boiler design and zones

TerrS

Hi,

 I have a question about setting up zones on my boiler. Currently I have technically have a 1 zone system, ie 1 pump and 1 thermostat, even though I have 4 supply and return lines.

What I would like to know is it possible to keep the same single pump, but add 4 zone valves to each supply line? I want to then add another thermostat upstairs and wire two zone valves to 1 thermostat and two to the other new thermostat.

Would this work?

Jamie Hall

If you do it right, it will work just fine.

hot_rod

what size boiler? Any idea on the heat load of the zones? You could end up with some serious short cycling if you micro zone and have an over-sized boiler. So a bit more info, please.

TerrS

Hmmm some of this might be tough to answer, but here goes. From my previous question about boiler sizing or right sizing as I will call it. My current boiler is 150k btu, and way over sized. We all determined around 90k would work better. So the upgrade efficiency, errr downgrade BTUs was being planned but my chimney decided it wanted attention. And $2k later I have a new flue liner and 4 dozen less brick because it was totally blocked. Which took money from the replacement. So next years plan now.

Anyhow, 3 of my supply lines are 3/4" and the main first floor is a 1" copper pipe. So my thought was for now, put main floor and basement on 1 thermostat and the 2nd floor and attic on its own thermostat. So anytime any thermostat called for heat. 2 zones would open. So that if the upstairs is cold it gets heated and vis-versa. So I was hoping to limit that short cycling with 2 zones open.

It would be much better if I was also lowering my total btu boiler size but probably will not happen this season.

hot_rod

Not a great candidate for 4 zones with that much boiler oversize. that boiler will bang on and off every few minutes with a small zone load and 150K boiler output. A very bad operating condition leading to inefficient $$ cycling and possible corrosion in the boiler and flue, from short cycles.

bburd

The basement should really be on its own thermostat, because ground temperature varies seasonally at a different rate than air temperature. The basement heating load will be lower in the fall and higher in the spring in relation to the first floor load.

IMO, short cycling is a less significant problem than an uncomfortable house. 

TerrS

bburd said:

The basement should really be on its own thermostat.....

I guess my thought was it can't be any worse than now. With one thermostat. So anytime my first floor needed heat, the 3 basement flant-fins would get some heat. The same with my 2nd floor that has 42ft of fins and the attic has 30ft of fins so put them together.

As @hot_rod said, because my my boiler is severely over sized, is that short cycling a concern? 

A few points to remember, the cast iron tank in my boiler is 6 gallons, plus factoring in my proposed configuration, I would be heating around 8-10 gallons of water depending on if both thermostats call for heat. So if both call for heat its just like it is today, let's say early in the morning and warming up the house. But the 2nd floor takes longer to warm up,  but because the thermostat is on the first floor the 2nd floor is cold. So with the addition of that 2nd thermostat that water and pump would continue to run until the 2nd floor gets warm.

I think my differential is 2 gallons of water. Which I would not think affect the cycling that much.

Thoughts?

hot_rod

Again, you need to put some numbers on the problem. A 150K (btu/hr) boiler running 8 or 10 feet of baseboard with a 4- 5000 btu/hr load is not a very desirable condition, regardless of 2 or 10 gallons of water

Most often advise from pros here it to minimize zones, combine them when we get short cycle questions, on standard non modulating boilers. A lot of short cycle questions come across HH.
You are going the wrong way.

Here is an example of what a short cycle does to an oil boiler efficiency. Not to mention possible flue gas and boiler condensation issues, and relays, gas valves or oil burner short cycling.

Is putting you equipment at risk, running up fuel costs less important than a comfortable basement? Your choice I suppose. Invest in a good CO detector also, if you do micro zone the beast

TerrS

hot_rod said:

Again, you need to put some numbers on the problem.

Yep apparently I am lost again. But here goes..

So the total system has 115ft of fins.  Between the 2nd and 3rd floors, this amounts to around 65ft of fins. Between the basement and 1st floor has the balance. Or around 50ft of fins.

This is why I would do 2 zones but 4 zone valves, 2 would be wired to one zone/thermostat and 2 to the other zone/thermostat.

