Running 4--1" insulated pex underground

[MyOutdoors]

I'm going to be in the process of digging up my existing dual insulated 1" pex and adding another dual 1" line. Heaterman was helping me out but hasn't been on the site for a little while (assume he's busy working). My lines will meet at the OWB as well as inside my house. I need to connect the lines via a homemade T of preferable manifold meant for this application. Can someone recommend where to find such a manifold? Also, I will be tying into the existing single 1" copper supply/return (60') line once inside the house, which connects to my 50 plate HX. Will this "kill" what I"m trying to accomplish with the dual supply and return by funneling down to a single line again?

My problem last season was the boiler puts out 120k BTU, my heat load is 53k plus DHW. I heated my home last season without any problems excepet for the extremely high head in the system which caused the pump to cavitate. Any xtra help, thoughts, input will help. Thank you.

 

[sdrobertson]

Anytime you throttle the flow down, you'll increase the head. I'd go the extra feet and hook up your manifold at the closest point to your exchanger. I made my manifolds out of black pipe using "T"'s and short nipples. Depends on what you have on hand but it is not hard to make one, just takes pieces. I don't have any link to on-line sources of premade ones as I never researched them.

 

[Hydronics]

Doing so won't negate having the 4 1" for the major part of the run. You will further increase your flow if you also double that to 4 1". Can you leave the 2 exisitng copper runs & add 2 1" pex runs in the house or is there an obstruction?

 

[MyOutdoors]

no obstructions. Any thoughts on what pump to use?

 

[jebatty]

Determine your heat load btu requirement. Divide that by (delta-T x 500) to get your gpm's. Then determine pump head in your system at the required gpm. Go to circ selection curves and pick a circ that can provide the needed gpm at the pump head, ideally in about the middle of the pump curve.

 

[heaterman]

I'm going to be in the process of digging up my existing dual insulated 1" pex and adding another dual 1" line. Heaterman was helping me out but hasn't been on the site for a little while (assume he's busy working). My lines will meet at the OWB as well as inside my house. I need to connect the lines via a homemade T of preferable manifold meant for this application. Can someone recommend where to find such a manifold? Also, I will be tying into the existing single 1" copper supply/return (60') line once inside the house, which connects to my 50 plate HX. Will this "kill" what I"m trying to accomplish with the dual supply and return by funneling down to a single line again?

My problem last season was the boiler puts out 120k BTU, my heat load is 53k plus DHW. I heated my home last season without any problems excepet for the extremely high head in the system which caused the pump to cavitate. Any xtra help, thoughts, input will help. Thank you.

Heaterman had burned through about 75 hours by Thursday night last week and then things went downhill from there. I'll try to get back up to speed on this and get back with you.

Basically, you want to assemble a little manifold configuration out of two tees. I use either steel threaded or sweat one up out of copper fittings. The inlet or outlet will exit one end, your lines will both enter/exit on the side and the remaining end will be pliugged. This will be best for keeping the flow as balanced as possible in both of your tubes. Doesn't have to be fancy.

 

[MyOutdoors]

You may have saved me some serious time and $, Jebatty! I thought I was supposed to put in the max BTU the boiler put out, not the heat load my home requires? I was always putting in 150K-200K BTU's then divided by the (deltaT x 500). I have a heat load of 53K according to my room sizes. That did not include my DHW though. Does that sound right for a 6 year old 2700 sqft home? What would you put in for a safe Heat load, 80K?

 

[MyOutdoors]

What I'm hoping for is that if I double the insulated lines, I will be able to use a smaller pump and eliminate the problem I had last season, which was cavitation (plumber put in a 014) which for my current set up shows 33 gpm and 23 ft head. Totally wrong application.

 

[jebatty]

I thought I was supposed to put in the max BTU the boiler put out, not the heat load my home requires? I was always putting in 150K-200K BTU’s then divided by the (deltaT x 500). I have a heat load of 53K ... What would you put in for a safe Heat load, 80K?

If you plumb for max OWB output, which is more than your heat demand, you have lots of plumbing in place to provide heat that is not needed. Expensive. I agree that a plan for a margin of error above the heat load calc is wise. Your judgment as to the 80K; I'm no professional at this.

To the extent your OWB puts out more btu's than your demand or your plumbing capacity, the boiler will heat to maximum temp (about 185F), and then shut down, and then cycle on again as needed to supply the demand. Normal operating scenario. IMO you want to plumb for your demand + margin of error (do you plan any future expansion of heating need? If so, plan for that as well).

I can't speak for an OWB, as I have no experience which I can quantify, but for my Tarm, rated at 140,000, I estimate average output over a burn is 60-80%, or so, of maximum; and actual output over a good part of the burn is between 90-110K. My system moves about 9 gpm. With a delta-T of 20, that moves 90,000 btu. Since I also have 1000 gal of hot water storage, the delta-T usually runs between 20-40, and 9 gpm is normally plenty to take the full boiler output, whatever it is, during an entire burn, with no boiler shut down cycling.

 

[MyOutdoors]

Nice to hear from you again Heaterman. I figured you were busy.