hydronic heating a room that is kept cool, but occasionally needs to be warmed up
What good alternatives to FCU's can be used for a not-well-insulated space that is usualky kept cool, and occasionally needs to be heated up on-demand?
Background info:
I have an odd-shaped, insulated enclosed space between the main home and garage, about 400sf, which is multi-use… shop/gym/etc, and often a transitional space. Since it's multi-use and could have different furniture anywhere in the room, might be best to avoid radiators.
Original plan was to use (3) Myson Whispa III 9000 WM fan convectors as needed in the room, setup as a reverse return series with a remote TRV to control the trio. These are flush mount units that recess into the wall (framing already adjusted).
I've been using some of these same fan convectors in another area of the garage, and they are a lot louder than expected (the 30 year old FCU's were actually much quieter).
This space is to be kept at 55-60 degrees, and warmed up on-demand. One cold wall abuts the garage, and the slab is a huge uninsulated heat sink, though some insulation will be put on top of it.
Comments
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panel radiators if you only have low temp water available
fin tube baseboard or a hydronic unit heater if you have high temp water available.
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Matt - my bad, major detail not included. It is a two temp system on outdoor reset. Medium and low temp. Medium being 130AWT with a 20deg deltaT.
I had not seen hydronic unit heaters before, so that may be an option. I was thinking fin tube baseboard might not be so responsive. I'm not clear in such a situation (colder room needing occasional warm-up, possibly some colder walls) if heated air or radiant is better.
Maybe someone makes a quieter Fan
ConvectorCoil Unit?0 -
the first question is always how much heat, what is the btu load?
Next would be your definition of quiet?
The fasted heat delivery will be a fan forced convector.
Jaga makes some very quiet heaters, you might compare decibel numbers of the various forced convectors.
You can add small fan modules under their panel radiators. Its a series of “muffin” fans like used in computers. Kick the fans on before you use the room, then use just the panel as radiators, fan off.
I’ve never met a quiet unit heater, that would not be my choice both for noise and looks.
Radiant ceilings and walls are quiet, but not fast acceleration.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1 -
Good questions…
For a target temp of 65F, the heat load is likely is likely 29-33 BTU/SF / 10-12k BTUs (depending on how much insulation I add to the floor, which is currently under debate and weather or not we have damp soil under the uninsulated slab). Personally, I would keep the room closer to 55-60F.
Here's what Myson says are the sound pressure levels for the Whispa III 9000. They don't seem to make them anymore, which may be telling.
NO WAY! Misleading - those numbers would have been fine, and are closer to the vintage models. They're not connected (in another space) at the moment b/c I currently am replacing some PEX, which serves this room too, hence sorting out this room's plan. Gauging off a vocal test and a phone app, I'd guess they are 40+ dBA on low and 50+ dBA on high at 8'. Basically, standing within 6', they're slightly to moderately competing with conversation on low and significantly competing with conversation on high. That's probably OK, but not ideal in a garage/shop setting. This area is probably best suited for noise about half way between garage/shop tolerance and standard indoor tolerance. So, probably something a bit less than a typical ceramic space heater.
I love some of those Jaga designer radiators… I wish I could afford those for elsewhere - so cool. I will have a look at their fan convectors/coils as well as some of the fan assisted panel rads.
I think the big challenge with this flex space is that right now, with gym equipment, there's reasonably good 'visibility' for radiators, but come the day it is a art room or a shop with a lot of cabinets and workbenches, the room's usability is much more limited, and it is already an odd space. With the prior plan of 3 of these recessed into the wall, it seemed to be fine, even if one got covered up, and of course any number of them could be powered off/on.
Baseboard is doable, but could be significantly blocked at some point of use and running plumbing in the N wall is not possible, whereas running plumbing in the S wall is easy (chase). The left side of the room is the house, the right side, the garage (not well insulated). Red boxes were originally planned in-wall locations for the whispas (bad name for a noisy fan coil!).
So, fast acceleration, some colder features present (E wall), flexible wall space needs, minimal intrusion of space, low level noise OK. Probably no perfect solution :)
I'm assuming solutions that sit higher in the room (like above windows) are not so great for heating.
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Put baseboard in with a fan coil unit. Run the baseboard to maintain your lower temp. Have the fan coil on the same loop but keep the fan off. When you set the stat up turn on the fan with the switch as a booster to bring the heat up faster. When the heat is up and your using the room turn the fan off if it bothers you and the baseboard will maintain. Size the baseboard for the full load
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And it will come down to how "nice" you want the system to look. I think fin tube is on the low end, designer panel rads from Jaga or others on the high end. Plenty in between cast baseboard, cast radiators, homemade custom radiators.
I've built radiators out of copper, steel, even concrete. This 400 lb dog heated our bathroom and towels.
Radiant heat is a line of site, the energy travels at the speed of light, not unlike the heat energy from the sun. Radiant ceilings will also warm the floor that it can see.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream
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Thanks for the idea. I do like the sound of the hybrid solutions like you suggest or the panels with fans that hot_rod suggests.
