how long to reach delta t

ralman

If I have a design delta t of 20 degrees, and the thermostat calls for heat, the boiler and circulator turn on. Then I use an ir thermometer to check the temperature differences between the supply and returns. What is an expected time frame to reach delta T?

Brad White_131

\"It Depends

> If I have a design delta t of 20 degrees, and the

> thermostat calls for heat, the boiler and

> circulator turn on. Then I use an ir thermometer

> to check the temperature differences between the

> supply and returns. What is an expected time

> frame to reach delta T?

Brad White_131

\"It Depends\"

Depends on a lot of things, Ross. Starting temperature of the house, heat loss and outdoor temperature at the time. Water volume of the system, firing rate, mass of the boiler. Some days, especially mild ones, you may never see it; the house thermostat is satisfied well before then. In a low mass boiler you will get it much sooner. And if you never see it but the house still heats, it is but an incidental figure used to select radiation and flow rates....

Gordy

measuring Delta T

> If I have a design delta t of 20 degrees, and the

> thermostat calls for heat, the boiler and

> circulator turn on. Then I use an ir thermometer

> to check the temperature differences between the

> supply and returns. What is an expected time

> frame to reach delta T?



You can drive yourself crazy with this. It took ne a while to get past the 20* delta T design temp. I have an old ceiling Radiant system. My system delta T is around 17* at present day design temps. Individual loops can be anywhere from 7* to 15* delta T's at the end of the heating cycle.

This could mean alot of different things. Could mean the design temp. was a lower number back in the 50's. Could mean I'm over pumping on the entire system. Plus it could be all the variables Brad has stated above.

I remember flying all over my house trying to nail down system temps with my IR thermometer. The Mrs. looking at me as though I was nuts, Ehmmm is there a problem? because we seem to have heat. Me I was only trying to learn/ understand my system. It works is the main thing.

Gordy

Mark_46

I'm wondering the same

This will be the first heating season with my new system. It is hydro-air, for now.

Using early measurents I've gotten from just starting the system to make sure it's 'ready', I get a solid 20 deg delta T when the boiler is up to 180 outlet and the T-stat is still calling for the first floor. However, the second floor has less than 20. I believe it is either too much water flow to the coil/air handler or not enough air flow.

Brad, would you agree in concept?

Ross,
How would you rate the accuracy, etc of the IR thermomoeter you are using? I was thinking of purcahsing two Digi-stat DS-60P by Azel Technologies but an IR device is a lot more portable with no setup time.

Mark_46

This will be the first heating season with my new system. It is hydro-air, for now.

Using early measurents I've gotten from just starting the system to make sure its ready, I get a steady 20 deg delta T when the boiler is up to 180 outlet and the T-stat is still calling for the first floor. However, the second floor has less than 20. I believe it is either too much water flow to the coil or not enough air flow.

Brad would you agree in concept?

Mark_46

IR device

Ross,

How would you rate the accuracy of the IR thermommeter you are using? What brand is it and where did you purchase?

I was thinking of purchasing 2 Digi-stat DS-60P but a handheld IR device is a lot more portable with no setup time.

Here are several:
http://buy1.snapon.com/catalog/tools.asp?tool=all&Group_ID=1362&store=snapon-store

Brad White_9

Not enough information, Mark

to agree or disagree. The variables are unknown to me. Too much water flow certainly can contribute to a lesser delta-T and that can also mean more heat output due to higher average water temperature. (Marginal but factual.) Airflow, same issue; no telling what the starting temperature was either...

In short, if the house heats well, the actual delta-T is academic.

[Deleted User]

IR Caution...

If used on shiny copper piping, the reading will be low and false. Always dull the brilliance of any material with a flat black spray paint before attempting to get readings.

THey make a crayon to dull the emmissivity of pipes and other materials for the same reason. I've used electrical tape, duct tape and liquid pipe dope to do the smae thing.

Proceed with caution... and don't get hung up in the numb-ers. So long as you are comfortable, and the boiler is not condensing, you've got nothing to worry about for now.

