Hi All - About to replace an older p/s piped watertube boiler (Burnham X-C series) with a direct piped UFT 80w and have a few questions. For a little background on my current system and why I'm moving to the UFT: I installed the current system about 5 years ago and it works ok but leaves a lot to be desired. Heat loss for the house is around ~57k btu - turn of century house in the lower Hudson Valley NY (Rockland Co) lots of windows, no insulation in the walls, 15* design day temp. Current boiler is 94K btu with a 5:1 turndown - modulates down to 20K btu - so it's quite oversized and short cycles more than I would like. It also requires a high head circ (taco 0013) for the primary loop which draws a lot of power and makes a lot of noise. Delta T for the primary loop is consistently ~5*, even at high fire, while my system loop delta t is almost a perfect 20* as designed. Manufacturer (Burnham) didn't publish any pressure drop figures for the heat exchanger. They just spec the max effective length for the primary loop and tell you to use the 0013 or the Grundfos equivalent if you're under that max. Design day supply temp is 160* so I should be in condensing range most of the heating season but the primary loop is killing efficiency. Image of current system is below:
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Current emitters are fin tube (two zones, around 100' total) with a couple of panel rads (on monoflo tees) where I couldn't fit enough fin tube. New system will be 3 under floor radiant loops of around 270' each for the first floor - extruded plates, insulated, etc - and a few panel rads as second stage. Upper two floors will all be panel rads. There will be 12 panel rads total on 8 circuits. 6 rads will be home runs, one circuit will have 3 rads in series with "H-Valve" bypass valves, and one circuit will have 2 rads in series with H-Valves. All panel rads will have TRVs. Floor loops will have actuators on the manifold. Rads are sized for 150* design day supply temp with a 20* delta T. Wish I could have gotten that down to 140* but there are lots of windows that go down to about a foot above the floor so wall space is limited.
I'm planning to pipe the UFT direct, ODR, constant circulation with a Viridian 1816, 12 port Caleffi manifold. One design day supply temp (150 *) for both the floor loops and the rads. I have a t'stat with a floor temp sensor to make sure I'm not getting the floor surface over 85ish *. Trying to keep it fairly simple and not run a mixing valve, additional circ, manifold, etc for the floor loops. Ran the numbers and the 1816 will supply all 11 circuits.
My question is this: With constant circulation (tt shorted) on a direct pipe system how do I ensure the min flow through the boiler (1.3 GPM per HTP manual) is maintained if all TRVs close off most of the way and the floor loop actuators are closed? My thought, and this may defeat the purpose of the viridian circ in delta p mode, would be to add a press differential bypass valve set to ~ 2 GPM as a safety. Or perhaps the UFT control logic shuts down the burner if there is little/no demand? Also, being that two of the rad circuits are using bypass valves, there will be some flow through the system either way - not sure how to figure out how much. Is there any point in using a viridian circ in constant pressure mode in this scenario? This config (constant circ, direct pipe, TRVs/actuators) is all quite new to me so can't quite grasp conceptually how it should work. A (very) rough sketch of the proposed system is below for reference...need to work on my visio skills. Thanks in advance for any guidance.
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Current emitters are fin tube (two zones, around 100' total) with a couple of panel rads (on monoflo tees) where I couldn't fit enough fin tube. New system will be 3 under floor radiant loops of around 270' each for the first floor - extruded plates, insulated, etc - and a few panel rads as second stage. Upper two floors will all be panel rads. There will be 12 panel rads total on 8 circuits. 6 rads will be home runs, one circuit will have 3 rads in series with "H-Valve" bypass valves, and one circuit will have 2 rads in series with H-Valves. All panel rads will have TRVs. Floor loops will have actuators on the manifold. Rads are sized for 150* design day supply temp with a 20* delta T. Wish I could have gotten that down to 140* but there are lots of windows that go down to about a foot above the floor so wall space is limited.
I'm planning to pipe the UFT direct, ODR, constant circulation with a Viridian 1816, 12 port Caleffi manifold. One design day supply temp (150 *) for both the floor loops and the rads. I have a t'stat with a floor temp sensor to make sure I'm not getting the floor surface over 85ish *. Trying to keep it fairly simple and not run a mixing valve, additional circ, manifold, etc for the floor loops. Ran the numbers and the 1816 will supply all 11 circuits.
My question is this: With constant circulation (tt shorted) on a direct pipe system how do I ensure the min flow through the boiler (1.3 GPM per HTP manual) is maintained if all TRVs close off most of the way and the floor loop actuators are closed? My thought, and this may defeat the purpose of the viridian circ in delta p mode, would be to add a press differential bypass valve set to ~ 2 GPM as a safety. Or perhaps the UFT control logic shuts down the burner if there is little/no demand? Also, being that two of the rad circuits are using bypass valves, there will be some flow through the system either way - not sure how to figure out how much. Is there any point in using a viridian circ in constant pressure mode in this scenario? This config (constant circ, direct pipe, TRVs/actuators) is all quite new to me so can't quite grasp conceptually how it should work. A (very) rough sketch of the proposed system is below for reference...need to work on my visio skills. Thanks in advance for any guidance.
