??? - Adding An Indirect Hot Water Heater and Removing On Demand In My System???

[Piston]

I'd like to add an indirect hot water heater to my system.  

My present setup is:  
OWB Loop: OWB circulating through a plate type heat exchanger, back to the OWB.  

Indoor Loop: I have an older oil fired boiler in my basement.  The water from the heat exchanger goes into my oil boiler on the return side, circulates through the boiler and then into my two heating zones (one is for radiant downstairs, one is for baseboard upstairs/loft, which we almost never use).  Then back through the plate type heat exchanger, and back into the supply of my oil boiler. 

Domestic hot water (on demand): Heated through a heat exchanger housed within the oil boiler itself.  It doesn't work that well.  I'd like to stop using the on demand system entirely, and add a separate indirect hot water heater.  

Is it as simple as adding another zone to my heating system, and tying in the indirect hot water heater to the added zone?  
Then for the actual domestic hot water loop, just cut the copper supply/return to the on demand heat exchanger at my oil boiler, and replumb those pipes to go in/out of the new hot water tank?  

Or does it require a block off plate for the oil burners DHW heat exchanger?

Lastly, (for now  ;D) do you recommend a specific brand or model indirect water heater?  I believe I'd want somewhere in the 100 gallon range (it could somewhat double has 'storage' as far as I know?) 

Thank you in advance! 

[petefrom bearswamp]

My system is this.
OWB thru plate exchanger to oil boiler jacket.
Indirect water heater supplied by oil boiler jacket water, whether using OWB or oil boiler.
Switch between the 2 is made by a series of wall mounted switches.
Indirect is an Amtrol boilermate I think 40 gallon.
Works well.
I currently am burning year around using up my mill slabs and miscellaneous junk boards left over from covering lumber.
Only time i use the oil is when I go away so my wife doesnt have to fiddle with the OWB.

[mike_belben]

SuperStor is another brand and they arent giving them away. Its not going to care how you plumb it as long as hot water is going in and out one circuit and ground water goes in and out the other.  


The only way i see a 100G being necessary is if you are an oddly high demand user or trying to make batches of hot water last a day (like solar) rather than continuual fired.  100g superstor will be big bucks.

 If you are using a tempering valve to limit the entire house temp for children's sake then a big tank is handy.  I personally look at a tank as a btu storage chest.  The higher the temp the more btu inside, the more gallons of useage required to exhaust it, thus the 'longer it lasts.'  With a temp in the tank that is way too hot for your skin, the user modulates the temp to their comfort level at the faucet by using a lower flow rate from the hot side, just a drizzle.  Thus a 40G @160F is like an 80g @120F.

For a real world experience..  At a past house I had a woodfired preheater coil and a thermal siphoning loop keeping the gas 40G water heater from kicking on.. The water heater was about 160F.  I could take a 20 minute scalded lobster shower before the gas kicked on.  It would take about 40 minutes of shower, plus dishwasher and laundry on 'hot' to outrun that 40G heater.  It never happened, 2 adults with kids and constant dishes/ laundry. 


If youve got a full time 180F wood boiler jacket and dont run an automatic tempering valve i bet as small as a 20G superstor would work for normal single family needs.  A 40G @180 if theyre just plain wasteful.  But only if theres no little kids or sue happy renters etc to get burned.  If so then a tempering valve and a big tank it is. 

[Piston]

I am using a tempering valve off the hot water.  We use a fair bit of hot water, and will be using more.  There are 6 of us in the household and the kids are getting old enough to not want to take baths together anymore, so it's only going to go up from here.  
We are also getting a new washing machine which is used daily, currently have one of those fancy LG high efficiency ones and are tossing it in favor of a bare bones old school top loader that uses over 20 gallons per wash.  

In addition, I have an outside spigot with hot water for pressure washing tote tanks before/during maple syrup season.  

I don't know what size I "need", but I know my wife will kill me in my sleep if she ever runs out of hot water again. 

I am looking at this one:  80 gallon... 
Google

[mike_belben]

Understood.  Big tank it is.