Space-heating-only DHW Tanks

Mike Lampkin_2

The latest issue of Plumbing and Hvac product news has a
good article in regards to the province of Alberta clamping
down on DHW tanks in space-heating-only applications.
Apparently, there were two deaths and two serious injuries
from carbon monoxide poisioning and these incidents were
the result of on-demand DHW water heaters that had been
installed in space-heating-only applications. The Alberta
Standata states that under no circumstances can a DHW heater
be used for space heating alone, based on the the current
certification process. The new Canadian B214 code (Installation Code for Hydronic Heating Systems) also states
that a direct-fired tank type DHW heater shall not be used
solely for space heating. I was wondering how the code in
your different States deals with this matter. I was also
hoping to get your thoughts on why a space-heating-only
DHW tank could become so dangerous.
Thanks for now.

marc

i dont know of any hwt,s that are intended solely for space heating. some are listed for both, like combi-core, polaris, ect. in washington state hwt,s can only be used for their intended purpose.

Tom Meyer

Same in Wisconsin.

Presently, DHW heaters cannot be used for other than DHW.

Senior Designer/Trainer
Precision Hydronics
www.precisionhydronics.com

Tony Conner

The Biggest...

...danger I can think of would be the relief valve setting on domestic water heaters, as opposed to what is normally found on residential heating boilers. The much higher setting on water heaters might pull the installation under boilers & pressure vessels and pressure piping requirements.

With proper venting, and a correctly sized and set relief valve, water heaters shouldn't be a problem for space heating. But somebody has to pick the right relief valve. It's not just a matter of lifting at the required pressure, but also having enough capacity to handle the heat input under worst case conditions. I doubt that the water heater manufacturers have much interest in getting involved in that adventure, for what must be a tiny fraction of 1% of their business.

Mike Lampkin_2

Reasons for being cautious

I wanted to give an example of where a space-heating-only
DHW tank might be used. Someone builds a shop or garage
with in-floor radiant heating and uses a direct-fired oil
DHW tank as the heat source. Since no potable water is being
used, this application is illegal. So be very careful, if
you are called out to service the water heater and see this
kind of set-up.

[Deleted User]

I think the question might be

What code inspections are required in your area for hot water heating appliances. Is an ASME stamp required? Is there one on the heating appliance?

Noel

Mark A. Custis

I believe

Brandford White has an approved line of the tanks.

Mark

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[Deleted User]

Apples and Oranges...

If I read it correctly, the deaths came from situations where a TANKLESS style of water heater was used. Many of the atmospheric vented tankless water heaters have a modulating capability. I suspect that the venting system was oversized, the boiler was running at an extremely low input, was unable to establish and or maintain proper draft conditions, and consequently CO back spilled into the living space.

Pure speculation on my part.

I have a 40 gallon water heater heating my home, and have never experienced any dangerous situations. I suspect that it is mis application of the appliance that killed, not the appliance itself. My heater does not modulate. It also is not very efficient based on my studies. Can't wait for my mini Munchkin...

ME

Mike Lampkin_2

Thanks to \"ALL\"

for answering my questions. I guess the moral of the story
is to make sure that the appliance is certified to do both
potable and space heating. Take care.

rudy_2

No.....

The moral of the story is "If you don't test, you don't know"

Unknown

DHW cycling frequently

is also a problem. I have done some tests on a couple that have been in for a couple of years. The levels of CO were very high 300 to 400 PPM due to damage to the baffle because IMHO to much cycling for heating. DHW certainly does not cycle as often for hot water usage as it would for heating.

By the way the baffles on those heaters got changed and tanks cleaned. CO dropped to 35 to 40 PPM. The service company who installed them is now going to moniter them to see if they change.

In my opinion they are not very efficient.

Those CO readings are Air Free. I always forget to post that when I talk about CO.

Jack_18

Domestic HWT as heat source

I think the problem was the tanks were nearly in a perpetual condensing situation, that coupled with lack of maintenance makes a bad situation.

Mike Lampkin_2

Thanks for the great answers...

and I appreciate all of the help. I really want to warn
some of the building officials in my area on some of
these issues.