Oil to Gas Conversion Confusion


  #1  
Old 11-23-09, 09:55 AM
J
Member
Thread Starter
Join Date: Nov 2009
Location: Long Island, NY
Posts: 7
Upvotes: 0
Received 0 Upvotes on 0 Posts
Oil to Gas Conversion Confusion

I've been researching this for over a year and NEED expert advice. Current plumber experts only know what they sell and really don't know all the technology, just how to install it.

Setting:
Long Island New York w/50+ yr old tired oil boiler w/DHW (domestic hot water) coil, 82% AFUE tested. Chimney flue roof vent. 40gal DHW tank off coil. 2 heat zones. Trying to add a 3rd (break downstairs and upstairs to 2 zones currently one) 2100 sq ft house with oversized BASEBOARD in all rooms. 141' of baseboard equates to 84,600btus IFR. 3 person household 2 full baths, dishwasher, washing machine, possible add another zone for hot tub use. We currently use about 3.5 tanks of oil (275gals.) per year. Boiler is working fine. Supplemental heat with fireplace insert w/blower.

National Grid just installed gas service to the house now I need to make a decision and run with it.

Decision details:
Overview:
Spoke w/ 7 licensed master plumbers only got 2 quotes back. This is from Aug. 2009 it is now Nov. and I am pushing to get this done before it gets REALLY cold.

Recomendations:
Condensing vs non-condensing systems, Combi vs DHW seperate.

Understanding
HEAT:
Baseboard needs 170-180F water temp therefore condensing will not kick in and is unecessary except to get the one time $1000 rebate from Nat. Grid. Boiler for over 90% efficiency boilers. It will only really run at 82-86% AFUE no matter what.

Understanding DHW:
Tank (off-zone or boiler coil (current)) vs on-demand
Tank works better for pressure vs on-demand. I'm told on-demand is fine for us. Want to see a sytem and check it out for myself. No plumber I met yet has anyone I can talk to or meet. Except partner at Sime distributor who just installed a system for himself.

Models under Consideration ranked:
(1) Sime format.zip combi non-condensing modulating boiler w/on-demand DHW.
(2) Baxi Luna 3 combi non-condensing modulating boiler w/on-demand DHW.

SUMMARY
Research has shown many condensing boilers avg. 97% AFUE w/prices all over the place. No real science or research shown from anywhere for baseboard applications. Non-condensing avg. 84% AFUE not many with combination DHW.

QUESTIONS:
Where can I find a list of manufactures with non-condensing modulating combi wall mount units with DHW that are efficient with good warranties? Should I bother or just stick with the above two?

Should I just get a cheapo gas boiler and add a cheapo gas DHW tank? Total cost $3000 installed vs $6000+ for the fancy above units.

Will a modulating system modulate given baseboard requirements?

Is this the right way to continue? Should I even explore condensing boilers?

Thanks! Jeff
 
  #2  
Old 11-23-09, 10:11 AM
P
Temporarily Suspended
Join Date: Jul 2008
Location: NY
Posts: 10,265
Upvotes: 0
Received 0 Upvotes on 0 Posts
Did you call Universe in Seaford? They are the best in Long Island for heating. If you give them the job, just make sure that you tell them you want a separate circulator pump for each zone.

Call Rich & Tom's Ground To Chimney for chimney questions. I know them personally. They are honest.
 
  #3  
Old 11-24-09, 05:31 AM
H
Member
Join Date: Sep 2006
Location: NJ
Posts: 163
Upvotes: 0
Received 2 Upvotes on 2 Posts
For a house that size and the max GPM for fintube at 4, why the need for multiple circs?
 
  #4  
Old 11-24-09, 05:52 AM
P
Temporarily Suspended
Join Date: Jul 2008
Location: NY
Posts: 10,265
Upvotes: 0
Received 0 Upvotes on 0 Posts
That's very simple. If there is only one circulator pump for 2 or more zones & the pump goes bad, then none of the house will have heat. At least part of the house will be warm with other pumps.
 
  #5  
Old 11-24-09, 07:24 AM
J
Member
Thread Starter
Join Date: Nov 2009
Location: Long Island, NY
Posts: 7
Upvotes: 0
Received 0 Upvotes on 0 Posts
The price of the circ pumps is cheap comapred to not having heat. I'd put them on all zones.

I'll call Seaford and see what they say, Thanks!

