sealed combustion cast iron

Big Will

I have a system that is running at 180the deg. It has type b vent to the roof and must be sealed combustion. I really like the Viessman. However the GC does not think they are well represented here in northern California. I agree on that point. The current is a Ray Pack 750 k btu. I want to install two 400 k boilers so it is somewhat redundant. Ideas?

furnacefigher15

sealed combustion

What do you mean by that? Sealed burner box, or has to bring in its own fresh air also?

Alan (California Radiant) Forbes

Viessmann

There are quite a few contractors in the Bay Area that install Viessmann products.  They may not have a local rep. in every city, but access to technical support and parts is top shelf.  The best part about their products is that they are so reliable.  I don't hear a peep from my Viessmann installs.

Big Will

I talked to my vender

After posting this. He is the local dist. for Viessman. I guess they intend to bring in more of the product and related parts. Also Viessman intends to open a branch in southern Ca. I would love to use the Viessman and am hoping that these two things might swing the opinion of the GC. The Boiler that's in there now is a bit of an unknown locally. We are the fourth service contractor to work with it in 12 years and all four of us have never touched this model. Also parts have been locally unavailable and on site support is available out of state only. This definitely feeds the concerns of the GC with going to another product that has the same issues regardless of the products quality. 

Big Will

derect vented

specifically. there is no combustion air in the room only a duct to the outside.

furnacefigher15

direct vent realities

If direct vent/ sealed combustion non condensing is a requirement, then you're only options are going to be locally unknown.



If you are looking at Viessman, then price is not likely a big factor. What about a condensing direct vent?



Just scrap the b-vent and upgrade to higher efficiency.

Big Will

180 deg system design

That's the smaller issue with condensing. I know they will do it but they really don't seem to be designed to do it all the time. Bigger issue is the mech room is on the lowest floor in the center of a five story house. The house is very high finish so opening ceilings to run a flue and comb. Air is many thousands by itself. Cost is not the issue so much as inconveniance to the customer.

Big Will

does

Viessman wach this site? Just wondering if the west coast facility is idea or is it in the works.

Alan (California Radiant) Forbes

Viessmann

I called the Viessmann rep. that I had years ago and was sad to hear that his job was terminated by Viessmann.  As I understand it, they moved another person in their organization (Amy Givens) from the East Coast to be their Southern California rep., but we in the north, have been orphaned.



Who knows what the future will bring.  Either Viessmann felt that they weren't selling enough product here,  their sales were so good that they didn't need to be represented here or perhaps that Amy could handle the whole state.



"Same as it ever was."

furnacefigher15

400 k may be an issue

I did a quick search and for sealed combustion here is what I found:

Burnham ESC - just under 300 k input

Lochinvar EB - 300 k (Im not a fan of anything lochinvar)

Buderus Logano - 244 k in



Paterson Kelley - 750 mbh (these are pricey)



You know about Viesemann



Most manufactures shy away from sealed combustion, and those that have offerings don't have anything in the size you are after.



AT 300 mbh the Asme standards get more expensive.



Good luck

SWEI

condensing or not

180F design temp is not necessarily a deal killer if you include ORC and can increase your delta-T a bit.  That may well leave you in condensing territory most of the season.



Some condensing boilers have approved venting configs with intake at or near boiler level and exhaust higher up (much higher for a few.)

 

SWEI

sealed combustion 399

Triangle Tube PS 399, plus a few others now using the same HX.

Big Will

I might have to give up

It seems that the biggest hitch is the ultra low nox. We are inside the bay area air quality district and it limits my options even more. So one more question to all. If I use a Lochinvar Knight fire tube it will spend its life running at 180 deg. Its the long term effect that bothers me. If we have to open some walls we will but what is that running temp going to do to my boiler. I have Knights running that condense less than 50% of the time that have been in operation for about three years. No related problems at this point. but there will be no outdoor reset here. The air handlers are already running at 120 deg. if i reduce the water temp I will get complaints about cool drafts from the air handlers. 

furnacefigher15

180 temp

You can maintain a 120 degree discharge air temp with 140 to 150 degree supply water. And the air handler should give a good 10 to 20 degree split on the water side, and cause a return temp in the 130 to 140 degree range, which should condense fairly well.



