| Author | Post |
|---|
eleent
Member
| Joined: | Sat Sep 11th, 2004 |
| Location: | |
| Posts: | 1565 |
| Status: |
Offline
|
|
Posted: Sun Dec 23rd, 2007 01:03 am |
|
Hello: So, it seems that throttling things closed just a bit more will increase the differential, causing the heater to fire more. The one problem that near continuous firing can do is create steady condensation, rusting the tank on the fire side. If you can get it to fire without steady condensation, you've got it as good as is possible 
Yours, Larry
|
shashalou
Member
| Joined: | Fri Dec 17th, 2004 |
| Location: | |
| Posts: | 22 |
| Status: |
Offline
|
|
Posted: Sun Dec 23rd, 2007 10:07 pm |
|
I'm confused. My basic physics says that the volume and temperature of the water are the only variables here; that there is more heat in x gals of water at 120 than there is at x/2 gals at 140 and that lower temperatures are more economical.
With an increase in outside temp today, the pump shut off. The water into the loop in a shart time rose 15 degrees. I have no idea why.
I turned the heater down 2 notches from max and the temp into the loop now is 125, out is 90 (the pump is on).
I appreciate your advice and your patience and dont want to keep infringing on them, but why do you think the temperature in the tank drops so much when the pump is on?. The same doesnt happen if a cold water faucet is left open.
And, to get back to the original question: are there any run of the mill residential heaters out there whose design might specifically address some of the things we've been
discussing?
|
eleent
Member
| Joined: | Sat Sep 11th, 2004 |
| Location: | |
| Posts: | 1565 |
| Status: |
Offline
|
|
Posted: Mon Dec 24th, 2007 07:57 pm |
|
Hello: I'm no mathmetician, but it seems we have an equation with multiple variables. These are, how fast heat is transferred out of the system and how fast heat is put into the system. We are trying to put the most heat into the system to start with. So, getting the heater to fire more is a goal. Slowing down water flow to get a greater differential will make the heater fire. As water flow is slowed, more heat is allowed to escape from each particular piece of water as it travels through the system. I know that running hotter water through the system will put more heat into the space, but it also prevents the heater from firing as much, So, there is a balancing point to be reached by setting heater temp and pump flow rate.
About tank temp, I can guess that stratification is being established as the pump is throttled down. This is good. Mixing tank water reduces stratification, preventing the heater from firing. Running hot water from a tap should introduce cold water into the bottom of the tank, promoting firing. Heating water coming back from the loops will not be so cold, making it harder to get the heater to fire.
It's possible that a condensing heater, such as Polaris, Vertex or Voyager could be controlled in a closer range as they are electrically operated, but that might add a level of cost, complexity and dependance on power you don't want.
A goal of mine, when troubleshooting is to build a working model of the whole system in my mind. Once I have that understanding, it's easier to see how any changes could affect things. For example, tank temp measurements could be quite confusing if stratification is not taken into account and stratification changes with the amount of water the pump moves 
I hope this is of some use.
Yours, Larry
Last edited on Mon Dec 24th, 2007 08:02 pm by eleent
|
shashalou
Member
| Joined: | Fri Dec 17th, 2004 |
| Location: | |
| Posts: | 22 |
| Status: |
Offline
|
|
Posted: Wed Dec 26th, 2007 03:47 am |
|
it seems we have an equation with multiple variables.
Yes, but volume and temperature are the ones I'm playing with. Cutting the volume requires a higher temp to produce the same amount of heat and vice versa. The temps I measured at full volume were around 120-105 (ave 113) -- the temps at half volume around 135-110 (ave 123). The question then is whether x gals of water @ 113 will produce as much heat as x/2 gals @ 123. In addition, lower temps are economically and physically preferable IF they can do the job and they will generally at 20* and up.
Fixing the IF is another problem to which you have given possible solutions, but I want to make sure of the above logic first.
I know that running hotter water through the system will put more heat into the space, but it also prevents the heater from firing as much,
I hope you misspoke there, since I dont understand.
stratification changes with the amount of water the pump moves
I'm picturing it, apparently incorrectly, as turbulence or some sort of forced mixing, not volume, that causes loss of stratification.
|
eleent
Member
| Joined: | Sat Sep 11th, 2004 |
| Location: | |
| Posts: | 1565 |
| Status: |
Offline
|
|
Posted: Wed Dec 26th, 2007 06:46 pm |
|
Hello: Part of this troubleshooting is using the same terms. I think we are just looking at opposite sides of the same coin. Volume and temperature are things that affect heat transfer.
Hotter water is run through the system by speeding up the pump. Water has less time to lose heat, so it's warmer exiting the heat distribution system. Also, at higher flow there is less differential between water going into and out of the system. This is what prevents the heater from firing as much. It needs 30 degrees differential to work. So, I didn't really mis-speak, I just mumbled 
When , for example you put a ten horse power pump on the system and whip that water around, you wind up mixing all the water in the system, (including tank) so there is essentially no stratification and almost no temperature difference in water coming or going. Now, put a one-thousandth horsepower pump on it and have it take a day for the same piece of water make the rounds once. You'll have great stratification in the tank and possibly a 60 degree differential between water going into the tubing and water returning from the tubing. I like silly extremes to clarify a problem  What you want is to move water slowly enough so it allows stratification to exist in the tank and to ger a 30 degree differential between water leaving the tank and water returning to the tank. That should keep the tank firing and it is one of the fixed pieces of this fairly fluid design that we cannot change without new equipment.
