I'm in the process of searching for a gas-fired water boiler replacement. I've had two plumbers over already to review my options.

Today, I have an 18-year old oil burning boiler retrofitted to burn natural gas. An energy audit concluded that we are probably burning at 70% efficiency. The boiler exhausts out the chimney which is in the middle of the house. I have 3 heating zones each with its own circulator pump on the supply side. Our domestic hot water is from an immersion coil in the current boiler.

Today, I have comfortable heat throughout the house. I keep the upstairs (1 zone) at 64 degrees most of the
time. The programmable thermostat is set to increase the temp to 68 degrees in the morning and evening as we're waking up and going to bed. I keep the main floor (2 zones) around 68 degrees 24 hours a day. We never experience a hot water shortage. We run multiple showers, the dishwasher and the washing machine and always have hot water. I want to maintain these characteristics with the new system.

Both plumbers have recommended Weil-McLain boilers with indirect-fired water heaters to replace our current system.

Plumber 1:
Says move the system to an outside wall (about 13' from its current location) for direct venting and to allow for outside air intake. This means more copper piping for each of 3 zones in and out of the boiler, but shorter PVC piping for intake and outake. He recommends changing to zone valves instead of using circulators on each zone. His quote doesn't show another circulator that I would expect to feed the zones, so I'm assuming that the boiler's internal circulator system allows for this. The boiler this plumber recommends has cast iron components (87% AFUE).

Plumber 2:
Says leave the system where it is, but I will have two PVC pipes hanging across the ceiling to reach the outside wall. He recommends running a circulator on each of the 3 zones and not using zone valves. I asked if my current circulators could be used in the new system and he said he'd replace everything. The boiler this plumber recommends has aluminum components. (I believe this is 90%+ AFUE)

Are there any benefits to moving the system and introducing more length of copper piping as opposed to keeping the system where it is and just introducing lengths of PVC piping?

Are there any benefits to using zone valves for each zone rather than using a circulator for each zone?

Any other advice?

 

How big is the inside of this chimney? What's your heatloss?

My preference would be to stay with multiple circs - hopefully they aren't oversized. The rationale for zone valves is that you are using less electricity but if the pumps are just big enough for each circuit then why bother with the hassle of a larger that is only properly sized when running all 3 zones... otherwise it should have a pressure differential bypass installed... pumps are cheap, more reliable than zone valves and if you have more than one, if one fails, the rest of the house still has heat.

The Alu HX will require more water maintenance. You'll need a special additive when it gets filled and then to keep the water chemistry tested on an ongoing basis after that. The Ultra is a very nice boiler - very economical and very problem free - just maintain good water chemistry. I'd try and vent it out the chimney if there is a 8x8 flue and the chimney has nothing else. The piped would run up through it and terminate at the top. I'm not a fan of sidewall venting... especially conventional boilers.

So back to the first questions... did they do a heatloss calculation and what size boilers are they recommending?

 

Plumber #1 is recommending W-M Boiler GV-6 - looks like their biggest one in the GV Series. I haven't received a written quote from Plumber #2 yet.

I don't know how big the inside of the chimney is.
However, if the exit vent for the current boiler which
exhausts into the chimney is an indicator, that vent is 6" diameter.

The energy audit figured the following heat loss in CCF/Year:
Air leakage - 400
Conduction Loss - 750

We are also retrofitting the house -- air sealing and adding more insulation.

Post retrofit, the heat loss in CCF/Year is expected to be:
Air Leakage - 300
Conduction Loss -- 700

 

How many square feet of heated space do you have? What area are you in?

 

We have 2325 square feet of heated living space.
We're in north-western Vermont. Our boiler will be in
regular use at least 7 months/year. :-)

 

There should be no way that a house your size needs a CG-6 unless you are missing a wall.

If you re going with a gas boiler, then for sure go with a modulating condensing boiler.

Are there only 2 contractors where you are?

 

The benifit of having zone valves vs. 3 circulators is if a vale goes bad, it takes 5 minutes to change the head(Taco head). While a circulator takes more time and then you have to bleed out the area you are working in and cost more money. The only downside to having zone valves, like Who said, is if the circulator does down, none of the zones will work. Thats where having a circulator for each zone is nice, but not required. The circulator that runs the zone values is a standard circulator, it isn't internal.

 

"The only downside to having zone valves, like Who said, is if the circulator does down, none of the zones will work.

That's a pretty big down side, ain't it ? 'Speshully at 3 AM on a Sunday morning, 0* outside, 12" of snow coming down and more on the way...

If the circs are installed with isolation flanges, the only air you introduce by changing a circ is whats in the pump. Auto-vent should take care of that all by itself.

I'm down with circs...

 

We've got lots more contractors around. I've got more scheduled to come out to the house. I just want to figure out who's taking the easy way for them and perhaps the expensive way for me -- both short-term and long-term.
Reading other discussions in this forum, I knew that I'd
get some feedback to help me discern the data I'm getting.
:-)

I visited a home show today to catch a few plumbers in one place. I asked some questions about venting. The answers were slightly different. One indicated that an updraft would be created as air blew across the chimney top pulling air up, thereby decreasing my system efficiency by pulling warm air out of the house. Another noted that the more efficient systems shouldn't be venting out very hot and in order to go up, you need heat to keep the exhaust from cooling and condensing. This means directing heat at your exhaust. Hence, both suggested side wall venting.

One of the plumbers I spoke with today said that the Ultra
model uses PVC piping for in/outtakes. Nothing too hot to
melt the pipes in either direction and the outtake can handle water from condensation. He mentioned the
GV-6 uses steel piping, not PVC. I'm guessing that may
be the reason why plumber #1 wanted to move the boiler to the outside wall -- to minimize the overhead piping where the choice is one of steel pipe for intake/outtake or copper pipe for the loops within the house.