This would make both zones close to each other in heating capacity/total footage of fins. Why heat the 1st floor at night if only the 2nd floor is cold.

This is a gas boiler with new stainless flue liner, but I think I eliminate some of the short cycling concerns.

What am I missing?

TerrS

MikeAmann said:

I am thinking that you spend most of your time on the main and 2nd floors. I think that you should make those one zone, and the basement and attic the second zone.

If I could get a wire to the 3rd floor, I would actually put a 3rd zone in, but at night I don't care about heating the first floor,  mainly because I have a fireplace I use to supplement my heat. However that means the furnace never runs because even though it's in a different room than that the living room the whole downstairs heats up.

So possible solutions, don't run the fireplace which will double my gas bill or find someway to make sure the 2nd floor still heats.

This is how I came up with my zoning layout.

hot_rod

so this  smaller zone will be able to transfer about 27,000 btu/ hr with that much fin tube

if the boiler is a 150 input, maybe 125,000 output

The boiler wants to move 12 gpm, your loop allows around 2.7 gpm to transfer that 27,000 btu/hr load 

keep in mind that only under design day conditions would that load be constant. So most of the time that 27,000 load will be a percentage, those days is when you will experience the worse short cycling. The fixed speed boiler trying to shed 125,000 btu into a zone with perhaps a 10- 15,000 btu/hr load much if the season

There is not an easy piping or control solution that can change the thermodynamics. Just don’t take a bad or undesirable condition and make it worse. 

The short cycling caused by zoning a grossly oversized boiler could in fact raise the fuel consumption. Additionally putting the system under a bad operating condition, condensing that boiler

You could possible get the same result by adjusting dampers instead of zoning. But the mismatch will still cause the short cycling

JakeCK

Wouldn't a buffer tank alleviate these issues? Use a delta p circulator to feed the zones from the buffer and control zone the valves with the thermostats. And run the boiler off an aquastat on the buffer? And if one really wants to smooth things out use a mixing valve and ODR on the zones.

EdTheHeaterMan

Too much thinking and not enough common sense.
1. @TerrS is thinking about getting a new smaller boiler in the next 2 to 3 years
2. Who cares if the oversized boiler short cycles and causes it to fail in the next 10 years... it won't be there then
3. Not heating the first floor at night and not heating the second floor during the day will offer some savings even if the setback is only 5°
4. Perhaps a smaller firing rate gas pressure (within the safe minimum pressure) could be used for the next 2 years to reduce the short cycling. Maybe some condensation of flue gasses will happen, but will the boiler fail in the next year from that? I believe it takes a little longer than a year of low temperature operation for that to happen.
5. many one thermostat homes with 4 heated floors get overheated on the top floors and this zoning plan will help to resolve that.

I don't see the down side of zone valves, unless there is a $2000.00 emergency every year for the next 10 years that makes that boiler stay there more than expected.

Just my 2 cents.

Go for it TerrS

TerrS

EdTheHeaterMan said:

Too much thinking and not enough common sense.

Thank you! So a few more things, the boiler will be 32 years old in December, it was 5mo old when I moved on, so I had no say on sizing and apparently the old owners took what the company sold them.

As far as efficiency. It's around 78%, my output Btu's are rated at 113k.  In a previous discussion on here, I talked about water temperature and with  165-170 degrees water I froze, but 180degree water heats the house comfortably.

This then brought up modulating boilers and everything I read states they don't work very efficiency with water that hot, because my return water only drops around 10 degrees, in my return loops, which is when the boiler fires again.

So at the end of last year, I installed a Beckett 7610 aquasmart as to only heat the water as hot as the demand requires, many days last season it was at its max of 185 degrees when our temperatures stay around 30 degrees outside.

So since an 85% efficient 90k output boiler was planned, is when my chimney had other plans, that project is now moved to next season. I am scared of my gas bills this year, Columbia gas went from .32 to .69 a therm!!!!!  So a 110% increase and I use around 200 therms per month, of which 170 of those are boiler in use.

