Compression vs. old expansion tank

mike faust

How does a " thermic " valve work?

mike faust

Compression vs. expansion tank

I am, installing a Laars Max boiler in an old home with a cast iron rad. system. The existing pipe system requires about 115k btu at peak load. A few questions:
1. Can I/ should I reuse the old expansion tank?
2. Should a properly sized compression tank be installed on the secondary side? (as i read in a recent piece of literature by laars)
3. Does it matter where I fill? (should it be connected in with the compression tank)

The system is being piped primary/secondary. The existing loop is tapped in with two tees about eight inches apart. We also added some future sets of tees for a possible radiant panel and small hydronic hot air heater for the basement.
4. If the comp. tank goes on the secondary side and my circ pumps away, will i need to repeat that on all the future secondary zones??

mike faust

PS Laars install manual states that " the old expansion tank may be used instead of a new diaghram type tank" ( just read this) but it does not say where to install it

Lil-Roc

Watch your tee spacing. For primary/secondary piping the tees should be 6" or 4 pipe diameters apart.

bobbyg_2

> A few questions: 1. Can I/ should I reuse the

> old expansion tank? (You can reuse but you need to have a way to get any air in the system 1. out of the water (air purger/separator) 2. into the "old style" expansion tank)

2. Should a properly sized

> compression tank be installed on the secondary

> side? (as i read in a recent piece of literature

> by laars) (No)

3. Does it matter where I fill?

> (should it be connected in with the compression

> tank)
Yes, see many of Dan's books to explain why.
>

> The system is being piped

> primary/secondary. The existing loop is tapped

> in with two tees about eight inches apart. We

> also added some future sets of tees for a

> possible radiant panel and small hydronic hot air

> heater for the basement. (The tee spacing is critical - see many of Dan's books)

4. If the comp. tank

> goes on the secondary side and my circ pumps

> away, will i need to repeat that on all the

> future secondary zones?? (The expansion tank should be piped in where all of the secondary have the piping in common. When it is piped this way, the "point of no pressure change" will be the common piping between the primary and secondary pipe -- and be sure to "pump away" from this area)----It's more of a pressure differential question rather than a expansion tank question. The expansion tank will work anywhere in the system, but the making sure the pumps will be "pumping away from the "point of no pressure change" is critical.

mike faust

THANK YOU~SIR!!! THATS EXACTLY WHAT WE'RE DOING. bE DONE IN ABOUT 3 HOUR..... LET YOU KNOW HOW WE MAKE OUT!!!!!!!! THANKS AGAIN

mike faust

Is this normal?

Does it normally take an hour for the primary water temp to come up to 160degrees. I have a large volume of water( 120,000 btu of radiators) and 100' ++ of 2"iron pipe. A longer run cycle is a good thing correct? It should in effect satisfy the t-stat on a milder day without reaching a higher temperature??? And when the out temp requires peak load a longer run cycle should raise my water temp enough to satisfy those peak loads?? Am I correct here? The water in my only common piping seeemed to be neutral( circ on the secondary side robbed nearly all of primary water. Upon start up secondary return temp was around 75f and supply 90f. After an hour secondary return 137f and supply 160f. Is this normal? Note: Yes the stat was jumped out.

ALH_4

Temps

You might post this as a new topic so you get more responses.

You dont mention the size of your boiler. I'm more concerned about condensation than run time in your boiler with 75°F return water.

It sounds like an outdoor reset control would be beneficial. At the least a Thermic Valve should be installed to protect the boiler. Your boiler will come up to temperature more quickly, but the system will still take the same amount of time. The issue is your boiler output compared to the radiator output and the volume of water in your system.

mike faust

sizing issue

Sizing was my intitial thought as well? This is in my personal residence and I purposely sized it for the radiator load only. ( didn't consider the piping loss)I am still a bit of a greenhorn in the vast world of hydronic heating. However, saving grace may be that we are planning on reinsulating and replacing the windows. I'm hoping that in rooms with 2 rads i will be able to shut one off. Is this a bad idea?