ME

ralman

IR brand

I have a fluke mini 62. I like it very much, it is very convenient to measure temps in hard to access areas. I just saw Sears Craftsman had one on sale, not sure if it still is or not. I was not suggesting the fluke was on sale, rather that they had an IR on sale, most likely their own brand. It was half the cost that I paid for the Fluke brand. I can not speak for accuracy, I have never attempted to try and calibrate it, or test it against a known temp. I know that the temp of iron supply pipe may not exactly match the temp of the fluid flowing through.

Brad White_9

So long as

The pipe is black or painted, the readings will be close enough. They do not work on shiny metal. I could read a copper pipe with 180 degree water and it said it was practically room temperature. A shot of flat black paint as a target is a good thing. (EDIT- Sorry- I just read Mark Eatherton's post- he nailed it.)

The less expensive ones are not adjustable, the more expensive ones are for emissivity (IR absorbtion and reflectance). I calibrate mine with boiling water (212) and ice water (32) as standard reference points. Even my non-adjustable one works fine.

If you enjoy this sort of thing, Azel makes a dual-channel digital thermometer for about $75 which will do nicely. My Azel sensors (suspiciously like Tekmar's!) are curved to fit pipe and you should insulate over them. Mine are inserted into thermowells with heat conductive paste for better reading.

Any good multi-meter will also have thermistor temperature sensors which are highly accurate.

ralman

It is all a mystery to me, since I am not a pro

I have difficulty interpreting the data. An example, I have a 180 degree temp on the boiler gauge, my aquastat high limit is set for 180 high. I measure the supply pipe before the check valve, 140*. Then I measure after the check valve 90*. Check valve seems to be working properly. I measure again, before the check valve during a call for heat and leave the IR thermometer on for the duration of the heat call, which never, ever lasts longer than 5 minutes. Temp goes to 168*, but before the cycle is over it declines to 152*. I figure this may be a function of original 180* mixing with much colder return water. The 180* water moves past the test point on the pipe before it can raise the pipe to 180*. Due to the flow rate, 180* water is not at the test point long enough, as it is replaced by cooler and cooler water temps as a result of return water mixing in the boiler. The boiler gauge does not react as quickly as the IR, so the numbers don't match. What do you think?

Brad White_9

A Few Questions

1) Is the house heating well?

2) If so, and assuming you are not spending a fortune in pump energy, why worry about Delta-T?

3) If the house is not heating well, that is another issue.

Like the bumblebee, mathematically proven by aeronautic engineers not to be able to fly, he buzzes along merry in his ignorance.

Delta-T is a design basis and only becomes a finite determinate at design conditions.

The rest of the time, like the Tao of Pooh, "it just is".

ralman

Delta T

1) Is the house heating well? Not at all, and to refresh your memory, I have the Monoflo T system with the 3 CIBB connected across the split, and 2 CIBB direct coupled supply to return. You have looked at my system diagram a few times and helped me with some questions. I can't determine that a total redesign(repipe) will resolve my problems, but that is my guess. Thanks to you and others I have an extensive list of repairs that need to be made to the current system. Due to the cost and difficulty of these repairs, I wonder if the effort should be directed at something else. I have a newer boiler installed two years before I purchased this home. I see it connected to a 56 year old piping design that may have never been done correctly and I wonder, might the hydronic technology have changed in 56 years? Could I benefit from a repipe using current methods? The 6 companies that I have had look at this say absolutely NOT! I am not convinced.

Brad White_9

I think we established by consensus

that a re-pipe is necessary, at least for those problem radiators. No short-cuts unfortunately, Ross. You are simply not going to get flow through those radiators which are piped across two supply lines.

Last time that happened was at Lourdes, when thousands of wheelchair-bound pilgrims rose in unison to dance Zydeco to CJ Chenier.

Never happened.

