Residential Boiler Replacement Questions

[Al Marulli]

My parents are getting quotes to replace a 30 YO oil fired boiler that has a small "add-on" hot water tank. He is looking into getting a gas fired unit so that he can replace his very old electric stove with a gas range.

AC is not part of the equation because he already has a separate central air system.

They live in Western Massachusetts in a brick house that is not well insulated.

Another factor to consider is that it's just the two of them, except for a few times a year when the rest of us visit. During these visits there could be up to 14 people in the house for 3 - 4 days. During these visits, both showers are in use at the same time, lots of dishes get done, etc.

I know next to nothing about boilers, so this is the best I can do to describe their current system:

They have a thermostat that controls the boiler for the baseboard hot water radiators and a timer switch that controls the same boiler for the hot water tank. There is a large (1=94?) pipe that runs through the hot water tank, so I assume that the water is heated via heat transfer from this pipe. The tank is not directly fired.

The timer has a "Hold" position so that they never run out of hot water when the house is full of guests. The boiler does not run constantly when the timer is set to hold, so obviously there must be a thermostat associated with hot water tank also.

OK, so here are the options he=92s been given via a few quotes:

1 =96 A combo unit that will include a water heater built into the boiler. 2 =96 A boiler just for heat and a separate 40 gallon water heater.

BTW=85no one has suggested an instant water heater in any of the quotes, but my dad and I discussed it and he feels the expense would not be worth it, considering their age. He=92d like to do what=92s best for the house as far as resale value, but the extra cost of the instant water heater doesn=92t seem to make sense.

The other issue is the efficiency of his choices. The quotes he has received so far are for 85% efficiencies, but the rebates from his utility don=92t start until the units hit the 90%+ range.

So my main questions are these:

Which makes more sense in this situation:

1 - A combo unit or a boiler and separate water heater? 2 =96 85% efficiency or a higher efficiency with the rebate offsets? The rebates seem to be in the range of $1000 - $1200 but I don=92t know how much more a 90%+ boiler would cost.

Thanks for any thoughts you have on this matter.

[Ed Pawlowski]

Add some insulation while you are at it.

NO NO NO NO terrible efficiency.

Good possibility

Take a rebate. You pay for it in your gas bills. Get your share and save more money

I just replace a boiler for work. The high efficiency was more money, but the rebate covered most all of the difference. We will also save more along the way with fuel savings.

This is what I put in two years ago to replace my old oil burner

My fuel use dropped 39% over the next two years. Gas does not cost as much (right now) as oil but just on the last fill of the tank this week, I saved $389 compared to what my old boiler would have cost to run for the 10 weeks.

I have a separate water tank and it uses a heat exchanger to make hot water. It never runs out, even with two showers going at the same time.

Do NOT get a combo unit. They are not well insulated, they run far too often to maintain temperature and waste a lot of fuel. If someone is quoting that, they have no clue as to what high efficiency units can do.

You may want to check with Peak Heating in Uxbridge about the Munchkin gas units that are very efficient. They are in Uxbridge. I don't know if they go that far west but worth a call.

[RBM]

If I were you, and assuming natural gas is an option, I would go with a good quality "mainstream" boiler like Weil-Mclain, or Peerless in a standard 85% +- efficiency. Definitely get an indirect water maker, which is what you have now. Forget the timer on the indirect, it's well insulated and will hold the heat for a long time, and make unlimited hot water. I would also have incorporated into the system, an outdoor reset controller. This is a device that will determine the most efficient boiler temperature, for the outdoor temperature and boiler demand. Unlike oil burners, you can get gas condensing boilers with a very high efficiency rating, and you can get a rebate for them. The issue I have with this type of boiler is it's complexity. There are a lot of things going on inside these units, all subject to failure, which would cause a shut down and complete loss of heat until you can get a "specialist" to come and fix it. Your garden variety gas burner is pretty basic, so repairs are infrequent, and easily done. The same holds true for specialized oil burners. Your typical oil burner service company isn't going to carry hybrid parts, or have the technical knowledge to do the repairs, leaving you at the mercy and availability of a specialist. Again, just my opinion. I believe reliability should be priority one, and efficiency second. I wire oil and gas heating systems for a living and have had experience with Weil-Mclain, Peerless, Crown, Buderus, Triangle Tube, Burnham, Biasi, Munchkin, Energy Kinetics, and Viessmann, to name a few

[hrhofmann]

I would go with the two separate units, one for house heating and a separate unit for hot water for faucets. Much simpler controls, and if anything does happen to either one, much easier to find someone who can fix.

[Eternal September]

Agree 100% with upgrading insulation. Since they're in Mass, they should get Mass Save in to do a free energy audit.

