Fin Tube and Tekmar 361

VDBLU

My house has 228 feet of 3/4" fintube with 52 2.5" X 2.5" fins. Looking at the chart for a comparable Slant-Fin radiator my radiators should produce 760 BTUH per ft or 173,000 BTUH for the house at 3GPM and 180 degrees. A heat loss calculation on the house shows a loss of 134,000 BTUH. The same chart also shows that the BTUH per ft at 1GPM and 160 degrees is 570 or 130,000 for the house.

I have a new cast iron condensing boiler sized to the house. I am planning to use a Tekmar 361 injection pump controller to control the system and run the system loop at a mix design temp of 160 degrees to get the radiator's output to match the requirements of the house. The 361 will also do outdoor reset and boiler protection.

Does this sound like a valid approach to dealing with the oversized radiators and do you see any pitfalls to avoid?

Thanks,

Mark

Gary Jansen_4

Without knowing your system piping

I'm a little confused as to why you would use an injection controller on your system. You stated you have a condensing boiler, no need for boiler protection. A Tekmar 261 would be a more appropriate control for your system. The 261 will give you outdoor reset,(partial or full) depending on your system needs, boiler protection if you need it, pump output and control, wwsd. The 261 as well as the 361 are on/off controls. Would or could your boiler use a modulating control instead? Tekmar 263 or 270. 

VDBLU

Looks like I'm confused on the condensing part

Gary-

Thanks for taking the time to respond. I was wrong when I said it was condensing. It's a conventional cast iron boiler (Crown Aruba to be exact).

My system piping is 2 zones of fin tube. The upstairs zone is one loop at 83ft of radiators controled by a zone valve. The downstairs zone is two loops controled by one zone vale. The south loop is 68ft. The north 77ft.

Currently installed is a B&G Series 100 circulator and a 35/40 year old Hydrotherm 300,000 BTU boiler.

I've been playing with Taco's HSS if you use that. I've attached the file if you are interested.

Thanks,

Mark

EricAune

Pumps

If you change the system to injection mixing, which sounds like a solid approach given the emitters, you will then need three circulators.  (1) Boiler circ. (1) Injection circ. and (1) system circ.



If the B&G sizes out right for the baseboard you can reuse that.  I would prefer a Taco VS for the injection.  The boiler circ will be much smaller than the 100, say maybe a 007.  Consider a Delta "T" circ. for the system to maintain a constant delta "T" throughout the system which will increace the system efficiency.

VDBLU

Pumps

Eric-



Thanks for your repy. I'm not planning to reuse the series 100. It sounds like a meat grinder, and it appears to be too small while drawing more electricity. I've calculated the system to need 13.4GPM at 15.18ft of head. The series 100 curve tops out at 8ft. I think the system currently has better than a 20 degree temp drop. Do you think this could explain the noise?



Taco HSS is suggesting a 0013 for the system pump. I've noticed the DeltaT circulators on their site and like the idea of not needing to buy a pressure balancing valve. Probably less work for the installer (me and my HVAC tech brother) as well.



I just ran the Tekmar e021 calculations for the injection and came up with a Taco 003 or a B&G NRF9. Any preference? Also you mention a VS pump. I was under the impression that the Tekmar control would hook up to a standard wet rotor circulator. I don't see a VS pump without some type of built in controls unless I'm missing something? (Which is possible and is why I'm here.)



Finally, the boiler came with a 007. It looks about right for the primary loop as you suggested.



Thanks again,

Mark

EricAune

Some more info on some puming options

I have been partial to any pump or control that is green in color for a while, so I am biased.  The Tekmar will control a standard pump.  I like the 003 option over the B&G because of the simple stater (cartridge) replacement option. 



