Temperature Recovery Time

Ken_22

With a properly sized boiler (baseboard hot water heat) on a 30 degree or so day, approximately how long would it be expected to heat a zone up from 68 to 72 degrees (other zones not calling for heat during this time)?

30 mins? Hr? 3 Hrs?

Plumbob

Yes.

Ken_22

I'm Sorry

But I thought it was a valid question.

Is more information needed? Are there different ways things can be hooked up so that you can either get a quick heat rise or a slow, steady heat rise?

I recently had a new boiler put in and overnight it dropped to 68 and the temperature called for 72 at 5:30am and by 8:30, it was only at 71. Is that a possible problem?

Plumbob

Hot water heat is a chain with multiple links. The boiler might be "properly sized", but that's just a matter of whether it will supply the BTU needed on a design day, over the whole day. It doesn't mean it heats the water instantaneously. Second, even if the water heats fast (i.e. oversized boiler), it does not mean that the room heats fast; the boiler just heats the water to the set temperature and holds it there. Room heating is then limited by the output of your baseboards and the water temperature setpoint and the outdoor temperature. It doesn't matter how many zones you have, or how big your boiler is, if this is the limiting factor.

You are asking for a formula that tells you how fast the zone "should" heat, but there isn't any. Hot water heat is supposed to be slow and steady. If you have outdoor reset, the system may never recover from setback (and this is how it's supposed to be).

If you want fast recovery, and the only thing that has changed is the boiler, check whether you have outdoor reset (in which case you should not use setback at all). If you don't have outdoor reset, check what the water temperature is (find the aquastat on the boiler somewhere); in your old boiler it was probably 180 or 190. Turn it up to one of these values if necessary. But I recommend keeping the water temperature as low as possible, for efficiency and (most importantly) lack of overshooting i.e. increased comfort.

Ken_22

Temperature Recovery Time

No, I don't insist on a fast recovery. I just am trying to make sure nothing is wrong.

So as long as the baseboards are constantly warm (they don't get cold while the house temperature is recovering), it's no problem if it might only recover at a degree an hour, is that basically correct?

The high limit is set to 180, the low limit is set to 140. I've never seen the temp gauge get above 170 and I think I've seen it as low as 160, but I'm not certain exactly how low it's gotten. My old boiler was making hot water too via a coil, so I think perhaps they had it set at 180 or higher, but I don't recall.

Is is actually desireable for a slow steady recovery? I presume heat recovery works by the baseboard heating air to a point that's hotter than the current room air in the room to bring the overall room temp up. If you blast real hot air in, it may actually feel too hot while it's recovering or does that make no sense at all and it's best to recover as quickly as possible?

So basically everything appears normal then as long as the thermostat temp is maintained once it's hit regardless of the outside temp?

Mike T., Swampeast MO

Are you using a programmable thermostat with "intelligent" recover?

Plumbob

> long as the baseboards are constantly warm (they

> don't get cold while the house temperature is

> recovering), it's no problem if it might only

> recover at a degree an hour, is that basically

> correct?


I can't tell you there is no problem in your new system, but slow recovery is not in itself a problem.

> If you blast real hot

> air in, it may actually feel too hot while it's

> recovering


Correct, and the temperature will overshoot. Many modern systems use outdoor reset, where the water temperature is varied based on outdoor temperature, so that it is always just barely enough to heat the house. This gives gentle, steady heat, without a "blast furnace" effect.

> So basically everything appears normal then as

> long as the thermostat temp is maintained once

> it's hit regardless of the outside temp?


That last point is the only relevant one. If it works in extreme cold weather, which you don't know yet, it is fine. If your boiler is undersized, it won't work then.

Ken_22

No, Basic Thermostat

Using a LUX TX9000 (older model than the TX9000 that's on their website). Standard 7 day programmable. Not sure what you mean by intelligent recovery, but I'm pretty sure it's got very little special logic in there. I do see on the boiler controls that the zone calling for heat the whole time.

jp_2

its up to the designer,

you can design for minumum heat requirements or you can go hog wild. as in radiant floor heat you could have your tubing design for 8 or 10 inches apart or have them at 2 inches apart. the designer knowingly or unknowning dicatates recovery time. you question is valid and there is a valid answer, which is best solved by YOU doing an experiment with a clock & thermometer.
jim

Paul_28

No setback?

Can you comment more about your statement of not using a setback at all if I have an outdoor reset? How would the temperature be lower at night??

Rich W

outdoor reset

The boiler temp. will be lower when the outdoor temp.is higher.(you don't need as much heat when it's warmer outside).If the outdoor temp. rises in the morning when you are trying to raise the house temp.- it will take longer due to lower boiler temps. Also, make sure your fin-tube is clean,the damper is open and the bottom is not blocked by carpet etc. If air can't pass through the fin-tube, you're not getting the efficiency you paid for. Most companies consider it your duty to keep these clean.

Plumbob

"Setback" means that the temperature is lower (e.g. at night). "No setback" means the opposite, temperature is not lower.

If you have outdoor reset, PROPERLY SET, the water temperature will be so low that it will take forever to recover from any setback. The efficiency gain of outdoor reset outweighs the efficiency gain of setback. If it recovers rapidly, you may have outdoor reset in principle, but the curve is not as low as it could be, so you are not getting the full benefit of reset.

Paul_28

setback

Can you explain your statement,”check whether you have outdoor reset (in which case you should not use setback at all).” Why should I not use setback if I have an outdoor reset.