It looks like you can also still get pretty substantial rebates on insulation work - 75% rebate for up to $2000 worth of work. There used to also be a credit on Federal income tax for insulation work.

We did this through Mass Save three years ago. After rebate and tax credit, $2700+ of additional insulation work cost us about $475 out of pocket. We've got more than that back already by our reduced oil bill.

[DerbyDad03]

Hide quoted text -

This is the OP...I accidently posted my question under a friend's account.

First, am I correct is saying that a "combination unit" and "a boiler and indirect water heater" are *not* the same thing? If that's correct, are you suggesting a system that has a main boiler for the heating system and separate storage tank with a heat exchanger "piped" to the boiler for domestic hot water? That's an indirect water heater right?

Here's why I ask:

One of the quotes Dad got was for a Burnham ES2 85% boiler. The option for the Outdoor Reset was included and we understand how it works and why it's good thing. (BTW If you know anything about the quality of Burnham boilers I'd appreciate it if you'd share your opinion)

However, the quote also included an A.O Smith 40 gallon water heater, not an indirect unit. Per the brochure, Burnham can supply an indirect water heater with the boiler, but the company that gave Dad the quote opted for the separate tank. At the time, we didn't know enough about the choices so he didn't think to ask why.

Now that we know the differnce, he plans to ask them next time they talk, but we'd like to be armed with some knowledge. Why would a contractor suggest a separate, direct fired water heater as opposed to a indirect unit?

Is an indirect water heater that uses the main boiler as the heat source more or less efficient than a direct fired tank? I'm thinking that in the summer months the main boiler has to come on in order to heat the hot water, right? Is that burner more efficient than the burner in a separate tank?

Thanks for your help.

[Brian V]

Hey Ed, you didn't happen to teach at ATI did you? I had a teacher with your name back in the late 80's.

-Brian

[RBM]

quoted text -

I'm assuming that by combination unit, he's referring to a boiler with a built in coil. It would be the least expensive option. Coils tend to work OK when they're new, but loose their conductive properties as the get deposit buildup on them over time

I would opt for one burner, one set of controls. I just prefer to keep these things as simple as possible. The indirect system is just a very large coil within the tank, that operates just like any other zone on the system. The only exception is that you usually wire an indirect zone to have priority over heating zones. I believe it would be less expensive during the non heating months, to have a stand alone hot water heater, the only caveat to that is that I believe that the boiler manufacturers recommend the boiler to be kept at a minimum temperature to prevent some kind of flue gas damage. I'm not sure what that's all about, and I'm trying to get some information currently from Buderus. My interpretation, from things I've read, is that it's not good for the boiler to be cold and damp. You also get a wild swing on the expected savings for various types of boilers and components. The savings achieved from using an outdoor reset system, is anywhere from 35% down to 15%, depending upon who you're believing. Personally, I'll be real happy with the 15. If he's going to get a reset system. Taco makes a really nice one that integrates very easily with their EXP circulator control panels. The thing I love most about it, is that if anything goes wrong, you simply flip a switch, and it acts just like any other aqua-stat controlled boiler. It doesn't go into some humble mode like some systems.

[Ed Pawlowski]

Not me, the only thing I taught people was not to get caught.

[DerbyDad03]

w- Hide quoted text -

Yes, First, when discuss "Coils tend to work OK when they're new, but loose their c "The indirect system is just a very large coil within the tank, that operates just like any other zone on the system."

So the obvious question is: Aren't the coils in the indirect system subject to the same build up as in the combination units?

If so, why did you say "Definitely get an indirect water maker" in your original response?

I'm not arguing, I'm just trying to learn.

[RBM]

Hide quoted text -

That's correct, when the domestic hot water zone is set for "priority", it overrides any outdoor reset and is only limited by the aquastat on the domestic tank, and the high limit on the boiler.

No, it's a good point. Keep in mind, I'm an electrician, not a boiler expert. I just happen to wire lots of boilers, so I see things and ask lots of questions. It may be because the coil on an indirect is just much larger than on a domestic coil. It also may make a difference in that a domestic coil has potable water running through it, where an indirect coil has boiler water recirculating through it. That water wouldn't have a constant new supply of minerals to be deposited .

[Ed Pawlowski]

You can get some information here

With oil, we have little choice as a separate oil fired water heater is very expensive and electric is costly to run. With gas, you have the option of an indirect fired tank or a stand alone system. If you already have a new stand alone gas heater, it is, or course, less costly to just replace the boiler. If both have to be replaced anyway, look at the efficiency as the high efficiency boiler will probably cost less to operate.