outdoor boiler should heat all my domestic HW, right?

When I built my house two years ago I got an outdoor wood boiler to heat it - works great. I hired a plumber to connect it to my radiant floor system and through a heat exchanger to heat my domestic hot water. However, the hot water heater (propane) kicks on every time we do a load of wash, take a shower or run the hot water tap. The plumber says the hot water heater is "topping off" the heat of the water (set at 115-120) - i.e. the outdoor boiler and exchanger only take it to a certain point and the hot water heater supplies the rest.
The water leaves the boiler at about 180 degrees and travels less than 100 feet undergroud in an insulated pipe. MAYBE it loses 20-30 degrees along the way, and perhaps heating the house takes some more heat away from the water, but shouldn't there be "enough to go around" for the hot water heater as well? I assumed the hot water heater would NEVER turn on? Am I an idiot or do I need a new plumber?

Barold wrote:

When I built my house two years ago I got an outdoor wood boiler to heat it - works great. I hired a plumber to connect it to my radiant floor system and through a heat exchanger to heat my domestic hot water. However, the hot water heater (propane) kicks on every time we do a load of wash, take a shower or run the hot water tap. The plumber says the hot water heater is "topping off" the heat of the water (set at 115-120) - i.e. the outdoor boiler and exchanger only take it to a certain point and the hot water heater supplies the rest.
The water leaves the boiler at about 180 degrees and travels less than 100 feet undergroud in an insulated pipe. MAYBE it loses 20-30 degrees along the way, and perhaps heating the house takes some more heat away from the water, but shouldn't there be "enough to go around" for the hot water heater as well? I assumed the hot water heater would NEVER turn on? Am I an idiot or do I need a new plumber?

Why is your boiler so far away ? And why *outdoors* ?
Graham

"Barold" wrote:

When I built my house two years ago I got an outdoor wood boiler to heat it - works great. I hired a plumber to connect it to my radiant floor system and through a heat exchanger to heat my domestic hot water. However, the hot water heater (propane) kicks on every time we do a load of wash, take a shower or run the hot water tap. The plumber says the hot water heater is "topping off" the heat of the water (set at 115-120) - i.e. the outdoor boiler and exchanger only take it to a certain point and the hot water heater supplies the rest.
The water leaves the boiler at about 180 degrees and travels less than 100 feet undergroud in an insulated pipe. MAYBE it loses 20-30 degrees along the way, and perhaps heating the house takes some more heat away from the water, but shouldn't there be "enough to go around" for the hot water heater as well? I assumed the hot water heater would NEVER turn on? Am I an idiot or do I need a new plumber?

No pipe insulation I've ever seen is perfect. Unless you are heating the house constantly, the first few gallons of water from outside have probably sat in the pipe long enough and cooled enough (probably to close to ground temperature) to trick the water heater into powering on when it is drawn into the tank. You could install a circulating pump and keep the run constantly heated all the way to the propane water heater, you could install a flush valve before the interior WH and drain the cold water each time before using hot water (time consuming and wasteful), you could eliminate that propane heater from the circuit, or you can live with it.
The cost of constantly pumping water and having it cool in the pipe run offsets the cost of propane used to "top off" the hot water, so you won't save much (if any) money unless you eliminate the gas water heater entirely. If you do that, you trade off convenience and reliability in return for not consuming any gas to heat water or keep it stored above ambient temperature. Frankly, I wouldn't obsess over it, and I probably wouldn't bother to fire up the boiler in summer unless I did once a month laundry, and fired it up the day before, then starved it until the next big use of hot water. This is obviously a guess based on thin information, and YMMV

Pooh Bear wrote:

When I built my house two years ago I got an outdoor wood boiler to heat it - works great. ...
Why is your boiler so far away ? And why *outdoors* ?

