Using a Garn to feed Baseboard only

[Garnrules]

I'm feeding a HX in a forced air furnace and want to retro fit the house for baseboardand run a low temp of water (140f). I am heating about 3500 sq.ft. and figure the heating load a little over 100kbtu/hr. I think about 200 feet of baseboard will work nicely and I envision 3 loops downstairs and 1 upstairs. My existing furnace is an open loop geothermal with a desuperheater installed.I'd love to hear from anyone who has done something similar. Question - Can I feed the baseboard directly from the Garn in a series loop? Does it make more sense to establish a pressurized closed loop and use a water to water HX to heat a storage tank. If so, can I use the geothermal to heat that as well via the desuperheater? Thanks in advance for your thoughts.
Vincent

 

[benjamin]

No offense, but these sound like amateur questions. You're in luck cause I'm the guy to give you some amateur answers.

It's theoretically possible to feed the baseboard directly from the garn. Assuming your garn is at ground level and the second floor is above the top of the garn it would take a bigger pump than you would want and cause noise from air. Adding a closed baseboard loop and a heat exchanger kind of defeats the purpose of adding the baseboard, using the lower temperature water.

The desuperheater is designed to heat domestic hot water, especially during air conditioning. In heating mode there isn't enough superheat there to add much if anything to 140 degree water.

Instead of adding another system on top of a garn and geothermal, what about adding another coil in series in the air handler, or some staple up radiant in series after the air coil in order to use lower temp water? Or reduce your load to get the same result?

 

[Como]

http://www.runtalnorthamerica.com/bisque/calculating_btuh.html

I think you initial problem is that your output per foot assumes 180F Water, according to the above link you need to multiply by .57 for 140 water, or nearly double your length.

Can put in radiant under floor.

Garn installs usually involve a heat exchanger.

 

[flyingcow]

Ayuh,... In my experinces, Baseboard heating needs Higher temps to work well... like 180°

Generally it's designed for 160 to 180. BUT it can be used for 140, but you need a lot more linear footage(as mentioned above). You need to look up "Heatermans" posts. Low temp radiators could be what you want to do.

 

[heaterman]

You can do it but you need to rethink your plan for 200' of BB. That would equate to an actual output of 500but/ft of active baseboard. Water temps need to honestly be in the 180-200* range to achieve that over the long term. Realistically you should figure an output of about 300/ft which means about 330' of baseboard. That will let you drop into the 140* range on your water temp. Any system using storage, should be able to "digest" a wide temp range otherwise the storage becomes pointless.

 

[Garnrules]

Thanks Everyone. Well at least a few of you didn't think my questions were amateurish. LOL

Seriously, you guys are great and I have found this forum to loaded with hard to find and valuable info.

I have actually found a few high output baseboards - MultiPak 80, Sterling System6, and Embassy all do 490 - 500 btu/ft at 140f at 4GPM. I have also found very high ouyput radiators from Myson and Gruntal. I'm pretty sure I can do this with lower temp. water but I can increase that as needed. The bigger question is - can I simply set up 3 or 4 series loops directly to the Garn or do I need a pressurized system.

Thanks again

Vincent