Happy Boxing Day
Yours, Larry
|
shashalou
Member
| Joined: | Fri Dec 17th, 2004 |
| Location: | |
| Posts: | 22 |
| Status: |
Offline
|
|
Posted: Wed Dec 26th, 2007 08:45 pm |
|
As it dawns on me--the volume is constant, since the length and size of the loop are constant, I dont have to divide the volume by 2 when the pump is halved. The average temp in the pipe, 113 with valve open, 123 when halved, represents the relative amount of btus transferred. The measurements say the water is hotter in the pipe when the pump is slowed.
But then you say
Hotter water is run through the system by speeding up the pump.
which contradicts the evidence: the ave temp is 10 deg hotter when the valve is halved.
It needs 30 degrees differential to work.
My system has worked during all but the coldest weather without that, but I'll accept it as a standard.
What you want is to move water slowly enough so it allows stratification to exist in the tank and to ger a 30 degree differential between water leaving the tank and water returning to the tank. That should keep the tank firing...
At coldest outdoor temps it's what I want, but at 30 deg, which is most of the winter, it gets too warm and I'm saying (please correct me) that speeding the water and reducing the ave temp in the loop might be more suitable at 30 deg outside.
Thanks again, Larry, for your expertise and forbearance. I've learned a bit that I will soon put to use and I agree that the terminology is the biggest block.
|
eleent
Member
| Joined: | Sat Sep 11th, 2004 |
| Location: | |
| Posts: | 1565 |
| Status: |
Offline
|
|
Posted: Thu Dec 27th, 2007 12:49 am |
|
Hello: I think we're getting close. Average temperature is going to be a useful number in understanding what scenerio is really putting the most heat into the living space. As water moves faster, difference between in and out gets smaller.
During most of the time when you don't need full output of the heater to stay warm, try changing only one variable, like heater temp. Changing two variables at once confuses this poor plumber's brain and prevents getting closer to a system that can readily be understood and controlled Actually, it occurs to me that if you could put a rheostat on the pump, or even better, a proportional control based on outdoor temperature (something like outdoor reset), your system could cruise along without needing your attention. That would be nice !
Yours, Larry
|
shashalou
Member
| Joined: | Fri Dec 17th, 2004 |
| Location: | |
| Posts: | 22 |
| Status: |
Offline
|
|
Posted: Wed Jan 23rd, 2008 04:29 pm |
|
I'm still here, lurking in all the appropriate forums, checking temperatures and opening and closing valves and thermostats.
My adjustments seem to no avail, the heater does exactly what it wants, what it wants is inconsistent enough to be immeasurable and there are no specs out there that risk stating what the thermostat is designed to do.
All those ideas out there--hysteresis(?!), standby losses, deadband problems, stack effect--seem to me gibberish designed to apologize for a poor design and until a retrofit that works can be found, the problem will remain. I have asked Honeywell--no response as yet.
|
eleent
Member
| Joined: | Sat Sep 11th, 2004 |
| Location: | |
| Posts: | 1565 |
| Status: |
Offline
|
|
Posted: Wed Jan 23rd, 2008 11:59 pm |
|
Well, now you know what it feels like at times to be a plumber We get a lot of the same mushy answers and wiggly science. However, there may be a way out of the mumbo jumbo. Hobo is a brand of inexpensive datalogger that can show you how your system is performing over time. For troubleshooting, it really beats individual measurements for seeing cause and effect. http://www.onsetcomp.com/ is a good site to look at.
I suppose, like computers, if we don't have good info going in, we don't have good decisions coming out
Yours, Larry
|
shashalou
Member
| Joined: | Fri Dec 17th, 2004 |
| Location: | |
| Posts: | 22 |
| Status: |
Offline
|
|
Posted: Sun Jan 27th, 2008 12:37 am |
|
I think I'll pass on further science for now, but thanks for the link. In the meantime, I came across this:
http://www.sears.com/shc/s/p_10153_12605_04233443000P?vName=Appliances&cName=Water+Heaters&keyword=gas+water+heater
|
eleent
Member
| Joined: | Sat Sep 11th, 2004 |
| Location: | |
| Posts: | 1565 |
| Status: |
Offline
|
|
Posted: Sun Jan 27th, 2008 07:56 pm |
|
Hello: This is interesting... The Honeywell control is new and I have not had the pleasure of meeting one. Honeywell has been a player in the water heater controls market, but more recently, Robertshaw and White Rogers have had nearly all of it, from what I see. I'll be interested to learn what you find out from Honeywell when they get back to you.
Yours, Larry
|
shashalou
Member
| Joined: | Fri Dec 17th, 2004 |
| Location: | |
| Posts: | 22 |
| Status: |
Offline
|
|
Posted: Sun Feb 17th, 2008 06:09 pm |
|
A lot of wierd stuff on that Sears water heater I linked.
Google, a number of times, calls that model "State Industries Kenmore" but no search in AO Smith will reveal it.
The gama list shows only one with the model 33443. It's listed under Sears (1 hr rec 70, ee .63, rec eff .82).
The instruction manual is not to be found anywhere and when I go to Kenmore's parts diagram the replacement thermostat is soso not the new "hydrosense".
The blow up shows the stat labelled Honeywell Hydrosense controller but a search of Honeywell will not respond to those terms and they have not answered my inquiry.
|
elenano
Member
| Joined: | Sat Sep 11th, 2004 |
| Location: | USA |
| Posts: | 1322 |
| Status: |
Offline
|
|
Posted: Sun Feb 17th, 2008 07:01 pm |
|
Also try State Industries' site, which is listed under Resources. Kenmore has always been Sears' house brand, and for years, it has been manufactured by State. State has its own site, even though it's a subsidiary now of A.O. Smith.
Randy Schuyler
|
Current time is 04:26 am | Page:   1 2 |
|
