Do These Pump Numbers Sound Right To You?

[velvetfoot]

I have been trying to dial in my pumps. I have three, leaving the oil boiler out of it. They are all infinitely adjustable B&G Ecocirc Varios.
The boiler nameplate is 15kw at 176, so 51,182 btu/hr.
House is 10 year old 2000 ft2 colonial, 1000 ft2 on each floor in upstate NY.
First floor baseboard emitter: 24,000 btu/hr @ 176F
Second floor baseboard emitter: 27,500 btu/hr @ 176F

I've been using Taco's HSS program and these are the numbers it came up with:

Second Floor:
2.5 gpm
11.5' head loss

First Floor:
2.8 gpm
6.8' head loss

Boiler:
5.3 gpm
5.7' head loss

Calculated baseboard at 176F heat load is 51,500, so boiler is just a tiny bit small when running at its max temp of 176.
I can see 5.3 for the boiler, but the other numbers seem high.

I am also now trying some thermometers on the return to shoot for a 20 degree drop.

This is for the max. How will things work at lower output?

Thanks.

 

[velvetfoot]

I charged the tank to 181 and am running the zone pumps.
I set the pumps using the info in the previous post and the pump curves here: http://documentlibrary.xylemappliedwater.com/wp-content/blogs.dir/22/files/2012/07/A-139A.pdf
Return temps being measured by an Azel gauge, sensors under insulation near pumps, buffer top by a Ranco with sensor at top of Froling Energy Tanks mounting bar, under insulation

Are the return deltas supposed to get smaller as input temp drops?
Once the input got to the 140s, they seemed to settle at 14/15

Zone return temp deltas:
buffer top 1st/2nd
181 24/26
179 22/24
156 20/19
152 17/19
147 14/15
142 14/15
140 14/15
139 14/15
137 13/14

The thing, if I optimize things for boiler setpoint of 176, what will I get when I'm running 165, which I like to do to get a better fill of the buffer tank?
I guess if I spend enough time in the basement I'll find out...or not.

 

[velvetfoot]

To continue the never-ending basement saga...

I should've used the temperature gauge first.
The boiler started a little while ago. One zone started heating up, but the other not so much. The boiler pump needed to be bumped up to 'cover' the flows from the two zone circs. Too much, though, and too much flow goes into the top of the buffer tank and then cold water goes back to the boiler, which is not desirable at this point since I want all the heat going to the zones.

 

[velvetfoot]

So, I believe I had the pb pump balanced with the two zone pumps such that no heat was going to buffer tank.
That's a beef of mine on my system: if the boiler pumps more than the zones, the tank gets hot, taking energy from the zones and cold water is pushed to the boiler from the tank bottom. If the boiler pump is less than the zone pumps, some water is drawn up from the tank to the zones and they don't get hot.

The zones returns came up in temperature and the boiler started modulating down to 70%, but then the zones were satisfied and the the boiler went up to 100% to heat up the tank (which will be a while since I set the thermostats down from 72 to the normal 68). That's another thing that bugs me, as I've said: why 100% just for the buffer tank-it should be more like 30%, and then too, if there was sufficient heat in the tank and a zone came on, the boiler should continue to modulate at 30% while the zone was satisfied by tank water. I just can't figure out a solution though.

Setbacks make everything more complicated, I think.

 

[maple1]

I guess I'm not seeing a problem with some heat going to storage when your zones are pulling.

 

[velvetfoot]

It increases the amount of water to be heated, diverting it from the zones.

 

[maple1]

Hmm, yes, I suppose - but I was thinking that you are wanting to heat your storage too, anyway? Then if the load pumps pull some from storage too, the water going to zones shouldn't get cooled. Would that be called buffering?

Not sure what an 'elegant' solution would be - the boiler would see a varying heating load depending on how many zones are calling. So I'm not sure how you could get your boiler pump to match the flow of your zone pumps all the time when heating. Was going to say maybe a ZV to close storage flow when heating & boiler is running - but that might be clumsy.

(I know nothing about your boiler though & intricacies in how it modulates itself).

 

[velvetfoot]

Hmm, yes, I suppose - but I was thinking that you are wanting to heat your storage too, anyway?

Yes, I do want to heat storage, but not at 100% power; preferably 30% power.

Was going to say maybe a ZV to close storage flow when heating & boiler is running - but that might be clumsy.

I was thinking of that. Maybe, "if a load pump on then block storage". Would mean having boiler pump and a load pump going into half the load.

If I could control return temperature to the boiler with mixing valve, replacing the boiler protection valve, I might be able to reduce the output of the boiler to 30% during certain conditions. Return temp high, boiler backs off power.

But, how many machinations to go through? It's only a buffer tank, after all.

 

[velvetfoot]

It's weird how things react.
I just saw how, when things are pretty hot, when one or two zones kick off and the boiler is pumping right through the buffer tank, the top tank temperature going down because of the cooler water being brought in from the bottom of the tank.

 

[PassionForFire&Water]

This is maybe the key to what you are looking for:
Check out the NYSERDA presentation under presentations: http://www.nyserda.ny.gov/Contractors/Become-a-Contractor/Renewable-Heat-NY-Contractors

 

[maple1]

My setup is the two pipe diagram above. Not that it matters, likely.

 

[velvetfoot]

Thanks Marc. Will read that asap. I saw something similar from Bob Rohr from Caleffi's Idronics on tanks the other day. I have a 2 pipe configuration. It would be nice to reduce the incoming heat rate when not needed for heating load, while keeping the boiler running.

Do you see any future in using a mixing valve in place of the caleffi thermomix, for boiler protection and to raise return temperature to induce a lower output and also, I guess flow rate, when charging the tank the tank? I think I can see a plus, generally, in keeping the return temperature constant, but I'm not sure it's worth it.

 

[Karl_northwind]

I do the 4 pipe configuration nearly always. allows proper hydraulic separation, air separation and dirt removal. even with a forced air circuit (the reason for the buffer, as it can go from 0 load to 100,000 btu in a couple minutes) it keeps everything happy. 4500 hours on the biowin so far and only like 2000 starts. that's a biowin 26, on a 2000 sf ranch, 1 zone forced air, 2 zones panel radiators and one DHW indirect zone.

 

[velvetfoot]

Karl, (incidentally, that's my name too), do you find that zones can draw down the buffer tank some even when the boiler is running? I find it's a one-way street with my 2-pipe setup: the buffer only gets discharged while the boiler is off and it's pump not running.

I'd consider changing, maybe to a 3-pipe, lol, with the return still bi-directional. I don't think I can wrap another pipe in there.

That seems like a good cycle time, especially with a 26kw unit in 2000 sf.

 

[Karl_northwind]

should have mentioned that there is a 40 gallon buffer in there as well, and variable speed circulators both for the boiler and feeding the 4 zone valves. I'm sure that all the zones calling could pull down the buffer, but that some or all of the loads are satisfied before that happens noticeably.

it is set up on an aquastat in a well in the bottom element hole of the buffer (which is a water heater tank) I think it's set to 140 and 160? which is part of the long run time I'm sure. in the long run, most if not all of my boiler systems are getting buffer tanks, from 38 gallons to 2500 gallons, it always seems to be worth it.