Adding Radiators to Existing Loops


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Old 02-17-16, 07:42 PM
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Adding Radiators to Existing Loops

Hi all: I have seen some of the online calculators for estimating radiator lengths, but they don't seem to fit my needs. I have a one-zone system with 4 loops. One room in my house is consistently 4-5 colder than the others, and radiators in the others are already closed. I would like to add heat to this cold room to better balance the house.

I have been tracking temperatures of my system. Supply is at 200 currently, and though the total temp drop is only 11, the loop I would like to expand already drops 20 as it has the most radiators (34 linear feet, ~21,000 BTU) on it. The cold room has 10,000 BTU (17') of radiators already.

Knowing I'd like to warm the room a few degrees, and knowing that I will be working with a slightly lower water temperature, what's a good way to estimate the required BTU to add? I am looking at adding a Runtal wall panel radiator, so I can effectively choose whatever amount of BTU I need. I would rather be conservative, but don't want to cook myself by drastically overestimating heat loads either. Any resources you would recommend?
 
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Old 02-17-16, 08:02 PM
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Need more info..

What size are rooms?

Thats alot of rad length you have. Something maybe dont add up..

Why a 200F boiler temp?

Make and model of boiler please.

4 zones you say? Circs or zone valves?

How many total ft of rads and how many on each zone?

What are the return temps to the boiler?

Do you have a bypass installed.

Does the boiler ever reach 180F or does it struggle to make temp?
 
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Old 02-17-16, 08:50 PM
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The room in question is 18'x10' but has significant window area and also connects to the entryway, which is poorly insulated with a door. The room is an addition to the house. Poor insulating in walls and floor has resulted in significant leakage and heat loss in this specific room compared to the original house, and I'd rather add more heat than tear down the walls to air seal/insulate.

4 zones/loops, but only one circ pump. Manual valves only. 4 loops have 34, 31, 30, and 28 feet of radiators, respectively.

Return temps to boiler are 190, only a 10 drop, but the loop I want to expand has a return temp of 180, a 20 drop.

200 boiler temp is a recent discovery - the boiler is set to 190 and the dial thermometer reads 190, but infrared thermometer is showing 200 when scanning black tape around the supply pipe. I may turn this down if needed, but would want to be sure my thermometer is accurate.

Boiler does not have trouble heating up. It is oversized - 112,000 BTU rated output but I only have 120 total feet of radiators, or 74,000 BTU (600 BTU/ft) demand. Boiler is a Lennox CWB-5D.
 
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Old 02-18-16, 03:46 AM
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4 loops have 34, 31, 30, and 28 feet of radiators, respectively.
Is this sq ft of radiation?


With a drafty room and on the high end a 18x10 room needs about 6300 btu of radiation.

Read here and what rads do you have..


http://www.columbiaheatingsupply.com...ty%20Guide.pdf

You may be better off to get blown in insulation first and weather seal best you can before adding rads IMO...


and radiators in the others are already closed.

You mean its so warm in other rooms that all reds are off in there? Whats heating those rooms?


sry for questions but I am just trying to understand what you have and what may be the real issue...
 
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Old 02-18-16, 11:24 AM
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Sorry, I wasn't clear.

4 loops have 34, 31, 30, and 28 feet of radiators, respectively.
Those are for linear feet of standard baseboard slant fin in each zone. Various rooms have different lengths of slant fin, but this is really the only room which is cold.

You mean its so warm in other rooms that all reds are off in there? Whats heating those rooms?
I have closed the slant/fin vents on the baseboard radiators upstairs to limit their heat output.

I have investigated blown-in insulation and air sealing, but the reality is this odd little addition to my original 1920s house was done in 3 phases over several decades and needs floor & wall insulation. It would have to be gutted to studs inside, and re-sided outside (to air seal) to fix properly. It's frankly cheaper to buy a wall panel radiator and add heat and spend a few bucks a month on the gas. Also by adding heat to this room, I can turn down my thermostat overall (since I only have one for the home), which is left couple degrees higher than normal to keep this room comfortable. I could also eliminate the 1000W of electric heat I use as well, which has high operational cost compared to gas. This room was terribly constructed and leaks like a sieve.

I am trying to estimate the BTUs needed to bring up the room 5 because I know that the 1000W heater = 3,400 BTU, and it is not enough to overcome the heat loss.
 
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Old 02-18-16, 11:48 AM
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Can you take a pic of your boiler? I would like to see the piping...

OK so cast iron baseboard... OK..


I am home for lunch and will post back later with suggestions......
 
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Old 02-18-16, 01:45 PM
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A couple of photos of the boiler are below. I actually have an entire separate thread here trying to better understand the oddities of my system. Some additional research suggests this is a Dunkirk PWB boiler then sold by Lennox. The link below is a PDF brochure. 99% sure I have the Dunkirk PWB-5D. Input MBH and Heating Capacity MBH matches.

www.dunkirk.com/sites/default/files/1683_0.pdf

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Also, to be clear, the baseboards aren't cast iron. They all look like this:

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Old 02-18-16, 01:49 PM
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Also, to be clear, the baseboards aren't cast iron. They all look like this:
LOL...

OK

How many feet of baseboard in the room in question..?
And your mesurment is element only right? Not the covers... ..

Sometimes the covers are say 10 ft but there is onlt 5 feet of element under them..

And all the fins are straight? And free from dust and furnitiure in front of them?
 
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Old 02-18-16, 02:00 PM
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I just edited my post below to include a link to a brochure of my boiler. It's actually a Dunkirk resold by Lennox.

17' of actual element in the room. I have taken the covers off to inspect & straighten fins, as well as clean them.