Anyhow that still doesn't solve my cold upstairs when sleeping, so that's where the 2nd thermostat and zones came in.

@hot_rod I really appreciate the input and expertise it's helped a lot and I am learning. Or I think I am.   My thought process was how much water is circulating and am I heating. Now it's the whole system around 10 gallons or so. If I zone, I stop around 2 gallons from that total. But when my upstairs needs heat it would be able to ask for it with that thermostat.  So I didn't think it would cause the boiler to short cycle any differently than its doing today.

WMno57

TerrS said:

I use around 200 therms per month

That's because you heat your attic. Stop heating your attic.

WMno57

Forced air heating is like fast food. Hydronic heating (what you have) is like a gourmet meal. You have to wait. Unless you call the chef a couple hours before you get off work and order ahead.

TerrS

WMno57 said:

That's because you heat your attic. Stop heating your attic.

That's not as easily done, I mean yes I could cut those supply/return lines and cap them, but that extra 1.5 gallons of water, should not be using that much extra fuel.

 But I think that might have a side effect. Much of my house has been insulated as I remodeled rooms, but never made it to the attic. Because even though there is 700sq ft of walkable space in the 2 full size rooms up there,  it's 1940 plaster vintage.

So I am basically using that as a buffer between the bedrooms and roof.

WMno57

If your house was my house, I would:

• Cut and drain the fins in the attic
  
• Valve off the basement (I doubt it will freeze)
  
• One thermostat, One zone
  
• Set the thermostat to whatever is comfortable (its just a number)
  

If there were a temperature difference between the first and second floors, I would restrict the flow to the warmer floor until things balanced.
I'm cheap, thrifty, frugal (take your pick). My parents grew up during the depression. Mom was from Pittsburgh (Dormont). The only thing I would maybe buy is a thermostat that I could call in to and order up the temperature a couple hours before I left work. If you have a regular schedule, a programmable thermostat could accomplish the same thing.
Stay warm my Pittsburgh friend.

WMno57

The volume of water you are heating is not that important. More water is good. More water is more Thermal Mass which allows your home to coast through cold overnights.
If you haven't insulated the joist bays in your basement you should. Not the entire floor, just the part against the foundation.

TerrS

@WMno57 lol, that's okay I can deal with criticism. In this forum I would not dish it back like I would in person. Plus I am looking for expertise for things I didn't think of might come into play.

Lastly whatever my decision it's been this way for 30+ years. It's only in the last 2 years, with all energy prices doubling that it's getting my attention for options.

And then it's always cost Vs ROI. I can't quote numbers but HVAC people are insane for 10hrs of work. I have the skills and friends to do it myself. Just need those 4 strong friends to carry the old boiler out and new one in..  lol

Thanks!

WMno57

You could have the attic floor carpeted. That would provide some insulation.

hot_rod

here is some number crunching you can do.

Steady state will be the most efficient operation. heat output÷ energy input
you would need to clock your gas meter with nothing else running to get this number. A clean properly adjusted boiler probably runs around 84% cycle efficiency.

Cycle efficiency total output over a timed period ÷ energy content of fuel consumed over that period

Run fraction burner on time elasped time
example burner on 5 minutes off 20. 5 minutes ÷ (5=20) = 20%

In you case, using the numbers you have 27,000 btu/ hr load on design day on the smallest proposed zone

27,000 ÷ 150,000 = 18% run fraction
Use this graph developed by Brookhaven National Labs and plot that number.

notice at 30% run fraction that efficiency drops like a rock.

So if you added some internal gains into the calculation, oven running, refrigerator, lights, shower, and days below design, probably 90% of the years. You may get down in to the 50% or lower range.

A properly sized, and better yet a modulating boiler would keep that number in the mid to high 80% range.
I understand that is not in the cards for this heating season, but try not making the efficiency drop with what you have and potentially put the boiler into a dangerous operating condition.

I can't imagine any seasoned pro putting his reputation and liability on the line to encourage this operating condition. Would you?

