OWB plumbing question

[joecool85]

I have a couple questions about plumbing an outdoor wood boiler. I have an existing baseboard heat system, oil fired boiler, 2 zones and domestic hot water. 1200 square foot two story house, central Maine. I'm mostly interested in using the wood to heat my house, I can worry about the hot water later.

I'd like to only run the pump for the owb when heat is called for, so I was planning on wiring it so that if either or both zones call for heat, the owb pump kicks in as well as the regular baseboard pump(s). Is this possible?

Also, plumbing wise, would I need two plate exchangers (one for each zone) or just one? If just one, how do I hook it up to the large "black pipe" style water pipe feeding my oil furnance?

 

[highpointtree]

owb

I got great prices from www.altheatsupply.com if you need the exchangers and other supplys, like pumps, etc. You can use just one exchanger for both zones and domestic hot water. I would let the pump run 24/7 so you don't have to wait for heat. shop around for price and quality and if you buy from altheatsupply in connecticut, they will help out a great deal and all parts come with very simple instructions. I started with a plumber and he was over-engineering everything aND SCEWED THINGS UP. So I got rid of him and finished it myself. heat exchanger goes on the return just before it enters the boiler. I have a seperate water tank that runs off another zone for domestic hot.....good luck. just keep it simple

 

[Butch(OH)]

I don't know squat about indoor boilers so I cant help you with your exchanger question. I can tell you there is no reason to switch the OWB pump circuit on and off, the circulators use almost zippo for electric and supposedly will last longer of left running. Mine are 4 years old and run 24-7 for 7-8 months a year. Also most OWB manufacturers say run the pumps all the time. Hardy is one exception that I know of. If you enjoy working out complications and engineering them then have fun but as Highpointtree said, there is no other reason for it. I kept mine simple so I wouldn't have to pay the furnace man extra money to sit there and figure out what I had done. (when the gas furnace needs service). I have forced air, all I did was install a heat exchanger in my duct and control the fan with an additional 'stat. domestic water is heated via plate exchanger too. It works well, I have burned not a cubic foot of gas for heat since the fall of 2006.

 

[joecool85]

I don't know squat about indoor boilers so I cant help you with your exchanger question. I can tell you there is no reason to switch the OWB pump circuit on and off, the circulators use almost zippo for electric and supposedly will last longer of left running. Mine are 4 years old and run 24-7 for 7-8 months a year. Also most OWB manufacturers say run the pumps all the time. Hardy is one exception that I know of. If you enjoy working out complications and engineering them then have fun but as Highpointtree said, there is no other reason for it. I kept mine simple so I wouldn't have to pay the furnace man extra money to sit there and figure out what I had done. (when the gas furnace needs service). I have forced air, all I did was install a heat exchanger in my duct and control the fan with an additional 'stat. domestic water is heated via plate exchanger too. It works well, I have burned not a cubic foot of gas for heat since the fall of 2006.

I was doing the math and it looked liked a pump would be running about 2kwh per day, since I average 12kwh per day in the winter, that would be a big increase in electricity usage.

 

[farmerhelper]

pump

I run my pump 24/7 and that keeps the water circulating and avoids hot spots in your boilers water I believe.

 

[Butch(OH)]

I was doing the math and it looked liked a pump would be running about 2kwh per day, since I average 12kwh per day in the winter, that would be a big increase in electricity usage.

Mine combined are pulling just over an amp, for conversation here (I cant remember the exact amps) I will use 150 watts. At my rates that is just under $11 per month. How much switching them on and off effects the life of the pump I can only guess? I have to run mine 24-7 anyway as my OWB requires it.

 

[joecool85]

Mine combined are pulling just over an amp, for conversation here (I cant remember the exact amps) I will use 150 watts. At my rates that is just under $11 per month. How much switching them on and off effects the life of the pump I can only guess? I have to run mine 24-7 anyway as my OWB requires it.

Yeah, that math sounds about right. I suppose thats not that bad. Technically this isn't an OWB, it is a 30 year old indoor unit that I'm going to be installing in a 5' x 6' steel shed with insulation.

 

[Butch(OH)]

Yeah, that math sounds about right. I suppose thats not that bad. Technically this isn't an OWB, it is a 30 year old indoor unit that I'm going to be installing in a 5' x 6' steel shed with insulation.

