Help me understand...

Tom_133

Ok, so as I posted a few months back that this past summer my wife and I purchased a 70 year old house. It has FS-A Convectors in it. As is normal they are grossly over sized. I also installed 2 Buderus wall panel heaters Model 21 (kitchen/bathroom/. These I also oversized so I could run a much lower water temp.

My goal was to just allow the boiler to run 24/7 and work that outside reset. Well, goal has so far been met. I am running at a .66 slope curve. Which means that this morning at 12 degrees outside my rads were at 131 and satisfying my 70 degree indoor temp.

Ok, so my problem is the boiler I have (NTI FTVN 150C a freebie) only drops down to 15K and it will just chug along MOST of the time and never shut off. On average my water temp will be 125. We average 20-30 degrees outdoor where I live with the occasional real cold week even seeing down to -20 air temp.

I am trying to see where allowing the boiler to burn 15k all the time is better than bumping it up and maybe being off for an hour or so? I know I can get 1 hour on 1 hour off if I fiddle, but not sure whats the best for efficiency and longevity on boiler.

The house has bad windows and will probably get tightened up next summer. Which will allow a drop in the slope!!

Robert_25

Tom_133 said:

Ok, so my problem is the boiler I have (NTI FTVN 150C a freebie) only drops down to 15K and it will just chug along MOST of the time and never shut off. On average my water temp will be 125. We average 20-30 degrees outdoor where I live with the occasional real cold week even seeing down to -20 air temp.

How is that a problem? If the boiler runs continuously and your house is comfortable, you have done better than many!

Tom_133

Robert, not a problem, I just want to understand how 24/7 is more efficient? I cant see it in my mind, therefore I cant grasp it. Im not worried about the Kwh of the pumps and boiler running, thats pretty minimal. I just cracked open the modern hydroponics to reread condensation what it is and how we get efficiency from it.

PC7060

The independent variable in the equation is amount of BTU required to keep your home comfortable. For any given day, the required BTU will be the same regardless of boiler run time; ie short hot runs versus low temp long runs. The only thing you can impact is comfort and efficiency. And in most household that is a non-negotiable value set by the power that be. 

With a condensing boiler the lower the return water temperature, the more efficient the boiler will operate.  ODR with boiler SWT curve tweaked to supply the lowest temperature supply water will maximize the time the boiler is operating in condensing mode.  

If you disable the ODR or tweak the curve to increase the SWT the boiler will run shorter time but at lower efficiency (more wasted energy vented out of the house). Comfort will also be impact since the average temperature will swing up and down based on boiler operating cycle.
 

So the ideal curve is one is that provides the lowest continuous BTU required for the current day/time with the lowest return water temperature thereby optimizing boiler efficiency and comfort. Fingers crossed! 

Zman

I like to think of it as city vs highway driving.

PC7060

Good way to think of it @Zman

@Tom_133 - Regarding energy capture from condensation; that is a function of the Latent Heat of Vaporization occurring  in or out of system when energy flows during the change of phase.  

The change is exothermic when the system releases energy such as when when the H2O vapor produced during firing condenses from gas to liquid when exposed to the return water through a heat exchanger. The lower the return water, the more energy is captured.  

Since the return water is warmed by this process the boiler was less work to do to produce the desired SWT so less gas is burned. 

This site is a good reference for the topic.

https://norenthermal.com/resources/phase-change-technology/?lang=en

Jamie Hall

Agree with all of the above. Your very best investment will be tightening up the house and doing as much insulation as you can. One word of warning, though, on the windows. From that age, I can well see that the existing windows could be bad. However, I would suggest investigating high quality storm windows (either inside or outside) as an option. But if you do decide to replace them, insist on top of the line replacement windows. They aren't cheap, but mid to low line replacements are cheap in all senses of the word, and you will be disappointed.

PC7060

Yes, agree with Jamie.  We put high quality some windows on our old house. Very clean look and really help with drafts and provide protection for the historic windows. 

Insulation and airsealing are the best long term investment to reduce energy costs and improve comfort. 

Tom_133

So you guys have got me thinking. As for the air sealing, I went to work on that early and its seems to be paying off. I do have storm windows, and they are ok. I have 2- 60x80 single pane picture windows that I got interior storms, and plastic on, and they still are condensing. Those I plan on changing next year.
I may want to do a better storm though that may freshen up the exterior look as well.

Honestly the place is 1500 sqft above ground and if heat, hot water and gas cook top are less than a 1000 gallons a year, I may not whine TOO much.