EdTheHeaterMan

I understand that is not in the cards for this heating season, but try not making the efficiency drop with what you have and potentially put the boiler into a dangerous operating condition.
I can't imagine any seasoned pro putting his reputation and liability on the line to encourage this operating condition. Would you?

WOAH!

adding zone valves = dangerous condition.

Explain that one @hot_rod ?!?

PS. I look up to you Bob Rohr for your much more experienced than I. I only had about 4000 to 5000 different customers over my lifetime. As a trainer for a manufacturer you have access to hundreds of companies customer's. Some of those companies have more than 5000 customers. That is a much larger pool of problems to solve. So I am not saying you are wrong, I'm just wanting to know what you perceive as dangerous in adding zone valves as @TerrS proposes?

And I think of you as much older that I. Well, more experienced might be a better way to say it. LOL

TerrS

@hot_rod thanks, I have many issues lol.

 The first is last year I put my boiler in hot mode for 1 week, always keeping the water at 110 degrees, this made a huge difference in how long it took for my house to warm up in the mornings, by a factor of 35 minutes or from before when the furnace was doing cold starts. It was saving fuel because the first 20 minutes I technically waste just trying to get the water up to temperature.

With back to cold starts I am at 40 minutes before my fins Start to radiate heat starting around 155 degrees.

However because my boiler jacket isn't insulated very well , my boiler would run 5-6 times an hour for about 5 minutes each time. Which then caused me instead of around 10 therms per day, when it's cold out, to 11 therms. So it was a trade off immediate heat vs fuel spent.

My grandfather ran his boiler this way back in the 90's.

This is the conversation we got into a month or so ago, about boiler tank size 2.8 gallons on new boiler vs 6 on current. How much energy to heat the water in-order for it to do its job.

It's that car analogy, my 2 barrel vs that 4 barrel holly double pumper. How quickly can I get to 100mph and how much fuel.

My analogy to myself was boiling water on my stove, which I took as the same premise as a boiler.

 There are a few other tests I briefly mentioned before was I have ball valves on each of my zones. I did this mostly to cut the amount of water going to the attic. Just enough so the pipes didn't freeze and maybe to provide residual heat.

And never had any boiler issues.

Remember the issue I am trying to resolve is make sure my upstairs stays warmer.

Do I just move that 1 thermostat upstairs??

So my last question to you because I see zones on many boilers, is it because my boiler is so oversized?? That's causing your concerns???

WMno57

Just for the record, I have no idea if @EdTheHeaterMan 's zones are dangerous or not. I personally would not add zones because I'm thrifty, lazy (work smarter, not harder), and follow the philosophies of "if it ain't broke, don't fix it" and K.I.S.S. . I do believe that preventative maintenance is a good investment.
I once lit a fire under a truck that wouldn't move. The transmission and transfer case were full of a frozen mixture of 90 weight oil and water. That did the trick, and I was able to plow out my road. Add charcoal briquettes to the Winter list of preparedness.
I love Winter!!!!!!!!!!!!!!!!!!!

hot_rod

EdTheHeaterMan said:

I understand that is not in the cards for this heating season, but try not making the efficiency drop with what you have and potentially put the boiler into a dangerous operating condition.
I can't imagine any seasoned pro putting his reputation and liability on the line to encourage this operating condition. Would you?

WOAH!

adding zone valves = dangerous condition.

Explain that one @hot_rod ?!?

PS. I look up to you Bob Rohr for your much more experienced than I. I only had about 4000 to 5000 different customers over my lifetime. As a trainer for a manufacturer you have access to hundreds of companies customer's. Some of those companies have more than 5000 customers. That is a much larger pool of problems to solve. So I am not saying you are wrong, I'm just wanting to know what you perceive as dangerous in adding zone valves as @TerrS proposes?

And I think of you as much older that I. Well, more experienced might be a better way to say it. LOL

Putting a grossly oversized boiler into a microzoned condition, driving efficiency down and fuel cost up is my point. Nothing more nothing less. I think my numbers and actual observation of the system proves that clearly?

If that condition leads to flue gas condensing in the boiler and flue it could set up a CO concern.

