Class A Gravity system

Unknown

Perhaps a little, but not much. How many stories are we talking about now?<BR>Remember the building was designed for this(those old guys knew what they were doing), so everything will have to be a complete re-design.<BR>In my opinion, convert the boiler to "forced", but leave the system side as <i>natural</i> as you can, just be sure those mains are all insulated well.<BR><BR>Dave

Lynne

Gravity system

WE are going to look at a boiler replacement for a converted classic gravity system, 3" up to the attic falling down into radiators. Would it behoove us to remove the 3" riser and repipe the radiators from the basement? I'm wondering if we would save energy by heating less water.

Mark Hunt_6

The building was designed for that system?

Are you nuts? Since when has a building been designed around the mechanicals? And the old timers weren't always right. Just as many knuckleheads back then as there are today. Genetics assure that. How is it better to use more water to do the same job that less water can do? Those old guys had no choice. We do.

tim smith

Stay with the overhead feed system. The best for air removal

of piping systems made... Easy to purge out etc.

Mark Hunt_6

Because air removal is the most important thing

And you have been in the heating business how long? Keep the system because of air removal? Do people buy heating systems or air removal systems? How many "Save the Tyrannosaur" posters do you have?

Steamhead (in transit)

I see

we have another troll.

Does this make the 40th alias you've used? If not, it has to be close.....

Can't wait for the new, no-troll Wall!

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Steamhead (in transit)

Lynne, that system will convert well

to a newer boiler. No need to change any of the system piping. The danger is in the circulator sizing- it's way too easy to over-pump a classic gravity system. The only thing the circ has to so is move the water thru the boiler itself, or in and out of the primary loop if the new boiler is installed with a primary-secondary pumping system.

Also, the sheer amount of water in that system will mean the returning water will be cold for a long time after the boiler starts. If a non-condensing boiler is used, it must be properly piped to keep the returning water temp high enough to keep the exhaust gases from condensing in the boiler or flues.

Some newer boilers are made to take advantage of this condensing process to recover more heat. But some of these newer boilers don't last well- we've seen their heat exchangers leak after five years or so. And they cannot be exhausted into a standard chimney.

Where are you located?

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Dave Stroman

Geez, Where did you come from? Of course the boiler can be replaced. But why tear the house apart to replace the piping? Because you can? Or because you do not know how to make the beautiful old system work? It will work like a charm if you know what you are doing.

Dave Stroman

Unknown

Nuts perhaps,

but no idiot like you!
What I meant was "the system was designed for that building".
True there were many "knuckleheads"(as you seem to know), but most seemed to apply weights & measures to the systems advantage.
That`s the end of my "rant", so unless you intend to be sincere, SCREW-OFF!!

Dave

Lynne

We're in NH

The boiler has already been converted to forced circulation, now the time has come to replace boiler; I'm pretty sure they will stay with oil. My main question is this: is this system less efficient due to the large water content? The house is three stories, the third being a converted attic. Thanks Steamhead

Lynne

insulation vs. efficiency

Thanks Dave, hopefully you read my response to Steamhead, if this customer had enough financing, would it be more efficient to eliminate the 3" riser, due to heating so much water?

Lynne

insulation vs. efficiency

Thanks Dave, hopefully you read my response to Steamhead, if this customer had enough financing, would it be more efficient to eliminate the 3" riser, due to heating so much water?

Unknown

insulation vs. efficiency

Lynne, Thanks for your reply.
Insulation always adds to efficiency. "If" this customer was going to do a complete structural remodel anyway by moving walls etc., then changing this system may be worth looking-at.
"If-not", then I would say the savings would never outweigh the expenditure to do such a task for just the heating alone.

Dave

Lynne

what about zoning

Thanks Dave, the customer is interested in zoning, i'm reviewing Dan's How Come book, and zoning seems touchy.

Unknown

Zoning

Lynne, TRV`s are a very good choice.
100% control of each room & relatively simple to install on each rad,, just a thought.

