low delta t on manifold

Empire_2

Your pump head is a fixed figure bases on the 007 taco perfomance chart. GPM that it will deliver at that given head is also fixed. What are your zone pipe diameters, length of longest pipe run, and (BTU net) of the boiler you are working on? If you are moving only 1gpm, why would you want to slow the FLOW down at all?

Matt_21

i have a 4 zone

manifold with a powerhead & thermostat for each zone. with all zones calling, i have 5.3 ft hd and 1 gpm. i currently have a taco 007 installed. with all zones calling i only am getting a 10* temperature drop and with only 1 or two zones calling only 5-7* drop. my thinking is a smaller pump or variable speed. will a variable speed modulate based on flow requirements or does it only let you set a low, med, high speed.

hr

Some radiant purists

consider a 10° delta t ideal on radiant loops. I generally design around 15-20, higher yet on commercial shops, often.

Remember that delta t is ever changing. Starting a cold slab may present 20, 30, 40, or even higher delta t. As the slab and space warms that delta t will drop (the load changes). Maybe to a few degrees just before the call for heat is satisfied.

It's the load of the system at any given time that determines that delta T. When we design radiant we select a delta t at a given set of factors, somewhere along the heat cycle it should actually see that condition.

Is the room warm and comfortable? Good floor temperature and temperature spread?

hot rod

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Empire_2

Im Sorry,................`

Didn't know you were working on a slab radiant system.. Do not have much experience with that. I think Mike T montana or weezbo can probably help you out......

Matt_21

the delta t

doesn't appear to change all that much. last week on a 5* day the delta t was 10*. today on a 45* day, with all zones calling, it is 10* and with 2 zones calling 5*. i haven't shot the floor to get the temps yet. two of the rooms are in the basement so the load isn't very high and they satisfy quickly. my 2nd floor bathroom seems to always be at 69* between 10-35 degrees outdoor temp. (i keep it set at 71. i like in warm after the shower) when the weather is in the single digits, it drops to 67 or 68. i knew when i designed it i was a little short on heat but i figured we didn't have too many of those days so i could deal with it. my thinking is i'm pushing too many gpm and i'm not extracting all the btu's i could.
on a side note, i was thinking in the 2nd floor bathroom of installing climate panels in the attic on top of the sheetrock. i could loop the tubing between the 3/4" void left by the ferrin strips to a set of climate panels in the next bay, etc, etc. to make a radiant ceiling. all this would be covered by the r-25 insulation in the attic. do you think this would work?

Weezbo

What size tube and loop lengths do you have?

in the seperate zones? on variable speed injection system,4 way mixer,modulating mixer, porportional fixed mix....are you using set point zone valves or ones with outdoor reset ? i only ask this to determine what if anything you are doing to get the delta T you are seeing...are you reading it off supply and return gages or sensors ? i like fairly tight operational delta t's not everyone does.the taco pump block is a really handy critter and the supply and return on the injection side is like 40 degree, on the system side its like 5- 10...i would really like to get better control of it to closer to room temps..however it seems to like where its living.. best i have managed to squeak out of a system is like 3->4 degrees difference in supply return and room...tek mar guys think it is not economical to do it that way however i weened myself off teck mar a long time ago take a look at Caleffi now i think that entire lash up ROCKS! and last friday i caught the opening and the closing on the weil mclain gas com Ultra deal John and Dave were giving at associated General contractors and a few days earlier Roth Sirriani's introduction for the renai...to me it seems that life is changing for the better and with the cost of fuel it couldnt be at a more opportune momment...er oops ...i digress...:) being able to change speeds on pumps and motors and out door and indoor sensors pipe sensors and intergration of a few more variables makes distributing BTU's amore fun than a barrel of "minkies" In fond memories of the Late Great Peter Sellers.a genius in his own right