EdTheHeaterMan

@hot_rod. You did make that point earlier. Thanks for the clarification. Sometimes what is in ones mind that makes all the sense in the world, (i.e. zoning = savings and comfort) occasionally has an opposite result.

And the point is well taken when one says for example "That is the way I was taught and I have done it that way for 30 years" only to find that the circulator on the supply pumping away from PONPC really does make a difference just one example

hot_rod

EdTheHeaterMan said:

@hot_rod. You did make that point earlier. Thanks for the clarification. Sometimes what is in ones mind that makes all the sense in the world, (i.e. zoning = savings and comfort) occasionally has an opposite result.

And the point is well taken when one says for example "That is the way I was taught and I have done it that way for 30 years" only to find that the circulator on the supply pumping away from PONPC really does make a difference just one example

Troubleshooters like us want to make things better, help out the customers whatever it takes. A noble endeavor I and others here I hope continue to learn from one another.

In this example turning a single zone into 2 or 4 I think makes matters worse. And the $$ to make the change, parts and labor gets wasted.

Fuel costs, or projected increases drive desperation!

Usually the pros on this site can come up with numerous small improvements, I'd spend time and money on lowering the load. Blanket the windows for example if that what it takes.

TerrS

@hot_rod if I have a right sized my boiler, would 2 zones work? To make sure my second floor stays warmer?

Again do I move my thermostat upstairs or hook 2 to the same circuit so it knows the upstairs needs heat, even though the downstairs doesn't..

WMno57

TerrS said:

I have ball valves on each of my zones. I did this mostly to cut the amount of water going to the attic. Just enough so the pipes didn't freeze and maybe to provide residual heat.

This works until a black swan event comes along. Any one of the following events could freeze your attic fins:

• You are away on vacation and a neighborhood kid breaks an attic window
  
• extended boiler outage
  
• extended power outage
  
• extended gas outage(least likely, but not impossible)
  

The infamous Texas power outage of 2021 killed 246 to 702 people. No one planned for it, but they should have.
https://en.wikipedia.org/wiki/2021_Texas_power_crisis


The polar vortex dropping down to our latitude is no longer a black swan event. Chances are we will have more of these cold snaps in our future.
https://en.wikipedia.org/wiki/Polar_vortex

TerrS

@WMno57 probably true but in 31 years knock on wood I have been fine. So I will say very low probability

WMno57

My favorite short story:
https://en.wikipedia.org/wiki/To_Build_a_Fire
I should quit goofing off on the internet and get back to work preparing for Winter.

Peter_26

I would look into adding a buffer tank as @JakeCK suggested.

hot_rod

TerrS said:

@hot_rod if I have a right sized my boiler, would 2 zones work? To make sure my second floor stays warmer?

Again do I move my thermostat upstairs or hook 2 to the same circuit so it knows the upstairs needs heat, even though the downstairs doesn't..

Certainly much better result and efficiency with a right sized boiler.
Better yet is a modulating type boiler that could adjust exactly to the zone that is calling.

Like Ed, I'm an old dog willing to learn new tricks, boilers components. A properly sized mod con could do wonders for both fuel consumption and comfort.

You may be sick of hearing it, but the building shell will dictate the heating cost. Once you are convinced you have that as good as you can get it. Then a good room by room heatload calculation. With older construction a blower door test can point out areas that are stealing heat also.

In almost any area of the country heating systems only rarely need to work at full capacity. It's quite possible you may be able to run much lower temperatures to your fin tube, if an assessment shows you have enough fin tube to cover loads at lower temperatures.

These are a couple of my favorite graphs to show seasonal temperatures. You could build one with local area data.
Design day in Syracuse is somewhere between 0- 5F. You need to design for that days, but a good portion of the year you load is a fraction of design. In my mind this seals the deal for a modulating boiler, whether it condenses or not. Put into the home exactly what it is losing at any given time.
January low in Syracuse is 15, its 19 in Chicago, so this is a close example of what your area conditions may be.


