Tankless heater as boiler for Hydronic system

BCMatt

I'm planning on using a Noritz Condensing Tankless Hot Water Heater as a boiler for my hydronic heating system. Will also use another THWH for domestic water, as code will only allow the use of a heat exchanger system, which ends up being more expensive than 2 seperate wall-hung boilers.

It will be a staple up (using aluminum heat transfer plates, screwed to the subfloor) for the main floor, and transfer plates above wood sleepers in the basement.

- Does Dan's famous "Pumping Away" module work for these types of layouts (vice the regular boilers)?

CMadatMe

Scratching My Head

Why didn't you just use their wall hung boiler (link below) and a flat plate if your not looking for the higher efficiencies a condesing wall hung boiler would provide. Seems your doing yourself a disservice by not using a mod/con. With radiant you would be in the 90 percentile AFUE all the time. If the house is 100 percent radiant it would also take care of raising and lowering your water temps needed for the radiant based on outdoor temperature. The on demand heater just runs the same water temp 24-7.



http://noritz.com/professionals/products/view/nh_series_nh199_dv_nh_2001_dv_tankless_hydronic_boiler/

BCMatt

More info

Chris, not quite understanding your reply. Maybe I need to clarify.

I'm using a Noritz NRC-111-SV (NG)(http://noritz.com/professionals/products/view/nrc111_n_0842mc_series_condensing_tankless_water_heater/) Condensing boiler for the Hydronic system. Unit is sitting in the garage waiting for the install. Will end up using the same model for DHW. So I don't see where we can still be getting a higher efficiency or where I'm doing myself a disservice.

As we aren't allowed to run an open loop as per our code, by the time I would get the heat exchanger, DHW priority valves, the extra circulators etc., I'd be more expensive than getting the second THW unit, which is the only reason I'm going that route.

We just have to do a bit of planning re the  location for these as our codes are slightly different up here re the venting and location of the vents in relation to windows/doors and our enclosed patio. Need a bit more clearance vice most places in the USA.

My main question here is if I can (and should) be 'Pumping away' (as Dan preaches) from the TWH or if this only applies to the regular, old fashioned boilers. Can't seem to find a lot of info in this regard.

Sorry for the confusion and thanks for the help.

CMadatMe

It's a Water Heater

I love Nortiz and sell alot of them but its a water heater not a boiler. The 93% rating you are seeing is thermal efficiecy rating which is how water heaters are rated. Since it's already in the garage the goal is to help you out. Attached is what you are looking for. Best of luck.

Charlie from wmass

take the one in the garage and use it for your hot water

go buy a boiler for your heating. I am not for using things not as they are labeled. If I do this as a professional I can be sued if it goes wrong or out of pocket for damages when my insurance says sorry you should know better.

CMadatMe

Agree

I agree with Charlie here. It might not even be code in your area to use a water heater for heating. I know in some areas here in NY you can't.

NRT_Rob

If it's not rated for heating

it's not code to use as a heater. problem when you go to sell the house. I don't see any indication that they warranty for heating either but I didn't look that hard, maybe I missed it.



you can in some cases do dual use with the heat exchanger in situations you can't do dedicated heat only... odd, but there you go.



you would be much better off using a real heating appliance for your heating though.

BCMatt

Tankless heater allowed per code

We are allowed to use a tankless heater in this application per our building code. Matter of fact, quite a few plumbing companies install them, either hydronic only or combo units using a heat exchanger. However, that wasn't the question.

Can / Should the THW heater be plumbed in using the "Pumping Away" module, or will this only work for regular boilers? In other words, should the circulator go after the THW heater or before it? I see Chris's earlier reply (Thank You) with the pdf drawing shows the circulator pumping toward the THW heater.

The unit presently in the garage is slated for the DHW installation, so theoretically I can still go with the boiler...

NRT_Rob

I'd be interested to know

what code you're following in that case. I keep running into the requirement for dedicated heating to use a heating rated appliance.



pumping away refers to an expansion tank, not a heater.



You still want a boiler, even if code allows otherwise, unless your heat load is very, very small. In which case, you want a tank heater.

