Re: Extra heat
Posted by Sylvan Tieger on May 22, 2004 at 23:09:52:
In response to Re: Extra heat
: I'll try to make a long story short... I am very familiar with forced hot air heat, however my new house has an old boiler (radiator and hot water). At any rate the system is common to my understanding- cold water coming directly in for hot water and radiator water circulating with the use of a pump. The house must have been renovated (orginally built 1948), 2 old cast iron rads still exist, and the new Slant baseboard water rads were added. My problem is this- When I cut the thermostat off during the summer, one set of the new baseboards remain fairly hot. I have traced the pipes and this pipe does not come from the circulation pump side, but from the other side of the boiler which is connected to the hydronic expanison tank. I've studied the set up and besides the air vent there is a control valve (colored red) that is in line with the pipe to the hot rads. Is this a "valve" that can be closed to stop this heat during the warm months, or will shuting this valve off cause problems for the boiler. Please advise, and sorry for the long story.

: daves

You did not mention if you had a hot water heater or if these other lines are connected to a tankless coil within the boiler.

Lets assume you have a seperate hot water tank as only a real moron would use domestic (potable) water to for heating also as "plumbers" know that heating water in a boiler and using it for anything else is dangerous to the people and boiler.


Knowing hot water is lighter then cold and hot rises a lot of times you get stratification of the hot water molecules this is how the older gravity systems work.

With over sized piping to keep friction losses to a bare minimum the hot water moves up the heavier cold drops down and thus you now have circulation.

Over the years folks used smaller piping and used circulators as a cost cutting measure.

To keep the hot water from flowing to places not wanted or from continuing flowing heating folks use a flow control valve which is nothing more than a weight that the hot water cannot lift without the aid of a circulator.

With that in mind the newer connections was most likely performed as any decent heating contractor does not mix copper (fin) and cast iron on the same heating lines (circuit) as the heating would go totally erratic.

So the installer possibly decided to use the tankless coil already in the boiler and treat it as a separate zone which is not a bad idea if the right black flow preventers are also installed with a relief valve to protect against excessive pressure build up.

If you like you can E mail me a few digital pictures OR call a local heating contractor who holds a valid master plumbers license.

Sight unseen I can venture lots of guesses,

In my area we use hot water heating off a steam boiler and there are lots of games one can play with hydronics, like non electric zone valves that when closed will not allow the valve to go below 40 degrees at this affords freeze protection and they can balance out a system without bothering to look up heat loss charts.

Check to make sure your domestic hot water is not coming from the same coil as your heating supply.




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