I really was hoping the gang on the forum would enlighten me as opposed to talking to another shop that would specialize in 'their' equipment. I'm looking for generalist engineering first and product second.

Thanks, Jeff
 
  #6  
Old 11-24-09, 02:58 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 19,710
Upvotes: 0
Received 8 Upvotes on 6 Posts
Jeff, if you are thinking that because you have 85K of baseboard, that you need an 85K boiler, well, that's wrong. You need to do or have done, a heat loss calculation on the home and size the boiler according to that. Anyone that tells you otherwise is wrong.

Your understanding of the water temperature in the baseboards is also somewhat in error... you only NEED 180 water in order to achieve the RATED OUTPUT of the baseboards. You probably have more baseboard than you need, and that's GOOD, because it means that you CAN run cooler water in the system. Example: Let's say your heat loss calcs reveal that one of your rooms needs 5000 BTU to heat it, and you have 15' of baseboard in that room. With 180 water, that 15' will output around 8500 BTU, which is more than you need, right? OK, so run cooler water! There's a temperature point where the 15' of baseboard will output the 5000 BTU that you need to heat that room (or your whole house for that matter).

Also, keep in mind that the heat loss calculation is for DESIGN TEMP... the coldest part of the winter... for 99% of the winter, you aren't going to need anywhere near 5000 BTU to heat that example room... no, it's gonna be way less. So now you can run even COOLER water!

I can't decide for you whether or not a mod/con will make sense in your situation, but you need to look at it factually, and the fact is that a properly set up mod/con WILL be capable of condensing for a significant portion of the heating season.

Will a modulating system modulate given baseboard requirements?
Not exactly. A modulating system will modulate given HEATING requirements. It doesn't care what the heat emitters are... baseboard, cast iron rads, radiant floors, whatever... it will calculate the BTU input required to supply the required temperature water to heat your home.
 
  #7  
Old 11-24-09, 04:12 PM
F
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 16,321
Received 38 Upvotes on 30 Posts
Something else you need to understand is that your present boiler is NOT 82% AFUE. AFUE (Annualized Fuel Utilization Efficiency) is a laboratory calculation and it cannot be ascertained in the field. It is only used to compare between competing boilers or furnaces.

What your 82% efficiency figure refers to is the instantaneous combustion efficiency of the boiler and burner at the time of the test. Depending on several variables the test may not even be repeatable to the same figures.

It would not be at all unusual for a fifty-year-old boiler to have a combustion efficiency in the low 80%+ range but the system with this boiler would likely have a low AFUE rating if one could be calculated. Simply replacing the old boiler with a more modern unit, even one that had an AFUE in the low 80% range would likely gain much in fuel savings over the old boiler.
 
  #8  
Old 11-24-09, 04:52 PM
D
Member
Join Date: Aug 2009
Location: USA
Posts: 4,344
Upvotes: 0
Received 1 Upvote on 1 Post
From reading this forum, getting your hot water from a coil in the boiler is the worst way to get DHW. Use an indirect tank if you don't get a separate tankless. I have a 35 gallon indirect on my system and I could take a shower all day with it and not run out of hot water. Works great and is more efficient than a stand alone gas water heater.

If no one is willing to do a heat loss calculation for you, do it yourself. I used HVAC Calc from HVAC-Calc HVAC Software The Heat Loss Calculator HVAC, HVAC/R, HVA. Cost 50$ for 2-3 months use. I believe Tekmar has one available on their website for free. I haven't used it so I don't know what it's like.

If your boiler is 90% AFUE or better, you will qualify for up to $1500 from the feds.
 
  #9  
Old 11-24-09, 05:36 PM
X
Member
Join Date: Nov 2005
Location: USA
Posts: 2,338
Upvotes: 0
Received 0 Upvotes on 0 Posts
The posts above cover most of the issues, especially Trooper disabusing you of some misconceptions.

To amplify a couple points:

1) The only way to size a boiler is by doing a heat loss for the building.

2) It is very likely that you could condense for much of the heating season. Your heat loss and some estimates of baseboard output at various supply temperatures relative to heat loss at less than design cold outdoor temps will tell you.

3) Avoid 'circaholism'. With a new ECM circulator (e.g., Wilo ECO or Grundfos Alpha) and zone valves, you can get proper flow in all your zones, and save a bundle on electricity for years to come, compared to 4 circulators.

