Commercial Hot Water Tanks & BTU's

Donnald

I have hired a contractor to replace a leaking Hot Water Tank (commercial), 100 gallons and 275K BTU. The contractor replaced it with a unit that did not have the ASME rating, and needs to be replaced as it did not pass inspection. I have suggested replacing the unit with a lower capacity, and lower BTU HWT. The contractor has implied that because the HWT is tied into a primary HWT (same capacity and size) that he can not dial down the BTU on just one unit. - "is he right"?



This building is a 46 unit residential apartment complex, centrally heated with 2 boilers. The HWT's are only used for faucets, showers, and central laundry. The units are all one bedroom & efficiencies. I do not believe the demand (even during peak hours) would necessitate 550K and 200 gallons.



So my question is "Is the contractor right"?



If my understanding is correct, the primary HWT tank fires and is used until its capacity is reached (it is set up in some sort of modulating capacity) and then the secondary unit is fired to supply additional hot water. Regardless both units are constantly keeping 200 gallons of water at 125 degrees when it is not all needed all the time.



I am getting the usage numbers from the building owners to run the numbers myself but have never heard of the BTU's needing to be the same on commercial hot water tanks when the are tied into together.

pipeking

to get past the asme

ratings u r going to have to keep that water heater under 199,000 btu. as for combining it with the one that is ASME rated, i want to say yes, but don't quote me, on that. just ask your local official, no big deal, he has to come out and inspect it anyway. just call him, remind him of the job, and what is goin on,  u want to install a wh that doesn't have to comply with ASME (199,000BTU or under). if i find my ASME book I'll give u a definite answer.lol!

pipeking

to get past the asme

ratings u r going to have to keep that water heater under 199,000 btu. as for combining it with the one that is ASME rated, i want to say yes, but don't quote me, on that. just ask your local official, no big deal, he has to come out and inspect it anyway. just call him, remind him of the job, and what is goin on,  u want to install a wh that doesn't have to comply with ASME (199,000BTU or under). if i find my ASME book I'll give u a definite answer.lol!

pipeking

to get past the asme

ratings u r going to have to keep that water heater under 199,000 btu. as for combining it with the one that is ASME rated, i want to say yes, but don't quote me, on that. just ask your local official, no big deal, he has to come out and inspect it anyway. just call him, remind him of the job, and what is goin on,  u want to install a wh that doesn't have to comply with ASME (199,000BTU or under). if i find my ASME book I'll give u a definite answer.lol!

pipeking

YES

 u can install a asme exempt water heater with one that is complient. ASME ratings r for each individual appliance and r not to be comined for ratings or approval. still run it by you local official.

.

Zman

Your tanks...

Your tanks are piped with an equal header configuration.Both tanks get the same flow. If one of the tanks is a different model the flows will not be equal.

You may end up with one tank doing most of the work , thus running cold. With your present piping, I think your contractor is correct.

Carl

heatpro02920

Tanks

I would use the same tank you have there, is the existing correctly rated? I don't like to mix and match with paralleled tanks, in series it wouldn't matter...



I have a couple Dry cleaning/laundry customers, I have switched 2 of them to Rinnai tankless systems and no more issues.. Them commercial water heaters are expensive and HEAVY, they seem to have a short life lately too, I was using AO Smiths and I have had a few fail months after the warranty period...

pipeking

i don't

like mix matching in this configuation either, but i do beleive if they have the same size tappings and u use the side tappings, the differances in flow will be minamal. i was just answering the question at hand, but if u wanted more info then what was asked then let us know, but since it was brought up i would try my best to match the appliances.