Single Pipe Hydronic - Poor performance

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Old 02-15-20, 04:54 AM
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Single Pipe Hydronic - Poor performance

Hi All,

Hoping for some suggestions and guidance. Its cold out, and my heat system is getting a good workout. I've noticed several time over the past few years that the system struggles when we hit these cold spells. I also heat with a wood stove, so I'm not super conscious about performance, but last night I was really thinking things were not up to spec.

The system is a 4 zone single pipe hydronic with a Viessman boiler, Reillo burner, single Taco-007 circulator. 2 zones are barely ever used (living room with wood stove and basement office), while the other 2 zones get the lions share of work with 1st floor and 2nd floor, plumbed with 3/4 copper for each loop.

The second floor works fine, though could benefit from a couple bleeder valves as I had some recent work done with new baseboard put in with a riser, and seems to catch air. I'll have the plumbers fix this when they remodel the next bathroom.

The first floor is the weak performer. Its a mix of slant-fin and three under cabinet toe-kicks.

Last night I noticed the return at the boiler for the first floor was not very hot with a heat call. I walked the loop and checked each emitter and noticed that as we got toward the end of the circuit the emitters were barely warm. I could also hear trickling of water in these lines. The last emitter on the circuit is a toe-kick and it was not turning on.

I then went to the basement and noticed the cob job that was done to install this last toe-kick. Seems is was a retrofit at the past homeowners kitchen remodel. Its feed is plumbed in series (no scoop-T/monoflow T). the line transitions from 3/4 to 1/2 upstream, goes up under the cabinet and returns to then transition back to 3/4 and finish the run back to the boiler return. Seems they cut out an old section of 3/4 to plumb in the toe-kick in series using 1/2.

Soooo, first I'm thinking this is a restriction to the whole loop. The toekicks are old and could be replaced as they are full of debris and dog hair and they are LOUD (when they do come on).

My thoughts would be to cut out all the 1/2, return back to 3/4 to decrease restriction, and to plumb in monoflow-Tees to feed a new toekick heater. I would add the necessary bleeders at the toekick and hopefully call it a day.

Next question is the 007. How does one determine if the 007 is underrated to push 2-4 zones, 2 of which are fairly long and have a lot of 90s and a few up/downs? The boiler easily hits its high cut off on very cold nights, so I'm thinking I'm not pushing enough water/btus to the emitters. Would upsizing the circulator be of any benefit?

I"d appreciate any help from the experts. I'm handy, try to read up, but admittedly know just enough to get myself into trouble.

Many Thanks,

Bryan
 
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Old 02-15-20, 06:55 AM
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Dog hair certainly could be an issue. I know it is at my place.
The toekicks should be piped with diverter tees.
Regarding the circulator sizing: Try to get a reasonably accurate measurement of the total pipe length in that loop giving you trouble. And a count of the number of 90* ells. Knowing that & the verticle you can determine the "feet of head". Compare that number to Taco's circulator chart. I have a basement loop with over 200' of 3/4" copper, a dozen or more ells, & a 007 with no issues at all.
 
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Old 02-15-20, 09:18 AM
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1st floor run is about 180' and maybe 25 90s @3/4", plus 10 ft of 1/2" with another 4 1/2" 90s before transitioning back to 3/4" 55" of fin and 3 toe kicks.

2nd floor run is about 180' total, 95' of fin and maybe 18 90's all 3/4".

Living room (seldom used) run is about 85' with 45" fin with16 90s all 3/4".

Basement run is 65' with 18' fin and probably 10 90s all 3/4"

I have one 007 serving all 4 circuits.

When is it advisable to put an individual circuit on each circuit?

I think my first priority should be replacing the toe-kicks, getting them on 2 monoflows/unit, adding bleeders where necessary, and ditching the 1/2" copper hodgepodge.

Then maybe think about individual circulators for each zone?

Thoughts?



 
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Old 02-15-20, 10:47 AM
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Did a bit more research...

With the above numbers, I have a total or 510' assuming all zones are running.
I found a quick 1.5 multiplier to account for 90s, etc. that has me at 1.5 x 510 = 765'

765' x 0.04 = 30.6 head-feet, and more realistically 21.6 head feet with just the two zones and 10.8 head feet with a single upstair or downstairs operating.

3/4" copper wants to flow 3.2 - 6.5 gpm.

Looking at the chart, seems the Taco-009 is my best bet, no?

Looks like my 007 can only handle one zone at a time....
 
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Old 02-15-20, 12:04 PM
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The Taco 009 would be way too much pump. You only need to calculate the loop with the most resistance, all others will go along for the ride. A quick calculation of 275' (pipe and element) of 3/4" pipe, 51 equiv. feet of pipe for ells and not including the kick space and 1/2" pipe as that needs changed you are about 3.5 ft head @ 4 gpm.
The 007 is good at that flow rate to about 7-8 ft head.
Move the pump to the supply side after expansion tank connection, make sure you have an air separator, install purge set-ups if you don't have them and eliminate any automatic vents in the high part of the system, use 12-15 psi on a two story home or less and your problems will go away.
 