.

I give up.

Weezbo

I think 7 hours approximately...:)

7?atilde;F an hour would be my Guess...or something close....it has alot to do with a host of details...EDIT ,, OOPS i miss read for some reason i thought you were saying from 30 to 79 ish..if it is like from 68 to 72 i would say closer to 34.mins 30 seconds Here is what you are after with baseboard, keeping the zone,70 degrees F on the coldest designe day ...anything over that is ok just not a requirement.however,having said that some people like it to be Warmer when its colder..so if it can "Get There" and stay there Fine...if you are unable to Get there then some how the structure is losing more heat in that zone than calulated ,the boiler temp is too low, there is not enough baseboard,there is something Wrong with the zone valves in the surrounding rooms,the floor covering is of higher insulating value that you were told ,someone has a window open, the hrv installer didnt balance the system, there are Holes between floors that have caused some sort of variant stack effect,or maybe there is something clogging the inside of the piping to the zone like somepiece of rubber off a zone valve or a wood chip something along those lines...to me if it takes 4 hours to respond to the heat difference there must be something off the mark with your system especially at this time of year ... radiant might respond more slowly however if one of my slabs cant change 3-4 degrees in an hour i think it needs different control the slab i have is 68 right now ,it is 8 16 according to my very weird clock,i boosted the temp up 8 degrees on the water supply its radiant...i expect it to ramp to at least 70 in the next half hour. its about 10 outside right now...lets test it ..........8 36 by my weird clock,return water temp is 74,in about ten mins or so it should be 3 circulations lets see,77 degrees , so room temp should be jumping up to 70 pretty soon...i think it tends to like to hang out in about room temp + or - 3->5 degrees...my dog wanted out for a run ..and i just let him back in ten mins ago...kinda freakin with the experiment rotten mutt )ok so now my weird clock says its 9 oclock, the water temp in the slab is about 76 i think i will go check outside temp... i guessed it was 10 degrees,maybe thats wrong... It is now 1 degree outside , the room temp feels warmer it only shows one degree temp change though....the rreturn water is 77 now... man this is making me angry )This zone used to ramp really faster:) the room temp is slow to ramp:( i ramped the water temp 9 degrees buh the rooms dragging its feet:( now i am sad for it...it should be at least 70 by now it "feels" Warmer buh it is only one degree warmer in the room........ my radiant system is a POS ))..................It Gets Better! Yesterday i shut one of my 125' 3/8" loops Off! Thanks ! yikes! no wonder it was acting like a POS ! ))........I'm Ba~Ack! ) now its definitely hammering the heat to the place:) oki:) I Habby again Thanks for posting this or id not have even realized id turned it off and forgot to turn it back on yesterday...i am constantly thinking of things to do to my radiant, to put it through changes:) Alaska is a severe place,and i am into trust buh verify.......Well this was a lot of fun your baseboard should react faster than radiant...

Unknown

Chuckles

By properly resetting the system water temperature, you are simply matching the output of the system to only that amount needed to keep the building at the desired indoor temperature. This is accomplished by modulating the water temperature to satisfy that requirement. Room temperature setback will most certainly work with reset controls. Many controls such as the Burnham EC-5000, 370 and 371 Tekmar controls incorporate both features. They also, however, have the logic to distribute the zone demand as not to overtax the boiler during recovery. I will agree that a grossly undersized boiler may be prohibitive to proper setback recovery, but then again an oversized boiler is not the answer either. That's why proper boiler sizing is important.

Glenn Stanton

Manager of Training

Burnham Hydronics

www.burnham.com

.

> By properly resetting the system water

> temperature, you are simply matching the output

> of the system to only that amount needed to keep

> the building at the desired indoor temperature.

> This is accomplished by modulating the water

> temperature to satisfy that requirement. Room


In short, it will work if you have water temperature boost using indoor temperature feedback. I agree. Most reset controllers (the Tekmar 256 is by far the most popular) and most reset logic built into boilers do not have this additional feature.

> temperature setback will most certainly work with

> reset controls. Many controls such as the Burnham

> EC-5000, 370 and 371 Tekmar controls incorporate

> both features. They also, however, have the logic


The Burnham EC-5000 is just a rebranded Tekmar 370. These models do have water temperature boost.

Unknown

Not really

The EC-5000 was introduced at about the same time as the 370 House Control but is not the same as the 371. The 371 has two heating curves, one for high temperature zones and one for low. I would like to clarify though that if a system has a standard "run of the mill" reset system without indoor feedback that is set to maintain a 70 degree temperature at the thermostat regardless of whether the outdoor temperature is -10 or 40 degrees, then it will have the same recovery time with low water temperature on a warmer day as high temperature on a colder day as it is always trying to stay matched to the heat loss by modulating water temperature.

Glenn Stanton

Manager of Training

Burnham Hydronics

www.burnham.com

lchmb

WOW

Alaska is not only hard on heating system's I see!!! Glad to see you passed your test..LOL

Weezbo

*~/

Today the inspector said ,"both dwvp and potable water tested to twice the required pressure:))))) I guess ,i am a bit severe on things:)))well, in 75 below zero, mother nature is gonna make that seem like an act of Kindness )) oh~, if you look real close to Mars Tonight,you may see my other three inch red rubber pressure plug orbiting nearby clearly it has left the vicinity of the building i was testing:)))