How much glycol

joe_130

Hello Everyone

I have to add glycol to a system that has heat lines run in an uninsulated crawl space.  Lot of helpful info on here as always but none on how much glycol in a system is enough.  Could someone help me out with that?  Also,once the gycol is in the system, how do you bleed the air? 

Thanks 

Any and all help appreciated

hot_rod

how cold

do you want to protect to? Generally 35- 40% is adequate in most climates. With a good brand HD fluid that should provide burst temperatures around -20- -30F.



Don't mix any richer than need as it takes more pump power to move glycol and the heat transfer is less than water.



Knowing how much to add is a good question, if you don't know what the system capacity is..



You could drain down and blow out the system and measure the amount that comes out in buckets, then replace with the glycol and good quality water.



Other than that it will be a guesstimate as to how much to add.



Be sure the system is leak free as you do not want a feed water valve opened on a glycol system.



Add a low water cutoff switch to protect the equipment should a leak develop.



You will need a transfer pump to push the fluid in and a means of purging the air out of the zones as you pump the fluid in. it's a bit of a job to do it properly and you may want to add some Webstone isolation purge valves.



hr

World Plumber

Pipe length and diameter

If you have baseboard heat you can measure the length and the length of the pipe. 100 feet of 3/4 copper tube holds 2.5 gallon do the math then add the boiler volume. I usually add a little extra for valves and loops. I pump into the boiler drain with a hose from the purge vale into my supply bucket. I use a utility pump with a bypass loop to avoid pulling air into the system while refilling the bucket. I run the pump until there is no more bubbles. Then close the purge valve and pump the remaining fluid int the boiler building the pressure in the boiler. I usually get 12 psi from the pump. 

Ironman

Pre - Mix the Glycol

Pre mix the glycol and water in a large bucket and then pump it in. Allow the purge hose to discharge into the same bucket to catch any mix that comes out with the air. Of course, the system has to be thoroughly drained first.



Unless your in a severe climate, you may not need much (if any) glycol to protect lines in a crawl space. It usually stays close to ground temp.



As already stated, don't use more than needed. Glycol decreases the heating capacity of the water it's mixed with as well as making the pump work harder and decreasing the GPM.