Oil to Gas conversion options

Tinman_2

I REALLY want to change from Oil to gas this summer. I presently have a 16 yr old Peerless - 214 btu/hr. I've met with a few contractors and I am wrestling with all of the information I have received to make a decision.

We've been in this 80 year old home in the Northeast for 8 years - hot water radiators on the first two floors; fin tube on the third. We have an issue with the third floor, but I will mention that later. Since the boiler was put in by the previous owner, all of the windows were replaced before we bought. There isn't much insulation in the stone home (16" walls). The existing boiler heats the house well, but we burn ALOT of oil.



Contractor #1 is suggesting a Chimney vented 84% AFUE Burnham 308. He also quoted a Weil McLain ultra 230 direct vent boiler. However, he also is promoting the chimney boiler stating "The chimney boiler, although less efficient is dramatically more dependable, less technically complicated and dramatically longer lived when compared to any condensing boiler - To the point that two or three condensing boilers will be bought over the same period as a conventional gas boiler"

He also stated that there is additional maintenance expense for a condensing boiler to ensure the acidic condensate does not cause problems - what kind of problems? Contractor #1 did not do a heat load calculation.



Contractor #2 suggested a Lochinvar KBN-211. He did a full heating load calculation. I'm very comfortable with this contractor, but there is the added cost for a condensing boiler.



1. IS there merit to what Contractor #1 says about reduced life cycle for a condensing boiler?

2. If I go with a condensing boiler, will I have any issues with my existing chimney by venting my water heater in the chimney (DHW is gas fired also - 75 gallon tank and installed when we renovated house) without the draft created by the exisitng boiler?



3 Re: 3rd floor. When the third floor calls for heat, the piping on the third floor cracks, pops and makes alot of noise as the hot water comes up. I have asked around and there are a few theories:

A. Contractor #1 believes I need a flexible tubing connection - I'm not a fan of this in case it ever leaks.

B. Contractor #2 believes that the modu-con will not send 180 degree water there, so the sudden burst of hot water will not occur.

C. My own theory is that the circulator pump may be too big for the third floor zone. It is the same size as the pump for the other zone for the first two floors, which have large radiators. The high flow rate at high temp may be causing the noise in the winter.





I'm throwing alot out here. Looking forward to your input.

SWEI

Some answers, plus questions

1. Yes, there is some merit to the lifecycle argument -- especially for a condensing boiler that uses an aluminum heat exchanger (such as the W-M Ultra.)  There are several designs which have better track records.



2. Condensing boilers are direct vented, usually with plastic vent materials such as polypropylene.  The venting is frequently installed in an existing chimney, but this can not co-exist with another appliance which vents directly into the chimney.  You should seriously consider an indirect water heater, which will make use of the new boiler.



3. B. Contractor #2 is probably correct.  The gradual temperature variation which outdoor reset control provides frequently mitigates expansion noise issues.  You may also be correct with C, but some investigation and perhaps measurement will be necessary to verify this.



If you decide on Lochinvar, I would strongly recommend a WHN over a KBN -- much better heat exchanger design.



What was the calculated heat loss?  How large is the home? Conventional heat loss calculations do not properly account for thermal mass, and you have plenty of that.



With the firing rates you're looking at, a mod/con boiler should pay for itself even if you have to replace it in 15-20 years versus say 30 for a conventional cast-iron boiler.  It's also going to provide increased comfort due to the outdoor reset control, which (if you added it and a buffer tank to the conventional boiler) would pretty much zero out the cost difference.

HomeOwner1

Just did ours earlier this year

I am a homeowner in the Northeast as well.



We went with a Navien Ch-240 for our 3850 sqft home. Also services 3 baths and hot water for us just fine. We are happy with our choice and fit our lower-end budget.



We put in the outdoor sensor so it modulates as well as condense.



As far as sounds on copper fin tube, that is pretty normal from what I have seen. Copper expands quite a bit when hot water flows. The fins make some noises when they expand. Obviously, under extreme situations of house settlement or really tight conditions, a re-piping could be feasible to provide some clearance. Good to consult the professionals on that one.