There are also some injection pump curves included here, check it out. 





http://www.taco-hvac.com/uploads/FileLibrary/OM02.pdf

CMadatMe

Why make so complicated

Small project requires easy install and control. Conventional cast iron boiler, I would use a Taco RMB. All my injection piping is done as are both my injection pump and system pump. And it will handle the load based on your heat loss. It also will give you boiler protection. KIS all the way. Don't be worried about the overrated house that's a good thing. Nobody ever said that you must maintain a 20 degree delta t

EricAune

Chris, I agree to keep it simple

But, the RMB is only rated for transfer of up to 120,000 Btu/hr.  Heat loss at design is quite a bit higher.  Hate to see everything work fine until it dips below that average temp. Just a thought.  Sometimes its not always the best to keep it simple.

CMadatMe

I agree

on the 120 but I would recommend that he have a pro revisit that heat loss. Based on his loss his house is somewhere the the 5,000 sqft range or it is uninsulated with crappy windows and in the 3,000 sqft range in a zero design climate.

He has plenty of board to increase his delta t out to 30 providing he protects the boiler. This application drools for a mod/con. He needs to size those pumps based on a 30 not a 20 delta t. He stated in his post he needs 13.4 GPM but also states that his delta t is larger than 20 so he is contridicting himself. Can't come up with that 13.4 unless it is a 20. 

VDBLU

Heat Loss

Chris



The house is a 2,400 sqft bungalow built in 1922. Brick. There is very little insulation and the windows are the originals. The design temp used in my city (Decatur, IL) is -5. Looks like you called it. I had one contractor's supplier calculate the heat loss, and 2-3 others eyeballed it at the same amount. If you really think it needs redone I can get out the measuring tape and plug it into TacoLoad.



I will try the Taco HSS model  with a 30 delta T. I got the 13.4 by dividing the heat loss by 10,000. Your saying the larger delta T will give me a lower GPM requirement? I know I've seen a calc for the 10,000 rule of thumb. I'll have to look it up.



I also agree that the mod/con would be really cool. It would also let me move the boiler to a better place in the basement. However I'm wanting to do this economically because of neighborhood issues and the value of the house if we decide we have to move. The mod/con would cost 10% of what I can sell the house for. So far I'm in for about $1100 for the boiler and control. Pumps and pipe may get me to $2000. I'll get that payback in a couple years hopefully.



Thanks for the discussion.



Mark

VDBLU

The RMB is neat but

Chris and Eric-



I've looked at the RMB and I think it's just a little too small. As you mention the heat transfer rating is smaller than my heat loss and I also don't think it can overcome the head loss. My longest loop is 253' of 3/4" copper (I'm counting the baseboard length in that as well). If I calculated it correctly that is 18' of head.



I really appreciate having someone to bounce these ideas off of.



Mark 

CMadatMe

GPM and Head

Based on the info you are providing and I may be a little off but here is what I come up with for a system pump.

20 degree delta t would require 13.4 GPM at 15.16 ft of head = Taco 0011

30 degree delta t would require 8.9 GPM at 15.16 ft of head = Taco 0014

This is all based on you delivering 134,000 btus, the longest loop length you provided and that you are zoning with zone valves.

Personally I would use a Grundfoss 26-99 Pump. That will cover both curves with the turn of a dial.

The Steam Whisperer (Formerly Boilerpro)

Heat loss...

I'm quite a bit north of you and design for 0 to -5 (Moline).  According to my older ASHRAE data, Springfield design is +2F( just west of you)    This would give you a conservative design heat loss for a two story brick home (1200 sq ft/floor) of only about 92,000 btu/hr (with only 2 inches attic insulation).  Also brick homes have so much thermal mass, that the middle of the night 2F is not really felt inside because the brick mass flywheels the heat over a couple of days.  Heat travels through masonry materials at a rate of about 4 inches per day, so if you have 3 courses of brick, it takes 3 days of continous 2F weather before the heating system actually sees the load.  A boiler with an output of about 80,000 would probably make more sense, particularly if you plan to add insulation to the attic. Well maintained brick homes with quality windows (even if older) tend to be very tight.



Boilerpro