Need a new boiler oil or gas/combi or separate

StephanieNew

Hi, I live in an older brick home in Maryland, built in 1940, I'm at the point where my old (1977) oil summer/winter hot water boiler needs to be replaced. I have natural gas available in the house, so I have the opportunity to rework my heat and hot water system completely.
I am fairly confident that it is worth making the change from oil to gas even though oil boilers are cheaper and I will have the added expense of running a gas line from one side of the house to the other.
My main question is should I buy another combi? (not sure that is the right term) boiler for both heat and hot water or buy two separate units, heat boiler and water heater? Any thoughts on the best way to go? I assume the separate units add more to the installation, but does the cost of the type of unit add to or offset that? In other words does a single unit cost less AND save on installation?
As of now I am getting one quote on a 84% efficiency Burnham boiler with a Separate 40 Gal Water Heater. The estimator said I will need a chimney liner and he measured all the radiators.
The second quote will be for a similar Columbia boiler also with a Separate 40 Gal Water Heater AND an optional quote for a High Efficiency Columbia boiler that can be vented with PVC. This estimator did NOT mention needing a chimney liner until I brought it up to him in reference to the first quote. He also did NOT measure the radiators.
Neither Burnham or Columbia boilers seem to be rated as top 10 boilers, but it is hard to find reviews. Are they good products and are dealers/installers limited to sell certain brands only?
I want to purchase the best system within a reasonable budget, but more importantly I want to make sure the company I deal with knows what they're doing. I don't need them quoting things that aren't needed or leaving off things that are. Sorry if this is confusing. but any advice you have is greatly appreciated. Stephanie

Jamie Hall

First off, I have to say I'm not a fan of combis. Mostly because it is rare that you have a combination (!) of heating and domestic hot water loads which the same unit fits both ways. Better to have two separate units matched to the load.

Having said that, on the heating side it is absolutely essential that your installer measured the heat loss of the house -- not the radiators. The heating boiler must be sized to match that heat loss; the capability of the radiators can then be taken into account by adjusting the water temperature which the boiler supplies.

If you do switch to gas, you will need a chimney liner (unless you should be so lucky that the chimney is already properly lined -- which is unlikely) or would need to go to direct vent.

StephanieNew

Thanks Jamie. Okay so then two separate units is the way we will go. I really liked the second company's representative better and the company has almost all 5 star reviews, but I don't like that he didn't measure the heat loss, if he did I didn't notice, since I don't know how that is done. I was kind of surprised he didn't mention the liner either, but maybe he was going to push the direct vent option, since it will be easy to run the PVC.
I guess the first company didn't measure heat loss either though so...who knows.

KC_Jones

@Steamhead is in MD and works on hot water systems in addition to all his steam work.

Where in MD are you?

StephanieNew

I'm in Baltimore County near Arbutus.

EzzyT

Definitely reach out to @Steamhead and have them come by and take a look at your system.
As @Jamie Hall has mentioned I also am not a big fan of combi units since the tend to be way over sized for the heating side.

retiredguy

@ Jamie Hall You said that if you do switch to gas, you will need a chimney liner (unless you should be so lucky that the chimney is already properly lined -- which is unlikely) or would need to go to direct vent. I am confused; are you saying that you don't need a chimney liner for fuel oil? Educate me.

StephanieNew

@ retiredguy I was wondering that myself. Thanks for asking.

Jamie Hall

In most cases it is my understanding that a gas fired boiler needs a metal lining in the chimney. Oil doesn't. I could be wrong -- have been before.

hot_rod

First I would do a load calculation, room by room. If any building shell or insulation upgrades have been made since 1940, the load my be lower, much lower. That would be great, as you could run the radiators at a lower temperature. And if so the the condensing boiler starts to make more sense.
As for the combi, it depends on how you use DHW. A 120,000 combi should give you 2.5 gpm, plenty for the average shower, even a high flow shower head. If you want multiple hot water draws at one time, the combi may not be you best option.
So the combi sizes to the larger load, maybe DHW, maybe heat.
Most all combis have 10-1 or more turn down, so in heating mode that boiler could be derated down to 10,000 BTU. The modulating and turndown of a high efficiency boiler can be as or more important than the low temperature condensing operation.
In your area maybe 80% of the heating season you are at below design. So with ODR in the package to boiler SWT is also modulated.
A good contractor will go over all these options and do the load calc homework.

