Increasing the Heated Mass to Improve Heating Efficiency

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kstills
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Post Mon. Aug. 06, 2012 10:10 am

hThat is the goal.

I have a LL110k which holds ~12gallons of water at whatever temp I've set it for. My system is ~70gallons, which creates issues when I get a demand call and the aggregate water temp has dropped well below the boiler temp.(lots of cold water returning to that little bit of hot water).

Alongside the LL110k sits my old GE boiler with ~40gallons of usable water mass. I'm planning on running a primare-secondary loop using a slaved recirculator on the primary and a thermostatically controlled recirculator on the secondary. With ~52 gallons of heated water in my system, I'm hoping that I can keep the house temperature where I want it to be (dropping it at night, raising it in the morning, dropping it when the house is empty during the day, raising it when everyone comes back home etc) without the longish delays that it takes now because of the limited amount of hot water I have to circulate in through the system.

In discussion with a friend (boiler guy), he's indicated that the old GE boiler acting as a thermal storage unit will lose more heat than would be worth the savings in having the higher mass at elevated temperature being used by the system. Something about the interior being hollow and without having the oil gun firing it would create more thermal loss. I'm trying to understand why it would lose more heat without the gun then with it, since it was a pretty efficient boiler for it's time (well insulated). My thought was to perhaps stuff some insulation up into the cavity where the oil gun fired, in hopes that this would decrease whatever thermal loss might take place.

I know some of you guys have done something like this in the past, so I'm wondering what your thoughts are about the thermal loss issues, and how you might have gotten around them when you hooked up yours.

Thanks in advance for the help.


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Rob R.
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Post Mon. Aug. 06, 2012 11:39 am

As I recall, you have an old gravity hot water system in the house? With a high mass system like that, the use of setbacks is usually discouraged. I think you would be better off to try and store the heat in the radiation system & living area rather than an extra boiler in the basement. Your friend's mention of heat loss through the boiler would make sense if is connected to a chimney, but if it isn't...it will just act like a big radiator in the basement. Adding the GE boiler to the mix will act like a flywheel, but I'm not sure it will save you any coal or improve the comfort upstairs.

Constant circulation provides the greatest comfort, and is easier on the boiler. You can do a simple primary/secondary setup with your LL110 and have a lot more "tuning" options than you do right now - it is nice to pump as much as necessary through the radiation without worrying about overwhelming the boiler with cold water. There are other options such as 4-way mixing valves, but that is a higher level of complexity. It all depends what you want to accomplish and how much you want to spend.

kstills
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Post Mon. Aug. 06, 2012 12:10 pm

Rob R. wrote:As I recall, you have an old gravity hot water system in the house? With a high mass system like that, the use of setbacks is usually discouraged. I think you would be better off to try and store the heat in the radiation system & living area rather than an extra boiler in the basement. Your friend's mention of heat loss through the boiler would make sense if is connected to a chimney, but if it isn't...it will just act like a big radiator in the basement. Adding the GE boiler to the mix will act like a flywheel, but I'm not sure it will save you any coal or improve the comfort upstairs.

Constant circulation provides the greatest comfort, and is easier on the boiler. You can do a simple primary/secondary setup with your LL110 and have a lot more "tuning" options than you do right now - it is nice to pump as much as necessary through the radiation without worrying about overwhelming the boiler with cold water. There are other options such as 4-way mixing valves, but that is a higher level of complexity. It all depends what you want to accomplish and how much you want to spend.
I've considered running the system constantly, but I would imagine that would involve quite a few trips up and down the stairs to keep changing the HL and LL settings, based on the weather. I don't have a lot of money to make changes, so balancing valves and mixing valves probably aren't in the cards either (given that I would be changing the piping along with them).

I could pretty easily set up the front or back of the house (5 radiators a side) as the primary loop, and then kick the other half of the house on if it got real cold. And just open up some windows on the warm days... ;)

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EarthWindandFire
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Post Mon. Aug. 06, 2012 12:34 pm

Adjustment to the coal-trol could also be made to improve response of the burner. This worked very well for me but must be made in small increments.
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kstills
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Post Mon. Aug. 06, 2012 12:38 pm

EarthWindandFire wrote:Adjustment to the coal-trol could also be made to improve response of the burner. This worked very well for me but must be made in small increments.
I have a hydronic system that the LL110k is piped into.

I agree about the gold standard, however. :)

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Rob R.
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Post Mon. Aug. 06, 2012 1:16 pm

kstills wrote:I've considered running the system constantly, but I would imagine that would involve quite a few trips up and down the stairs to keep changing the HL and LL settings, based on the weather. I don't have a lot of money to make changes, so balancing valves and mixing valves probably aren't in the cards either (given that I would be changing the piping along with them).
Constant circulation is normally accomplished with an outdoor reset control...it adjusts the boiler temperature automatically and saves the stairs. :)
kstills wrote:I could pretty easily set up the front or back of the house (5 radiators a side) as the primary loop, and then kick the other half of the house on if it got real cold. And just open up some windows on the warm days...
Is your system two separate zones?

kstills
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Post Mon. Aug. 06, 2012 1:24 pm

Rob R. wrote:
kstills wrote:I've considered running the system constantly, but I would imagine that would involve quite a few trips up and down the stairs to keep changing the HL and LL settings, based on the weather. I don't have a lot of money to make changes, so balancing valves and mixing valves probably aren't in the cards either (given that I would be changing the piping along with them).
Constant circulation is normally accomplished with an outdoor reset control...it adjusts the boiler temperature automatically and saves the stairs. :)
kstills wrote:I could pretty easily set up the front or back of the house (5 radiators a side) as the primary loop, and then kick the other half of the house on if it got real cold. And just open up some windows on the warm days...
Is your system two separate zones?
The system is not two seperate zones, the five front rads are 3 down, two up, the back are two down, three up. However, it would be easy to change over the piping to run either front or back as a primary loop and setup the other as the secondary loop. Moving the Tstat wouldn't be much of an issue, it sits in the middle of the kitchen atm but I could put it either at the front of the house or the rear, depending on which loop becomes the primary.