4) Combi units are ok, I suppose. My preference in that field would be a Triangle Tube Excellence.

5) Beware the hot tub, soaker tub, whatever. That raises hot water demand to a whole 'nother level. Example: no way you fill a 60 gallon soaker tub with a combi unit. It might have a continuous output of 2.5 gpm, probably less. 60/2.5 = 24 minutes.
 
  #10  
Old 11-24-09, 06:11 PM
P
Temporarily Suspended
Join Date: Jul 2008
Location: NY
Posts: 10,265
Upvotes: 0
Received 0 Upvotes on 0 Posts
xiphias What do you mean Avoid 'circaholism'? Do you belong to circaholics anonymous or something?

Who said anything about 4 pumps? There are only 2 zones. As I said, one pump doesn't make sense. If it goes, there won't be any heat at all.
 
  #11  
Old 11-24-09, 06:36 PM
D
Member
Join Date: Aug 2009
Location: USA
Posts: 4,344
Upvotes: 0
Received 1 Upvote on 1 Post
How long do you think you would be out of heat if you had a pump go bad? You can buy them at Home Depot if you had to, or keep a spare on hand if that is such a big worry.

What if you only had one zone? Would you pipe in two pumps in case one went bad? There are a lot of things in the system that commonly go bad that would prevent the system from heating, but I wouldn't go adding two of all of them.
 
  #12  
Old 11-24-09, 06:48 PM
X
Member
Join Date: Nov 2005
Location: USA
Posts: 2,338
Upvotes: 0
Received 0 Upvotes on 0 Posts
Originally Posted by Pulpo
xiphias What do you mean Avoid 'circaholism'? Do you belong to circaholics anonymous or something?

Who said anything about 4 pumps? There are only 2 zones. As I said, one pump doesn't make sense. If it goes, there won't be any heat at all.
The OP said currently 2 zones, wants to add a third by breaking one of them in two, and potentially add a zone for hot tub. That's four.

As to circaholism, I think there is a strong tendency to just slap a circ on every zone without regard to pumping requirements, system design, and overall energy efficiency. Zoning with circs is very often not necessary. It's electrically wasteful, particularly now that we have good ECM circulator technology. The logic of "if it fails there's no heat" would apply to hundreds of thousands of zone valve systems. Failure rates just aren't that high. If it's a real concern, keep a spare on the shelf and by all means use shutoff flanges for a 15-minute swap.
 
  #13  
Old 11-24-09, 06:52 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 19,710
Upvotes: 0
Received 8 Upvotes on 6 Posts
Very rare for a pump to go bad. I wouldn't worry about it, should not be a point of contention. Many other things more likely to fail than a circ pump.

Hic! pash me another chirc pleeshe! Beer 4U2
 
  #14  
Old 11-25-09, 08:56 AM
J
Member
Thread Starter
Join Date: Nov 2009
Location: Long Island, NY
Posts: 7
Upvotes: 0
Received 0 Upvotes on 0 Posts
BIG THANKS!!

I'm beginning to really understand this now! NJ Trooper made the condensing vs non clear and I assume the outdoor module along with heat calls drives the modulation of the boiler output sending the proper temp to the baseboards. Is this correct?

The baseboards are oversized according to all who have seen and measured. I have looked at the heat loss calc tools too. There is a free on here Heat Load Calculator that I played with.

My direction is now re-focused on modulating condensing boilers around 105,000BTUs with a indirect water heater. National Grid is selling the Alpine ALP105N for $2,389 and they give me back a $1000 rebate on the unit for a net cost of $1,389 for just the boiler. Any ideas on a 35gal. indirect DHW with this?

I'll also make sure to keep the system to one circ! With a shelf backup and ball valve setup for a quick swap. Awesome idea!

I kew about the $1,500 from the feds. Does anyone know if this will continue in 2010?

Thanks again for all the help!
 
  #15  
Old 11-25-09, 11:51 AM
P
Temporarily Suspended
Join Date: Jul 2008
Location: NY
Posts: 10,265
Upvotes: 0
Received 0 Upvotes on 0 Posts
As far as I know National Grid uses sub-contractors. You don't know who is coming to do the work. That's why I went with Universe for my father's house. They handled all the permists & inspections. The old burner was removed & a new burner & separate hot water heater were installed, all in one day.
 
