Gas Conversion - Combi vs Conventional Boiler

broncosejr

Hi All,

So I've had just about enough of my oil burner system and we are ready to make the gas conversion.

I had two companies come give us estimates and they proposed totally different things.

The first company proposed a Navien Combi Boiler.
The second company proposed a BURNHAM ES26 HIGH EFFICIENCY CAST IRON HOT WATER ATMOSPHERIC GAS FIRED BOILER and BRADFORD WHITE 50 GALLON 40K BTU GAS FIRED WATER HEATER.

We have a four bedroom colonial and from what i've read online, it sounds like the first proposal would not be a good idea for our size home. It almost feels as it was somewhat irresponsible to even propose this.

Thoughts?

Thanks for the help!

Jamie Hall

Two distinctly different approaches to the same problem: providing hot water and heat. A combi can work well in some applications. It has to be properly sized, and there is often a conflict between providing adequate hot water and not being oversized for the heating load. With the separate boiler and hot water heater, there is no such conflict -- each is sized for the load independently. Both approaches, however, can work well -- properly sized.

However, it may be that you have a very large missing piece to the puzzle: what is your likely hot water requirement? And more important, what is the actual heat loss of the house? Without those two numbers -- which are easily determined -- it is irresponsible to specify anything.

broncosejr

Jamie Hall said:

Two distinctly different approaches to the same problem: providing hot water and heat. A combi can work well in some applications. It has to be properly sized, and there is often a conflict between providing adequate hot water and not being oversized for the heating load. With the separate boiler and hot water heater, there is no such conflict -- each is sized for the load independently. Both approaches, however, can work well -- properly sized.

However, it may be that you have a very large missing piece to the puzzle: what is your likely hot water requirement? And more important, what is the actual heat loss of the house? Without those two numbers -- which are easily determined -- it is irresponsible to specify anything.

Thanks so much for the reply and info. How do I figure out the heat loss of the house? For the hot water requirement, we're a family of three and we have baseboard heating. Does that answer it?

Jamie Hall

The heat loss of the house can be figured with this application: https://www.slantfin.com/slantfin-heat-loss-calculator/ It takes a bit of thought to get used to, but it really isn't hard to use. The hot water demand is, oddly, a little harder to figure, as it varies so much with what fixtures you have and how they are used. One family may have the fixtures to run three rain showers plus the dishwasher all at once -- while another may have one low flow shower and never run the shower when the kitchen is in use. The best way for a residence is to see how people use the water, and then add that up. As a guide, if you need two showers at once in most of the US you would need at least 199,000 BTUh input. That will give you two showers, or a faucet and a shower at once.

EBEBRATT-Ed

@broncosejr

The most important thing is to pick the right contractor. You could check "find a contractor" on this site & post your location someone may have a recommendation.

What is the status of your existing equipment? Has it failed? Not running?

Emergency replacements in the winter are not the best.

It works out much better if you take your time and find the right contractor and the right equipment

Big Ed_4

What are you looing for ?

broncosejr

EBEBRATT-Ed said:

@broncosejr

The most important thing is to pick the right contractor. You could check "find a contractor" on this site & post your location someone may have a recommendation.

What is the status of your existing equipment? Has it failed? Not running?

Emergency replacements in the winter are not the best.

It works out much better if you take your time and find the right contractor and the right equipment

Thank you for the advice. I am indeed trying to take my time with it. Our boiler is currently working, but the number of problems we've had over the past few months is just getting to be too much

broncosejr

Big Ed_4 said:

What are you looing for ?

I am really just looking for a reliable, low maintenance solution that can heat my entire home without issue (including hot water). With the problems we've had, i'm going downstairs every day to check everything and ensure it's ok. I need peace of mind

kcopp

What Are you having for issues? Are you looking to go to Nat gas or LP gas?

broncosejr

kcopp said:

What Are you having for issues? Are you looking to go to Nat gas or LP gas?

We've had quite a few issues.
- Air in the pipes multiple times which seems to have been solved by the deaerator.
-Twice the pressure got so high on the boiler that the exhaust valve shot out a ton of water and flooded our basement (again seems to be solved for now... pressure remaining between 15 and 20 psi).
- The exhaust pipe on the water heater is always dripping water (even after we replaced the valve).
At one point, we had our boiler company here nine times in 8 days.

Even though all seems to be mostly working for now (except for the water heater dripping), we have a newborn in the house and it's just too much to be constantly worrying about the boiler.

We already have natural gas line in the house for our kitchen appliances. So would go NG.

Jamie Hall

And... none of those issues will be solved by a new boiler or hot waater heater.

The first two are almost certainly either a problem with the expansion tank or the pressure regulating valve -- or both. These are both things a competent heating person can check moderately easily (depends a little on how the expansion tank is piped).

The third is possibly a little more complicated. So I will ask -- are you on public water or on a well? And if you are on public water, is there any sort of check valve or pressure regulator for your domestic water (in addition to the one for the boiler)? If you are on a well, or if there is any sort of check valve or pressure regulator for your domestic water, you also need an expansion tank -- a different one -- on the hot water.

I'm not really happy with the boiler company -- they should have been able to fix these problems on the first visit.

hot_rod

What type of heat emitters do you have?

bucksnort

Well a combi would work, but run as fast as you can away from the Navien.