Water to Glycol heat exchanger placement for thermal storage.

[jplev22]

Hi,
I am currently planning upgrading my boiler room to add storage. Right now the system is completely filled with a glycol mix. The boiler room being in the garage heating the house (2000 sf) and a guesthouse (800 sf).

Thermal storage would be stacked 1000 lp tanks. The tanks would be filled with water since filling them with glycol would obviously be cost prohibitive. Tanks would be grossly oversized for the current Kerr TW2000 boiler which would be changed at later time.

Now, where would the Water/Glycol heat exchanger be best placed. Two options I can think of.

1 - I understand that typically the boiler and storage would share the same water and a loading valve would control thermal loading and unloading. The heat exchanger would then be placed just before the underground connection.

2 - Boiler would continue to be charged with glycol, heating directly the house when under demand. The HX would then be placed in a primary loop connecting the boiler and heating load. Loading and unloading would be controlled by a vfd pumping through the thermal storage tanks and the heat exchanger. The pump would be controlled by a controller such as a Vesta.

Does anyone have experience in setting up thermal storage as explained in "Option 2"? I do like it better since I do beleive it would have better control of loading/unloading or simply heating strictly from boiler. Also, would protect boiler from frost sould an extended and unattended power outage occur.

Would certainly like to hear from someone who set it up as such.

 

[jplev22]

Since a picture is worth a thousand words, here is a schematic of what I had in mind.

Any thoughts on how an arrangement as such would work out?

 

[cpeltier]

Since a picture is worth a thousand words, here is a schematic of what I had in mind.

Any thoughts on how an arrangement as such would work out?
View attachment 172321

I'm not sure how well the loading/unloading would work but I've used a 4 way valve with an actuator to do just that:
http://www.supplyhouse.com/Honeywell-V5442N1031-1-1-4-4-way-mixing-valve

Against one stop you load, against the other you unload. Requires only one pump.

 

[cpeltier]

Since a picture is worth a thousand words, here is a schematic of what I had in mind.

Any thoughts on how an arrangement as such would work out?

View attachment 172321

The HX will dramatically lower your useful storage as you will have a delta T to load and then again to unload unless your heating load is very small or the HX is oversized and running in a "close approach" mode. I understand you want to forgo the cost of glycol in the storage and glycol does lower your heat transfer capacity in the HX. If you could eliminate glycol all together and go direct it would operate much better and your effective storage would be larger.