Condensing with Fin tube

Mad Dog_2

that has been on its second heating season. No problem keeping up on the coldest days and condensing like crazy. I prefer the look of Panel rads to b.b., but If they want to keep the budget down and the technology high, b.b. works out well. Mad Dog

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Matt_51

Fin Tube and Condensing Boiler

I am in process of changing from scorched air to hot water heat. I want to use a condensing boiler and fin tube and run the water temp low to increase efficiency. As long as I install enough fin tube to contend with heat loss will it work?. I was looking at 120-130F at design temp for my area. I am also considering panel radiators instead of fin tube.
Is my concept sound or am I missing something?

CC.Rob_3

HO experience

I have a house full of fin-tube that was originally designed (30 yr ago) for 180F. With outdoor reset (first season) and some envelope improvements, I seem to be running at condensing return temps about 2/3 to 3/4 of the heating season.

My two reservations about fin-tube are: 1) sizing for low temps would take a lot of fin-tube. Might not be aesthetically pleasing to eat up all that wall space. 2) In this house, the practical lower limit to supply temp is around 115F. Below that, there doesn't seem to be enough "oomph" to really put out useful heat. Possibly lack of difference between entering air (65-68F) and supply temp resulting in insufficient convection. Maybe something else.

Modulation and condensing would be the deal.

Starting from scratch, I'd probably go with panel rads, but I have no direct experience with them.

ALH_4

panel radiators

I agree with Rob. Copper fin tube can work with condensing boilers, but panel radiators with thermostatic radiator valves will let you use lower temperatures more easily and will take less wall space. I am particularly fond of the VEHA panel radiators.

Ken_40

Having just built a new

home w/both radiant and HWBB (I'm the rare duck who still perceives HWBB to be less intrusive and better looking than flat panel rads) and found at outdoor design temp max. a design with 150F average (160 boiler supply-outlet) temps continues to let my boiler maintain 96-97% actual efficiency.

Since that only happened one day in the past 16 months (two winters) I am real comfy with that basis. My boiler however is oil-fired, not a gas or mod-con design

Bernie Riddle_2

another owner

With a ModCon and BB, Yes over sized is the way to go, but not to any extreme

Go to Slanfins website and they tell you what size and at what water temps you need

Best advice I can give is run constant circ> my BB [only]is only 1/4 oversized and runs down to 96° water and heats the stucture flawlessly

Uni R_3

How well insulated is your home?

I have fin tube and a modulating condensing boiler. The fin-tube was installed ages ago on a retrofit from electric BB long before I bought the house.

My home is pretty tight with fairly good insulation for the mid-70s. When installing, all calculations pointed to needing temps in the mid-150s under design day conditions. In reality it is only 140° at design day with the kitchen's heat temporarily removed (or it would be even lower). Most of the true winter here is about 30° higher than design.

I have 116' of baseboard in a 2400sf house - and 20' of that is in the crawlspace. Most major rooms have the equiv of one wall being about 75% covered. My HWBB is far from wall to wall. If you're well insulated, you won't have to go nuts on the wall coverage to stay in condensing range.

Brad White

Properly sized

any radiation makes a good choice with a mod-con. I am partial to cast iron or radiant panels (if not radiant floors)for the radiant effect (say Ahhhhh somebody!).

But even convective elements will give you that warm film of air up the walls, a mean radiant temperature to keep you snug.

Even if the fin-tube was sized at 180 degrees, the Brookhaven National Laboratory determined that there are still sufficient hours in a year -with outdoor reset properly applied- to get you below the condensing point enough to make it worthwhile.

Personally, I would size as you are and condense longer, even in the coldest weather. You are doing well!

Weezbo

i have some thoughts...

to me, the insulation and vaporbarrier integrity is a Biggie. controlled ventilation is the ticket.

the reason i say this is because despite everything and anything telling me uh uh .. i have some applications where the convector baseboard i roll very cool water temps through them.

designe is more than X= good Y=bad

there are some who might say it this way, you can indeed get too much of a good thing.

some times a Parka can keep you warm...sometimes a self drying wind breaker...to me, when you are thinking long term you want to carefully consider the course you are embarking upon..serendipitous performance is not the way to designe your heating system. when the variables are in Your favor then you might push the barrier of the "frontier"..

the designe of your home may not really be all that great for baseboard(convectors)...i happen to like radiant heat and low temps. control strategy of the moving of and distribution of BTU's is a type of fun for me...i like to dial things in so that it seems somewhat outside of the laws of Physics:) i Hate baseboard.

What about an Indirect ?...That is high heat. True...yet it can be insulated like a penguin chick the prioritization can make it a very quick and relatively painless change in a systems overall efficiency. recently i have rolled very cool water temps through radiant...it is near 35 below and turned the boilers off about 3 and 1/2 hours ago....radiant slab, has the advantage of long response time when the heat goes out for lack of fuel or electricity.

Because i type slow i posted this...

allow me to babble on *~/:)

With a modulating.....condensing boiler i could drop temps to the point that would seem unreal yet, it would still be moving and redistributing btu's . baseboard is hard pressed to do that, as it is a completely different means of distribution ...even panel rads can hang in there in severe conditions. i would think you would be dollars ahead to check all of the variables First...then consider your choice and its return on investment and its Strengths.

oh! and get a second opinion:)

remember "expensive is expensive. buh Cheap, cheap is not cheap."

Mike D_7

operating fin tube at low temps

I have a thirty year old "Deck" house with a lot of glass and original fin tube radiation.
I converted the heating system to a primary/secondary system with Tekmar outdoor reset.
The baseboard runs as low as 80 degrees (F).
Right now it's 30 degrees outside, 69 degrees inside, and the secondary is operating at 125 degrees inlet and a return temp of 110 degrees. (15 deg delta T)
The fin tube is on 100% of the outside walls except for closets and the front door.

Bernie Riddle_2

Hi Mike Don't know how you are achieving a 15* delta T!,You must have the emitter loop choked down to a crawl.

What do you think is happening in the boiler loop?.

Ken_40

It's a \"deck house\"

with lots of glass.

15 dT is not unusual at all.

Mike D_7

Delta T

Hi Wiltz,
I aways thought of Delta T as having an inverse relation to flow. That's what is happening here.
In mild weather, when the water temp in the secondary loop to the fin tube radiation is low, the Delta T goes down as low as 8-10 degrees. That's because the GPM flow is constant, but the fin tube baseboard can't pass as many BTU's per foot out to the rooms.
Ive installed a Taco variable speed pump on the secondary loop and set the Delta T to 15 degrees. I'll let you know how that works out.
The old system had a Taco 007 pump feeding all three zones at boiler temperature, and the Delta T ran close to 30 degrees.
This is a difficult house to pipe, and the main zone has too much baseboard and more els than I've ever seen.