Panel Layout Feedback

Gods

Hi all, it's me again. Now that I have a pex layout, I'd like to get some feedback on my boiler room design.



TRV's will have remote sensors for each room (what's the maximum allowed capillary tube length?)

The idea is to set an upper and lower threshold on the supply lines. When the upper threshold is reached, flow is routed through the boiler. The flow will remain that way until the lower threshold is reached, where it will reopen the valve at the boiler.

Example: High flow switch set to 4 gpm and low flow set to 1gpm. As zone flow increases through the TRV's and the high flow switch is triggered, the circuit below the boiler flips and closes the valve at the boiler, routing all flow through the boiler. As demand decreases and supply flow reaches <1gpm, the low flow switch will turn off, causing the circuit to reset and reopen the boiler valve routing flow through the closely spaced T.

This will require the pump to run 24/7, so the question is, will this be "cheaper" than running thermostat-controlled zone valves with a controller?

GroundUp

Or just pipe it per the install manual with primary/secondary piping and a delta P circ, and eliminate all the BS that comes with flow switches. KISS

JackW

Here is my two-zone system.

hot_rod

what is your goal with that piping? You could just use a delta P circ with trvs and let it rip.

Gods

I must admit, this is the first I’m hearing of delta P’s… how do they work? Where is it placed in the circuit and how does it prevent short cycling?

hot_rod

Delta P circulators. They are able to sense they system and change speed and flow rate. So, as zones or circuits open or close, the circ speeds up or slows down. So no need for a pressure bypass.

More info on how they work here.

https://www.caleffi.com/sites/default/files/coll_attach_file/idronics_16_na_0.pdf

Gods

Wow, that’s great info. Thank you!

I still can’t figure out how this prevents short cycling. Let’s say the boiler triggers at 1gpm, won’t the delta P pump cause the flow to hover at 1gpm once the equilibrium is found? Or is the boiler activated by some other means?

JDHW

JackW@
I think you should rotate the heads at the left of you board. The cable should enter at the side or the top so that any leaks do not run down into the electrical connections.

John

JDHW

i should have said pump heads!

hot_rod

Gods said:

Wow, that’s great info. Thank you!

I still can’t figure out how this prevents short cycling. Let’s say the boiler triggers at 1gpm, won’t the delta P pump cause the flow to hover at 1gpm once the equilibrium is found? Or is the boiler activated by some other means?

The boiler will cycle based on the load it sees and the lowest turndown. All boilers cycle to some extent, rule of thumb is a 10 minute or more cycle when the fire up. Either a smaller boiler or a buffer tank is the best way out if that.
Tricking the pump or flow path doesn’t change the load to boiler minimum.

Gods

I think I may be overestimating the response time when a zone is activated. If it were near instant, then the short cycling I’m imagining might exist.

back to capillary tubes, in reading in TRV manuals that capillary tubes come in different lengths, but only up to 16’. I have a couple rooms that would need 30-40’ of tube. Is that even possible?

hot_rod

Gods said:

I think I may be overestimating the response time when a zone is activated. If it were near instant, then the short cycling I’m imagining might exist.

back to capillary tubes, in reading in TRV manuals that capillary tubes come in different lengths, but only up to 16’. I have a couple rooms that would need 30-40’ of tube. Is that even possible?

Did you check Oventrop?

JackW

@JDHW, that's a great idea, don't know why I didn't think about that. Was actually wondering why they didn't make them like my newer model. Ha, ha.

JDHW

There are four allen screws to remove and then just rotate the head and re-fix. The casing and the head are sealed with an O ring so you will lose some water. You have nicely placed isolating valves so should be simple enough.

John