OWB fired today, domestic water ?

[iCreek]

Wow, we had a nice day today in the midwest, 50 degrees this afternoon. Worked out great for getting my Hardy outdoor stove fired up and running. I attached some photos, it was good to see smoke come out the chimney.

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Not sure I have my domestic water working correctly though. The way the pump works at the stove end, it pumps when a relay is triggered from the furnace needing more heat. When the inside home thermostat gets below the set temperature, it turns on the pump and pumps water into the Pex lines (see below pic) going to my AIC water to water exchanger to heat the domestic water, then that heated water goes into my water heater tank. After the hot (stove in) leaves the water to water heat exchanger, it goes into the air to water heat exchanger, to provide heat for the forced air furnace. What I noticed was that the water lines get cold inside the house, where the Pex terminates into the exchangers. This happens when the pump sits idle for a few hours, it was warm today so the thermostat did not kick on much today.

My question is do most people that heat domestic water inside, run the pumps all the time? I think I can do that, but others in my family that run these Hardy stoves, have the pump turn on only when heat is needed, they heat the domestic water out at the stove with an additional pump and two lines. The guy that hooked up my relays and thermostat said it could be hooked up either way. I guess the only way for heated water to flow through the water to water exchanger at all times is to run the pump all the time? This might not be an issue as it gets colder outside and the pump runs more frequent, but today I noticed the inside Pex pipes getting cold,75 degrees, after a few hours. I still have my propane pilot set to Med., I was just wanting to drop it down and save more propane $$. Any ideas or suggestions?

(additional question about water to air furnace exchanger)
Another thing I noticed this evening, when the furnace first kicks on, the air at the registers is cold/warm, then it warms up after 1 -2 minutes and feels hot. I think this has to do with the water cooling down in the lines, going into the heat exchanger, then warming up as the pump circulates the warmer water into the system, is this normal?

Here is a pic for reference, AIC water to water heat exchanger on top, then the water to air heat exchanger in the furnace below. The Cold Soft Water to OWB is for filling the water levels.

 

[alan mesmer]

I may be misunderstanding you here....
Do your pex lines contain anti-freeze? The only way I would consider only having my circulating pump run only on demand is if you have an antifreeze solution. My lines would freeze if they only ran on demand.
My circulating pump runs 24/7 providing unlimited hot water. When needed it provides on demand via a 3 way solenoid valve located inside the house controlled by a themostat, providing hot water to my heat exchanger. That is the only way that I have ever seen it set up on units that do not use antifreeze but maybe your setup is different than what I am used to seeing.
If your circulating pump is not running or your lines do not have a antifreeze solution you may very well freeze in below 32 deg weather. I'm not sure that a second zone line coming from your OWB should be on demand either. Typically a second line is used for a seperate zone (garage, etc.) which is usually set up in the same manner. You may get away with a on demand setup where outside temps. stay above freezing but I don't think it will work well in below freezing weather.

Alan

 

[iCreek]

alan - no my lines do not have antifreeze, just have plain soft water. We buried my Pex lines at 3 1/2 feet deep, have them insulated and in a 4" sleeve. Missouri winters get cold, but not as cold as your northern winters. My in laws (up the road) have been running this configuration for years with no freezes, and theirs are not that deep in the ground. I am going to go feel his exchanger inlets in the house and see if they stay hot, or are cold like mine when idle. I have an IR temp gun, and mine read about 75 degrees when idle for a 3 or so hours. Our house is pretty new and lots of insulation, heck tonight I have it set to 73 and the darn thing has not even kicked on, the house has been staying at 73

I guess these pumps are made to run all the time, I might just do that and then not have to worry about it. Thanks for the info, hopefully some others will jump in also.

 

[Mike Van]

Not an OWB, but same principle - My Harman add-on boiler has a circulator pump between it & the furnace, it runs 24/7 as long as the wood boiler water temp is 140F or more. We NEVER run out of hot water. I can't see my set-up working "on demand", too much lag time. As long as my circ. pump is going, the furnace will not kick on.