Get a heat loss estimate on the home so you know what size unit you really need. For combis, the other factor is it is often sized on the hot water demand side and modulation takes care of the heating load adjustments. Our unit goes all the way down to 20kbtu for heat turn down.



Good luck.

CMadatMe

Hey HO1

How do you plan on overcoming this heat loss with the Navien Unit? Please do explain in detail.



SWEI is spot on. Contractor 1 is playing a card out of the deck that guys who don't do condensing pull out all the time. Ask you self this. Do you really need an oil change every 3,000 miles? Why? Could it be continued good gas mileage, longevity of car life. Just saying..

SWEI

Forgot to ask

Where are you located?

Tinman_2

Located outside Philly

The calculated heat loss was around 190,000 btu/hr. The home is about 4300 sq ft, not including the basement.

I haven't heard of a buffer tank - is that the DHW tank?

JStar

Boiler

Don't let Contractor #1 back in your home. No heat loss, a bag full of excuses... No thanks!!



That heat loss seems a little big, but maybe not wrong.

SWEI

44 BTUs per square foot

that's a lot of heat.  Thermal mass can mitigate that -- you may want to consider having someone who understands how thermal mass behaves in your climate take a look at the calculations.  As an example, if your design day is 14F (Philadelphia) but you only see that temperature in the middle of the night, say with a daytime high of 25F, you might have an average temperature for that day of 20F, which thermal mass may allow you to use as your system design temp.   OTOH if you see days where the high is 16F, that may not work at all.  You need someone with knowledge of the local climate and how it interacts with old, high mass buildings.  It's worth the time (and a bit of money) to be sure you have the boiler sized correctly.



A buffer tank would be installed between the boiler and a motorized mixing valve (which controls the system loop temperature via outdoor reset.)  This allows the boiler to have decent runtimes even when your heat demand is low.

HomeOwner1

Here we go again....

Let's start off with, we are both biased.



You don't like Navien or combis, I own one, know people that have one and we are happy. We will agree to disagree on this one.



His current unit is sized that big at 214k. I know for one, my previous unit was way over-sized. So a good contractor should not assume the existing unit is sized correctly off the cuff. Is that input or output BTU? If input, then the Navien would handle such a load just fine.



To answer your question for even higher output needs, the Navien could be cascaded with multiple units as an option in such a circumstance, if his heat loss is indeed that high. One could surmise that it would be cheaper than the stated options and a low cost for operation as well.



Fact is, they need to get the actual heat loss to size. You know that!

HomeOwner1

We live in Cherry Hill - heat loss sounds high

We live not far from you. Our home is 3850 sqft and had a heat loss calculation of 80-90k, without the basement as well. Our home is about average as far as insulation goes with lots of high ceilings. Can't imagine you would have an additional 100,000 kbtu heat loss for an extra 450 square feet compared to my home.



Given our experience with our new unit, this calculation has proven itself to be correct.



Take a look at the combis as an option as well and make up your own mind.



We were originally looking at a weil mclain with indirect for about four times the budget but chose the Navien. It was the same price installed as the lower-end 80% cast iron boilers we were looking at. Very happy with our choice. We did a lot of research before pulling the trigger though, as should you.



Also, with the Navien and probably most other modulating condensing units with an outdoor reset temp sensor, you can adjust the heating curve and tune the unit to your particular home. This takes down the loop temperatures and heats the home slower based on higher outside temp, which is more efficient. Stops the short cycling effect that happens on over-sized units of the past, which is highly inefficient. This is a setting that can be adjusted and played around with for optimization.



Good luck and hope this helps.

HomeOwner1

More info

Also, a good portion of our home is cast iron with the rest as copper fin tube. Sounds similar to yours in that respect as well.



The unit we bought has a PVC exhaust up the chimney with a few circulation pumps.



