Getting Ready for Gas in Central CT

WalnutFarmer

It's a combo fan coil (heat) and AC air handler. Not sure of brand. I'll have to climb in to find out. I think the manuals are down there too.

WalnutFarmer

Looks like a "First Co." Model is 24HBXB-HW.

It is a dual speed fan.
Manual says the jumper is factory set to LOW for heat operation.
Also suggest 140F for water temp. I imagine it's running at whatever my current oil burner is set at.

WalnutFarmer

Looks like the fan coil has 43,500 BTU/HR capacity at 180F water temp! Room load according to my calcs is around 8,000 at 68/0 design temps. Can you say OVERSIZED?

Rich_49

How large is the garage in cubic footage ? Check out FanHandler

WalnutFarmer

Thanks Rich. I'll check it out.

The fan coil is not in a garage. It's in a basement air handler below a 400 sf addition (family room and office). We couldn't make baseboards work with the design of the addition, so we ran hot water from the boiler and added a hot water coil to the AC air handler. The room it serves is about 3600 CF.

njtommy

How big of an AC unit did they install for that space too? Having a longer heating coil will work out better for you especially with a mod con boiler and if you add that fancy control Rich posted sounds like you will be golden for that space.

Rich_49

Probably do not need to move more than 90 cfm to do the job dependent on unit placement .

WalnutFarmer

@Charlie from wmass @Rich @njtommy @Brewbeer @Paul48

Guys, Thank you all for your guidance so far. I'm getting closer, but it's TIME FOR A REALITY CHECK.

Based on my past oil use, some assumptions on efficiency gains and current gas prices, I expect my annual gas bill to be $1500 or less after I convert. We have been wrestling with how to design a system for my existing house that will take advantage of condensing mode efficiencies.

However, that comes at a price. By the time I add a buffer tank, FanHandler for the fan coil, etc., I'm guessing I'm talking about $1500-$2500 of extra upfront investment. If those changes improve my efficiency by 10% across the board, that means gas savings of $150/year, which would take 10-17 years to recoup the extra investment. I suppose reducing short cycling could also buy a few extra years of life and/or reduced maintenance costs. Given that I'll have a few months of 25F+ temps that might allow some condensing operation, I also suppose the net efficiency gains might be less than 10% (meaning I will be able to achieve condensing mode without the other updgrades.)

Of course, these are all back of the envelope estimates, and gas prices could rise, but you see where I'm going with this. I don't want to get lost trying to design an exquisite system that costs me more in the long run... or one that is more difficult to operate and maintain for a minimal savings gain.

Care to comment??

Many thanks.

Brewbeer

@WalnutFarmer, I went through the same analysis when designing my system! Take a look at my post near the bottom of the first page of the thread about my system design:

http://forum.heatinghelp.com/discussion/154385/fha-to-hwb-conversion-project/p1

Given the higher installation and maintenance costs, and shorter expected boiler service live, for my application I concluded that the life cycle costs of the condensing boiler technology would likely be higher than conventional boiler technology. And this was for a system that was specifically designed for low water temperatures, as opposed to the retrofit you will be doing.

If lowest total life cycle cost is your primary driver, the standard efficiency boiler is probably a better choice. The high efficiency modulating condensing equipment becomes a more favorable choice if non-pecuniary considerations also factor into your decision.

Even though the high efficiency equipment will probably be more expensive in the long run, the higher degree of comfort provided by the modulating condensing technology (more even heat, quieter operation), lower fossil fuel consumption, and being able to afford it, were key factors for me in choosing the mod-con technology.

Rich_49

Look at the HTP Pioneer . If you have questions check back in , I'll offer whatever help I can .

Charlie from wmass

You could ask me for a quote?

ChrisJ

Agree, you should ask Charlie for a quote.

Also agree the payback often isn't there or isn't realistic. Same reason I still have my 150 year old windows.

But definitely ask Charlie to some quote you regardless.

WalnutFarmer

I pm'd Charlie to explain some extenuating circumstances. But I'm not ruling out the possibility.

Charlie from wmass

We communicated. I understand where @WalnutFarmer is coming from. 4 system choices going with the smaller boiler and a 50-gallon indirect with mixing valve for domestic Hot Water Production you will have a system that will function quite adequately in most conditions. If you install the boiler and leave room to later install a buffer tank should the short cycling become an issue.