EdTheHeaterMan

I believe that you will see savings with a Modulating Condensing (Mod/Con) gas boiler, especially when compared to a 1977 vintage oil boiler that maintains temperature for DHW. I also believe that a 40-gallon power vent water heater is both affordable to purchase and to operate. However, they won't last as long as your 1977 oil boiler (be it cast iron or steel). The reason is twofold, the heat exchanger will be made of aluminum or stainless steel. and the condensing flue gas and byproducts of combustion including some trace elements (like carbonic acid) will cause corrosion to eat away at the heat exchanger over time. With a Combi, you will be lucky to get 15 years and on a heating-only boiler maybe 20 or so with proper maintenance.

The condition of the water inside the boiler is also a factor in the longevity of the boiler. Since your cast or steel boiler lasted over 40 years, I'm thinking your water is not too corrosive, but unless you plan on sticking with the less efficient cast or steel boiler (either gas or oil), you will want to test the boiler water annually and add treatments as needed. It is just another cost of the high-efficiency boilers. They cost less to operate but more to maintain. Usually, the savings outweigh the maintenance.

Your other option is to KISS. Keep It Simple S... and use the basic entry-level gas boiler and vent it in the existing chimney. You will need a Liner if you use Oil or Gas. Since many new oil boilers are operating at lower exhaust temperatures, it is recommended that you line the chimney with stainless steel, but your existing terracotta liner may be adequate, but it may not be. it depends! Recommended them with every new oil boiler I installed, and if the customer elected not to get one, I would inspect the liner at the time of install and at the first tune-up 1 year later. (that was included in my price). The "Free Tune-Up" was a chance to get the customer to purchase a maintenance agreement so they could get another "Free Tune-Up" next year... and continue the "Labor Warranty" for another year. But that is another whole markering thing for another time.

So your choice is to spend more for lower fuel cost but the equipment will not last as long. OR... Go economy on the equipment and pay a little more for fuel for the next 30 years. Think about what condition you will be in when it is time to purchase that new heater. Will you still own the place? Will you be well into your senior years and not really be ready for a $$$ new boiler then? Let me say that I never thought that I would be retired by now, but a disability sidelined me and now I'm depending on my investments to outlast me for now.

Maybe I can get a job as a stand-up comedian... in a wheelchair... Or would that make me a sit-down comic?

Yours Truly
Mr.Ed

hot_rod

I'm not convinced the modern cast iron boiler is a 30- 40 year product anymore. I saw a small cast boiler on a display that weighed a few lbs more that the fire tube mod cons.

Honey they shrunk the cast iron boilers.
How many times have we seen a cast steamer come across this list, DOA after 5 years

Both water content and cast thickness has shrunk. Controls are approaching mod con complexity also, electronic and digital throw aways. So control repair and replacement costs are closing in on each other.
Only if your distribution can run at condensing temperatures and you embrace the modulating, step firing, anti cycling, ODR, and boost functions.
Cast iron doesn't come close to those features. It's biggest selling features are, or were, simplicity and longevity.

The biggest unknown with mod cons is the lifetime maintenance costs. Plenty of 20 year mod cons still running. 35 million Sermeta mod cons out in the world somewhere! Kiturami claims millions of FTs in operation.
I had a Laars Mascot (Baxi 330) run 15 years without a single repair, only opened it up twice for a cleaning in those 15 years.

As is usually the case, we tend to see the failures not success come across a site called "HeatingHelp"

Steamhead

Thanks for all the kind words. We've scheduled an appointment to look at this, laptop in hand to do the heatloss.