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Posted by HeatPro on January 25, 2005 at 11:10:47:
In Reply to: Re: Replacing boiler posted by Pat S on January 25, 2005 at 09:24:26:
As you have R-30 ceiling and R-5 walls, that does explain why your losses would be about 29 btuh per sq ft. The design at 70F DTD also explains why you don't maintain below 0F outside.
There are probably some things you could do at no cost, like set your temperature control on your boiler to the settings they were designed for when the house was built: 220F high limit, 200F low limit and 20F differential. The cast radiators were originally for steam which operates at 215F, so they can't be harmed by water warm enough to do the job. You probably have the settings lower than that in the interest of saving fuel.
When you set the tempratures up, it is a good idea to have a tempering valve so the cold water mixes with the hot water, giving you almost twice as much hot water.
If you did so, you might only have to blow insulation in the walls from the outside to bring your comfort up and guarantee your existing setup gives you heat at more fuel savings.
It is possible the old tankless coil in the boiler is limed by now and having it cleaned could increase the hot water along with a good tempering valve.
There is a bit of confusion yet, as you state you have an external coil and a domestic hot water coil, so they are conflicting information.
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