If there were one or two simple things to get you where you want to be with what you have, it would have jumped out by now with all the expert eyes on this thread. You can do some trial and error, but you need to measure and confirm what effect it has. If you only get data on a monthly fuel bill, that is too late, the horse is already out of the barn

Do you have a readout on your gas meter? Go online and see how to read it on a daily or weekly basis.

As Sheryl Crow sings. "Its not about having what you want, but wanting what you have". Especially when large sums of $$ are involved.

TerrS

@hot_rod thanks for all your help. I think next year I am going to downsize the boiler but add the upstairs thermostat. Yes an extra $600 for the valves but hey if I'm spending $2100 on the boiler. Then I will probably install it myself to save those cost..I love my supplyhouse.com!!!

JakeCK

Working off of what hot_rod said about building envelope, please for your wallets sake look at the building envelop. Look for the low hanging fruit, the biggest bang for your buck. Make use of a heat loss program to really pin down the numbers.

For me it was the foundation walls. @ design conditions of 5f I was losing about 35000btuh through the basement walls. By adding 2" of polyiso and eventually sprayfoaming the rim joists I will have reduced that to less than 5000 btuh. Then you have air sealing, after I finish up insulating down there my heat loss via air change rate will now be 17% of over all heat loss just in the basement. Another strategy is insulating the floor joists and making sure to minimize any losses to appliances such as boilers and hot water tanks. The problem with that strategy is if the basement is appreciably warm at design, you are heating it and it is thus part of the building envelope intentionally or not. At least if you design around it being part of the envelope now a large % of the standby losses of your appliances goes back into the structure.

You see similar behaviors on the upper floors as well. Even if your attic is under insulated if it already has some insulation, say 5", spending the money to bring it up to code minimum will have a REALLY long ROI, especially when compared to the ROI of insulating the 2x4 walls below it if they aren't insulated. Another example from my house. Once I insulate the walls my largest heat loss on the first floor will then become air leakage at 55%, and 20% of that leakage will be due to the fireplace, similar story on the second floor with 46% loss due to air leakage vs 3% to the ceiling.

hot_rod

Forgive me if I mentioned this already. There is some excellent reading here to help plan the big upgrade.
I would certainly zone the system if you have a modulating boiler in the future plan.

https://www.caleffi.com/sites/default/files/file/idronics_25_na.pdf

WMno57

Another possibility is keep your existing boiler and install a Heat Pump next year. This would:

• upgrade your AC for summer
  
• probably be cheaper to run than a mod con spring and fall
  
• allow you to keep your simple tried and true Boiler for winter and heating redundancy
  

The Department of Energy will be announcing details soon on the rebates and tax credits. Some Heat Pumps installed next year will be zero percent funded by homeowners, 100 percent paid for by other taxpayers.

JakeCK

WMno57 said:

Another possibility is keep your existing boiler and install a Heat Pump next year. This would:

• upgrade your AC for summer
• probably be cheaper to run than a mod con spring and fall
• allow you to keep your simple tried and true Boiler for winter and heating redundancy

The Department of Energy will be announcing details soon on the rebates and tax credits. Some Heat Pumps installed next year will be zero percent funded by homeowners, 100 percent paid for by other taxpayers.

This is why I'm holding off on adding a heat pump right now until next year at the earliest. I doubt I'll qualify for the juiciest of rebates but it will still be advantageous for me to wait. I'm also hoping the manufacturers of a2w heat pumps build up their offerings in response. 

TerrS

@WMno57 this funny, ironic. This is how the whole topic started. I was having estimates to install a 4-head mini split in my 1903 house. And they asked me about my boiler age. The mini split was way more money than I wanted to spend because of the work involved getting the lines and condensate tube back to outside.

So this became okay what about a 30k btu mini split. 15k kitchen/first floor and 12k basement. Jan 1, the 30% credit is supposed to kick in. Then I would still upgrade, err down size the boiler and move the thermostat to the upstairs.

That plan is still in the making waiting for the last bid.

TerrS

@JakeCK the interesting thing about the inflation reduction act from what I have read they are credits, at least in my tax bracket. So you have to pay taxes to get thr upto 30% credit back on taxes owed. But 30% is 30% so an option I am looking at.