Weezbo

my apologies once again.. what you are stating is clear.

you are not particularly enamoured with the existing system married to the new boiler.

this is true for many things in life. we cannot generally marry something old up to something new and expect free sailing.

it is a value judgement that individuals make when they proceed with the idea.... there is a distinct learning curve or hurdle that needs to be surmounted before methodically throwing a boiler at a system that is not working correctly.

modifications to your existing system(field) despite, well...considerable opinion to let it be ....does not appeal to you as you have to Live With It and you are definitely not liking it. you have some good advise here to tune this or that to help it a bit the idea being if there is a way to restore it to a functioning state with little or no disruption o the existing system most sane people would be all for it. from what i have seen and from what you are saying you might consider upgrading the system a bit with the pex al pex like you were mentioning. the thing though is we have some fairly snazzy components that can be used to change a variety of parameters in the equation....

as you have some time to consider what to do next winter being a little ways out still....you might want to direct your attention to each and every aspect of the system that just buggs the heck out of you ...crank the heat up and check every room with the Ross meter. you are the one who lives with it and you know when you do or don't feel comfortable.then hire on someone to dial it in that you can ask what he would do to make the system function like You would like. it may be that the system is deficient in some ways and it just has to be done...

i type slow. and after reading Brads last post i am inclined to agree with what he is saying.

ralman

The identified deficiencies ar clear, the solutions are not.

The consensus does indicate a repair is necessary, but I am not clear on the solution. Maybe I am not asking the right questions or understanding what those who contribute to my posts are saying. Which is my better option repair and keep the monoflo System. Or would this be a good time to repipe to say 3 zones, main living area, sleeping area and basement? Or is there an even better option? What option do I shop for?

Brad White_9

MonoFlow Systems

have their limitations. Great for isolated smaller buildings or defined areas within them. One step above series loop because you can balance each emitter separately. You still have to compensate for dilution of temperature at all downstream radiators.

Short term, we identified three radiator situations that were piped across the supply side of a split; coincidentally these were poor performers. Not sure about others. You can re-pipe these and see where that gets you. A run of Pex-Al-Pex can go a long way for short money as a test. If one works, do the others if incrementalism is your way.

Or you can do a re-pipe.

My own house had a MonoFlow system. I ran new copper reverse return mains in parallel then switched over the radiators one at a time. I was done before I knew it. All radiators get hot water at the same temperature at the same essential time. Of course, copper was cheaper back then~

Each radiator gets what it needs for no particular circuit has an appreciably different delta-P. And guess what? My delta-T's are close to design every so often.

You can install manifolds and rum Pex-Al-Pex if copper kills your budget. You have options! Sitting in discomfort should not be one of them.

Weezbo

zoning is always an intelligent decision

individual areas that can be controlled and each room within the zone is definitely a superior solution. balancing any system is better than having it run unregulated.

shop for someone who will adress the things you are not liking. you might need to put some attention to many dis similar variables .

ralman

This is vey helpful, Brad.

My thoughts have been to repipe in order to get the same water temp or at least a higher average water temp to all baseboards. I think the comfort level would drastically improve if I could get this. I am researching the methods to do this. Trying to compare reverse return, zoning with circulators or zone valves, and just running all baseboards separately from a manifold with pex-al-pex. If I could nail down the best method, or at least the pro's and con's of each, shopping for a repair will be easier.

ralman

What are the dis similar variables you refer to?

Brad White_9

Any of those

will do the job, Ross. Reverse return in my case made sense because I already had a 1-1/4" homerun in place for the return. Roughly the same amount of piping in parallel down each side of the house. (My house is all one zone but with TRV's on all radiators).

Do a quick sketch for yourself of each and scale off how much piping each entails. Reverse return will have more typically and direct return is not such a bad thing.

On my Susan's house I did a loop, 1" reducing to 3/4" with 1/2" runouts to the old gravity risers. I expect with the TRV's that the flow will dynamically change thoughout the day but that the pressure gradient across any radiator will be very similar. Also water denied to a radiator will go elsewhere where it is needed more.

As I said, sketch it out and compare. They best systems design themselves.

ralman

Thank you

Gordy

It Depends

I just have a 50.00 radio shack IR that I originally bought to find the pipes in the plaster so extreme accuracy was not important, I was only interested in temp difference.

I used black tape on the pipes I was shooting seemed to be as accurate as several other types of thermometers I compared it to. the angle at which you shoot also has some bearing on readings shoot 90* to the surface.

Sounds like you have some issues for a professional to look into though.


Gordy