Im starting to understand the condensing component more and why the return temps need to be low. This helps me to explain it to others more clearly and not just spitting out facts, and rules of thumb.

Its kind of a bummer that i piped the boiler primary secondary, this keeps the return temp to the boiler 10-15 degrees higher than the return of the system. I feel its better for the heat exchanger, and longevity of the system. Oh well, its 30 outside now, and its at 118 water temp!

Thanks all, for the earlier observations.

Jamie Hall

Condensing may be very hard to cure, depending on your interior humidity. Not that it can't be done -- it can -- but it requires that there be a very tight seal between the inner and outer panes of glass which is not thermally conductive, and that the air -- or whatever -- in the space between panes be very dry. This really is one area where the top of the line windows obviously and visibly outperform mid line and low line windows. It is also, unhappily, one area where even the very best windows have a limited life.

pecmsg

Condensation on the windows could be due to not enough air changes. Get a blower door test performed. 

Tom_133

Its just a poor single pane window. I will send them packing next year when its not so cold to have a massive hole in my house!

Hot_water_fan

Another factor is that for the same return temperature, the boiler is more efficient at lower modulation, as more condensing can happen (I think it has to do with surface area of the heat exchanger when compared compared to the amount of exhaust gases). 

mattmia2

With storm windows the furthest in window needs the tightest seal then progressively less as you move out so the dry outside air keeps things below the dewpoint in the intermediate layers.

If it is condensing on the inner storm then both of the outer seals are too loose. try rope caulk or temp weatherstripping tape on the primary window.

hot_rod

In a perfect heating system, the boiler would fire on the first day of a heat call and modulate to the ever-changing load without ever shutting off. Any, all cycling is wear on components fans, gas valves, relays, etc.

Jody at Viessmann has some excellent slides showing how the condensing plays into efficiency. A large 150K heat exchanger firing at 15K should be very efficient, lots of HX surface exposed to that small burner modulation should really condense, as @Hot_water_fan mentioned.

Comfort is usually the best at constant circulation also. The run cycle you describe is what we all strive for, let it rip.

The building shell dictates the energy, keep on upgrading that.

JakeCK

To help with condensation on the windows look for that bronze spring weather stripping. A lot of old window and doors had it haphazardly installed and then painted over and abused. But if installed right, and kept clean of paint and debris it looks amazing on old weight and pully windows and can really button up the window. It also allows it to slide up and down better. instead of painted wood on wood(and modt likely lead paint) you'll have painted wood gliding on bronze. Much smoother. It will also work for casement windows and doors. If you have non-operable picture windows getting fogged up find out where the interior air is leaking in at. There is no reason for those to be leaky.

I also want to add that replacement windows will NEVER have a positive ROI. nada, zip, zilch... The issue is that just about every modern window on the market is designed with a 'usable life'. They will about fall out of the house before you recoup your investment. If all you're after is saving money, look elsewhere. For comfort weather stripping and storms can get damn close to new triple thermopane windows. My front windows I completely took apart and restored, back when I was younger and had more time. New storms, wood sashed removed and stripped of all paint. new putty, rope latches and handles... They still look darn good 10 years later. Our couch sits in front of those windows. I love laying there watching the tv above the fireplace with the snow falling in the winter. I don't feel anything even resembling a draft. Now ask me about the 2 vinyl pocket windows in the master? I'm about ready to kick them out of the wall. And they'd probably fly too if I tried. Garbage.

PC7060 said:

Yes, agree with Jamie.  We put high quality some windows on our old house. Very clean look and really help with drafts and provide protection for the historic windows. 

Insulation and airsealing are the best long term investment to reduce energy costs and improve comfort. 

Those storms look amazing, where did you get them from?

Tom_133

Thanks all for the comments. I knew it was a good thing to make it run, and run, and run. Just couldn't explain it well to others. I got the concepts a bit more clearly now.

Just to reiterate, the only condensation I have on windows are on the single pane 60x80 window no exterior storm. I have plexiglass interior "storms" trying desperately to add a little air sealing but it doesn't help all that much. So I put shrink plastic on one of them to see if it would help, but not much if at all. I could get out the peel n seal, and seal up the around the plexiglass inner "storms" to make them a tighter seal but not sure how much it would help.

mattmia2

Where is the condensation?

Robert_25

Tom_133 said:

Thanks all for the comments. I knew it was a good thing to make it run, and run, and run. Just couldn't explain it well to others. I got the concepts a bit more clearly now.