Dave

kpc_73

Where in....

NH? I am in Dover and have done a number of these conversions. TRV's are a nice touch....kpc

Steamhead (in transit)

Not

if the pipes are well insulated.

Make sure you get a boiler that can handle some cold returning water. The Burnham MPO or Buderus G series, or the more-expensive Viessmann, come to mind. These boilers are also "3-pass" types which are much easier to service.

"Steamhead"

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Lynne

We're in

Marlborough, just east of Keene...........it's looking like this homeowner would like to discontinue the 3" riser, and run pex to each radiator, there are only 6 radiators, seems like a lot of piping to heat just those.

Buzz G.

Removing big pipe

just to remove it doen't seem useful (or efficient). That pipe goes up to the attic and undoubtedly runs up inside an inside wall. The original system had many gallons of water in it and the 3" pipe will hold about 13 gallons if it is 20 ft long and truly 3" ID. It has about 17 sq ft of radiation. This is not where you are going to lose much as the heat from that riser and the one that returns to the boiler is still inside the house. Taking out the pipes is expensive and involves usually damage to walls &/or floors and if they aren't leaking doesn't make sense either.
Just go with a new boiler. Don't add materials that are oxygen permeable and make sure you have a good expansion tank sized for the boiler, radiation, and piping.
Been there done that.

Lynne

leaving the pipe

The 3" riser is exposed on the first floor, boxed in on the 2nd floor, and exposed third floor and across the ceiling, so probably closer to 40' a little under 15 gallons, it then splits into two 1-1/2 drops to the lower floors then the basement, another 60' and @5 gallons of water. The drops to the 6 radiators are all exposed. We will leave all of that piping in place and pipe to individual radiators and zone parts of the house. The homeowner is thinking that there is a lot of wasted heat by running hot water through all of that piping, even with TRV's, hot water will still have to circulate throughout won't it? I appreciate your input

Unknown

As long as that 40' pipe is contained in the insulated living space, the heat radiated by it is not lost. It simply serves a long central vertical radiator. If pipe were removed, the heat given off by it would have to be made up somewhere else, like by all the other radiators.

When you heat the extra 15 gallons of water, the heat energy is not lost but just stored, to be given up to the radiators when circulated. As long as the piping and the water contained by is within the heated building envelope, all of that heat energy goes into useful heating.

scott markle_2

If the riser is within the interior heated space then the heat is not really "lost". Mass can be a good thing, especially with fixed firing rate equipment that may short cycle in low load conditions.

Mass can create issues with thermal inertia, in your case the extra water is not going to make a big difference, most of your systems mass is probably in the cast iron radiators. The problem with inertia is that when a thermostat is satisfied the radiators continue to give off heat and you will consistently overshoot your desired room temp. ODR and constant circulation can save a considerable amount of energy by narrowing these indoor sine wave temp variations.

Basically mass can work for you and against you, sounds like this is high mass system removing the riser is not going to change that. ODR and TRVs are the key to a efficient conversion. Massive gravity systems are awesome!

Unknown

Scott brings up a good point. High thermal mass and water content can be beneficial if the system is properly designed to take advantage of it. In fact, designers seeking greater efficiency sometimes purposely add buffer storage tanks to increase water content and thermal mass.

If zoning is your concern, then as mentioned previously by others, TRV's are the way to go. In effect, each room becomes its own zone and is individually controllable. Its also much simpler to implement than individual zone valves, or multiple circulators which can offset fuel savings by increased electricity useage.

Dont be so concerned by the exposed risers and drops to the existing radiators. Just think of them as part of the radiation, since the heat given off by them contributes to heating the rooms. If the piping passes through any unheated spaces, then it should be insulated there to reduce losses.

You may actually be worse off if you run exposed PEX in an unheated basement to all the radiators, rather than the vertical risers and drops which now pass through and contribute to heating the occupied spaces!