Technically speaking, with options of a FCU, a radiator with intermittent fans, or baseboard with FCU (or even direct mounted fans) - is one of these a less lossy solution when the E wall may be a cooler wall? I wasn't sure if the panel radiators, putting out more radiant would be less efficient.
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The noise level and how it is perceived will depend a lot on the space it is in, how it is mounted, and the frequency content of the noise. I think that the unit heater I have in my garage is pretty quiet in that environment but in a smaller space it would be more of an issue.
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Matt, I'm curious which brand and model you're using, given I don't have much trust in mfg published acoustics.
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Love the dog, Bob!! Edit: curious - modeled after a former dog of yours?
How does radiant (versus heated air) fare in a room like this, with the room being a BTU hog and cold features? I guess pure radiant won't give me the speedy ramp-up, anyhow, but more of a question about baseboard with intermittent fan vs panel rad with intermittent fan vs FCU.
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baseboard or panels aren't just radiant, they have a significant convective element. a convector cabinet can have a pretty high passive output but they generally need higher temp water for good output.
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It was some Grainger/Dayton unit heater I got off of e-bay that someone had sitting in a box somewhere for a long time so I'm not sure the model but it is the ones that are rated for steam and hot water so it has a core and tanks instead of just a long finned tube. It would be loud if it were in my living room but it is fine just under the collar ties in my garage.
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If you have a cold wall in my opinion baseboard the length of the wall will counter the heat loss better.
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Thank you, Ed. I am sure that is a solid technical recommendation. In this case, I am likely to be a rule breaker because the wall will either be a climbing/bouldering wall, or it will end up with a row of storage cabinets and then it will end up disabled.
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if you pick something with a motor that can be controlled with an electronic speed control you could use a relay to run it high/low speed, when recovering connect the motor direct and have it be loudish, when it is at temp run it through the speed control at a lower speed.
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Thanks, Matt. That was kind of the intent with the FCU's 1,2,or3 on low, then high when the temp gets turned up. They just had some misleading marketing :(
I'll keep your idea in mind for other products too as I sort this out. I'm also not sure I want to put the discontinued recessed mysons in, unless I find other products that will fit the same hole (incase one dies).
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sound levels measured in free space may be very different than what is measured installed in a hollow wall in a small room
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NFN but instead of hybrid baseboard and FCU jsut use the FCU as baseboard with no fan most of the time and use the fan to boost it. I have a building with FCUs and taking it a little into account with the setback, many of the tenants don't run their fans or just turn them on to boost heat. so whatever the dBs you would only experience during the boost and if you get the boost and depending on the tenure of your activity in the space you could turn them off if they bother you.
I've got to say these 55 year old trane FCU i have are not that noisy (as you have experienced with older tech) unless the fans are dirty. Maybe those heavy old fan motors aren't as efficient and the effort to reduce the weight of fans and motors has lead to more noise. i'm not really sure and I never dBed any of 'em but I never found the noise bothersome.
when you say 130 AWT, does that mean average water temp? and is that feed, return? I know you are looking at 20 degree delta but which way? and are you running setback. It sounds like you are mixing or somehow making two different temps for your radiation/emitters. is the 130 the higher?0 -
@hot_rod gone to the dogs eeh. . . but how did you get that thing to weigh 400 pounds. doesn't look like that much concrete. my approach (which I can't believe you can't buy this) is to wrap tubing hooked up to the warm floor around a soaking tub and keep it full with a spa frog in it. so i got frogs instead of dogs doing the work :- ).
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Yeah, that is a good callout. I'm not sure they will put out enough heat in that mode to keep it 55, but maybe? I currently have one of the 45 year old mysons hanging on the wall (you can barely hear it running on low), and sometimes it is turned off and you are right - you can still feel the heat rolling off of it. Of course, it is a surface mount version where natural convection can more easily take place, whereas the newer recessed units may be a little less good at this.
Yeah, the noise difference old to new is crazy. Seems counterintuitive, and a bit of an acoustic insult after the ductless minisplit AC, whisper quiet. Not sure why they don't run DC with variable fan speed on the newer ones - maybe less efficient. Then, you could set the fan really low most of the time.
140F supply with a 20degree delta T, if that helps.
Yes, cast iron boiler. Mixing valve with outdoor reset on half of it. One running radiant floor in parts of the house and the other will run at 140F.
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@rossn while the inset in the wall (aesthetically clever but usually not great for insulation!) can slightly impede convection, it is the height of the unit that contributes the most. these tranes I have are 24 or more inches tall and that really helps.
I've got a pair of stagedf modcons hooked up to these trane units and long ago I removed all the onboard zone valves and just run them constantly under set back, but this would need higher temps than your radiant floor so grabbing the high temp side with no fan I bet would work depending on how really wanting the insulation of that space is (can you dig and insulate the exterior edges of the slab and ground underneath it vs. insulating the slab away from the space? and then how is the rest of the space insulated.anyway, with a tall FCU and insulation/infiltration dependent )I think that 140 would more than take care of the space for your minimum heat norm without a fan (although not sure how wide/how many nom btus it is, maybe 9M in accordance with the model number?). I assume you got a condensing boiler or mixing/bypass setup so return water temp to boiler isn't a problem?
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