New Harman PB105 installation--question about underground pipe sizing

[katman]

I'm about to start the installation of my new Harman PB 105. It will be a remote install, going in a pole building about 100 feet from my house. I plan to tie it into my existing oil boiler/baseboard system. I've been evaluating several options for the underground piping. My initial preference was to run 1 1/4 inch iron pipe, foamed in the ditch. Compared that to 1 1/2 oxygen barrier pex that I would wrap with insulation and pull through 6 inch PVC. Both are about the same price. The least expensive option (for what I would consider an acceptable solution) is to use Thermapex at approximately $12.50/ft. I think the Thermapex is a nice product and it would actually be considerbly less expensive and less labor. The downside is the size of the pipe --the one inch is actuall a little less than an inch ID. My plumber and I figure the thermapex would carry the BTUs we need but we would suffer a bit in performance. Wondering how others dealt with the tradeoffs and if those who have used smaller pipe diameter in thermapex or other products are satisfied?

 

[woodsmaster]

you can get 1 1/4" thermopex or logstor for about $16/ ' I used 1 1/4 Thermopex on mine and have no drop in temp on
my 85' run that I can measure.

 

[kuribo]

I'm planning my system at the moment and am trying to figure out the size of my underground supply and return as well...My system will have a Econoburn 200 in a small outbuilding 50 feet from the house. House will have roughly 1000 sq feet of in floor on the first floor and 1800 sq feet in the basement. I will also plumb in DHW. Will have 2 500 gallon propane tanks horizontal in the basement....From what I read, it seems best to size the pipe to keep flow velocities lower....From online charts it looks like 10 gpm would be a good figure to shoot for. Using that, I think I need 1 1/4" with a 30 deg delta T. Then I read that people have problems topping off the storage with lower flow rates and that 20 gpm would be better....Maybe a variable speed circulator that can adjust the flow to match the boiler output/load would be best....Woodmaster, your system seems similar to what I will have...What gpm and delta T are you seeing? Are you able to run your boiler full out without idling to get those last BTU's in storage?

 

[woodsmaster]

I can get my storage up pretty high before it starts idle any. I have my storage right by the boiler with 1 1/2 " pipe
split with a T and reduced to 1 1/4" going to each tank parallel I usually have a 15 to 25 degree delta t threw the boiler
depending where it's at in the burn and temp of water going in.

I Know the circulator isn't turned right in the picture.

 

[katman]

Anyone know a source for the 1 1/4 thermapex? My local cental dealer just has the one inch. Called Central and they won't sell direct.

 

[woodsmaster]

Can't he get it for you ? Any other outdoor boiler places around that may be able to get logstor ?

 

[katman]

He doesn't seem interested in ordering. I'm trying to get hold of another guy in Delaware; I'll start checking VA and PA today.

 

[salecker]

Hi
When i was doing my underground lines i wanted to go with 1 1/4",it was really expensive,so i was advised to run two runs of 1" each way.Turned out to be a lot cheaper,my runs were 120' each way.Was faster to get the 1" as well.
Thomas

 

[katman]

Well, finally connected with the guy in Delaware and turns out he is bidding a job close to my place so he will drop off some the the 1 1/4 inch thermopex. At $17/ft it is about the same as my cost for foaming in ditch 1 1/2 inch opex. temp is a little iffy for foaming right now so this will work!

 

[woodsmaster]

That spray foam don't work very well when it's cold. I used to use it at work and we had to keep the lines really warm to work
right so I think your probably making a good decision.

 

[eriesigtau]

Fisher & Father in Cranberry,PA (near Franklin) sells both sizes. Call them first though. Thermopex is the way to go. I have it and have zero heat loss.