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Topic: Boiler Question Condo Building  (Read 7917 times)

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Offline joeatuml

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Boiler Question Condo Building
« on: December 14, 2009, 10:54:54 AM »
See attached drawing (currently the way the heating system is setup at my condo).  What would be the reasons to not have a valve / check valve in the indicated position.  To me it would seem that with a valve or check this would force all the water to the boilers to be heated. 

The problem arises that the boiler outlet temp is reaching 180-190 and then the boilers are shutting off where the main header is only hitting 140-150, so I don't think it is mixing well enough with the main header.

Offline typhoon2028

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Re: Boiler Question Condo Building
« Reply #1 on: December 14, 2009, 02:02:39 PM »
I dont understand your drawing very well

Offline bigcanuknaz

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Re: Boiler Question Condo Building
« Reply #2 on: December 16, 2009, 04:37:56 PM »
It depends a bit on what kind of hot water boiler you have.

Most hot water boilers are sensitive to cold water "shock" where the entering water is too cold, and the temperature gradient accross the boilers is too great.  If this happens, you can have very expensive boiler repairs caused by the temperature gradient and warping/twisting of tubes and other boiler componets.

I am guessing that that part of the circuit is open because there needs to be some recirculation of hot water.  Even if hot water recirculation is taken care of locally at each boiler (and not diagrammed), it would seem that the boilers would contribute as much heat as possible, and only excess water demanded by the pumps (that the boilers could not supply) would come through the "black" section of the header.  I would guess that the boilers would not like *extra* cold water drawn through them by those transport pumps.

One way to raise the temp in your transport loop, when the boilers cannot keep up, is to use variable speed transport pumps.  This can be based on the temp of your transport return, and can save a *lot* of electricity.

(Though not increase maximum capacity, if this is what you are after...)

naz

Offline Grundalizer

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Re: Boiler Question Condo Building
« Reply #3 on: December 16, 2009, 05:31:57 PM »
I don't know jack about boilers, but I've read numerous articles in all sorts of magazines about installing a water heater timer.  It's just a small 30 or 40 dollar device that you can program to heat water when you will need it.  For instance, turn down the gas heating the water at night since no one is making any use of the hot water, and have it turn back on two hours before you wake up for a shower.  Me personally, I hate showering in the mornings, so I turn mine off when I go to bed, and don't turn it back on until I get back from school/work in late afternoon.  Saves boatloads since for half the day I'm not burning gas for no reason. 

Offline joeatuml

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Re: Boiler Question Condo Building
« Reply #4 on: December 17, 2009, 06:53:58 PM »
Thanks for the replies.  I did think of the shock issue.  We have about 145 F going out to the units and approximately 10 F lower coming back. 

The boilers themselves also have their own heat exchanger with pump and temperature diverting valve.

You can find additional information on the boilers here http://www.heatmaker.com/category-s/20.htm if you are still interested. 

However I believe we found the issue, which is the exhaust temperature is getting to hot causing them to short cycle.  We talked with the manufacturer and they seem to have issues with the heat exchanger collapsing in on the other causing it to heat up hotter than it should.  So they said "Replace the heat exchanger and send it to us and we will determine if you get a refund"  Which to me says, yeah we know we have a design flaw with these...

I may suggest replacing the boilers with something with more capacity.  Currently the boilers are both 200,000 BTU/hr and we have 15,000 sqft.  The condo is in Massachusetts as well.  Doing a web search netted me with going with something around 700,000 BTU/hr total.  Any suggestions on a good boiler manufacturer company?

Offline bigcanuknaz

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Re: Boiler Question Condo Building
« Reply #5 on: December 19, 2009, 09:18:53 AM »
Thanks for the replies.  I did think of the shock issue.  We have about 145 F going out to the units and approximately 10 F lower coming back. 

good.

Quote
We talked with the manufacturer and they seem to have issues with the heat exchanger collapsing in on the other causing it to heat up hotter than it should.  So they said "Replace the heat exchanger and send it to us and we will determine if you get a refund"  Which to me says, yeah we know we have a design flaw with these...

I may suggest replacing the boilers with something with more capacity.  Currently the boilers are both 200,000 BTU/hr and we have 15,000 sqft.  The condo is in Massachusetts as well.  Doing a web search netted me with going with something around 700,000 BTU/hr total.  Any suggestions on a good boiler manufacturer company?

Expensive.  But if you do decide to replace or upgrade, I would suggest going with a *good*  *local* boiler sales and maintenance company.  These guys know what works best in your area, and provide invaluable expertise in installation design, and maintenance help and support.  Even if you decide to keep what you have, and possibly retrofit the design to try and increase capacity, a local boiler sales company is a good choice.

naz

Offline bigcanuknaz

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Re: Boiler Question Condo Building
« Reply #6 on: December 19, 2009, 10:08:58 AM »
Joe:

Replacing perfectly good boilers that don't quite give you the capacity you need is not often the right solution.

You can also get an "energy audit" done.  Here in Canada, our natural gas utility covers half the cost.  They will look at all the inputs and outputs of your system.

Possible ideas:

1.  Add capacity with some other possibly green means, such as a rooftop solar heater and hot water storage.  you may be able to get a grant for this.

2.  Reduce consumption with low flow shower heads, added insulation, better windows, etc, etc.  Again, grants may be possible.

3.  Add hot water storage.  This may be best with option #1.

Just a couple of ideas.  Many more are out there.  good luck!

naz

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