Need advice on gravity boiler system

**glenl** · 10-06-2005, 01:42 PM

Need some help to make informed decisions on boiler replacement.

Went to bleed the radiators on the first 30 degress morning of the year. Heard a few noises as I let extra water in. Always seems to need a bit in the fall. One noise was dripping and hissing from the boiler. Cripes. Water was dripping right onto the pilot light and it had gone out. (Can you say $$)

I fired it up anyways to see what would happen. Nothing blew up but after a ten minute burn the water continued to drip.

The unit is a 100000btu/hr unit from Monkey Wards that has to be 50 years old. No pump, just the two pipes for gravity cycling. Natural gas fired.

Any chance this thing is repairable?

I've already started looking into a replacement. Makes me wonder a few things.

Are there separate product lines for pumped versus gravity boilers? I'm not finding any boilers that say they're for a gravity system. Is it just plumbed up to the input and output or is the pump put in anyways?

What are good product lines for these types?

Anything special info a guy should have?

Thanks!

**Noel Murdough** · 10-06-2005, 01:56 PM

That system would be considered medium mass, low temperature. It would fit a condensing boiler pretty perfectly.

Pumping the system (the radiators and pipes) and pumping the boiler might need special care, in that the system has almost no resistance (head loss) and condensers usually have a high head and a high flow rate requirement.

The boiler will come with instructions for itself, and here is what you need to know for pumping the system...

http://www.heatinghelp.com/newsletter.cfm?Id=125

Noel

**glenl** · 10-06-2005, 02:22 PM

So...

You're suggesting a condensing boiler. Then it'll just vent outside without using the chimney.

As for the pump, looking at that link I'd need a 20 GPH pump at 3.5' head to go with the 100000 BTU/hr. (Right?) That sounds like a lot of flow. I expect this will require re-balancing the flows.

Am I getting this? And thanks.

**Noel Murdough** · 10-06-2005, 02:27 PM

it will be a pretty small (relatively) pump.

The whole idea is to keep the flow where you WON'T need to rebalance.

Keep in mind that the SYSTEM will work with NO pump, but the boiler wouldn't be pleased.

Noel

**glenl** · 10-07-2005, 12:52 PM

Thanks, Noel.

I was wondering if there was a model or brand that would work well, and last, with just gravity and no pump.

Also, I'm not finding much good info on relative quality of brands.

How would you guys rate Burnham vs. Peerless vs. Hydrotherm?

**Noel Murdough** · 10-07-2005, 01:42 PM

Those are all good choices.

I work for this company, in the Technical Service Dept.

http://www.slantfin.com/boilers.html

Check this out, it just came out...

http://www.pmengineer.com/CDA/Articl...atures__Item/0,2732,161636,00.html

Noel

**Freezeking2000** · 10-07-2005, 11:30 PM

I think what you were looking at was condensation from the cold flue gas caused by the low water temps. Fire it up good and it will most likely pass!

**glenl** · 10-07-2005, 11:48 PM

I did fire it up until the radiators got warm. It wasn't leaking at all until I opened the feed valve. Now a day later, with the pilot out, the pilot and that part of the burner is wet.

It seems that the moisture from the pilot running all summer accelerated rusting right above it. Drip. Drip. Drip. $. $. $.

**markwolf** · 10-07-2005, 11:59 PM

Originally posted by Freezeking2000
I think what you were looking at was condensation from the cold flue gas caused by the low water temps. Fire it up good and it will most likely pass!

That could be a potentially hazzardous thing to do!I would not tell that to someone with a boiler that old & not knowing what safeties were in place.Or weather or not they have operational safeties.I run across "scary"boilers at least three times a year that I suggest replacement or at a minimum a safty device upgrade.

**markwolf** · 10-08-2005, 12:01 AM

If you get a non-condensing boiler insist on having a thermostatic bypass installed so the boiler will come up to operating temperature quickly,helping to avoid potential combustion problems.

**glenl** · 10-09-2005, 11:40 AM

Thanks, Mark.

I'm getting close to pulling the trigger on this.

One thing I'm not clear on is the need to re-work the expansion tank. The existing piece is connected to the return line. The schematics for the boilers that I've seen call for a tank connected off the top of the usint and, I guess, boiler itself.

Is this done for convenience or is it required for good operation?

**Noel Murdough** · 10-09-2005, 12:34 PM

http://www.heatinghelp.com/shopcart/pdfs/16.pdf

http://www.heatinghelp.com/shopcart/...?category=2-16

**glenl** · 10-10-2005, 06:43 PM

You're probably right about that. Being October in Minneapolis, I've gotta get in gear.

Re-checked that expansion tank. It's actually on the supply side of the boiler. It looks good on the outside. Do these have internal bladders? What's the requirement level to replace it?

Thread: Need advice on gravity boiler system

Thread Tools

Search Thread

Display

same boilers

the low head is the key

I hate to pick one

Wish it were so

I think you would enjoy this book

Posting Permissions