I'll have to look into those reset controls. :)

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Rob R.
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Post Mon. Aug. 06, 2012 1:50 pm

If your number one goal is to keep the boiler from getting slammed with cold water, that can be accomplished without a reset control. You can create a primary loop around the boiler (control that circulator off the triple aquastat), and connect your radiation via a closely spaced set of tee's and a separate circulator. The circulator on the secondary loop can be wired off a separate relay, so it runs whenever the thermostat calls for heat...the circulator on the primary loop will stop if the boiler reaches the low limit setting on the aquastat...this prevents flue gas condensation and allows you to use the tankless coil.

What I just described is a common way to hook up radiant systems with non-condensing boilers...here is a diagram from Taco that shows one of their mixing valves:

Image

Do you have two sets of supply and return pipes feeding the radiators? Lots of old gravity systems did...and if you don't need to heat the entire house all the time it would make sense to split the system into two zones.


kstills
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Post Mon. Aug. 06, 2012 2:24 pm

Rob R. wrote:If your number one goal is to keep the boiler from getting slammed with cold water, that can be accomplished without a reset control. You can create a primary loop around the boiler (control that circulator off the triple aquastat), and connect your radiation via a closely spaced set of tee's and a separate circulator. The circulator on the secondary loop can be wired off a separate relay, so it runs whenever the thermostat calls for heat...the circulator on the primary loop will stop if the boiler reaches the low limit setting on the aquastat...this prevents flue gas condensation and allows you to use the tankless coil.

What I just described is a common way to hook up radiant systems with non-condensing boilers...here is a diagram from Taco that shows one of their mixing valves:

Image

Do you have two sets of supply and return pipes feeding the radiators? Lots of old gravity systems did...and if you don't need to heat the entire house all the time it would make sense to split the system into two zones.
It's been a while since I've actually thought about this, but I'm starting to remember some of our old conversations. :)

I think the easiest solution, one which would protect the boiler and provide the least amount of issues either from a comfort or efficiency standpoint would be the installation of the ODR. I assume that overrides (or works in conjunction with) the triple aquastat in order to adjust the boiler temps up or down. From discussing the issues with LL, they are fans of continuous operation for efficiency, and I like the idea of not having to make any major changes to the pipework at the moment.

The ideal solution would be to install a two zone system, eliminating the 2 inch mains in the basement with 1inch lines to decrease the water used and then to go ahead and install balancing valves on each radiator. Once I went ahead with that plan, I could install the bypass, mixing valves and such to provide extra protection for the boiler (although Axeman says that the boiler is self bypassing). But that's going to have to wait for another couple of heating seasons.

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Rob R.
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Post Mon. Aug. 06, 2012 2:47 pm

kstills wrote:It's been a while since I've actually thought about this, but I'm starting to remember some of our old conversations.
Yes, I sent you that same piping diagram when you were piping the boiler the first time. Everyone wants things "good, cheap, and fast"...but you usually only get to pick two.

Having the boiler at the proper temperature is only part of the equation, you still need the proper flow to the radiation and the system must be balanced.

kstills
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Post Mon. Aug. 06, 2012 4:56 pm

Having forgotten all these figures, I went back and re-did the home heat loss and radiator output of the house and system.

I'm running about 30k btu/hr loss at zero degrees, with ~80k per/hr output potential (the radiators could put out 126k, but the boiler can't supply them). So I should be easily able to run the boiler flat out all heating system long by adjusting the output temperature up and down. My understanding is that is what the ODR would do, if so that would seem to be the best option at the moment.

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Post Mon. Aug. 06, 2012 5:11 pm

I think you need to find out what the actual return temperature is
before doing a lot of plumbing work. My return temperature is not
"cold" by any means. Maybe a few degrees below feed temperature.
If your load is 30 and your boiler is 80+, your return will be almost
equal to the feed unless your circulator is just barely moving the water.
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Post Mon. Aug. 06, 2012 5:45 pm

Has anybody thought about a bypass loop like it shows in the EFM manual. Cheap and not alot of moving parts :)
I think a man does what he can, untill his destiny is revealed. Right now that is trying to sell my EFM plate boilers in 520 and 700 sizes.

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Rob R.
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Post Mon. Aug. 06, 2012 6:54 pm

Scottscoaled wrote:Has anybody thought about a bypass loop like it shows in the EFM manual. Cheap and not alot of moving parts :)
It would be a big improvement compared to straight piping return water from cold radiators into the boiler.

kstills
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Post Tue. Aug. 07, 2012 1:52 pm

Rob R. wrote:
Scottscoaled wrote:Has anybody thought about a bypass loop like it shows in the EFM manual. Cheap and not alot of moving parts :)
It would be a big improvement compared to straight piping return water from cold radiators into the boiler.
I just yesterday figured out how this would work (after one full year of hearing about it).

I run the 20gpm primary and the 10gpm secondary and then the boiler runs flat out until the house temperature comes up to the tstat setting, correct?

No extra controls, except for running the tstat to the secondary recirculator and slaving the primary to a 24/7 365 mode.

I like that a lot. :)


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