DHW from boiler outside of the heating season?

[Badfish740]

Is it possible/cost-effective/common to set up a gasification boiler to supply DHW when it's not heating the rest of the house? Just a random thought I had. When we finally build our dream house a gasification boiler is on the must have list, but I'm also planning on doing a flat-plate collector solar hot water heater as well. This guy built one for $1000 from stuff you can buy at Home Depot:

http://www.builditsolar.com/Experimental/PEXColDHW/Overview.htm#Objectives

It looks professional and supplies nearly all of his DHW even in the winter-I figure I'd want to rely mostly on that during non-heating months, but lots of cloudy days/rain could necessitate the need for supplemental heat for the boiler. I guess my question is, if the solar is going to supply most of the DHW, is it even worth it to integrate the DHW with the boiler? Or is it maybe not as difficult as I'm imagining? Combining the two is attractive to me because at least in theory I could supply all heat and hot water using nothing but firewood and the sun-no propane or oil needed unless we happened to be away for more than a day or two during the winter months.

 

[Adios Pantalones]

Lots of folks here have heat storage- the boiler is fired to heat a water tank to hold the heat, and a coil draws the heat for DHW from the tank. The boiler is fired a couple/few times a week in the non-heating season depending on the size of your storage tank. The solar could charge this tank in the summer.

Very common. I'm planning to do this- buying before the end of the year.

 

[tom in maine]

We started out making tanks for solar systems. The wood boiler thing came later.
A storage tank is a thermal storage system and it really doesn't matter where the heat comes from. A wood boiler system with solar for the non-space heating times of year is very simple, regardless of whether it is a
pressurized or non-pressurized system.

There is no joy in burning wood in the summertime if you don't have to. With a well insulated tank, a large tank can provide DHW in the summertime with a modest sized solar system.

I am a little nervous about PEX DHW hx. I like the corrosion resistance, but am concerned a little bit about the leaching of estrogen-like materials from plastic into potable water.
I know that PEX vs. Copper is a never ending debate, but PEX is not usually used in an immersed DHW hx mode where it is always hot. It is usually a carrier of hot water from a heat source to the tap and as such is
not hot for very long. And the standing water (which has usually cooled off) is flushed with water that has not sat in the tubing for any period of time.

 

[Badfish740]

We started out making tanks for solar systems. The wood boiler thing came later.
A storage tank is a thermal storage system and it really doesn't matter where the heat comes from. A wood boiler system with solar for the non-space heating times of year is very simple, regardless of whether it is a
pressurized or non-pressurized system.

There is no joy in burning wood in the summertime if you don't have to. With a well insulated tank, a large tank can provide DHW in the summertime with a modest sized solar system.

I am a little nervous about PEX DHW hx. I like the corrosion resistance, but am concerned a little bit about the leaching of estrogen-like materials from plastic into potable water.
I know that PEX vs. Copper is a never ending debate, but PEX is not usually used in an immersed DHW hx mode where it is always hot. It is usually a carrier of hot water from a heat source to the tap and as such is
not hot for very long. And the standing water (which has usually cooled off) is flushed with water that has not sat in the tubing for any period of time.

Good point-I wonder how much exposure you would really get from it though. Sometimes if I need to boil a large pot of water (for pasta, etc...) on the stove I'll start with hot water in order to start the boiling process a little quicker, but I can't think of too many other instances where hot water from the tap is finding its way into or onto my food. We wash veggies with cold water, cold water goes into the coffee maker, filtered drinking water pitcher, etc... Of course we shower in hot water, but could those chemicals actually be entering through the skin? I don't know enough about it.

 

[mr.fixit]

I based my solar hot water system on Garys design from Build It Solar .It works great.I built my storage tank per his design but I also put a copper HX coil in the tank that is tied into the boiler.During the warm months if it looks like cloudy weather for 2 or 3 days I fire up the boiler and heat the storage tank.Winter months the Ranco temp controller that operates the DHW zone valve is powered through a timer to come on in the late afternoon after no more solar is available. Then the boiler picks up the slack.The self constructed solar storage tank holds around 200 gallons--2 teenagers drain the heat out of that in no time! By the way-Thanks Gary!

 

[nate379]

My folks just run an electric water heater in teh summer. Makes more sense then burning wood.

 

[muncybob]

My folks just run an electric water heater in teh summer. Makes more sense then burning wood.

This is also what we do...partly due to the heat loss that rises from our boiler into the living room....don't need that on hot summer days/nights!

 

[Badfish740]

My folks just run an electric water heater in teh summer. Makes more sense then burning wood.

I suppose I could pair the solar hot water setup with a propane fired tankless heater (we're definitely going to have propane onsite if for nothing more than cooking gas) for a stand alone system.

 

[mr.fixit]

I do have a tankless electric dwh tied into my system also.It very seldom turns on.My boiler is in an outbuilding so excess heat isnt a problem. Ican see where it would be if your boiler is in the basement.Anyway I just dont like the high and ever increasing electric bills.It is just amazing how fast and with how little wood these gasification boilers can heat water.Some people (like me) are cheap and would rather start a fire vs. pay a high electric bill.Everybody does their own thing!

 

[Adios Pantalones]

If I got a new gaser- on the 30-40 KW size, how much excess heat would I really be seeing if I fired a couple times a week?

 

[mr.fixit]

My boiler is in a detached garage and it does warm up in there when the boiler is running.Not so much heat off the boiler itself but off of the chimney and the near boiler plumbing.Alot of heat comes off uninsulated black piping.It really should be insulated regardless where the boiler is located.

 

[woodsmaster]

My folks just run an electric water heater in teh summer. Makes more sense then burning wood.

I think that wether or not it makes since to burn wood for dhw in the summer depends on how much hot water you use, price of elec., cost of wood , free time to make the fire, and if the boiler is in the house.