I like homemade, post pics!

 

[joecool85]

I like homemade, post pics!

Will do. The install won't happen till this summer, but I'll keep you guys posted.

What pumps are you guys using? I'm thinking of a Taco 008 or 009. The boiler is only going to be 30' from the house.

 

[mtfallsmikey]

Will do. The install won't happen till this summer, but I'll keep you guys posted.

What pumps are you guys using? I'm thinking of a Taco 008 or 009. The boiler is only going to be 30' from the house.

Depends....how much flow do you need, total ft. of head, Total BTU required???...Look at a multiple-speed pump. Most OWB's require 24/7 primary pump operation. You SHOULD do a heat loss calc. on the house, and/or see what the total ft. of BB is, so you can size your lines/pumps/HX's properly.

 

[joecool85]

Depends....how much flow do you need, total ft. of head, Total BTU required???...Look at a multiple-speed pump. Most OWB's require 24/7 primary pump operation. You SHOULD do a heat loss calc. on the house, and/or see what the total ft. of BB is, so you can size your lines/pumps/HX's properly.

Multi-speed pump might not be a bad idea. Like I said though, it's actually an INDOOR wood boiler that will be put outside in an insulated shed, so mechanically it is a little different.

Zone #1 has 26' of baseboard, Zone #2 has 40', we really should have like 35-40' in Zone #1 because right now when it dips below 0 the house won't stay warmer than 66 or so. Luckily we don't get a lot of that (a few days to a week most winters), and we normally keep the house 68-70 so it's not too bad.

Doing a calculation of 600btu per foot of baseboard, that means our house is only using ~40,000 btus. So a small pump would suffice. That said, I'd like to deliver 50-60k btus so if we upgrade our heating system (more baseboard) it would support it.

However, if the oil kicks in on those really cold days its not a big deal to me. Right now we burn ~650 gallons / year and in the summer it is using 15-20 gallons/month. We are looking to cut our consumption down to 150 gallons to start with, and after we add a hot water storage tank down the road and hook up our domestic hot water, we are hoping for pretty 50 gallons or less/yr.

 

[joecool85]

Taco 00R looks good: http://www.taco-hvac.com/uploads/FileLibrary/102-226.pdf

5-10gpm at 10' of head, and runs between 85-125 watts depending on the setting (3 speeds). I could set it on low and use 2kwh/day or high and use 3kwh/day. I bet most of the time I could run it on low and have enough heat. They're cheap too, under $100.

 

[itn]

I have a system very similiar to what yours. I have an lp boiler not oil. 2 zone with valves to throttle, one pump,1200 sq ft, outside boiler is about 35ft away.

I tied my system together. The CB water comes in, runs through the water to water heat exchanger and heats the domestic hot water. it is then piped to the suction side of the in house boiler and pump. if the in house thermostat is not calling for heat, it runs through a (bypass)control valve which returns it out to the boiler. If the in house themostat is calling for heat, the in house boiler pump starts, the (bypass)control valve closes, it then goes through the baseboard heat before being retuned to the boiler.

I've done it this way for 5 years. Taco 009 pump I think, Replaced the head on the bypass control valve this past fall.

 

[joecool85]

I have a system very similiar to what yours. I have an lp boiler not oil. 2 zone with valves to throttle, one pump,1200 sq ft, outside boiler is about 35ft away.

I tied my system together. The CB water comes in, runs through the water to water heat exchanger and heats the domestic hot water. it is then piped to the suction side of the in house boiler and pump. if the in house thermostat is not calling for heat, it runs through a (bypass)control valve which returns it out to the boiler. If the in house themostat is calling for heat, the in house boiler pump starts, the (bypass)control valve closes, it then goes through the baseboard heat before being retuned to the boiler.

I've done it this way for 5 years. Taco 009 pump I think, Replaced the head on the bypass control valve this past fall.

Interesting how you do it all with one pump. My current setup has a pump for each zone, and I'm going to be adding a pump to come from the OWB. Making 3 pumps total.

 

[mtfallsmikey]

Interesting how you do it all with one pump. My current setup has a pump for each zone, and I'm going to be adding a pump to come from the OWB. Making 3 pumps total.