Even if you have to run 180 (which I doubt) that should not hurt the boiler. Worst case they'll have a 85% efficient boiler.

Big Will

The air handlers

take in untempered outside air so they need the 180 also there are a lot of areas with just wall Rads that have trouble keeping up at 180. Believe me when I say I looked into it. 

SWEI

not keeping up

How many days does the system "not keep up" when running at 180F?  Sounds like you need to take a serious look at the whole system.  Was it properly

designed in the first place?  For 100% MUA, a low restriction preheat coil that tempers incoming air to something like 55F can dramatically lower the overall design temp without requiring a forklift upgrade. You can run two different OR curves and dynamically split/combine the boilers with the right controls setup.





Triangle Tube PS series currently meets SCAQMD NOx limits (14 ng/hr, which BAAQMD adopts in 2013 if I'm reading them right.)  No problem running all day at 180 or even 190 there, but of course you lose a bit of efficiency.  The Lochinvar WHN series uses the same HX (and has an M7 option described as California Code) so I suspect they would perform similarly. 

Big Will

Its a diferent kind of customer

They expect to be able to entertain in January with people using the patio and in and out of the house and still keep the house warm. i work with these kind of customers a lot and generally speaking any common area or area for entertaining is over engineered by a factor of two. The design is more than enough for normal operation but these are not normal customers. I know without a fact that if I put something in that reduces performance I will be hung out to dry. 

Jean-David Beyer

return temp in the 130 to 140 degree range, which should condense fairly well.

I have the chart (Figure 3-11) on page 60 of the Third Edition of John Siegenthaler's "Modern Hydronic Heating" in front of me  It is Boiler Efficiency vs. Boiler Inlet Temperature. If it is for any particular boiler, he does not say which one it is. I imagine it is for a typical condensing boiler.



For a boiler inlet temperature of 40F, it is a little over 99%, but is clearly not 100%.

When it is 60F, it is about 98%

When it is 80F, it is about 96%

When it is 100F, it is about 93%

When it is 120F, it is about 89%

When it is 130F, it is about 87%

At that point, it stops condensing.



As a homeowner, I would no longer characterize that as condensing fairly well at such warm temperatures. At 130F to 140F it has pretty much stopped condensing. It seems to me if the return is more than about 110F, while it is technically still condensing, you are losing most of the benifits of a condensing boiler. This is why, it seems to me, you want a modulating boiler with outdoor reset, to get the return water temperatures as low as possible as long as possible.



I imagine these boilers really excel at snow melting and running radiant slabs or suitable radiant panels in walls or ceilings. It does pretty well in my baseboard zone where I have 14 feet of baseboard in each room where, with 180F water, I would need only about 5 feet.



Do you think John Siegenthaler is being too conservative in his chart? Or does condensing require lower boiler inlet temperatures than I think you said?

Mike Kusiak_2

It depends...

The efficiency figures you are quoting were probably taken under full fire conditions.



 Condensing at higher return temperatures are a strong function of firing rate. At low fire, the condensing increases relative to that at high fire. Here is a graph of efficiency vs. return temp and firing rate of a Vitodens condensing boiler. Your figures pretty much correspond to the full load conditions, but if you look at the 30% end of the graph the efficiency remains in the high 90% range right up to the condensing limit.



So depending on the operating conditions and heat load, appreciable condensing and efficiency gain can still occur in the 130-140F range.

Jean-David Beyer

That is a wonderful chart.

I see what you mean. I have no idea under what conditions Siggy's chart was made, but you are probably right about that.



I agree with all the rest of what you said.