Gary Collier said the following to Mike Ross on the subject of
power source/pump (21 Jan 98  16:40:13)
 MR>So why can't heat convection be used to move the whole water mass?
 GC> I don't know enough about how those systems work, to really
 GC> respond...but I thought those were High pressure boiler systems.
There are many types of radiator heating among which is high pressure
steam as you noted. Generally high pressure steam is used for larger
dwellings such as multi-apartment housing.
The type of gravity hot water system uses water who's temperature never
gets much above 180F and operates at atmospheric or more typically at
utility water line pressure. To accommodate changes in volume due to
temperature expansion, it uses either an expansion tank or a pressure
regulator from the water utility feed.
The main problem with the gravity hot water system is that radiators
further from the source must be larger because the water is cooler at
the end of the pipe. The main advantage is the more even temperature
fluctuations though steam and pump fed water will respond more quickly
to demand. Basically it's a design which requires more skill in
selecting pipe sizes than steam or pump circulated.
 GC> I just don't think the system I envision will have
 GC> enough capacity to be effective w/o a pump. Is this the type of system
 GC> you had???
Yes, I had a gravity hot water system without any pumps. From what
you've described so far it seems your projected system will have a
relatively small capacity. I think gravity feed could work well in a
small system, provided the pipes are of adequate size, since the
difference in water density only results in small forces. For example
3/8" tubing might just not be up to it.
Which reminds me, in a mechanical flow system, one way the pump is kept
from getting hot is to install it at the cold end instead of the source
side. Of course circulation will probably be less than if the pump is
designed for vacuum operation.
 GC> I have considered an auger feed at some time...but right now I
 GC> mainly want to get some heat in the house ASAP.
 GC> If and when I do
 GC> decide to is their any basic programs in shareware for a
 GC> project to automate this sort of project? I would probably be
 GC> looking at a temperature sensor or two and possibly an o2 sensor
 GC> to monitor combustion. I am already looking at utilizing a 286 or
 GC> xt board to monitor temperature at the heat exchanger in order to
 GC> turn on/off the blower motor, combined with an inside thermostat
 GC> and monitor.
I must admit to only having cursory knowledge of heating systems so that
I can't give you the many details you will undoubtedly need to complete
your project. I strongly suggest you get over to a public library and
get a hold of the many resources on the subject.
The computer control programs themselves are rather trivial to
implement. I would probably concentrate more on the physical aspects of
your project 1st to ensure its success since you have a pressing need.
... Ice Storm of '98 refugee.
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