multi zone hydronic efficiency
Last Post 28 Sep 2013 05:43 PM by jonr. 1 Replies.
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28 Sep 2013 05:07 PM
Hey all.  I know nothing about how to operate my heating system efficiently and am hoping to get some advice/comments and/or confirmation of my conclusions.

I have a NG gas boiler (think its an Allied MG-75) supplying hot water to in floor heating (in concrete) to my main floor (slab).  Upstairs has baseboard hotwater radiators.  I have 4 thermostats up, 4 down.  2 pumps, larger pump for upstairs to baseboards, smaller pump supplies in floor downstairs.  Whole system is about 12 years old now.  All of my thermostat except one are bimetal/mercury

 I've operated 3 different ways.
1.  All zones valve locked open and heat controlled by 1 thermostat.  Programmed to 22C heat during day (3pm-8pm) and 19C (8pm-3pm).  What I found is that it seems the boiler size is not designed to supply the whole house and would be on for hours to heat from 19-22.  In my opinion this didn't seem very efficient.
2.  All zone valves locked open and controlled by 1 thermostat Always at 22C.  This seemed to operate better than option 1, but still, any time heat was needed the boiler seemed to run for hours just to heat 1 degree.
3.  Multi-zone.  All zone valves controlled by their own thermostats.  So i set all the thermostats to 20C and 22 in the main living area.  Boiler seems very effecient at heating 1 zone at a time when it called for heat (on for a short period of time to heat one zone), but with multi zones calling for heat it seemed the boiler was constantly on/off.

4th option in the future is to run multizone with all digital programmable thermostats.

Lastly, Option 3 seems to lower my electricity usage.  I noticed my electricity consumption was reduced approximately 29% over a 12 month period.  I didn't notice an major changes in gas consumption.

So my question is to anyone with experience with a multizone hydronic system, what is the most efficient way to operate?  Multizone or 1 zone?

My personal conclusion is that due to my boiler size I'm likely better off running multizones as the single zone set up seems too much for the boiler to handle.

Thanks in advance for advice/comments.

Here is my gas usage for last 2 years.  2011-2012 was option 2.  2012-2013 was option 3.

Bill From Date Bill To Date # Days in Bill Period Billed GJ Average Temperature
 Sep 22, 2011  Oct 20, 2011 29 4.9 13
 Oct 21, 2011  Nov 22, 2011 33 17.4 6
 Nov 23, 2011  Dec 19, 2011 27 16.4 3
 Dec 20, 2011  Jan 20, 2012 32 22.8 3
 Jan 21, 2012  Feb 17, 2012 28 16.4 5
 Feb 18, 2012  Mar 20, 2012 32 15.5 5
 Mar 21, 2012  Apr 19, 2012 30 11 9
 Apr 20, 2012  May 17, 2012 28 2.3 12
 May 18, 2012  Jun 18, 2012 32 5.7 14
 Jun 19, 2012  Jul 19, 2012 31 0.4 17
 Jul 20, 2012  Aug 17, 2012 29 2.7 19
 Aug 18, 2012  Sep 19, 2012 33 1.7 17
 Sep 20, 2012  Oct 19, 2012 30 2.6 13
 Oct 20, 2012  Nov 20, 2012 32 12.9 8
 Nov 21, 2012  Dec 18, 2012 28 18.1 5
 Dec 19, 2012  Jan 23, 2013 36 25.4 1
 Jan 24, 2013  Feb 21, 2013 29 14.4 5
 Feb 22, 2013  Mar 20, 2013 27 13.3 6
 Mar 21, 2013  Apr 19, 2013 30 10.3 9
 Apr 20, 2013  May 21, 2013 32 5.1 13
 May 22, 2013  Jun 18, 2013 28 4.1 14
 Jun 19, 2013  Jul 19, 2013 31 2.6 18
 Jul 20, 2013  Aug 19, 2013 31 2.4 19
 Aug 20, 2013  Sep 17, 2013 29 2.1 19

Hydro Usage.  July and Sept 2007 was a meter reading error.  I believe Jan and Mar 2012 are also bad readings.



jonrUser is Offline
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28 Sep 2013 05:43 PM
I would do option #1 (setback) for the baseboards and leave the slab at a constant temperature (but lower in zones where that is comfortable enough). Make sure that even with just one thermostat calling for heat, there is still 6 gpm of flow. Fewer thermostats can help with that.

Slow response does not imply inefficient.
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