BCMatt

Most Canadian Codes

Most (if not all) Canadian Provincial Building Codes allow the use of a THW heater to be used in a hydronic application. Some provincial and/or municipal codes require the use of a heat exchanger to keep hydronic seperate from the DHW, others don't.

From my research, Heatlink even manufactures dedicated panels for these applications. There may be others out there I haven't come across. See http://www.heatlink.ca/en/product/heatlink-heating/hep080v1/hep-80-mbh-isolation-heat-exchanger-panel for an isolation type THW panel, or http://www.heatlink.ca/en/product/992 and http://www.heatlink.ca/en/product/1055 for others. These units are approved by code here. Therefore, I don't see why the negativity in regards to these applications. I am also familiar with tankless hydronic systems in various western US states.

Yes, boilers have their place... and price.

BTW- my heatloss calcs show a heatloss of 31,250 BTU/h . But our change in windows and upgraded insulation should bring this below 29,000 BTU/h.

NRT_Rob

in a heating climate

that's a small boiler appropriate load.



it will pay back on efficiency improvement (most tankless heaters will only hit low 80's efficiency in heating). Very high end tankless heaters may do better than that on heating system efficiencies... but they are not that much cheaper than boilers, and they still won't hit the boiler efficiencies in most cases. Then you get into lifespan and warrantee questions.



Most canadian codes do not allow a potable appliance to be used as a *dedicated* heating appliance, last I knew. but I am only parroting back what canadians I know tell me. http://municipalaffairs.gov.ab.ca/documents/ss/STANDATA/plumbing/P-G-Combo08-02.pdf



anyway, allowed or not they are rarely the right choice. and I don't sell boilers, for the record.



there are times it's not a horrible choice. Single zone slabs, for example. but it's rarely the *right* choice. You can do mid to low efficiency cheaper with a tank and you can do higher efficiency better with a boiler. tankless heaters are basically an overpriced middle ground with questionable lifespan and warrantee issues in most cases.



Particular units may be exceptions to this. As a class though, that's what my research and numbers indicate.

BCMatt

Thanks

Thanks Rob. much appreciated.

CMadatMe

IBC

Since you in the great North why didn't you consider an IBC boiler. It gets down to 15k?

BCMatt

Never heard

Never heard of them before. But will check them out.

Thanks for the tip. Did look at Viessmann / Buderus though...

Jack

Tankless as heat

I represent Rinnai in my local market. Rinnai pulled their approval for use of their tankless products inclosed loop heating a few years ago. Personally, i never considered it a good idea. Tankless are excellent water heaters. A water heater has variable flows and high delta T's. You take a product designed to this spec and put it in as a boiler and you get pretty much fixed flow and low delta t's. Precisely the opposite of its design criteria. It may work, but how long will it last?



I think you will be much better doing as suggested above. Put your " water heater" in for hot water and get a boiler. Good luck with your project.

NRT_Rob

Jack

that is refreshing honesty from the on demand crowd. Thanks for posting.

Jack

That...

is all you will get here, Rob;)

BCMatt

Rinnai

Interesting that you mention that Rinnai has pulled their blessing on these installs.

My local heating contractor is just working out a quote for me using one of their units... Hhhmmm. Told me that it was the bestunit out there for this kind of thing.

Makes one really wonder...

Jack

make sure we are talking about

Rinnai's tankless and not their new boilers. Last fall Rinnai introduced a line of wall hung modcons that have proven to be excellent. They are a true boiler with all appropriate listings. One of the reasons Rinnai pulled their listing for closed loop heating is that it made no sense in getting ASME for the whole line of water heaters. Rinnai does have one water heater that has ASME, but we use it only for those commercial hot water jobs where codes require it. If your contractor is talking about the boiler being just right for the application he is absolutely correct. As well, I am not sure of Canadian specs or limitations, but I'll stand by original post on this topic.

BCMatt

Wasn't wondering

Jack, I wasn't wondering about your original post, rather what someone was trying to sell me. Now that I am more informed, I know what to look for.

Thanks.