Our entry hall joins this room and is a major culprit of the heat loss, as there is no door separating the room and hallway. As a test, I strung a curtain across the hall and temps in this room went up a few degrees, and the hallway dropped 10. I am sure constructing a door would improve results further, however, my wife really doesn't want a door there, which is one reason I am investigating adding heat instead. Also, I know there are other leaks and poorly insulated walls based on thermal imaging, so while building a door would help, it would not 100% resolve the situation.
 
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Old 02-18-16, 02:55 PM
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Is the element 3/4" diameter.
What is the height of the opening from bottom of front cover to the top of floor/carpet.
 
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Old 02-18-16, 03:52 PM
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If we start with a guess that heat loss will be less than 25BTU/sqft
1800 X 25 is 45,000 BTUH
installed radiation 61,200 - 73,200 BTU/HR (510 - 610 BTU/HR/FT)
Dunkirk PWB-5D output DOE 113,000 BTUH

Q:What is the linear feet in the addition and what is the square feet of the addition + hallway.
 
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Old 02-18-16, 04:03 PM
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10x18 room needs 6300 btu's with the real drafty calculation... ( normally you would need 4500 btu of baseboard )

With that said you have 17ft there already... Thats 9350 btu...

Seems something wrong .. That 17 ft if all element should heat the room you describe..
 
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Old 02-23-16, 07:20 PM
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The room(s) in question are an addition to the original 1920s house. In fact, the room(s) are 3 separate, small additions joined together into one space from over the decades. It's really 3 separate spaces from a exterior framing standpoint, though there are no interior walls or doors between them. This piecemeal construction only adds to the leakiness of the overall addition. The main room is 11.5'x17' with 17' of element. The entry hall (back door) is 3.5' x 11.5' and has no heat. There is also a nook that is 11.5' x 8' with 6' of element. Lastly a small bathroom connects to this space, though it does not touch any exterior walls, it adds another 4.5'x3'. These areas are all separated from the original house except for a couple of door-width openings, so there is not a ton of air flow between the original house and this cold space. Overall that is 341 Sf with 12,650 BTU, or 37 BTU/SF. I understand this already matches the need for a drafty space. This is compounded by the fact that basement access is also to this room, with no door, and basement temps are 58-62 in winter (unheated). So any air drawn up cools this room further.

The thermostat is NOT in this room. My theory is that the system heats up the thermostat room too quickly due to a design imbalance. The thermostat room is 11'x12.5' with 12' of element, for 48 BTU/SF. Upstairs is even more unbalanced - the master bedroom is the worst with 60 BTU/SF, for example. Obviously, even with slant fin vents closed, the upstairs gets hot. Original house is also less leaky than this cold addition. Less windows, no doors, etc. It's simply poor design.

So I figured I would add heat to this cold space to make it closer to the 50-60 BTU/SF the rest of my house is, to help balance the design loads per room. This may have a negative result in short cycles with the boiler.

I suppose, thinking this through, I could also try to reduce the heat loads in the rest of the house. I am not sure how to go about that though. The slant fin vents are already closed. I have read I can wrap element in aluminum foil to reduce output further, but do not know what to use for a BTU/ft for element wrapped in foil, or if that even works. I would like to avoid cutting fins off, for the moment.

In theory, reducing heat output elsewhere would make my cycles longer and introduce more heat to the cold space (proportionally) compared to the rest of the house. What are your thoughts? Sorry for the rambling post, I am thinking this through out loud.
 
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Old 02-23-16, 07:38 PM
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Second thought - another reason I was considering adding heat, was because I only have a 10 drop between supply and return water temperatures. I suppose I could try turning my pumpdown one speed, but that's almost an entirely separate issue
 
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Old 02-25-16, 03:29 AM
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If I understand your system ( I don't ) there are four circuits with 3/4" copper returns.
Circuit flow to move air in downward piping, for 3/4" Cu @ 2.0 feet/second = 3.2 GPM
System flow at pump: 4 X 3.25GPM = 13 GPM
UPS15-58FC/FRC speed 3 ( 5 feet of head @ 14 GPM, 5.0 feet of head @ 13 GPM, and 6.0 feet of head @ 12 GPM w/check valve.) The pump is working very far from the middle of the curve.
Leave the pump on speed three.

Adding radiation reduces short cycling, removing radiation, or reducing system design temperature, or zoning, or insulating, increase short cycling.

To balance the house re-size the terminal units or change the design temperature to match the heat loss or go to multiple zones.

Resizing the system, feet of active element if down sizing Radiation in ft = (Btuh required) - (Btuh installed) / (radiation Btuh/lineal ft), ex. (3000 Btuh) - (6000 Btuh) / (550 Btuh/ft) = (-3000) / (550) = (-5.45 ft). (not including residual output from covered fins.)

Cover fins with a "hat" of aluminum flashing or foil.
Bare tarnished copper 3/4" Heat loss BTUH/ft 9@10F, 17@120F, 30@150F, 45@180F, 61@210F
 
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Old 02-25-16, 06:31 AM
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Thanks. Your description of the system is accurate. It sounds as though you would recommend reducing radiation via aluminum foil in warm rooms, versus adding radiation via additional elements in the cold room. Is that correct?

Also, is the assumption of head simply based on the size of my system?

Lastly, how does reducing radiation increase short cycling? If I have reduced radiation, shouldn't the system pump for a longer amount of time to maintain temperatures?
 
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Old 02-25-16, 06:43 AM
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Actually, I think I answered my own question regarding cycling. Reducing radiation will result in longer pump cycles, because the system will call for heat for a longer time. But, it will result in shorter boiler cycles, because the temperature drop is lessened. Is that correct? In design, are you typically worried about pump cycles or boiler cycles?
 
 

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