Tekmar 361 Question


  #1  
Old 06-10-09, 05:23 PM
B
Member
Thread Starter
Join Date: Jun 2009
Location: United States
Posts: 14
Likes: 0
Received 0 Likes on 0 Posts
Tekmar 361 Question

My System:
Oil Boiler is a Burnham V84 Boiler with a Honeywell L8124AC aquastat, and Taco circulator. Piping is a mono flow system that feeds individual copper fin baseboards. (Slant fin). System is not used for (DHW)

Tekmar representative suggested the 361 with full reset. This would involve adding 2 additional pumps (system, and variable speed injector pumps controlled by the 361. Also Primary/secondary piping.

Burnham representative stated the this model of boiler should always operate at temperatures over 140 Degrees in order to prevent flute condensation.


Questions:
1. The manual states when boiler sensor on the supply side the 361 should be the only controler that operates the boiler. Does this mean my aquastat is no longer connected?

(The Tekmar 260 Boiler 9/10 pins normally are wired to TT of the L8124AC aquastat)

2. Since A361-1 doesn't require my L8124AC Do you use the Tekmar 361 Boiler 9/10 pins to switch the 120V L to the Burner?

3. Manual states boiler pump should operate continuously or in parallel with the system pump. Since this would now be a cold start system should it What are the advantages of parallel vs continuous when using baseboards.

4. Would the thermostat be connected to the Tekmar 361 pins 1/2 to create demand?

5. Currently my boiler circulator is on the return, should it be moved to the supply like in A361-1?

Thanks!!!
 
  #2  
Old 06-11-09, 05:54 AM
B
Member
Thread Starter
Join Date: Jun 2009
Location: United States
Posts: 14
Likes: 0
Received 0 Likes on 0 Posts
I didn't realize that the burner had TT connections therefore my question about wiring pins 9/10 pins was a dumb question to all the professionals.

I am trying to educate myself with the most efficient way to utilze my 5 year old boiler since it's no longer used for (DWH).

A cold start with Tekmar and boiler protection appears to be a worthwhile investment for comfort and hopefully the savings will recoup the installation costs in about 5 -7 years or less if oil prices keep rising.

All opinions are welcome.
 
  #3  
Old 06-11-09, 05:59 AM
X
Member
Join Date: Nov 2005
Location: USA
Posts: 2,455
Likes: 0
Received 0 Likes on 0 Posts
361 and all that p/s piping/pumping seems like potential overkill. Good for some specialized applications (I know of one system like this), but quite often unnecessary to achieve good performance.

What are the heat loss specs on the building? How many feet of finned element? How many zones? Outdoor design temperature? Let's first see how the boiler is matched to the building, and what kind of water temperatures you might expect to use, before jumping into a relatively complex and expensive system.

You might be better off with a simple manual bypass and a simpler reset, e.g., tekmar 256, Taco PC700.

For oil, you can go lower than 140 on the return. 115-120 if you have reasonable burn times.
 
  #4  
Old 06-17-09, 07:52 PM
B
Member
Thread Starter
Join Date: Jun 2009
Location: United States
Posts: 14
Likes: 0
Received 0 Likes on 0 Posts
I have a single zone mono flow system with about 900 square feet to heat. I still need to do a heat loss calculation but I believe that Boston's outdoor design is around 5 - 9 degrees. In door design would be something like 70.

The boiler is now oversize because it's a 4 core in order to get sufficient hot water out of the tankless coil. We no longer use it for domestic hot water and we have updated windows and blow in insulation.

Now we run a .85 nozzle which is about 127(DOE)/110(IBR) according to the documentation and get about 85% AFUE. I have "Slat/Fin 15" 3/4 baseboards with 1/2 pipe to the monflow tees and 1 1/4 main loop.

Are you suggesting a tekmar 256 with a simpler boiler bypass for protection?

I was considering a Tekmar 260 since it runs off 120V and can control the pump with out a relay and eliminates the need for a 24V transformer.
 
  #5  
Old 06-18-09, 09:02 AM
F
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,495
Received 37 Likes on 29 Posts
...and get about 85% AFUE.
I can't offer any advice about the Tekmar controller but the above quotation is wrong.

You cannot ascertain AFUE (Annual Fuel Utilization Efficiency) in the field as it is a test done under laboratory conditions. Most likely your 85% figure is your combustion efficiency and is calculated from the stack gases exit temperature along with the excess oxygen and percentage of carbon dioxide in the stack gases. While combustion efficiency is important it is NOT the same as system efficiency or even boiler efficiency. Furthermore, unless done correctly the combustion efficiency testing is likely to be overstated as I suspect yours was.
 