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Old 02-15-20, 12:48 PM
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rbeck is far better at this type thing than I. If he says that 007 will work with the changes, it likely will.
 
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Old 02-15-20, 08:21 PM
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Something to consider with toekicks is the temperature of the water being delivered to them. I don't know what brand you have but Turbonics is prevelent in my area.

They have a built in aquastat so the fan will not blow cold air. These are figured for 180 deg water going to them to get the designed BTU output they specify. The water must be at least 120* for the fan to operate and it will automatically shut off if the water temp drops below 105*.

My point here is that it might not be the pump. The pump may be circulating through the zone but by the time it reached the last unit may have been to cool for the fan to operate even though the water was circulating through it.

The length of the zone is one thing but the amount of element is another. A 3/4" pipe is good for 50,000 btu's of heat. Every foot of element on your baseboard is figured at 550 btu's @ 180* water running through it. If you are running your boiler at a lower temp then your BB will produce less heat and you will have that much cooler water to feed your TK's at the end. You have quite a bit of pipe and element. I would run 180/200 to get the output your units were designed to put out if you are having trouble staying warm.

I usuall figure 600 btu's a ft @ 180. Depending on the brand of BB it gets 550-600 btu's a ft. For example if a room comes to 6000 btu's of heat loss you know you need 10 ft. of BB to heat that room if you run 180* water. If you run 160* you will need more basewboard to heat that room. I mention this because people are trying to run at lower temps now adays but often the house wasn't designed for it but with all the new enery upgrades they sometimes get away with it.

Although 12-15 would most likely get the job done I run my systems at 20 psi. I get better circulation and it helps with cavitation in the pumps and no air in the system. As rbeck said, you don't need the high vents.

This is just a personal prefference that works for me if you continue to have your problems.
 
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Old 02-16-20, 05:20 AM
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Good information guys. Thanks.
Iím aware of the aquastats on the toe kicks and thought that may be the cause but when things are warmed up the return for that zone at the boiler is too hot to touch so I think Iím getting heat.

Iíll do as you guys suggest and replumb the old toe kicks, up my operating pressure, run 190-170 and report back.

stupid question, what are high vents? Auto vents? I was planning on installing a few manual bleed 90s at the BB with decent risers under them... Is this what you mean by purge system?

many thanks guys.

Bryan
 
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Old 02-16-20, 07:42 AM
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High vents/auto vents, same/same. One thing to keep in mind is anywhere you have diverter tees you need a means of venting air, be that means manual or auto is up to you. I don't like to see auto vents concealed. If the whole loop is piped in series, a purge station needs to be installed on the return near the boiler.
 
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Old 02-16-20, 11:25 AM
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Tell me more about the purge station, and where it is needed.
I have 4 zones, in parallel with the boiler, coming off EZ headers and returning through EZ headers.
My Taco-007 in on the supply side past the supervent and expansion tank.

What do you think about the flexible hose kits they sell with the toe-kicks. Seems like an accident waiting to happen... I was thinking copper all the way but maybe its time for me to be pre progressive?

Thanks,

Bryan
 
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Old 02-16-20, 03:49 PM
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A picture or two of your boiler would be helpful.
I'm with you on the hose. I've seen them but not a fan. I'll take copper anyday.
 
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Old 02-16-20, 05:11 PM
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My 60 year old, original boiler, single pipe system has 13 enclosed elements fed from below with monoflow/diverter tees.

All enclosed elements have Watts-Automatic-Vent-Valves. Venting is completely automatic, even when opening system at boiler level. Rarely has there been a problem. If element is not heating just swap in spare $8.00 AV valve.
https://www.supplyhouse.com/Watts-05...-Vent-3679000-

A “purge system” would add needless complexity, costs and issues.

System is now split to 8 zones. 5 zones fed with modern auto-sensing pressure controlled pump. It automatically adjusts to varying loads as zones switch on an off. Pump can be left powered on and will go from stop to needed flow. Three single element zones are fed with a small Grundfos pump.

The Grundfos Alpha2 pump uses 50% less power, has 7 automatically controlled pressure or volume flow settings, LCD display shows power and GPM flow: The Alpha costs $175.99 has higher GPM, many advanced features than old technology fixed flow, single speed pump TACO 009 which cost $259.

https://www.supplyhouse.com/Grundfos...w-Terminal-Box

https://www.supplyhouse.com/Taco-009...8-HP-1985000-p

This thread is classic example of old technology versus new technology. The new usually has better features and lower cost that the old. Take your choice.
 

Last edited by doughess; 02-16-20 at 06:42 PM.
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