 

[iCreek]

Furnace Temp readings (sidenote)

I asked my father in law this morning, his copper lines (pre Pex) get a little cold also when the pump is not circulating, and he said there is a little delay in hot air when his furnance first kicks on also. Does not notice his hot water temp, but his domestic water is on a seperate pump and line system, coming from the stove.

Not sure about my water temps yet, as my water heater can still heat any water in the tank with the propane burner, I am just heating the water prior to going into the tank, have not noticed the burner turning on yet...

Here are some reading from my floor duct work vents using a Maverick Infrared Laser 'BBQ' Surface Thermometer aiming in through the vents. I guess this is OK, anyone know what Temp I should be getting out of forced air furnance floor vents? Do these readings look OK?

ps. I got a 14 hour burn last night, and when I went to fill it up this morning, still had 3 logs on the bottom grate. It was 23 low last night. My goal is 12 hr burns all winter

First turn on heat
76 degrees

After 1 minute
85 degrees

After 2 minutes
98 degrees

After 4 minutes (different floor registers)
116 - 122 degrees

 

[HUSKYMAN]

Well running the pump all the time will give you instant heat instead of the delay, and will decrease your furnace fan's run time. It will also give you hot water faster and eliminate all these relays that will eventually fail over time.

My Taco pumps only draw an amp or two and my electric bills are only $90 a month, so I would just eliminate the unnecessary complication in the system and run the pumps all the time. Having the extra heat stored in the lines may give you better burn times in your boiler too.

 

[rx7145]

just let them run 24/7. I have two pumps that I run 24hrs a day. Lots of hot water and instant heat.

 

[Blazin]

My pumps also run 24/7 I just have the house themostat to kick the furnace blower on for heat and the exchanger on the Domestic hot water tank circulates continously by convection(no pump)....Everything is hot when needed.

 

[iCreek]

Thanks...

OK sounds great, I will probably bypass the relay on the stove, and plug those two wires into each other, then the pump will run all the time. My friend that is an installer for furnaces and wood stoves who helped hook up the relays and the thermostats, gave me that option the other day. I will probably write down the Taco model and order a spare cartride and gasket to have on hand, already have a spare blower motor.

The frost line is about 30" in our area, so I should not have a problem with freezing lines, I am at least a foot deeper, but the instant heat at register and circulating hot water into the water heater will be nicer.

I 'Googled' the average temp at floor registers and found the below, I hope to get better than my 122 degrees with the pump on, and like HUSKEYMAN said, it should run my furnace fan less to get to desired temp in the house.

Propane Hot register temperature - Approx. 115-135 degrees

Natural Gas Hot register temperature - Approx. 115-135 degrees

Heat Pump Heat feels cold - register temperature Approx. 80- 95 degrees

It got to the high 50s today, so did not burn much wood today, second day... But we are suppose to have some cold weather mid - late this week... Kind of sick wanting some cold weather, so I can try this thing out.

 

[oneoldbanjo]

I have a Woodmaster and my pump runs 24/7. The heat exchanger for the water supply (water coming into the water heater) makes the water so hot my water heater never comes on....and I have the circuit breaker shut off so the heating elements don't run at all. The normal way that the furnace works is that the hot water goes through the coil in the duct work all the time, and the second thermostat for the woodburner would turn on a fan center (solenoid) and turn on the blower when heat was required in the house.

My heat pump has a variable speed motor and could not be used with a second thermostat controlling the fan - so we had to install a zone valve and control the water flow to the coil. We set the fan to run on the slow setting 24/7 - and the hot water only flows through the coil when the thermostat calls for heat. It is nice having a low speed air flow in the house all the time as it keeps the temperatures constant and there are no hot or cold spots in my house.

I would suggest that you run your pump all the time and have a thermostat control your furnace blower when you need heat - or use an eletric zone valve to direct the water flow to the furnace coil.

 

[MAK 74]

I have a H4 and my pump kicks on when the themostat calls for heat. And my domestic hot water has a seaperate pump that pumps the water through a copper coil in the tank of the stove. I have the gas turned off on my hot water heater, as long as someone takes a shower every day the water stays hot in the tank. My wife filled the stove @ 6:00 am and i filled it @ 8:00 pm when i got home and it stll had 4 logs in it and she has the thermostat set on 75.