  #6  
Old 06-18-09, 09:20 PM
X
Member
Join Date: Nov 2005
Location: USA
Posts: 2,455
Likes: 0
Received 0 Likes on 0 Posts
In my view, for your application the main virtue of the 260 over the 256 is the ability to add an indoor sensor. For a single zone system, a properly placed indoor sensor would really allow the system to run at its most efficient and provide outstanding comfort. You would still need some form of reliable boiler protection (a simple bypass might do, but that's a specific design question that requires more homework).

The 260 also controls an indirect water heater, but you wouldn't need that functionality.
 
  #7  
Old 06-19-09, 11:19 AM
B
Member
Thread Starter
Join Date: Jun 2009
Location: United States
Posts: 14
Likes: 0
Received 0 Likes on 0 Posts
Please excuse my misstatement, because I am a novice. Your are correct because it was 85% combustion efficiency, which used to be 82.5 when it had the larger nozzle when we used the coil for DHW. The energy Guide states 86%, but who knows accurate they are. I read somewhere that the jacket off and no insulation would result in higher AFUE.
 
  #8  
Old 06-19-09, 11:29 AM
B
Member
Thread Starter
Join Date: Jun 2009
Location: United States
Posts: 14
Likes: 0
Received 0 Likes on 0 Posts
Question1:
If we use the Tekmar 260 and Boiler Bypass with a thermic bypass valve what do you think the boiler min would be set to?

Example: Lets say I now have a Delta T of 20 degrees return without a Boiler Bypass so the Boiler Min would be set to 160 degrees. With the bypass since Hot water is being injected into the return could the Boiler Min be 150 Degrees?

Question 2 (Partial Outdoor Reset)
If there is a call for heat would the Tekmar 260 automatically use the Boiler Min that i set to 160 even know it calculated a boiler min of 100 due to outdoor temperatures?

Thanks!!
 
  #9  
Old 06-19-09, 04:37 PM
F
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,495
Received 37 Likes on 29 Posts
Originally Posted by BoilerNewbie View Post
Please excuse my misstatement, because I am a novice. Your are correct because it was 85% combustion efficiency, which used to be 82.5 when it had the larger nozzle when we used the coil for DHW. The energy Guide states 86%, but who knows accurate they are. I read somewhere that the jacket off and no insulation would result in higher AFUE.
Of course removing the jacket and insulation would give a higher AFUE because much of the heat that escapes up the chimney would be released to the interior of the house.

Unless you have a condensing boiler I have doubts about that 85% combustion efficiency figure. If the boiler was not thoroughly warmed up before taking the combustion tests then the stack temperature would be low and that would skew the results to a (false) higher combustion efficiency. Few heating systems are constructed that actually allow a true combustion analysis to be performed because the burner shuts off before reaching equilibrium.
 
  #10  
Old 06-19-09, 05:12 PM
B
Member
Thread Starter
Join Date: Jun 2009
Location: United States
Posts: 14
Likes: 0
Received 0 Likes on 0 Posts
The original combustion efficiency figure stated 82.5 and was performed by the installer. It was setup with a larger nozzle for 1.35 GPH. Here were the numbers on the TAG

Stack Gross - 500
Stack Net - 450
Co2/o2 - 12%
Smoke - 0
Breach Draft .02
OverDraft .02

The 2nd and 3rd measurements were done after the .85 nozzle was installed and air adjusted. The readings were 84.5 and 85 performed by the installer and another time by a service man.

The yearly cleaning will be due in August/September. What should the boiler temp and stack be in order to get an accurate combustion efficiency measurement?
 
  #11  
Old 06-19-09, 05:16 PM
F
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,495
Received 37 Likes on 29 Posts
What should the boiler temp and stack be in order to get an accurate combustion efficiency measurement?
The boiler should fire continuously until the stack temperature reading is stable, neither rising nor falling. Then, and only then, should combustion testing be relied upon to give a true combustion efficiency.
 
  #12  
Old 06-19-09, 07:34 PM
X
Member
Join Date: Nov 2005
Location: USA
Posts: 2,455
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by BoilerNewbie View Post
Question1:
If we use the Tekmar 260 and Boiler Bypass with a thermic bypass valve what do you think the boiler min would be set to?

Example: Lets say I now have a Delta T of 20 degrees return without a Boiler Bypass so the Boiler Min would be set to 160 degrees. With the bypass since Hot water is being injected into the return could the Boiler Min be 150 Degrees?