To learn more: (Not to be a shill, Darin) about hydronics:

www.heatinghelp.com

 

[Kevin in Ohio]

I, Like ITN have a setup like you talking about. Hot water comes in at far right. Then to the water heater off pic. Water comes down the middle pipe to bottom to the heat exchanger. If not needed for the house it bypasses and goes back to boiler. If 2 garage zones need heat(pumps above) they draw as needed.

I run the pump for the boiler constant. I had hot water oil burner prevoius so all I did was tie into the main line from that system and use that on the OTHER side of the heat exchanger. The Oil furnace circulator pump runs constantly as well. I used the existing thermastats to control the heat exchanger. Virtually No change to old system other than a wire change and one tie in to main line. Running pumps constant keeps the baseboard from "ticking" form sudden heat up or down.

Going 6 years. Only thing replaced was the Zone valve head after 5 years. Ask away with questions, I'll answer if I can. Kevin

View attachment 122202

View attachment 122203

 

[mtfallsmikey]

Nice layout, Kevin....

I would love to see someone integrate outdoor temp. rest into a wood boiler system someday...

 

[joecool85]

Nice layout, Kevin....

I would love to see someone integrate outdoor temp. rest into a wood boiler system someday...

You mean like this: http://www.energysavingsusa.net/catalog/item/1603486/1049385.htm ?

I have a feeling folks are less likely to do that due to the fact that OWBs tend to be a bit smokey as it is since people frequently install "too large" of a btu boiler to help on load times (long load times, larger firebox). This makes it smokey on warm days when it isn't working very hard, damping the fire down to a smolder. If you turn down the temp in warm weather, its going to smoke even worse because it'll be damping the fire down so hard.

 

[joecool85]

Did some math, and like I said before, according to 600btu/ft of baseboard, we should have a max output of almost exactly 40,000 btu here. I did some more math and during our coldest month (January), we used about 150 gallons. At 132,000 btu/gallon of oil, that ends up at ~27,000 btu/hr usage all month average. So I'd say 40,000 btu is probably our max right now with the amount of baseboard we have. I've read that 1gpm carries 10,000 btu with hydronic heating systems, so I would need a minimum of 4gpm to make sure I get all the heat I need. If we add another 6' of baseboard downstairs like we are thinking of doing, this would put us at a max usage of 43,200 btu. To be safe, I'd bank on a 5gpm pump.

Now to calculate head loss. For 1" PEX there will only be a friction "head" loss of 3ft or so, and my lines will only have 2ft of head on their own. So I need a pump that can handle 5gpm at 5ft of head.

Since it appears that running the pump 24/7 is a good idea (at least to start with so we can keep it simple), I want the lowest wattage possible that still does the job.

According to the data sheets, a Taco 006 puts out 6gpm at 5ft of head, so that is a contender. 62 watts of power consumption. Prices vary, but seems to go for about $150

The Taco 00r 3spd pump is a contender. At 5ft of head it pumps 9, 11.5 and 14 gpm depending on what setting it is on and uses 90, 102, or 132 watts also dependent on setting. Seems like this is actually quite a bit overkill for my application. Sells for average of $85 online.

The final contender is the Grundfos UPS 15-58 3 spd pump, a pump that I found out about because the Taco 00r is a "direct replacement." At 5ft of head it pumps out 5, 10, or 14 gpm at 60, 80, or 89 watts respectively.

Seems the Grundfos is perfect, on low it should cover all of my heating needs, and just in case it doesn't it can triple it's output and only raise it's wattage by 50%. Also, it's only $80!

I was worried about quality, but I've read a lot of good reviews about the Grundfos, and think I will probably go that route when it is time to buy my pump. I can live with 1.5kwh/day during the winter added onto my bill.

 

[joecool85]

Still not sure on heat exchanger. I have 1 1/4" in and out on my oil fired boiler, and it steps down to 3/4" for both zones, dhw is 1/2".

I was thinking I could build a side arm for each zone and that would take care of my heat, then I could add a sidearm for the dhw or add a zone and a tank later.

Or, would it make more sense to use a 30 plate heat exchanger and tap it into the 1 1/4" steel pipe cold side of the oil furnace?