How low can YOU go? (non limbo question) ME

Greg Gibbs

If Slant/Fin has a chart that shows 15 series and 30 series
outputs, we would be on to something... -Gregory Pex

[Deleted User]

Hot Water Baseboard and resets...

Wallsters, With the humongous influx of mod con boilers on the market, a question that often comes to mind, is in a typical residential setting, what is the lowest water temperature you would be comfortable running?

My good friend Greg Gibbs (AKA Gregory PEX) said he likes to start around 125 degrees F at 65 degree F OSA.

My partner, Tom (show me) Olds, says no less than 140 degrees F.

What say ye wallies?

And more importantly, when are you baseboard manufacturers going to print some information on exactly what your BBR does at a lower air temperature.

The time has come...

TIA

ME

Weezbo

i am thinking that with mod cons using nat gas,

a home designed well should have a heating system designed to meet or exceed its quality .

manually,turned on the heating system source yesterday, outside temp was 46 degrees F. internal temps of home on or as on as a Caleffi profile can keep it with constant circulation @70 degrees F. we take advantage of solar gain through the day . wwsd is something that depends on a great many minor technicalities. oh and perceived comfort by the individuals.:)

This is with an Oil Fired piece of equipment, non condensing.its turning winter folks. snowed in the 2500' level the past two days. Summers Over.


the shop is on WWSD with 62(-.01F) being the Inside temp governing the idea of When to ramp some heat....

I had wanted to install the Triangle Tube's, Prestige solo, three years ago to take advantage of its abilities for this time of year.

Base board? (convector fin tube type?) 78F

Steve Ebels_3

Daddy sang Bass

Ooops, wrong low, I was yakking with someone an another forum about singing........

I start BB systems at 115-120, CI rad and panel rads go all the way down to whatever the curve shuts down at and air handlers typically get dialed in about 125-130. The beginning air temp depends on the structure, the occupants and AC/H. (some like it cold some like it hot)

joel_19

well.....

That depends on how much baseboard there is. 110f is not out of the question works in my house. 140f? Me thinks most houses can get by with less if folks don't set the thermostat back.

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Boilerpro_5

I go full reset

I do have some that I set minimum temp to 85F in order to take the chill off on those slightly nippy days. Tekmar goes full reset on thier curves, with an obvious bulge in the curve at lower temps.

Boilerpro

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Tom Hopkins

90°F at WWSD of 58°

90° WT @ 58° OAT with a 0.83 slope from there to 139° @ 0°


I've found no problems with a linear slope and fin-tube.

R. Kalia_9

To repeat what others have already said,

(a) it depends on how much baseboard there is

(b) It depends on whether the reset curve is linear, or curved like Tekmar's.

So it's not a matter of how someone feels, what he prefers, etc. The reset curve needs to be determined for each house. The ideal situation is when the homeowner can adjust it based on actual experience. Otherwise, reset curves will inevitably be set too high on a CYA basis by contractors.

140F, of course, makes no sense unless the boiler is cast-iron and no mixing valve.

clammy

mod/con

Mark i have my munchkin set up at 10 degree outside temp 140 max ,for heat 1/2 of my home is staple up onoix with 2 nd stage baseboard and the rest slant 30 and it works excellent at about 125 for the baseboard theres no convention sort of acts like low temp panel rads and my bills are roughly about 30% less durning the coldest parts of the winter the shoulder months are much less then the previous systems bills it easier to track use then go by the bill alot of BS fees and taxes peace and good luck clammy

Perry_3

My system runs between about 80 F and 145 F

I have Cast Iron Baseboard on a monoflow T system.

The Vitodens 200, outdoor reset, with RS Sensor (for internal temp feedback), runs the system between 80 F and 145 F depending on heating needs - when the boiler is firing. On warm fall and spring days - the system temp can go down to 70 F as the boiler never fires for heating.

I agree with others that it depends on the house heating requirments and how much baseboard is installed.


Hope that helps,

Perry

singh

Perry

Cast iron baseboard is different than fin tube baseboard I think Mark is referring to. I have in my home 100* at a outside temp of 65* and 140* by the time the outside temps gets to freezing.
What I don't like is the cold 70* effect I feel on the milder days.

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Jeff Lawrence_25

You made me look

I haven't looked at the data in the heat loss program in a while, so I had to open the program.

