New CB 6048, plenty of heat transfer and piping questions!

[ovenmaster5]

Hello everyone.  I took the plunge and ordered a 6048 last week, looking forward to burning wood and getting away from the ridiculous power bills.  My dealer has been using a 6048 himself for over 10 years, but I'm struggling with his experience vs my knowledge of heat transfer.

Myself I did a stint in the Navy as a Nuke, learned more about moving energy from A to B than I ever cared to know, and now do it for a living as a civilian.  I'm working on sizing everything for my install, and I'm coming to conflicting points from how my dealer has installed the boilers he has sold and what "seems right" to me.  I have a tendency to overengineer things, but I'd rather have the ability to put too much heat to my house than wish I had done a better job in the first place.

I currently have 2- 20Kw forced air units in my home, one main floor, one upstairs.  Roughly 6,000 sq ft, built in 1889, in Nebraska.  This winter hasn't been harsh by any stretch, but my power usage is 10-14 MEGA watt hours per month.  My main floor unit can only maintain about a 50 degree delta from outside temperature.  Makes those 0 degree days a little chilly!  I have high main floor ceilings (~14 ft), and the main floor unit runs nearly constantly.  Upstairs will easily drive you out.

My plan for the install is as follows.  1- 120k BTU/hr HX on the main floor.  1- 80k BTU/hr HX in the upstairs.  1- 80k HX in the garage, a 26k BTU in the finished room over the garage, and a DHW HX.  Say 325k BTU/hr maximum demand with everything calling for heat.  Eventually I'd like to add radiant floor heat to my kitchen and basement as remodeling takes place.  I elected to go with the boiler first, and insulation in a few years after the boiler pays itself off.

What I'm really struggling with right now is my supply.  Ideally I'd like to have a 20-30 degree delta, so 155-165ish degree water coming back to my boiler.  I'm not going to get anywhere near that with 1" Thermopex and a Taco 007 pump.  Based on what I'm calculating for needed flowrate, I'm looking at somewhere around 50 GPM flow.  That can't be right.  I know that everything in the house isn't going to be calling for heat at the same time, but my fear is that I will be in the same shoes I am now next winter, just with a different heat source that can't keep up.

I'd rather run one loop to the house for cost reasons if possible, but it doesn't seem to me mathmatically that 1 1/4" Thermopex will be able to supply what I need.  I get the feeling I need to run 2 loops from the boiler to the house.

Additionally, I'm looking at ~30 feet of rise from my basement where the lines will come in to my unit in the attic.  I would think I would need another pump to get the required head to get up there and provide a reasonable flow rate to the HX there and in the room over the garage (~15 feet rise).

Any suggestions would be greatly appreciated.  As I said, I tend to overengineer things, but there's little sense in wasting money to do a job that isn't really there.

Thanks in advance.

[beenthere]

Welcome to the Forestry Forum.

Look forward to hearing about your installation.

[xalexjx]

how well is the building insulated?

[garret]

This winter hasn't been harsh by any stretch, but my power usage is 10-14 MEGA watt hours per month.

That's one huge E-bill for a residence!  May I ask what it is during harsh winter conditions?

Better get that 6048 stoked up fast.

[thecfarm]

ovenmaster5,welcome to the forum. I am sure no expect. But I would think you would need 2 lines and a bigger pump. But members that know what they are doing will help you out more than I can. 

[bandmiller2]

Be careful mate too big a unit and it will coke up from slow burning, I would rather see a slightly smaller unit running to capacity and burning clean. Sounds like windows and more insulation would be a large improvement. I would go with several zones you can adjust easily so where mommy is during the day and evening she's warm, bedrooms cool. Probibly the wind going through an old home is your biggest problem. It helps if you have dump zones like the cellar if things get too hot. Slant/fin co. has a free disc program they call hydronic Explorer it lets you estimate hear requirements and change things around to compare. Good luck mate enjoy it, its an interesting project . Frank C.

[Holmes]

 Welcome to the FF.  Do you know the distance from the house to the boiler, how much pex you will need for the supply- return piping?  Have you considered an 80 gallon buffer / storage tank in the house?

[ovenmaster5]

Thanks for the replies and welcomes, I'll be posting pics and whatever types of install I end up with.

As far as what the electrical usage would look like during harsh months, I shudder to think.  We bought this house last August, so I haven't seen a "bad" (for NE) winter.  We've only had one week where the high was single digits, I can remember 20 below nights and highs in the negatives.  As far as worst case, I'd be looking at ~29MWh if both heat coils were on 24/7 for 30 days...

Frank is pretty much on the ball as to what I believe my issues are.  Main floor windows are all thermopane and a couple years old.  Walls however are a different story.  Most of my walls are still plaster, and the plaster temps of the interior walls are quite cold, maybe 50ish at best.  There was what I assume was blow in insulation put in at some point, as there are caps all along the wood siding where it was blown in, but I haven't torn into a wall to see what is in there for sure.  Most of my outlets on the main floor have a breeze coming through them, if that is any hint as to what is (or isn't) in there.  It is entirely possible there is no sheeting under the siding, this place is old enough that the siding may be nailed straight to the studs. 

As far as insulation, whatever is here in the walls is no good.  The attic has some very old insulation in it, as an interim I'm laying down fiberglass batts this spring/summer until I can spray foam it.  As far as the walls, as funds permit all the plaster will come down and spray foam, house wrap and drywall will go up.  The wall remodel is probably a couple years out though, so for now I'm going to be wasting a lot of heat unfortunately.

As far as zoning goes, I plan on setting up 4 zones: main/basement floor unit, attic unit for the upstairs, small one in the daughter's toyroom, and the garage which will be more or less a heat sink.  I'm not planning on keeping the garage at 70, more like 50, but if I need to get rid of some heat then well, I can open plenty of windows out there =)

Piping distance will be 75-100 feet of buried pipe.  The indoor runs will be 20-50 feet to the first heat load.  I am not opposed to a storage tank in the basement.  I have room and can fab something up I'm sure to make the unit work better if that is what I need to do.

Am I correct in the assumption that 1GPM with a 20 degree drop equates to 10,000 BTU/hr?  That cuts me back to 32.5 GPM demand for the HX I plan to install with everything calling for heat.

Thanks again, any more suggestions or questions are welcome.  I appreciate the interest in helping me get this right. 

[VTwoodworker]

If I understand your situation you are planning on heating your house with the water directly from your boiler and you have 30' of elevation to the second floor.  If it were me I would set up a pressurized system in the house with multiple zones with thermostats and controls that will let you give priotity to different locations in the house during the extra cold days.  Thirty feet is a long way to pump the water in a non- pressurized loop.  You will not get the volume you want and the pipes will sound terrible.

You will want a pressurized system when you convert to radiant floor heat.  Otherwise it is nearly impossible to balance. 

With 100' feet of line in the ground you will want to buy the best insulated pipe you can find or you will be losing 30 degrees in getting the water to the house.  I have a 4500 sq ft house and a three car garage with an apartment overhead.  I have two 1" loops one to the house and one to the garage.  My house does not have the best insulation and I feel like I have alway had enough heat transfer capacity.

I do not understand why you think you will need to get rid of heat in a heat sink?  That is like saying I need to get rid of extra wood.  I heat my garage to 50 because that is where I want it.  It does take extra wood to heat it and I would not have paid for the garage plumbing for heat sink purposes.

Up sizing the pipes or extra loops will be real money for a 100' run.  You may want to consider spending that money on some insulation or windows now instead of pipe capacity that you probably won't need after your renovation.

Best of luck with the install.

Wayne