Making adjustments

gaabbee

I have a 5 zone radiant system that has been working well but my wife has recently put a large area rug in one of the zones (against my opinion). It seems to be struggling now to maintain temperature which I figured would happen. So choices are increase water temperature to all zones, increase pump speed, or try to insulate more? I have balancing valves on the loops but they are not used.

The pump is a taco vr3452 with lots of room for speed adjustments, and I could increase the ODR temps on the mixing valve. Which do you pick and why? I know it's best to just remove the rug but wife says no....

Zman

Whatever you do, stop talking about removing the rug
You have a non condensing boiler, yes? If so, turning up the outdoor reset shouldn't have a big effect on efficiency. I would start by increasing the curve and see if you start overshooting in other areas. You could then throttle the flow a bit in those areas to reduce the average water temps.
How thick is the pad under the rug? If it is a thick low density one, you might be able to make a change there.

gaabbee

Zman said:

Whatever you do, stop talking about removing the rug
You have a non condensing boiler, yes? If so, turning up the outdoor reset shouldn't have a big effect on efficiency. I would start by increasing the curve and see if you start overshooting in other areas. You could then throttle the flow a bit in those areas to reduce the average water temps.
How thick is the pad under the rug? If it is a thick low density one, you might be able to make a change there.

Thanks for the input! Non condensing is correct. I can increase the ODR from .8 to .9 and see how it goes. Not sure if there is a pad. I just came home to it already in place.

Trying to wrap my head around the effect on efficiency part. By increasing the curve wouldn't that increase the amount of hot water needed. I was looking at it as do I increase water temp (fuel usage) or increase pump speed (electric usage)

Zman

Your boiler is running high temps anyway so you don't get the savings on the combustion side. The idea is that you want to heat the space with the lowest temp water you can. This saves pipe loss heat and heat wasted to overshooting the desired indoor temp. The pump speed really only changes the gpm to the loops. With your .7 gpm, you probably have a delta of <10 degrees which makes for a nice comfortable floor. Increasing that will raise your average floor temp slightly but at a hefty electric premium. If you want to get nerdy with it you can measure all your delta t's for each zone with the system running at steady state and tweak your flow rates. My recommendation would be to increase the ODR. Not sure what type of reset controller you are using but it sounds like you are changing the curve angle rather than actual temps?

gaabbee

I do like getting nerdy and may look into that. Delta t design is 10* but at steady steady running state I've never see anything close to that. It is usually between 0 and 5* delta t for all zones running which probably means I should balance each zone more or back the pump off? I'm using a taco iseries r mixing valve with ODR. It is set to a min of 80* and a max of 150* but the curve set right now looks to max around 130*

Zman

Those deltas are pretty typical. You could play with your pump settings for fun and information. I love the info that pump gives you. My guess is that you will see marginal savings if you turn it down to .5 gpm and scary increase in consumption of you go much higher.