  #16  
Old 11-25-09, 12:08 PM
X
Member
Join Date: Nov 2005
Location: USA
Posts: 2,338
Upvotes: 0
Received 0 Upvotes on 0 Posts
You don't need a 105. An 80 will be fine.

Shop thoroughly for a contractor. The installation is the most important part of the whole deal.

As for indirects, a contractor probably has a favorite. There are a number of good ones. The HTP Superstor is a well-regarded coil-based tank. The Triangle Tube Smart series is a well-regarded tank-in-tank model.
 
  #17  
Old 11-25-09, 02:01 PM
G
Member
Join Date: Jun 2008
Location: Vermont
Posts: 93
Upvotes: 0
Received 0 Upvotes on 0 Posts
Originally Posted by JeffTan
I kew about the $1,500 from the feds. Does anyone know if this will continue in 2010?
Yes, the federal tax credit is for 2009 and 2010, but you can only get a maximum of $1500 over the course of both years. Assuming you get a mod/con, you'll get 30% of the total job cost back (with a $1500 maximum).
 
  #18  
Old 11-25-09, 02:32 PM
rbeck's Avatar
Member
Join Date: Jul 2007
Location: United States
Posts: 2,407
Upvotes: 0
Received 66 Upvotes on 55 Posts
Before you can choose a boiler and which may be best mod/con or not you need to do the homework. Too many people make the choice and then do the homework and may make the wrong decision.
What is more important, up front cost, maximum fuel savings or life cycle cost?
As many know I play the devils advocate and many times push for the underdog. This is what I preach.
First and foremost do the heat loss as everyone has stated.
Next measure the amount of radiation per zone and determine the water temperature required for different heat losses.
If that temperature will be below 126 most of the time than a mod/con makes the best sense. If it is going to operate above the 126 most of the time than a non-condensing makes the most sense. Of course you Will want to add ODR no matter what. The mod/cons come with the ODR and it would have to be added to the non-condensing models. The three top fuel savers is Proper sizing, ODR and proper adjusting of the heating curve.
The mod/cons do like larger zones as the more water volume the longer the run cycle and possible more condensing. When the mod/con is not condensing you loose the 9.6% of the input that cannot be removed from the condensate.
Last but not least I also suggest we look at the fuel savings difference between the two and add in the annual maintenance required on the mod/cons and parts that are more than twice as expensive. Ask the service company what they charge for the annual maintenance.
If they are installed in the proper system I think they are the cats meow. Larger water volume systems, in floor radiant, commercial applications etc...etc. I suggest mod/cons many times a day and sway people away many times a day. Apllication....application....application. Clean them every year and they should give you a long life. Every boiler should at least be checked every year to verify the safeties are working. How much do we spend for 4% to 6% more savings?
 
  #19  
Old 11-25-09, 05:16 PM
J
Member
Thread Starter
Join Date: Nov 2009
Location: Long Island, NY
Posts: 7
Upvotes: 0
Received 0 Upvotes on 0 Posts
Thanks again for all the GREAT advice! Very much appreciated.

Nat Grid is finally sending a sales guy Mon. I asked if they do the heat loss and fit on the boilers they provide and was told yes. We shall see Monday. I'll post up the results.

Warmest wishes to all for a Healthy Holiday!
Jeff
 
  #20  
Old 11-25-09, 10:54 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 19,710
Upvotes: 0
Received 8 Upvotes on 6 Posts
sales guy
Those words scare me... beware the 'hard sell' !
 
  #21  
Old 11-30-09, 04:15 PM
J
Member
Thread Starter
Join Date: Nov 2009
Location: Long Island, NY
Posts: 7
Upvotes: 0
Received 0 Upvotes on 0 Posts
As promised a post sales guy post:

Just met with the Natl. Grid ENERGY SERVICES sales guy. This is a private company wholly owned by Natl. Grid. They compete with their list of approved independants who clearly have a cost advantage over Natl Grid. He made it clear from the start he was expensive and was having a hard time selling their solutions. This guy is stuck to Burnham boilers and indirect water heaters. They only do a heat loss calc if the client is ready to sign. I did not BS him into doing it. I was honest all the way and he was too. He told me his brither just put in a Baxi 105K BTU system for his forced air system.