If you go our route, you will need to make sure the hot water is enough to satisfy your usage. We have a pretty full house with 3 full baths with newer shower heads and our unit does just fine. Never ran short of hot water yet. If enough, then you may be able to ditch the 75 gallon hot water heater and simplify your setup potentially. Our unit provides about 5 gallons per minute on the coldest day of the year with the lowest incoming water temp in our region. Otherwise more than double the flow. That means on that coldest day, you can only have about 3 people taking showers at the same time with the newer shower heads at most to put it in perspective as a potential worst case. You contractor can elaborate probably better than me though.



Funny part was, with every contractor we asked about different units, we got totally different opinions.

CMadatMe

His Heat Loss

Based on what was given to him is 190,000 btu/hr. The on board circulator pump in the Navien only moves approx 5gpm across the heat exchanger for a heating demand. The only way you would get 190,000 btu/hr out of the Navien is if your boiler delta-t was 76 degrees.



I have nothing against combi's. Sell Viessmann Vitodens and CombiPlus often and will be selling the new Vitodens 222F come September but those are boilers with a HX that has a lifetime warranty and made of 316 Ti-Stainless with a much larger passage way. They also approach DHW in a different way.



My point is that the Navien under his heating demand won't do the job based on the heat loss he provided.

HomeOwner1

It is rated for 199 KBTU Output - 240 KBTU input

It will provide 199 KBTU output all day long for heat.



The CH-210 is the smaller one at 175 KBTU out.



You are incorrect and would do the job. Call Navien then if you disagree and have them explain the engineering to you.



http://www.navienamerica.com/Product/Category-CH-ASME%20Series/Page1/Details/16



To the original poster:



It has a primary loop for heat for which feeds come off to where your circulation pumps push heat off the primary 1 inch loop. The heater keeps heating the primary loop around in a circle and the returns feed back the cold water to this loop. Hence, the internal circulation pump for the loop is designed. The technology works, if installed correctly. It is not piped like a traditional boiler, which is the difference. I believe there are other boilers out there now that also use a primary loop method as well. Ask your trusted installer to explain.

Rich_49

HO1

   This home is so much different than yours , you would not believe and many diffrenet dynamics than yours . Yours has R Value that retains heat , his has stone walls that have very little R value , hot and cold are always battling within them . That 450 sq ft you speak of is probably more like 1,500 .  The heat load shows this perfectly , there are so mant factors entered in a heat loss calc it would make your head spin . Luckily , on this site there are some very smart individuals who have the vast experience of servicing , fixing , scratching their heads asking "What was this guy thinking ?" . 

   Do you yourself know how to size a primary / secondary piping arrangement and that the higher temp zones should be first on the loop extracting heat from it and how many gallons you need to extract from the primary loop to keep the secondary at temp ?  I can tell you this , with the mix of differing emitters and probable Delta T's and head loss that Navien does not make a boiler that would do this home , especially on a COLD day .  I recently sat with 7 Navien guys from California and NJ ( Cherry Hill to be exact) at a 2 day class in Rhode Island . You should have seen the looks of amazement from these guys when they found out how this end of the business actually works and how some products just aren't capable of everything 

  Have you ever had to change out the 3 way mixing valve in a brand new CH ? It's no fun I tell ya !  Have you ever had to talk to a guy in California that only knows what's in his manual supplied by his employer that really has no idea what you are talking about , pretty frustrating . Not saying that all tech support guys are stupid but a vast majority are .  I live and ply my trade in NJ also and I have to tell you it'd tough to sell a new work job because there are so many guys installing and recommending that have no idea .  Good thing is that they give me plenty of work following them up and repairing or explaining to unsuspecting homeowners why their stuff isn't working properly .

 To the Original Poster .  Swei is right and has given you very good advice . Don't let contractor 1 back in your house . Contact a couple more contractors and make an informed decision and listen to professionals not other consumers .

CMadatMe

I Have On Many Occassions

The onboard circulator pump with only move 5gpm across the heat exchanger. So what's the only thing you can do to get the btu/hr you need? Hint....



gpm = btu/hr / (delta-t x 500)



Since the on board pump can only move 5gpm against the pressure drop in the HX, his heat loss is 190,000 and 500 is constant, what has to change?



If you want to stand up here and call me out please bring the math and fact. Support your case. Would also make for another thread.



I agree with all the others, need another contractor.