I am real close to installing my mod-con and indirect. I am calculating the baseboard with the lowest design temp available in the program, which is 140°. I'll have the WWSD set at about 65°. With this in mind, I'll hopefully never get the boiler output above 125° except in what we consider extreme cold (below 25°).

Tony_23

100

100 is where I usually start. Some of my customers complained about the chill at low end, so I bumped them up to 120. That's on retrofit jobs. On new, if they let me, I install enough high output (like Sterling Senior) to handle design day at 140-150.

At the price of bbd lately, panel rads are pretty competitive. I have a job soon that I'll full access to after the install for playing with the curve on panels. As long as Mom and Dad stay comfortable, I can experiment

tim smith

baseboard temp settings w/ reset

Good question, just a thought here. If we reset say to 100 degrees at 65 outside, and the client likes to reset thermostat down 8 degrees or so at night and during day. This would make the heat up really slow when stat first turns on in am when temps are milder, say 40 degrees outside. Do you all think it would be possible to boost temp w/ the domestic priority call and a two stage thermostat. This would allow to get house up to temp fast and then the reset curve should be able to keep up w/ loss. Would have to add a set of zone valves on priority piping if you had a inidirect. If not you just energize pump w/ either the domestic pump or heating pump contacts. ??? Crazy or not? Tim
I still wonder whether it would be more efficient to leave constant temp 24 hrs a day on this type of system or set back during day and night and use control system like above?

Dave Yates (GrandPAH)_1

Slant Fin BB

has a chart for lo-temp BTU outputs with BB

We've set up a few BB retros for full outdoor reset & they've performed without a hitch.

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tim smith

low temp baseboard output chart

see attachment, slantfin output chart

Plumdog_2

depends

I start even lower than Mr. Greg, but it seems to depend on how tightly the BB is sized to the design condition; ie if the BB output can exceed design by a good margin, you can start and STAY lower thruout the curve.
I am waiting patiently for residential multi-fin compact baseboard or cabinet heaters that are reasonable in cost, unobtrusive (perhaps partly reccessed in the wall) without having to go to commercial stuff. And how about making this stuff a little more durable?

Unknown

Then you're running a more aggressive curve than necessary at low temps. The output slope for fin tube is not linear.

Unknown

siggy has calcs on this. They are good for setting max temps, but you do need to address the minimum temp question.

We're running 90 minimums with a max of whatever which might be a little aggressive on the low end, but gives enough of a head start to stay ahead of the output curve (this is similar to what Uni mentioned). Generally 120 is quite easy to achieve. Most BB systems out there right now could run at 140 all winter long, without anyone trying to keep the temps low in the first place.

hot_rod

Mark, what do you mean lower air temperature?

lower than the 65F they use now? How much lower/

hot rod

Uni R_2

Maybe its a case of Theory vs Reality vs Practicality?

Don't forget that internal gains are a large factor near WWSD in any reasonably well insulated home and much less when the outdoor temperatures plummet - maybe that's why a flat curve works for my home?

The MCBA like many other ODRs does straight line only so that's what I have worked with. That said, based on my experience last winter while operating purely off the outdoor sensor, I was able to watch the internal temperatures stay flat while the outdoor temperatures went up and down like no other winter I could imagine. There were only 2 issues, the house would drop in temperature when the outdoor temperature plummeted quickly and it would have about a 3° rise on sunny afternoons from solar gain . Both factors stemmed entirely from my outdoor sensor location. It was in a very sheltered spot that didn't drop as fast as the other brick surfaces when temps fell, and it had no solar exposure. Shooting the outdoor sensor with a temperature gun quickly exposed the surface temp differences when temps dropped. Using the t-stat eliminated the solar gain.

I'm very pleased with the comfort of the fin tube using a modcon. The old oil boiler was also ODR equipped but it had to be floored at a water temperature above the condensing point so you'd notice the heating cycles in the shoulder seasons.

I should point out that to really dial in a modcon with a simple controller like the MCBA takes far more time than it could ever be worth to any contractor or even most homeowners. You really should do it purely off the outdoor sensor and it takes weeks and would be a nightmare to do if the house were zoned. When you think you have the curve pegged at frigid temps, you find out it's way off when it is balmier out. And then when you finally get the curve perfect for your house at any outdoor temperature along the curve, somebody will tell it's too aggressive at low temps! ;-)

Unknown

I didn't mean to sound so accusatory. you're absolutely right. We don't bother dialing it in for the low end either because it's wildly variable depending on what's going on.. less variable as it gets colder.

