Installing a Mod/Con to replace a 40 year old gas FHW boiler

Tim McElwain

If that was what you were looking to do what would be the list of things you would consider before moving forward with the installation? Sort of a check off list for this type of undertaking.

SWEI

I'd start with:

• Heat loss calc
  
• Emitter survey
  
• Evaluate venting options
  
• Compare fuel costs
  

Gordy

^^ ditto

modconwannabe

From a homeowner's standpoint a couple practical issues we ran into that may figure into your calculus as well:
Is your current gas line sufficient to run whatever new setup you'll be investing in (I went oil to gas so had to get a new gas supply line $$)
Is your venting in good shape: presumably not an issue if you already have gas going, but for us we were going to have to reline our chimney, which was also too small anyway, and so we ran new PVC intake and exhaust lines.
Primary/secondary as stated above. The pros will chime in here but I would assume reconfiguring a basic gas boiler into a primary/secondary system is substantially more work and expense.
Hot water: we went with indirect hot water, which is apparently way more efficient than a hot water heater and also allowed for less complications in terms of venting and exhaust and permitting (I'm in NYC).
Amortization. We spent a fortune installing this system. It was worth it, I think, because we got a wildly more efficient system (though oil prices have dropped), that's less intrusive, and more comfortable and seemingly future proof (ha!). But I don't know that we'll recover the cost outlay, ever.

The downside, depending where you live, may be finding someone who has any clue what they're doing with all the above. But then I suppose that's why this forum is so great

Good luck!

Paul Pollets

I wrote an article for Reeves Journal several years ago on the topic...Here's he link. It's free to register and read:

http://www.reevesjournal.com/articles/87592-mod-con-boiler-considerations?v=preview

hot_rod

Ask the customer about expectations
DHW needs
Blower door test for accurate load #
IAQ concerns
Hi, mid, or low technology acceptance
Life expectancy and yearly maintenance costs
Color of equipment

Gordy

You forgot caleffi.

Jean-David Beyer

"Is your current gas line sufficient to run whatever new setup you'll be investing in (I went oil to gas so had to get a new gas supply line $$)"

I was lucky. When I converted from oil to gas, the local gas company was looking for new customers. They installed a new line all the way from the street to where I wanted the meter placed for free. I did have to pay the town a street opening charge so they could connect the drop pipe to the main in the street. $175.

A year or so later, the gas company replaced the 60 year-old iron pipe with a larger diameter plastic pipe for their gas mains, and increased the pressure from the nominal 15 psi (actual 8 psi) to 50 psi. The regulator did not even need to be changed. It still delivers 7 inch pressure to my house.

Tim McElwain

This is my list that I go over in my classes. What do you think should I add anything?

Mod/Con Boilers Important things to
consider not necessarily in any order.
1. Radiation (Baseboard,
Convectors, Radiators ETC.)
2. Existing piping - gravity systems
3. Water Temperatures'
4. Outdoor Reset
5. Heat Loss
6. Piping (Primary Secondary -
Low Loss. Header)
7. Water temperature mixing
8. Control System (complexity)
9. Annual Cleaning (Maintenance)
10. Stainless Steel, Cast Aluminum,
Cast Iron.
11. Domestic Hot Water
a. On demand
b. Indirect
c. Storage
12. History of the new equipment

RobG

Tim McElwain said:

This is my list that I go over in my classes. What do you think should I add anything?

Mod/Con Boilers Important things to
consider not necessarily in any order.
1. Radiation (Baseboard,
Convectors, Radiators ETC.)
2. Existing piping - gravity systems
3. Water Temperatures'
4. Outdoor Reset
5. Heat Loss
6. Piping (Primary Secondary -
Low Loss. Header)
7. Water temperature mixing
8. Control System (complexity)
9. Annual Cleaning (Maintenance)
10. Stainless Steel, Cast Aluminum,
Cast Iron.
11. Domestic Hot Water
a. On demand
b. Indirect
c. Storage
12. History of the new equipment

The only thing I might add would be in the heatloss category of proposed upgrades to building envelope or future additions.

rick in Alaska

Whether you can get to a drain is also a consideration. Around here, if a unit is installed in a garage that had an oil boiler, there might not be an easily accessed drain to get to .
And, water quality is also an issue.
Rick

clammy

Awesome list of things to consider but how about the materal in which the existing system is constructed of copper ,steel and the need for either strainers or better yet a magentic dirt seperator for steel piped systems to help remove any debrie .Proper air removal and piping and pump location .Also the need for ifc pumps and chk valves on the supply and return of the idwh and boiler to prevent thermal migration durning heating off seasons when the boiler only runs for domestic .Also not on the list was condesate neutralizer and disposal of condensate some times areal issue when theres no floor drains or sinks and some times just cutting in a trap on a waste line leads to alot of other things like a trap primer if the inspectors pick up on it even though its a rare.I think another issue is making sure the HO knows that this not a no maintance boiler and that with all the parts which are not cheap that maintance must be done and at some point you must weight out weather its worth replacing parts or put in a new unit .On another note it seems that these HO forget why they put a mod con in untill you remind them of the 10 grand they save on a new masonary chimmey and the space it took i am face with this sititution now even though the HO has been extremely happy with there fuel bills its getting time to replace there 12 or 13 year old munchkin which has worked it butt off with nearly no issues its a tough call dump close to a grand into a new burner motor and burner or just put that towards a new boiler sorry to change subject and rant peace and good luck clammy

Paul Pollets

Venting considerations and proper vent materials; Condensate disposal and neutralization.