When it comes to points of failure, going with zone valves or circulators, it seems that both are pretty well proven
although there is the advantage of running other zones
if one circulator fails when using multiple circulators.
Given that there are other possible single points of failure,
it may not be worrying about this.

As for the one quote I received that uses zone valves and
doesn't mention a circulator and the note adamplghtg made about an internal circulator not being designed for total loop circulation, I'm guessing that it was either forgotten in the quote or one of the current circulators I have was going to used with the new system. I'll contact the plumber on Monday to find out.

I appreciate all this advice. Thank you!

 

We always get a circulator included with the furnace when we buy it(its packed with the furnace). Not sure if the brand you are looking at does the same thing. If you're looking for lower cost right now and in the future, zone valves are the way to go. If you're looking to make it so you don't lose your whole system if a circulator dies, then go with a circulator for each zone. The zone valves are great in most cases. If you have a HUGE house with lots of zones, zone valves are a better choice because you can set it up so there is a backup circulator installed also. It will also have a much neater look and take a lot less space. If you do circulators, do what NJ Trooper said and put valves on both sides so you can change it more easily.

 

My preference is also circulator over zone valves. Most of it has to do with reliability. Look at all the posts on this site where the issue is zone valve (verses circ pump).

You will not go wrong with either or.

 

The W-M GV Series brochure lists standard equipment and specifies, "Circulators supplied with boiler cannot be removed and cannot be used as a zone circulator in multiple zone systems." This implies that the quote
I received is lacking a key piece of hardware. (The
quote lists "3 - Honeywell zone valve", "1 - 1 inch
Honeywell zone valve for indirect tank", "1 - Taco
air vent" and "1 - Taco 115/24 transformer" but no
mention of any "circulator".)

Can isolation flanges be used in a system with zone
valves too in order to "easily" replace either the one
circ or any of the zone valves? Or can isolation
flanges be used just between circulators in a
no-zone-valve system?

Seems to me that isolation flanges would be the
real necessity to avoid the minimal cost related to
changing one of failing parts in any system (time involved
to drain and refill the system as well as the cost of any
additives, such as special antifreeze).

The difference being that if the one circ fails on a valve
system, that shorter-running service call couldn't wait
until a more convenient time.

We plan to be in this house another 15 years, so I'm
guessing that we can expect at least one circ or zone valve
failure during that period for whichever system we
configure. With 4 zones, is it likely I'd see more failures?

 

The very first thing which needs to be done is a proper heat loss calculation. Slant Fin has one you can download & is pretty accurate. I don't see how a heat loss calculation can be expressed in CCF/Year. To do so one has to know (or assume) a specific boiler efficiency.

On the subject of circs vs. zone valves; In my humble opinion, if they never made another zone valve it wouldn't hurt my feelings. With isolating flanges, I can change a circulator in 5 minutes.

I agree with Who on using the existing chimney as a chase for the air intake & exhaust pipes. Sidewall venting in your area, I think, is begging for trouble.

 

Any chance you could show pix of your current setup?

 

If the circulator is isolated, anlmost anyone could change it in 5 minutes. But you arn't always that lucky.

 

I've talked to more plumbers and a rep from our natural
gas supplier. It seems that the chimney exhaust may be
the greater hazard as other systems within the house
may pull the boiler exhaust back into the house via the
other stacks. ex. Bath fans, stove fan, dryer, etc. can all
redirect flow back into the house. I believe one person used the term "reverse flow".

If installed properly (ie. No leaks in the piping or around
the vents in the sidewall), there shouldn't be any reason
to worry about CO emissions back into the house. Even
if the exhaust pipe should be covered with snow, the
system should automatically turn off. Intake and venting
are both outside being pumped through in the appropriate
direction. Of course, this doesn't mean I should preclude
the use of a CO monitor in the area of the boiler as well
as in other locations within my house.

A little more research in the W-M Gold system indicates
that it does come with an internal system circulator.
However, depending on the pumping needs, an external
circulator can be added in a zone valve system. This
implies that if my system of 4 zones (3 heating, 1
domestic hot water), requires this additional pump for
normal and even heating operations, I could still have my
system operate in abnormal situations. I could lower the
heat requirement in one zone to effectively close that zone
if the external circulator dies and still get by with the
internal circ. Isolation valves can be placed strategically so
that any of the zone valves or external circ could be easily
replaced. A failure in the external circ or any of the valves
would not put me in a situation that I would be without
heat.

As for the recommendation of the first plumber to use
W-M GV-6 model, I'm guessing he's seriously overrated
my heating needs. The natural gas supplier rep has
said he's visited a lot of 2500sf homes in the area and
rarely sees anything bigger than a GV-4 installed.

It does sound like the modulating system (Ultra) runs
better as evidenced by its efficiency ratings. However,
it will come down to expected payback over the years
we plan to stay in this house that will lead me to the
boiler I choose.

I'm still waiting on quotes. I've had 4 plumbers visit
already and one more coming tomorrow. I'm finding
that I'm asking better questions as I learn more.

 

[I've talked to more plumbers and a rep from our natural
gas supplier. It seems that the chimney exhaust may be
the greater hazard as other systems within the house
may pull the boiler exhaust back into the house via the
other stacks. ex. Bath fans, stove fan, dryer, etc. can all
redirect flow back into the house. I believe one person used
the term "reverse flow".]

They're sure putting a lot of "fibre" into your knowledge diet.

Ever get my message?