Few questions about my HWBB system with Caleffi manifolds

cckriss

Facts about my system:

- 2-zone system, 1st floor & 2nd floor. 3rd zone is PRIORITY for indirect water heater but not in use, house under renovation.

- Taco ZVC404 Zone Valve Control

- Hydrostat 3250- Plus

- Z100P2 zone valves

- 1 pump, Grundfos UPS15-58FC 3-speed. Set to LOW speed

- 2 Caleffi manifolds 6686G5S1A-INVERTED

- Buderis Boiler

Questions:

1) How do I read the Caleffi flow meters? The orange indicator is so thick. The top of the indicator will be at 1 GPM but the bottom of the indicator is at 3/4 GPM. What reading is that? Do I read the middle?

2) Assuming the MIDDLE is correct for question 1: When 1 zone is on, the flow will read 1 GPM but I will only have a 10 degree F delta. If 2 zones are on, the flow will drop to 3/4 GPM, but I will have 20 degree F delta. Is this normal?

3) Is my system supposed to allow 2 heating zones to be on at the same time? I don't know what happens if my indirect water heater calls. I havent tried it yet.

hot_rod

I would read the bottom if the disc. What gpm do you need?  

Is this a radiator loop? At 1 gpm

The delta will move around depending on the temperature if the loop

You would expect a wide delta when the zone first opens, it will tighten up as the zone warms

cckriss

Each branch off of the Caleffi manifold goes to about 8ft - 12ft of Slant Fin 30 radiator.

I was aiming for 1 GPM because I thought that's how the BTUs are calculated by Slant Fin.

I thought there should ALWAYS be a 20 degree delta. I guess I am mistaken? I assumed the 3/4 GPM had a 20 degree delta because the lower flow allowed the water to release its temperature through the radiators.

hot_rod

when you design a system you select a delta tee to size everything to. 20 delta is a common number for fin tube

At design condition, proper flow, it could run at  exactly 20 delta.

If you increase flow , the delta will drop, the average water temperature will increase through the fin tube and the output increases.

It is not about how long the hot water is in the loop, you want the cooled water back to the boiler to be heated up again.

So faster flow= higher heat output, to a point.

If you over pump, flow velocity goes too high and you get piping noise. 4 feet per second is about as fast as you want to flow in hydronic systems.

Is the fin tube piped with 3/4 or 1/2” tube?

cckriss

hot_rod said:

when you design a system you select a delta tee to size everything to. 20 delta is a common number for fin tube

At design condition, proper flow, it could run at  exactly 20 delta.

If you increase flow , the delta will drop, the average water temperature will increase through the fin tube and the output increases.

It is not about how long the hot water is in the loop, you want the cooled water back to the boiler to be heated up again.

So faster flow= higher heat output, to a point.

If you over pump, flow velocity goes too high and you get piping noise. 4 feet per second is about as fast as you want to flow in hydronic systems.

Is the fin tube piped with 3/4 or 1/2” tube?

I am using 1” hePEX from boiler to caleffi manifold. Then 1/2” hePEX going to the 3/4” fin tube

cckriss

One of my manifolds 

hot_rod

12' of fin tube will give you about 6,600 btu/hr.@ 550 btu/ ft. that is at 180°SWT

If you design around a 20 delta you need about .6 gpm to that zone

1 gpm at 20∆ gives you 10,000 btu/hr.
Probably why 20∆ is used so often, the math is easy to do in your head.

About the most you would ever flow through 1/2" pex is 2.25 gpm, which equates to around 4 fps velocity.

So I imagine most of those zones need less that 1 gpm?

Of course output of the fin tube drops if you go with lower SWT

The installation looks nice.