New Boiler + Indirect Water Heater Question

JC_fixie

Hi:

New to this site and home heating in general.  I am looking to replace my old boiler.  The house is a 2 story 1900 Sqft house.  The existing hot water gas boiler has 5 zone-valve heating zones when I moved in and I want to keep it the same way.  My contractor is recommending the Weil Mclain CGA-5, gas boiler, 102K BTU net output.  He is also recommending to replace my 15 yr old hot water heater with a similar new model, it is starting to leak a little.



Assuming that the contractor sized the boiler correctly, can I use the Weil Mclain Gold Plus 40 indirect fired water heater instead of the conventional one he is suggesting?  Do I need to up-size the boiler for this indirect?  Do I just have it installed on a 6th zone-valve on a separate zone?  What about sizing the circulator, I do not know enough to do the calculation need to size it, but the spec says a 9gpm one is needed... is this correct?  I could possibly get away with the Gold Plus 30, but not sure if I need a little more water stored for heavier usage?



I understand that a higher efficiency boiler goes great with an indirect water heater... but is this indirect a good marriage with the CGA boiler (a lower afue boiler), or don't waste my money on indrects unless I get the 90+ afue boilers? 



Anyway, just want to get some info so that I know what I'm sort of looking at when I ask him for a quote/get the quote back.



thanks, JC

Robert O'Brien

An indirect

or a tankless  are both vastly superior to a conventional gas fired water heater

icesailor

New Boiler:

Weil-McLain makes better boilers than a CGA. If you are going to spend money in 2011, why would you pick a boiler with 1990's technology. I know that you didn't pick it (the boiler) but if you asked me, I would say your contractor is slightly behind the times or he is afraid to up-sell you for fear of loosing a sale and install.

I don't know you and perhaps you are a little squeaky, but don't get tight on something that will give you excellent service for years to come and will increase the value of your home.

If "I" were the one, I would try to sell you a Mod-Con boiler piped with a low loss header to run the 5 old zones, and run the indirect as a separate zone for the indirect. You have the makings of a nice system. Don't cut corners to cut corners.



Unless that is your goal in life.

JC_fixie

Not cutting corners

I'm not trying to cut corners... I did look at the mod-con units... they really look great.  But don't those units run at lower temps (140 deg F as oppose to the conventional units at around 180-200 deg F)?  I have existing baseboard heating and they are sized for the conventional units... so if I go mod-con, I would need to change those baseboard radiators out for larger pipe versions?... something that I am really not thinking of doing.  I would have to do it all over the house.  That is a large amount of work that I did not account for.



I'm sure the contractor may be slightly behind the times also.  Approx how much would the upgrade be to go mod con?  I'm sure it's not just a plug and play... I can't just replace the existing with a mod-con, right?... need to redo the exhaust and venting, the piping, and who knows what else.



I just thought this system is the easiest replacement with decent efficiency rating. Which mod con unit were you thinking? the Ultras or GV90+?



Thanks for the info though, I appreciate it.



-JC

lchmb

mod con

A mod con boiler is capable of reaching temps of 180 degree's. They generally run a lower temp when it's warmer outside (outdoor temp sensors) to save you money. You do not need to redo your baseboard but you would need to redo your boiler piping and venting. The plus to this is they run extremely efficient and quiet...btw, you dont size a boiler to the baseboard, you size a boiler to a heatloss done on your house, otherwise you may be over sized and wasting money.

JC_fixie

I see...

I understand that you don't size the boiler with the baseboard.  What I meant to say was the existing baseboard was installed with the higher temp boiler in mind.  And I thought with the lower mod-con boiler operating temps, i would need to replace the existing baseboards with lower temp/larger pipe/capacity baseboards instead of the using the existing smaller pipe higher temp baseboards.



If this is not the case, then a mod-con unit is worth considering.  The above info was given to me by HVAC engineers that design buildings and commercial interiors for law firms, hospitals, etc.  They said it applies to residentials... but what do I know and maybe they are wrong.  They don't install residential boilers so they may be on the wrong track.



in any case, if that mod-con does not pan out cost-wise, then my original questions still stands... is the WM indirect water heater a good fit with the conventional WM CGA-5 gas boiler?  what would I need in terms of circulators, or other stuff?  I forgot the other questions from the original post... maybe someone can answer them or take a look again?



thanks again,



-JC





 

JC_fixie

in addition...

my wife likes it a balmy 74 deg F and I live in the northeast US.  I usually start up  my boiler starting in October and it runs until end of May because she and our toddlers like it nice and warm. 

MrDucks

Buderus GB Nice Boilers

Check out the Burerus GB142 & Everything comes down to $$. Indirect is the way to go but make sure you size the pumps. Dont forget your priority call for domestic.

lchmb

I would

go with an indirect over a stand alone tank/burner. As far as a higher efficiency system, any  system is only as good as the install. If you do decide to look into one, make sure your installer is comfortable with the job..

btw, have a mixing valve added to the indirect and run the tank at a higher temp.

James Day_2

Heatloss

Have a room by room heat loss down.  It will tell you if you do have adequate baseboard in the house.  Most times there is more than enough baseboard to run a high efficiency boiler at 160degrees at design temperature which means it will spend about 90% of the year in condensing mode saving you money.  Use the find a pro to find someone local if your plumber is not willing to take the necessary steps.     James

icesailor

Heat Loss & Baseboard:

I would find it highly unlikely that the amount of baseboard to the heat loss for the building would be correct. It is my experience, that most designers over radiate the heck out of a system. Most all systems are over radiated. Most designers round off up, not down. If the loss equals 7.5' of baseboard, you would install 8'. Etc.

You need to have a very accurate heat loss done on your building. By someone who does residential heat loss. Commercial heat loss is another animal. You will probably find that the radiation on your building is more than adequate for your usage. That a Mod-Con will work fine for you.