Just to reiterate, the only condensation I have on windows are on the single pane 60x80 window no exterior storm. I have plexiglass interior "storms" trying desperately to add a little air sealing but it doesn't help all that much. So I put shrink plastic on one of them to see if it would help, but not much if at all. I could get out the peel n seal, and seal up the around the plexiglass inner "storms" to make them a tighter seal but not sure how much it would help.

Do you have a humidifier in the house? Gas cookstove?

Jamie Hall

Unless you manage to get a really tight seal, either inside or outside, a single pane window is going to condense unless you keep the interior of your house absurdly dry. It just is. Adding a quality storm window panel -- either inside or outside -- and making sure it is tight will limit that. It may not eliminate it completely, but it will go a long way. It's as much a matter of making the seals -- particularly on the inside -- as tight as you can.

Tom_133

Jamie,

That is it exactly.

PC7060

@JakeCK - thanks those are “Velvalume” built by West Windows.  

https://www.westwindow.com/windows/storm-windows/velv-a-lume-storm-windows

The windows are approved by the US National Park service along with our local and state historical preservation agencies. 

The windows are designed to fit within the slot for the original wood storms which are long gone. The floating frame design allows the windows to fit and operate smoothly even in crooked frames.  

JakeCK

Do they have a screen on them?

nicholas bonham-carter

If they were available prepainted in black, they would look better.too.—NBC

PC7060

JakeCK said:

Do they have a screen on them?

The windows come with screen installed on inner tracks. Those windows have the screens removed. 

This page has a cross section drawing of the windows. 

https://www.westwindow.com/content/westwindow/uploads/PDF/windows/velv-a-lume/velvalume-specs.pdf

PC7060

nicholas bonham-carter said:

If they were available prepainted in black, they would look better.too.—NBC

Well, I’m not sure my wife would agree on the black color for our house. She was pretty careful in her color choices. 

Their standard colors are white, bronze and tan but they may do custom colors for large projects. 

Jamie Hall

I have used "Innerglass" inside storm windows for very old houses -- very successfully. https://stormwindows.com/

Tom_133

So after a few months here are some results.

The house will stay at temp (70) with the reset ratio at 0.6 which means at 30 degrees outside the swt is 116 or so. The house never feels warm, it is 70 but drafty. My current solution is to shut the doors upstairs due to the junky replacement windows causing a bit of a chimney effect and making the first floor heat the 2nd. This has helped on warmer days (above 38) because sometimes the boiler will shut off for a little bit. I know, I know, you guys would like the boiler to run all the time on low, so would I but according to the fuel bill this is not working as efficiently as I would like. I realize I am using a high percentage of the fuel I am burning, condensing a gallon or more a day, but sadly I am burning 180 gallons in 35 days thats heat, hot water, and just a cook top for 2 people. Our winter has been a bit on the warm side as well.

I typically wouldn't care, but I only pre bought 1000 gallons and it feels like I am going to burn through all of that by March!! Which means our friends at LP company will hammer me on the extra gallons of fuel use. I based my quess on the use of oil in the house over the last 2 years before I bought it, and did some insulating. They only burned about 650 gallons of oil a year. For heat and hot water.

My foundation is partially exposed and that is causing me some loss, I will be insulating that at some point. I have poor windows with storms, but according to my thermal gun they are not terrible. I have very little insulation in the walls downstairs, since its a 1949 vintage house. Early fiberglass and not much of it.

Today I am going to bump up the boiler to run a bit warmer this will make the bride a bit happier, but I am bummed, its only a 1400sqft house that will take more than a 1000 gallons of LP to keep warm. Next will be a wood stove in the basement!

Am I looking at this wrong, or was I just a little fool hearty on my estimation of LP use?

Thanks all

Tom

Jamie Hall

I'm not sure I'd say you were fool hardy... a little optimistic, perhaps (1,000 gallons of LP is pretty close in terms of heating value to 650 gallons of oil, after all) -- but most of us are. You are not much off what Cedric burns for a 7,000 square foot house, on a square foot basis.

A wood stove is wonderful, if you can get wood inexpensively and are young enough to do it. However, you might see what can be done about better insulation (quite right about insulation in immediate post war houses!), as that would also help.

hot_rod

It’s really the building shell that dictates the amount if energy used. Upgrade as much insulation, weatherstripping, air gaps as you can

If You can do a before snd after blower door test, that would indicate the changes to infiltration, which is a huge energy robber.