I told him I was looking into the Fujitsu ductless for A/C and to possibly provide the heat in the spring and fall when temps don't dip below 32 degrees. He indicated that our NY KW cost at $.24/per is too high and that it is less expensive to use the gas boiler for the heat. I asked if there was a point on a efficiency graph where the 2 would cross and he thinks they would never cross. Does anyone out there have any thoughts on this? I do want the ductless for A/C and the heat pump otion is there to use or not.

He also stated that a condensing boiler would never condense for me. Simply because the return cool water to the boiler will never be cold enough to condense even if the boiler modulates and puts out lower temp water to the baseboards. He said condensing works better if the heat outsource were cast iron radiators. The baseboard returns never get cold enough to cause condensation.

So I'm looking at the Baxi or the Sime again because I like the idea of the on demand hot water as opposed to the indirect DHW. The pricing comes out nearly the same for a boiler w/indirect DHW or the on-demand DHW unit. I just don't have a tank with contant heated up hot water taking up more room.

Any thoughts would be greatly appreicated as always.

I'll post the heat loss I do for the house.

Tomorrow (Tues.) I meet with a green expert who suggested the Fujitsu for heat and A/C. I'll post those details too.

Thanks and still confused,
Jeff
 
  #22  
Old 11-30-09, 04:40 PM
P
Temporarily Suspended
Join Date: Jul 2008
Location: NY
Posts: 10,265
Upvotes: 0
Received 0 Upvotes on 0 Posts
May I suggest that you call the dept of consumer affairs before hiring national grid? Have you eliminated Universe completely as a possible contractor?
 
  #23  
Old 11-30-09, 05:06 PM
G
Member
Join Date: Jun 2008
Location: Vermont
Posts: 93
Upvotes: 0
Received 0 Upvotes on 0 Posts
Originally Posted by JeffTan
He also stated that a condensing boiler would never condense for me. Simply because the return cool water to the boiler will never be cold enough to condense even if the boiler modulates and puts out lower temp water to the baseboards. He said condensing works better if the heat outsource were cast iron radiators. The baseboard returns never get cold enough to cause condensation.
You do realize that that's a load of BS I hope? I'm in Vermont with fin tube baseboard and my boiler condenses up a storm. Why would the return water never get below 135* when you can use supply temps well below that for a good part of the heating season?
 
  #24  
Old 11-30-09, 07:15 PM
J
Member
Thread Starter
Join Date: Nov 2009
Location: Long Island, NY
Posts: 7
Upvotes: 0
Received 0 Upvotes on 0 Posts
Thanks for the feedback! I'm posting here to cut the BS. I really don't know and am trying to get opinions to make the best decision possible. I have yet to find any good white papers on this with actual studies done. Any links would be appreciated.

No, I have not ruled out Universe. I'll call them after tomorrows meeting to setup a date.

What is the lowest temp baseboard water should run at? What are the parameters (Outside temp vs. inside need supply temp)?
My ignorant thoughts on this are; the hotter the water say around 180 the quicker the heat up in the room and the less run time of the circ and boiler. The lower the temp the longer it takes to heat the room. Where is the critical efficiency? I know this all depends on heat loss but take that out of the equation for a thought. As a example:

Room set temp 70 degrees boiler/circ kicks on at 65 degrees in a windowless inside room 400sq ft. 180 degree water vs 130 degree water flow through the baseboard. Given a efficient boiler so it does not take that much more energy to keep the small amount of boiler water at 180 degrees than 130, Wouldn't the room heat quicker therby stopping the circ sooner with 180 degree water? I'm very curious about this.

Any other points on my prev. post?

Thanks again! Jeff
 
  #25  
Old 11-30-09, 08:12 PM
G
Member
Join Date: Jun 2008
Location: Vermont
Posts: 93
Upvotes: 0
Received 0 Upvotes on 0 Posts
The object isn't to make the space heat up quicker and run the circulator less. For maximum efficiency with a mod/con, you actually want the exact opposite. The circulator should be running continously with water that is just barely hot enough to replenish the heat that your house is losing. Since your house loses more heat as the temperature outside goes down, the water that is needed to match that heat loss must go up in temperature. Every house is going to have a different curve for maximum efficiency, and I haven't gotten mine perfectly dialed yet. But so far this year, I haven't seen water temps go above 120* with my thermostats set to 67* all the time. Right now my minimum water temp is set to 86* and the max is set to 144*. But with my current settings, the temp will have to be -8 outside before the water gets that hot. I'll see if it's enough when the temps get down there.
 