Rich_49

Brewbeer said:

Hatterasguy said:

From memory, the low fire on yours is quite a bit more than 8K?

The entire argument is based upon the premise of using a boiler with a minimum fire of 8K so I don't see the relevance?

If we are talking about comfort of the occupants, the discussion of the buffer is irrelevant. I can get the same comfort with or without the buffer.

If we are talking about the comfort of the boiler, that's a different story and, if you don't have a minimum fire of something close to 8K, the lipstick has to be put on the pig.

With few exceptions, an 8K minimum fire boiler doesn't need an buffer tank and you'd be stealing money from the customer by convincing him that he needs one. They are certainly not cheap.

Yes, it's the WHN055, which has a low fire of ~11K, or about 37% higher than 8K.

The boiler manufactures have done a good job of pushing down the minimum fire output of small mod-con boilers in the last couple of years, but they aren't to a point yet where small and/or low-temperature zones will keep the boiler occupied without cycling during shoulder seasons. Gonna need to get quite a bit lower than 8K to achieve that goal.

Is buffer on this system "lipstick on a pig"?
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If you know or strongly suspect that it will later need a buffer you may be able to get a comparable , maybe superior solution now for same money . A Pioneer with a 40 plate FPHX and 1 circ and flow switch for DHW can more than likely be installed now for same money and save space .

The one above that Brewbeer asked the question about is exactly the same situation . I knew it would need a buffer and spec'd one . It got left out because the H.O did not quite understand the need , Utica warranty for his old leaking UB90 was a factor also . I wanted to install the buffer right off the bat , even spec'd which one , it was passed on . Vent lengths were a bit long , boiler had a firing issue ( many of you probably remember ) . Jason Mangoes , myself and John went there to change out parts and re analyze after new controls . Lo and behold , excessive cycling because of 2 small zones . gas bills were still fantastic but will now get better . WalnutFarmer has the choice to not go through all that nonsense and hassle .

Since Charlie saw his issues , Emerson Swan has taken on the HTP rep duties and as a company I can verify they want replacement parts readily available at the local level . I have had no extraordinary issues with HTProducts that do not exist with every boiler / water heater out there with the exception that they perform better and have less issues due to the simplicity they allow . Just sayin

Charlie from wmass

Not arguing with you rich. Just can comment on myuniverse not yours. Same rep as always in my area.

njtommy

The Viessmann VItocrossal 300 cu3a actually fits your heating needs Its price may not be that fair off from lochinvar boiler. It will also control 3 different loop temps from its mixing valve options and controller. It may not be a bad way to go. Also holds a good amount of mass. No where near the HTP but still better then tankless.

Rich_49

Charlie from wmass said:

Not arguing with you rich. Just can comment on myuniverse not yours. Same rep as always in my area.

Not arguing either Charlie . If you have been retained , commenting should probably cease , if not WalnutFarmer may still be looking for input .

What suppliers were you using to get warranty stuff or parts from up there Charlie ?

WalnutFarmer

I'm back.... Hopefully you're all still watching. Otherwise I'll start a new thread.

My contractor shared his heat loss results yesterday. He walked the house with me and I provided construction details, so he had the same (or similar) R values and measurements that I used for my Excel based heat loss calcs. He used Wrightsoft to do his calcs (Manual J 8th Edition).

My original calculations came out to around 55k BTU/Hr. Wrightsoft came up with 76k. (See table)


He sent me the Wrightsoft report late last night. One thing caught my eye that might explain the discrepancy. 41.5% (31.7k btu) of the heat loss is through "ducts". Remember this is a hydronic system. I do have central AC, but I'd be shocked if the AC ducts are passively losing that much heat (or even 10% of it) during heating season. The AC systems are entirely separate from the heating system, except for one zone that has the fan coil (zone 3) and its own compressor. Hard to believe the ducts for a 400 sf "zone" could lose 41% of the house's heat!

When I look zone by zone, it appears that a standard 41.5% for duct load is applied to all zones.



Are any of you familiar enough with Wrightsoft to know if there is a setting he should have turned on/off to eliminate the impact of ducts? Or is this a normal outcome?

Thank you again. Obviously a 41% swing in load is a big decision factor!