Domestic Hot water conversion

 
t185
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Post by t185 » Thu. Mar. 29, 2018 7:18 am

Morning gents.

Quick question. I am currently running a EFM 520 from October to April as my primary heat source. The unit is located approximately 75 yards from my house. Heat is transfer from the boiler to the house via buried 1" pex piping that runs to a heat exchanger located in the plenum.

I am think about heating my DHW year round. Installing a DMW coil in the boiler is not an option since that would require the instillation of another buried line to the house.

My only other option is to branch off the existing pex line once it enters the house, install a holding tank and a DHW coil inside the tank.

DHW is currently heated with propane along with the dryer and stove. Average yearly consumption of propane is in the 400-500 gallon range at an average cost of $1.25 gallon. For arguments sake let's call it $600 per year.

My question. Is it worth the trouble? Or is it a fools errand?

On a side note. I am fairly handy so most of the work would be done yours truly.....


 
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Rob R.
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Post by Rob R. » Thu. Mar. 29, 2018 7:27 am

All you need is a plate heat exchanger. :yes:

How many people live in your house?

What is your coal cost per ton?

 
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lsayre
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Post by lsayre » Thu. Mar. 29, 2018 7:28 am

You will likely need to burn at least 15 lbs. of coal (and perhaps up to 20 lbs.) per day to both provide for DHW and sustain the fire. If ~17.5 lbs. of coal per day for the entire non-heating season costs less than propane this favors coal. If not, then propane is still a better option from the perspective of dollars.

 
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Post by Rob R. » Thu. Mar. 29, 2018 7:46 am

This project would be worthwhile even if only to provide DHW during the heating season. I would just put a plate exchanger on the cold water inlet of the existing propane water heater. If the air/water heat exchanger is kept hot all the time already, just add the plate exchanger in series.

 
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Post by Pacowy » Thu. Mar. 29, 2018 8:01 am

All else equal it would be better for the boiler to run during the summer than to sit. Probably not worth it if there is a substantial cost disadvantage. If not run, the boiler should be properly shut down and thoroughly cleaned.

Mike

 
t185
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Post by t185 » Thu. Mar. 29, 2018 8:26 am

Rob R. wrote:
Thu. Mar. 29, 2018 7:27 am
All you need is a plate heat exchanger. :yes:

How many people live in your house?-Four. Two daughters my wife and myself.

What is your coal cost per ton?
I purchase a semi load once every two years. With trucking my cost per ton is +-$150.

 
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Post by Rob R. » Thu. Mar. 29, 2018 8:34 am

3 women in the house + cheap coal = hook it up and let the EFM run year round.


 
t185
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Post by t185 » Thu. Mar. 29, 2018 8:38 am

Rob R. wrote:
Thu. Mar. 29, 2018 7:46 am
This project would be worthwhile even if only to provide DHW during the heating season. I would just put a plate exchanger on the cold water inlet of the existing propane water heater. If the air/water heat exchanger is kept hot all the time already, just add the plate exchanger in series.
I would need to install an inline valve to the heat exchanger during the summer months since the central AC unit runs through the heat exchanger.

My calculations on price per ton. $150/2000=$0.075 per pound x 15# per day= $1.125 per day

$1.125 x 7= $7.875 week
$7.875 x 4.33= $34.09 per month

$34.09 x 6= $204.59

I think the trade off to have an unlimited DHW is worth the change.

Now off to research this "plate exchanger" you speak of....

 
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Post by t185 » Thu. Mar. 29, 2018 8:44 am

Rob R. wrote:
Thu. Mar. 29, 2018 8:34 am
3 women in the house + cheap coal = hook it up and let the EFM run year round.
What size plate echanger? 175K BTU or larger
https://www.supplyhouse.com/Bell-Gossett-BP400-30 ... 83EALw_wcB

 
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Post by Qtown1835 » Thu. Mar. 29, 2018 8:58 am

You will also need to figure in the cost of the circulator running 24/7 unless you install additional controls. That cost may be negligible but it's something else to consider.

 
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Post by Rob R. » Thu. Mar. 29, 2018 9:04 am

t185 wrote:
Thu. Mar. 29, 2018 8:44 am
What size plate echanger? 175K BTU or larger
https://www.supplyhouse.com/Bell-Gossett-BP400-30 ... 83EALw_wcB
A 20 plate unit should meet your needs. One of our other members runs a S260 coal gun with the plate exchanger and has been very happy with the results. He was nice enough to post the info:

Post by Rob R. - Eshland S 260 Rebuild

 
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Post by windyhill4.2 » Thu. Mar. 29, 2018 9:32 am

I use 2 water to water plate units, 1 in each of the 2 houses,very pleased with them.1is in service since 2009,the other since 2011,both are 80k btu. If i ever replace them, i will install bigger units as the price is much lower for them than it was back when i bought mine.

Taco 007 operating expense is the same as a 60 watt bulb,so... if you shut the boiler down & put a lite bulb in to keep it dry.... :idea: running a circulator will cost no more electric than heating the cold boiler for the same time period.

The other benefit of keeping the boiler fired all the time is ..... if a chilly day occurs in June or September,you will have coal heat available at your t-stat. :)

 
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Post by t185 » Thu. Mar. 29, 2018 9:52 am

Rob R. wrote:
Thu. Mar. 29, 2018 9:04 am
A 20 plate unit should meet your needs. One of our other members runs a S260 coal gun with the plate exchanger and has been very happy with the results. He was nice enough to post the info:

Post by Rob R. - Eshland S 260 Rebuild
Would a indirect storage tank work?

 
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Post by lsayre » Thu. Mar. 29, 2018 9:59 am

t185 wrote:
Thu. Mar. 29, 2018 9:52 am
Would a indirect storage tank work?
Yes, but the cost of a plate exchanger will be far less.

 
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Post by t185 » Thu. Mar. 29, 2018 10:08 am

lsayre wrote:
Thu. Mar. 29, 2018 9:59 am
Yes, but the cost of a plate exchanger will be far less.
An indirect storage tank would not require an additional circulator, correct?


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