Question 2 (Partial Outdoor Reset)
If there is a call for heat would the Tekmar 260 automatically use the Boiler Min that i set to 160 even know it calculated a boiler min of 100 due to outdoor temperatures?

Thanks!!
1. boil min would be 80-100. the thermic bypass will take care of the boiler.

2. yes, but in application with boiler protection you wouldn't do that.
 
  #13  
Old 06-19-09, 08:29 PM
B
Member
Thread Starter
Join Date: Jun 2009
Location: United States
Posts: 14
Likes: 0
Received 0 Likes on 0 Posts
I Believe that the boiler is fairly over sized. Since the Boiler is rated @ 127(DOE)/110(IBR) I guessing that these rating are at a boiler temperature of 210 degrees since the manual recommends it for a High limit on Tankless coil installations.

1. If we are running the boiler @ 100 degrees what is the output 60 or 80 DOE?

2. Reading other threads states that best way to get FULL ODR is with Primary/Secondary with variable injection. It stated that using the thermic bypass valve could cause undesired results.

3. Would a primary/Secondary with variable injection with a 360 and indoor temp sensor save enough fuel over a 5 year period to break even on the cost. My goal is to maintain a indoor design temperature of 69 - 70 and use 275 - 300 gallons of oil.

Thanks for answering all of my question I am learning a lot.
 
  #14  
Old 06-20-09, 02:23 PM
rbeck's Avatar
Member
Join Date: Jul 2007
Location: United States
Posts: 2,675
Likes: 0
Received 56 Likes on 46 Posts
This is an oil boiler and adding ODR does not change the boiler rating. It is rated at input numbers and the input is not changing.
The ODR controls work off of heating curve. You will not always operate at 100 if that is what you are shooting for on the low side.
Do your heat loss and measure the radiation to determine the heating curve.
See link below.
A simple boiler bypass is all you need to make this all work OK. I would keep the system minimum limited to 130. You could try lower but check for condensation. With a boiler bypass it is allowing the boiler to get warmer and the system to operate cooler.
Outdoor Reset Explained
 
  #15  
Old 06-20-09, 08:08 PM
B
Member
Thread Starter
Join Date: Jun 2009
Location: United States
Posts: 14
Likes: 0
Received 0 Likes on 0 Posts
Thanks for all of the help.

I now understand that doing a simple Boiler Bypass will slow the flow of cool water into the boiler. I will probably set the Tekmar 260 to a boiler min of 140 to be safe. I also plan on installing a Tekmar Indoor Sensor so it can fine tune itself.

I remember reading that the Tekmar 260 doesn't have build in high limit boiler protection so you need to run it's terminals 11/12 into the aquastats TT in order for the aquastat to fire the boiler with high limit protection.

Which Honeywell high limit only aquastat do you recommend that allows for a cold start? My L8124C has a low limit but it only goes down to 110 degrees. ( No cold start option)

Once again thanks to everyone helping my understand Partial ODR and Boiler Protection.
 
  #16  
Old 06-20-09, 08:14 PM
rbeck's Avatar
Member
Join Date: Jul 2007
Location: United States
Posts: 2,675
Likes: 0
Received 56 Likes on 46 Posts
L7248C is a cold start electronic aquastat.
 
  #17  
Old 06-21-09, 07:50 AM
X
Member
Join Date: Nov 2005
Location: USA
Posts: 2,455
Likes: 0
Received 0 Likes on 0 Posts
Maybe start at 140, but watch the boiler run cycles, see if you get condensate forming in the flues, and go down from there. The lower you can go, the better. Theoretically, oil-fired appliances don't start to condense until 113-115F.
 
  #18  
Old 06-21-09, 10:48 AM
B
Member
Thread Starter
Join Date: Jun 2009
Location: United States
Posts: 14
Likes: 0
Received 0 Likes on 0 Posts
Thanks again to everyone for educating me on the best practical enhancement to my current heating system in order to provide conform and fuel savings. My next task is to cost out all components including installation.

Hopefully my boiler will last until 2019 (15 years old), then I go a do another heat load and switch to something like the Burnham ES2. Its a cast iron natural draft gas Boiler that requires little to no maintenance. It accepts 100 degrees return without any flue condensation issues. The rep also stated that their high end mod/con boilers require year cleaning and operating them
at temperatures over 140 degrees cases their efficiency to drop because your no longer condensing. (Makes sense)
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: