Steam boiler and indirect hot water

Bob_57-2

I have a Burnham Independence steam boiler and a Heat Flo indirect hot water system connected to the boiler. The system is 9 years old. During those nine years I've had to replace the hot water circulator pump that feeds the indirect two times. The plumber told me that it was because of the rusty boiler water flowing through the pump. Now I think I'm between a rock and a hard place. Burnham says that the makeup water for my boiler (IN6) should not exceed 2 gallons per winter. That's about what I use without ever doing any draining of the boiler during heating season. But if I don't drain the boiler (other than when the plumber does the annual maintenance) the circulator pump fails. It seems that adding an indirect system to an old steam system (90 years old or more) makes no sense.

Any advice?

ethicalpaul

Buy a separate water heater. Seriously. Why anyone ever thought it was a good idea to heat household water with an inefficient boiler with tons of standby loss and huge mass to heat (all summer long, no less) is beyond me

Bob_57-2

I tend to agree with you, Paul, but I'm not sure it makes sense for me to bail out of the indirect at this time.

Looking at some old posts on this site, I noticed that the type of circulator pump may make a difference. My plumber has installed a Taco wet rotor pump, but some posts here say that's the wrong pump and a bronze one should be used. Is that why my pumps keep failing?

ethicalpaul

Yes, you should always use a bronze pump with boiler water, but still, just buy a water heater.

I'll wager you have spent more on the parts and labor of your last two pumps to cover the purchase and installation of a water heater.

Plus you will be able to shut your boiler off in the summer and not be heating your house with its standby losses fighting against your AC.

JUGHNE

Paul, I agree with you on separate WH, but an indirect tank is no small change to toss out.

That is where the 3 piece B&G bronze circulator was recommended. Motor not in the water. Even add a strainer before the pump.

ethicalpaul

Well it is 9 years old.

But I looked back on the original post again...it seems like the real question is: is it OK to drain the mud out of my boiler such that I have more than 2 gallons of makeup water during the winter?

I think the answer is: yes you can

The 2 gallon thing is meant to "catch" continuous steam or water leaks. Draining some water to keep the mud down seems different to me. Maybe it shouldn't?

Also, where is the tap for the circulator pump's supply? Like how high is it in the boiler? My Peerless has nice taps created specifically for indirect heating, they are at about 1/3 the way from the bottom of the boiler to the waterline.

And @JUGHNE 's question about the strainer is something I'm wondering about. Does it have one?

ethicalpaul

Also, speaking of no small change @JUGHNE I see 3 piece B&G pumps available for $600 and $1600...which one were you thinking of? Even a heat pump water heater is less than $1600!

Here's a little one that's even cheaper, maybe this is what you are thinking of? https://www.supplyhouse.com/Bell-Gossett-106189-1-12-HP-Series-100-NFI-Circulator-Pump-3540000-p

But that one's cast iron

Bob_57-2

My Burnham boiler has a tap on the side meant for indirects and other hot water legs. It's about 3 inches above the drain tap. Not sure where that is relative to the waterline.

As Paul said, my main question is about how much I can drain the mud out of the boiler without causing significant damage. I don't believe there is a strainer next to the pump.

Before getting my current setup I had a separate water heater. Those things seemed to die like clockwork at 10 years. I thought the indirect would be better, not appreciating that the circulator pump was the weak link.

ethicalpaul

I'm personally interested in your situation because I'm about to implement a hot water loop on my boiler to feed a radiant floor in my bathroom.

I'm glad your tap is above the drain tap. Do you ever get to see the water that is going through your pump? Is it for sure grit from the water that is killing the pumps?

Like maybe it's rust being created in the pump due to the open nature of the steam boiler introducing some amount of oxygen

ethicalpaul

Oh one other question for you: are you treating your boiler water to raise the PH from the typical 7-8 of tap water to something higher that will prevent oxydation? Something like 10? My boiler's instruction manual recommends 11!

JUGHNE

They are proud of the 3 piece pumps. Probably less demand today in favor of wet rotor pumps. The 3 piece one could be rebuilt just about forever, they were the workhorse of the trade for many years, but today the replacement is the cheapest way to go.

The boiler water/grit probably attacks the wet rotor of the motor and chews up a plastic impeller.
Even a 3 piece iron body with bronze impeller should outlast a wet rotor IMO.

Paul, I can give you a great deal on used 100's, a couple are bronze, multiple repair parts etc. , if you pick them up.

JohnNY

Residential steam boilers run at 80%-82% efficiency. Tank-type hot water heaters run at around 65% seasonal efficiency.

I fully understand "efficiency" is a roughly-defined word.
But...
As far as "standby losses" go, one could make the argument that, in winter when the boiler is running for heat, some significant percentage of a steam boiler's standby losses are reclaimed and put into the domestic water heater. That's a nice feature.
By comparison, residential tank type hot water heaters that have a chimney connection lose something like 8° per hour. Compare that to a sealed, insulated indirect water heater that loses around 10° per day.
My numbers may be slightly off depending on which study you find, but not by much.

If there's an issue with the steam boiler/indirect water heater setup, I don't think this is it.

@Bob_57-2 Either you spoke to the wrong person or you misunderstood when Burnham said the boiler should use 2 gallons over the course of a heating season. That's less than typical.

ethicalpaul

As far as "standby losses" go, one could make the argument that, in winter when the boiler is running for heat, some significant percentage of a steam boiler's standby losses are reclaimed and put into the domestic water heater. That's a nice feature.

In winter it's great, the steam boiler is hot anyway, I agree completely. But in the summer you are heating all that steam boiler mass, and leaking all that heat into your hot house that you are presumably spending money to cool. A situation only an oil company could appreciate.

I'd choose even a resistive electric water heater before an indirect or hot water coil, with a heat pump water heater being my first choice but my thinking may be extreme on this topic, I accept.

Bob_57-2

John,

I got the 2 gallon per heating season number from the Burnham manual: http://bostonheatingsupply.com/Burnham/Burnham Independence I&O Manual.pdf

page 65

The low number surprised me given what my water feed manual says (10 gallons per month!)

I think JUGHNE is correct: the grit attacks the plastic rotors. My pumps have made a lot noise before failing

ethicalpaul

Please link to your water feed manual or tell me the model number, I have to see this 10 gallon figure!

Bob_57-2

the link is in my previous reply. Is the link not working? The manual is for all Independence models

Bob_57-2

sorry, I misread your post, Paul. I will see if I can find the water feed manual online

SuperTech

ethicalpaul said:

As far as "standby losses" go, one could make the argument that, in winter when the boiler is running for heat, some significant percentage of a steam boiler's standby losses are reclaimed and put into the domestic water heater. That's a nice feature.

In winter it's great, the steam boiler is hot anyway, I agree completely. But in the summer you are heating all that steam boiler mass, and leaking all that heat into your hot house that you are presumably spending money to cool. A situation only an oil company could appreciate. I'd choose even a resistive electric water heater before an indirect or hot water coil, with a heat pump water heater being my first choice but my thinking may be extreme on this topic, I accept.

I personally don't have any problems with using an indirect tank with my Peerless boiler and "all that mass". Mine is hydronic but its not much different from the steam version,  other than controls. 
@ethicalpaul you make it sound as if you would need to produce steam to heat an indirect tank. 160-180 degrees will do just fine.  No need to heat anything other than the block. My basement stays cool in the summer and so should one with a steamer and an indirect. I would never go back to any sort of electric water heater. 

EBEBRATT-Ed

@Bob_57-2

You need a 3 piece bronze pump a wet rotor pump will not last. Install a strainer (brass) and put one in that can be easily cleaned.

As far as draining the boiler drain and flush as needed it won't hurt anything. The limit Burnham proposes on make up water whatever it is is to prevent continuous injection of oxygen which come in with fresh water from causing boiler corrosion.

After you drain flush and fill the boiler make steam with it this will drive off any introduced oxygen. You will have no problems

Bob_57-2

Here's the VXT-24 water feed manual; see the last page. Note that there's a disclaimer: always follow your boiler's instructions

https://www.globalindustrial.com/site/images/universal/Hydrolevel/ModelVXT24Instructions.pdf

SteamCoffee

Gerry Gill has a smokin’ indirect on his mini tube system, go check his out! As has been pointed out, pumps work best on 1) clean water, cooler the better. 2) not steam!

Jamie Hall

Water feed manuals do have that 10 gallon figure -- or worse, @ethicalpaul . I have no idea why. Very misleading.

New England SteamWorks

ethicalpaul said:

I'm personally interested in your situation because I'm about to implement a hot water loop on my boiler to feed a radiant floor in my bathroom.

Don't do it! Radiant and steam are oil and water. Run the radiant with a standard gas water heater, or pipe in steam.