Outdoors means that all the wood, dirt, insects, ashes and all the rest of the mess of a wood burning boiler stay outdoors. It also means that the boiler can be large without taking up any valuable space inside the home.
Anthony

Thanks Harry. The pump at the boiler does constantly run, continually pumping hot water into the house - when the radiant heat circulating pump or the hot water heater call for heat, the hot water from the boiler provides the heat...I'm suspicous that the heat exchanger connected to the hot water heater isn't capable of taking the heat from the hot water fast or effecient enough to transfer the heat to the domestic hw. I assumed the boiler would supply all my domestic hw use.

Thanks Harry. The pump at the boiler does constantly run, continually pumping hot water into the house - when the radiant heat circulating pump or the hot water heater call for heat, the hot water from the boiler provides the heat...I'm suspicous that the heat exchanger connected to the hot water heater isn't capable of taking the heat from the hot water fast or effecient enough to transfer the heat to the domestic hw. I assumed the boiler would supply all my domestic hw use.

"Barold" wrote:

I'm suspicous that the heat exchanger connected to the hot water heater isn't capable of taking the heat from the hot water fast or effecient enough to transfer the heat to the domestic hw

Sounds like the right track. Figure out some way to measure the temps and you'll probably confirm that. You also might have a pump that cuts out for some reason?

"Barold" wrote in message

Thanks Harry. The pump at the boiler does constantly run, continually pumping hot water into the house - when the radiant heat circulating pump or the hot water heater call for heat, the hot water from the boiler provides the heat...I'm suspicous that the heat exchanger connected to the hot water heater isn't capable of taking the heat from the hot water fast or effecient enough to transfer the heat to the domestic hw. I assumed the boiler would supply all my domestic hw use.

If you're circulating water to the house constantly, I'd say you have the right idea. If the heat exchanger is relatively small, when the potable water flows through it it may not be heated enough to avoid starting the DHW heater.
Before you run out and buy a larger heat exchanger though, check to see what kind of flow rate you're getting through the boiler-side. If there is a throttle valve or other adjustment to increase flow through the heat exchanger on the boiler-side, it should help to raise the potable water outlet temperature.
daestrom

--Silly idea time: that's a looong pipe to connect between boiler and load. Howzabout moving the washing machine closer to the boiler?
-- "Steamboat Ed" Haas : Whatever happened Hacking the Trailing Edge! : to Porgy Tirebiter? www.nmpproducts.com ---Decks a-wash in a sea of words---

On 25 May 2006 16:19:14 -0700, "Barold" wrote:

Thanks Harry. The pump at the boiler does constantly run, continually pumping hot water into the house - when the radiant heat circulating pump or the hot water heater call for heat, the hot water from the boiler provides the heat...I'm suspicous that the heat exchanger connected to the hot water heater isn't capable of taking the heat from the hot water fast or effecient enough to transfer the heat to the domestic hw. I assumed the boiler would supply all my domestic hw use.
Harry, while I don't have a very clear picture of how the whole system

is interconnected, it seems to me that since you said they turning on a hot tap almost immediately starts the gas burner, then the gas burner is sensing water temp at a point at which the cold water enters. Question - is there a cold water connection to the to the water tank? or just to the hot water boiler?. If the cold water enters the tank and then is drawn from there to the boiler (for heating), then it could potentially trigger the thermostat. (I don't quite know how you heat exchanged is connected). It is a similar situation here with a water heating jacket in a woodburner, and the electric element in my hwc. If the shower is used, hot water is drawn from the top of the water cylinder, and cold enters the bottom. This turns on the electric element, even if hot water is coming in from the hot water jacket in the burner. To overcome this, I generally turn off the element when the woodburner is being used. Ideally there would be a second sensor or thermostat say half way up the tank (or whatever you choose), which would be used for the element when the woodburner is in use. This would ensure that only when you get down to a predetermined amount of hot water, would the "backup" turn on. It would ensure that the woodburner would do the heating job "first".
Again, as others, YMMV.
Eric Sears.