Boiler Controls


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Old 12-30-08, 10:36 AM
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Boiler Controls

Have fin tube baseboard heating. Heat loss per Slant/Fin @ 2* ODT is 59,486 BTU/Hr and per Man J, 62,210 BTU/Hr. Plan to have a Buderus GA124/23 boiler installed with the Logamatic R2107 Controller with a Room Sensor and also the Buderus ST-150 Indirect. Will have 2 or 3 zones, with constant circulation in the main zone, other zones controlled by T'stats.
In the above application which would be better, circulators or zone valves? How do they compare concerning noise, cost, dependability ect? Would a mixing valve be required?
 
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Old 12-30-08, 11:37 AM
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Sounds like a fine system.

You could zone with circulators, or zone with zone valves.

For a mixed constant/intermittent circulation system such as you describe, I would zone with zone valves. Two ways to do that.

1) One standard circulator, zone valves, and a differential pressure bypass.

2) One cool new Wilo ECO circulator that functions in a "delta-P" mode that eliminates the need for the differential pressure bypass, and zone valves.

The cost difference between these two approaches is probably around zero. The Wilo costs more, but the installer saves time by not having to pipe a differential bypass.

With a properly sized circulator, it's also possible that you don't even really need the bypass, assuming the flow rates through the zones and the boiler stay within reason.

The Wilo is also far more electrically efficient than a normal circulator, which is nice in a constant-circulation system. That said, if it fails, it would cost more to replace and might be hard to find at midnight on a Saturday in February. And at $300 a pop, not something like a $65 Taco 007 that you would likely keep as a spare on the shelf. (Although you could probably swap out a failed Wilo with a 007 for a while without any issues.)

For zone valves, I'd go with an electro-mechanical (as opposed to heat motor) valve that only uses electricity when opening or closing. Still trying to find one that fits this bill, but they are out there. Taco or Honeywell, most likely. Maybe Caleffi.
 
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Old 12-30-08, 12:01 PM
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The older white rogers used to drive open and drive closed. I do not know if they still make them or not.

xiphias do you prefer variable speed on pressure or delta-T? I am still kicking it around in my head as to which is best. I am leaning towards the delta T type due to more and more mod/con boilers being installed they will give you a lower return water temperature if set for like a 20f delta T. Maybe neither one is any better than the other. Maybe they are the same but different.
I have read other posts on some other sites about these pumps and they sound interesting. Unfortunately just because it is talked highly about there does not always make it so. It comes down to research and testing, thats what makes it so.
 
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Old 12-30-08, 01:31 PM
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As you know, there are reasons to prefer either dT or dP, depending on design and application. Certainly with a mod/con (not this application) dT makes a lot of sense.

I wonder with the R2107 control would using dT confuse the control. Maybe not. Might there also be issues of flow rate through the boiler. Dunno.

Regardless, one potential disadvantage of imposing a 20F dT might be very different heat output (and thus occupant comfort) at the end of some types of distribution systems (e.g., series loops) that never before saw more than 8-10 dT because they were overpumped for the last 20+ years.

The Wilo ECO has been around Europe for a couple years, and they are certainly a very large company with a long track record.

That said, I would very much like to see Taco come to the table with an ECM circ.

Apologies to Fred7 for the thread drift!
 
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Old 12-30-08, 03:18 PM
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In the above application which would be better, circulators or zone valves? How do they compare concerning noise, cost, dependability ect? Would a mixing valve be required?
A mixing valve shouldn't be required if all of the heat emitters were designed for the same temps.

My preference would be an all pump solution. Your true heatload is probably under 50 MBH in reality. Carving that into 3 microzones seems moot. I'd try and get it all functioning as one zone. If there are areas where you need additional control I would use TRVs for those areas. If 2 zones, I would use pumps, the only downside being that it's hard to find 20 watt pumps and that's all many zones actually need.
 
 

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