ALH_4

Output

Slant Fin's output chart for low temperatures is very nearly linear. Am I missing something?

It doesn't seem to me like it should be linear, but I'm sure people far more knowledgeable than me developed that chart.

Plumdog_2

What's More....

If you play with your heat loss program, and plug in different design temperatures to the same structure, the resultant "curve" closely resembles the output "curve" for the baseboard. To think that a couple or three years ago the standard mantra was "mod-cons don't work with baseboard because they need high temps". Poppycock.

Tony_23

ODR and setback

First of all, let me say I don't believe setback saves fuel if used less than 10 hours straight. That's from my own personal experiments and experience, so I know that it doesn't count until a lab does it under lab conditions. After all, we all live in a lab right ? (I do, in a sense)

Anyway, one of my mod/con retrofit clients sets back 8* every night for comfort. The way I cured the long recovery was a switch in the ODT sensor circuit. Open the switch, the boiler shoots for max limit as it thinks it's 20 below out. Close the switch, back to ODR and maintenance temps. I could've set the Ultra boost shorter, but that's not much of a reset, so I left it at 30 minutes the 1st winter. This year I'll try talking him into no boost and use his switch in the morning. Kinda high maintenance, but so is he

Unknown

That's an interesting fix tony.

Metro Man

timer

Tony - instead of a switch how about using a timer... say 30 min then back to ODR? Could set automatically or even on it's own set point. Say, below X temp timer is activated. We use timers on most snow melts and other intermittent loads.

Metro Man

[Deleted User]

HR...

I thinks you may have misread my question. It was at lower water temperatures, not lower air temps...

ME

Plumdog_2

You did what I was gonna do

Except my mod-con of choice has to be re-powered whenever the Outdoor sensor is disconnected, so a timer or relay would come into play for it to work. Also, I would like to incorporate an outdoor stat to provide WWSD at a lower temp than the on board control will allow. Fine tune and tweak. People still open windows as soon as the sun comes out; this behaviour must be stopped.

ALH_4

And even more...

To continue your line of thinking, who said that a mod/con needed temperatures below 140°F to condense? That may be the standard temperature to prevent a fixed-fire cast iron boiler from condensing, but it is not the limit for condensation in a modulating boiler.

Even if the emitters require high temperatures, when less heat is required, the burner can modulate down, which has a very significant effect on efficiency, even at higher temperatures that would traditionally be considered to be non-condensing. The 140°F limit does not apply to mod/cons in the same way that it applies to conventional boilers.

Baseboard may not be quite as good an application for a modulating condensing boiler as radiators are, and radiators may not be quite as good an application as radiant panels, but that doesn't mean that mod/cons don't make sense with baseboard.

Tony_23

Timer

That would work in conjunction with a programmable stat.
This guy's retired and has no schedule, what he wants and when, so the manual deal works for him.

Greg Gibbs

Cool,

question Mark! -Gpex

jp_2

heat @ 65F??

I'm shocked that a house needs heat when outdoors is 65F? absolutely no solar gain?

instead of installing a modcon seems customers need insulation?

how can you stop a modcon from cycling like crazy at 63F outdoor temps when your design temp is in the single digits?

Greg Gibbs

Most heating systems have

some sort of t-sat control...60-65 deg. would be a "start"
temp. based on outdoor temp. only...the t-stat(s) would decide if the system needs to turn on. -Greg

Greg Gibbs

From Slant/Fin...Series 15 ratings

I just pulled this of the Slant/Fin web site, you learn somthing new everyday! -Greg

[Deleted User]

Greg...

Do you know if that is the results of actual testing, or extrapolation from their previous tests?

Thanks for ocming up with the idea to ask the question...

ME

Greg Gibbs

?

I do not know, if someone from S/F does not chime in by Monday I will give them a call. Is Tom still a "unbeliever" ? -Greg

Plumdog_2

Oddly enough

the 1/2 fintube has a slight performance edge over the 3/4 from 160 degrees down.

Greg Gibbs

I should,

have some information today from Slant/Fin. -Greg