  #26  
Old 12-01-09, 03:39 AM
X
Member
Join Date: Nov 2005
Location: USA
Posts: 2,338
Upvotes: 0
Received 0 Upvotes on 0 Posts
Originally Posted by JeffTan
Given a efficient boiler so it does not take that much more energy to keep the small amount of boiler water at 180 degrees than 130
Actually, it takes a lot more energy.

For a system with a volume of 10 gallons, it takes 4200 BTUs to raise it from 130-180F. In a 24 hr period, that's 100,000 BTUs. An 85% efficient boiler (can't condense at these high temps) will use 115,000 BTUs to do that work.

Now say that you get about 4 months total of that 24 hour period spent raising the water the extra 50 degrees. That's 14 million BTUs. Which is about 138 therms (or ccf). A last year's NatGrid prices, that would be around $230.

Chances are that you can condense most of the heating season. I got a house full of baseboard and have only once or twice in the past several years seen supply temperatures above 135. And that was just for a couple hours. The other 18,000 hours it's been in the condensing range.

The lowest useful supply temp for baseboard is around 85F.

A lot depends on the building envelope, but don't let anyone tell you -- especially if they haven't done a heat loss and supply water / output calculation -- that you can't condense with baseboard.
 
  #27  
Old 12-03-09, 08:19 PM
J
Member
Thread Starter
Join Date: Nov 2009
Location: Long Island, NY
Posts: 7
Upvotes: 0
Received 0 Upvotes on 0 Posts
Great info! I'm waiting for the latest 'expert' to do his heat loss calc and pitch me 'his' system idea.

I spoke with a zero net use guy on Long Island and he is pointing me at Micro CHP. Yikes!! What an awesome idea! I still have not seen pricing on these puppies but will call a local reseller and get the low down tomorrow. The net is full of info. but no numbers that I found in my quick look. Anyone out there ever heard of this?

Jeff
 
  #28  
Old 12-04-09, 05:52 PM
X
Member
Join Date: Nov 2005
Location: USA
Posts: 2,338
Upvotes: 0
Received 0 Upvotes on 0 Posts
Originally Posted by JeffTan
Anyone out there ever heard of this?
Yes.

You would be an early adopter. At the residential scale, "commoditized" (off the shelf) co-gen is pretty new. The Honda/ECR version being pushed by NatGrid (see Freewatt) does seem pretty robust though. The Honda side is well-thought out, scaled down from larger applications, and draws on residential scale application in Japan.

The ECR (Dunkirk and Utica boilers are among their holdings) hydronic side is ok. The modulation range of the boiler is 80-200k, which is far more than a typical residence needs, but I think is required in order for the Honda co-gen side to function reasonably. They don't explicitly show one, but a large buffer tank on a normal-load residence would probably improve overall performance on the hydronic and the co-gen systems quite a bit.

It would not be cheap, but it would be cool. Run the numbers and see where you end up.
 
  #29  
Old 12-04-09, 06:15 PM
X
Member
Join Date: Nov 2005
Location: USA
Posts: 2,338
Upvotes: 0
Received 0 Upvotes on 0 Posts
Sort of an aside, but one of the oft-unstated reasons that utilities are pushing all this high-efficiency stuff -- be it boilers, efficient refrigerators, or co-gen -- is because it is much cheaper for them to mitigate the rate of increasing demand through end-user efficiency/utilization improvement than it is to upgrade the delivery system, e.g., larger gas mains, improved electrical grid. The electrical co-gen side of these systems is a good case in point. The efficiency of centralized electrical generation is really low. Almost always sub-50%, often much less. The potential efficiency of site-generated electricity is almost always >70%, often 85% or more if it's well designed and installed. (See comment above about how a large buffer tank might help improve performance, as would other heat distribution system and building envelope upgrades.)

The present generation of residential co-gen requires grid connection (principally for electric to run the stuff), but it's not a huge leap to make these things function in an environment of grid intermittency or even absence (e.g., battery storage for electric; propane or other gasified fuel for a boiler; or fuel cell technology). Ask people who live off-grid. It's not hard from the ground up, but in retrofit it's still pretty tough. We're getting there.
 
  #30  
Old 12-04-09, 06:38 PM
D
Member
Join Date: Aug 2009
Location: USA
Posts: 4,344
Upvotes: 0
Received 1 Upvote on 1 Post
I saw one of those setups on Renovation Nation. It cost something like $20k.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: