plumbing furnace and dhw heater

[curtis]

Getting ready to buy line for my garn install wich for the first year will be a heat exchanger in the furnace and then hopefully radiant panels next year. Im going to be using rehau 1.25 pex insualted line into the house and then switch to non-insualted rehau once im into the house. I found this on a central boiler site and am wondering if this is the right way to hook up my system. http://www.centralboiler.com/Tech/C110.pdf
Although im not really sure about the thermostatic valve and what its for. Does this seem like the correct way to hook up to everything? And do you guys see any problem with using pex for everything inside? I know at the garn I will have iron pipe then hook that to the insulated pex. But once im inside do you see any problems with hooking everything up with the pex?

 

[heaterman]

The mixing valve is there to limit the water temp coming out of the water heater.

 

[curtis]

Ya I got that one, what about the one on the lines coming in?

 

[heaterman]

No need for it with a Garn as long as you maintain anywhere above 100-110* water temp. Have never used on on a Garn in any of our installations.

 

[goosegunner]

That looks like a typical set up used with outdoor boilers. It is common to have the water circulate 24/7 through the side arm and then the furnace plenum. That is fine if you are maintaining a constant temp with the boiler. I don't think it would work very well with storage type system.

When your furnace isn't calling for heat hot water will be returning to the bottom of the tank. That will cause mixing that will give you cooler top of the tank temperatures than a stratified tank. With a forced air distribution system it would be best if you can avoid mixing in your tank.

gg

 

[maple1]

Will you be heating DHW with the Garn in the summer time - or only be burning during heating seasons?

If you are going to try heating DHW only in the summer, with a sidearm as the drawing shows, the thermostatic valve is likey a must. Otherwise the water going back to the Garn will be too hot and mess up stratification with increased mixing, as mentioned above (the sidearm won't pull enough heat out of the water - low delta T). If the sidearm will only be used during heating season, I likely wouldn't bother with it. I'm not sure I'd want all my flow going thru the sidearm all the time though - that will likely lead to some very high temp spikes in your DHW temps.

 

[curtis]

Ya I'm not sure if I am going to be running the garn in the summer for my dhw.