GW

Tom wow you are into this stuff, hats off😀

seems like you have your heating system covered pretty well. Trying to get good thermal envelope advice on a heating page is touch and go (as noted by your single pane glass comments above). Most of us are heating guys.

Many years ago I did some thermal envelope training, I have a blower door, duct blaster, IR camera, went to Flir training facility twice, I have a basic understanding.

One angle you may wish to ponder on: I have installed lots of high-efficiency boilers in the last 20 years. I’ve had a few high heating bill complaints. I don’t have exact science, but my simple understanding is the people that were complaining had poor thermal envelopes. At face value that may seem kind of like a “duh” statement. 

Think about it this way, think about your main mission in life is keeping a big balloon inflated. It’s the only job you have. In my fictitious example, there is a hole in the balloon. It’s a fixed size, until somebody else comes along and makes the whole smaller. That’s a different conversation.

Anyway, you have two choices. Option one is to somehow make your lungs exert a certain amount of pressure, keep blowing that balloon 24/seven. Option two is to give it one big breath, empty out your lungs, every hour or two.

Of those two examples, which is more work? Kind of makes you think about it a little bit. Is outdoor reset always the best answer?

You have propane, it’s more difficult to track fuel consumption.

If you have the time and energy, I might suggest changing your curves, hit your house with more heat, try getting away from constant circulation. See what happens. 

I appreciate the notion that the boiler will run more efficiently at lower water temperatures. But that ignores some of the building science rules that cannot be disobeyed. The Boiler’s job is to produce energy. The house, its job is to keep the heat from getting to the great outdoors. The boiler and the house, they have no idea the other one exists.

Your comfort level may decrease a little bit. But your heating bills may go down.

Or, get a good crew in there and tighten up your house. ( now THAT is a “duh” statement 😀)

Tom_133

Thanks for the comments, and all make good sense.

They did come in and sprayed sills and attic spaces with foam in 2014 and this year I put another 6" on the existing cellulose in the attic and filled sills with Roxul as well. I think step 2 will be foam board on the basement walls. Try to warm it up down there, and with a little wood stove that should help.

I am a penny pincher by nature (or nurture) but I kick myself for not locking in 1500 gallons of LP!! Typically when you need to buy more in spring that really WHACK u per gallon. I will do some work and share results in a month or two.

Robert_25

Tom_133 said:

Thanks for the comments, and all make good sense.

They did come in and sprayed sills and attic spaces with foam in 2014 and this year I put another 6" on the existing cellulose in the attic and filled sills with Roxul as well. I think step 2 will be foam board on the basement walls. Try to warm it up down there, and with a little wood stove that should help.

I am a penny pincher by nature (or nurture) but I kick myself for not locking in 1500 gallons of LP!! Typically when you need to buy more in spring that really WHACK u per gallon. I will do some work and share results in a month or two.

Tom, other than the drafty windows you mentioned you have taken care of the low hanging fruit. A woodstove in the basement will warm up the floors and make the house feel much more comfortable - go for it.

hot_rod

Robert_25 said:

Tom_133 said:

Thanks for the comments, and all make good sense.

They did come in and sprayed sills and attic spaces with foam in 2014 and this year I put another 6" on the existing cellulose in the attic and filled sills with Roxul as well. I think step 2 will be foam board on the basement walls. Try to warm it up down there, and with a little wood stove that should help.

I am a penny pincher by nature (or nurture) but I kick myself for not locking in 1500 gallons of LP!! Typically when you need to buy more in spring that really WHACK u per gallon. I will do some work and share results in a month or two.

Tom, other than the drafty windows you mentioned you have taken care of the low hanging fruit. A woodstove in the basement will warm up the floors and make the house feel much more comfortable - go for it.

You will need some combustion air for the wood stove. Ideally something that could close off when the stove is not fired or you bring more cold air into the home.

I think ME runs the combustion air duct down into a 5 gallon bucket to act as a thermal stop for cold air. I've never tried that, makes sense the cold air in the bucket would help stop some wind blowing in?

Or some motorized damper that would activate by the stove somehow, maybe a thermal switch?

Robert_25

I have a drop of 4” pvc bringing air into my basement about 12” off the floor.  I have never heard of the bucket “trap”.  Are there specific dimensions you need to use?

JUGHNE

Just a standard 5 gallon plastic bucket for the pipe to poke into.
I allows the air into the basement and then will diffuse it with the room air as it comes up out of the bucket.

Also it will catch any condensation that may come down the pipe from outdoors.

4" is not very large for combustion air but still better than nothing.