Instantaneous Gas Fired Water Heater Performance ??

[BravoCompany]

Has anyone out there had any relevant experience with instantaneous gas fired water heaters—particularly the Bosch Aquastar 240 FX or similar.

I am currently looking at a job requiring a considerable amount of hot water for domestic use with very limited space in the existing mechanical room. To make matters worse I am trying to add a factor of redundancy.

I’ve seen these units before but have absolutely no personal experience with their installation and performance. There is very limited information and that in alone is reason for concern. Would anyone like to offer any relevant experiences or information on this subject?

I have only done a cursory search and have not yet talked to any manufactures representatives.

Any help/info would be appreciated.

Thanks

 

[MarauderX]

I would mount the instant water heaters as close to the source as possible. Under the sink is typical, near the trap or garbage disposal. Don't forget to add a tempering valve if needed, as most of these pump out water at 140F. Any small instant water heater isn't going to have enough capacity for a shower. Average size for under-counter instant heaters is 1/2 gallon, but they can if you have the electrical capacity.

http://www.insinkerator.com/hwd.html

Why the redundancy if it is residential? Is the place a mansion? Then buy a normal small electric water heater and put it in the mech room/closet.

 

[BravoCompany]

Thanks for the information, however, I have used similar electric instantaneous water heaters in the past and nothing like that will work for this application.

I'm looking at the Bosh because their product is more than just a point of use system. I have seen them used in the past for Dishwater boosters they seem to be capable of delivering a sizable amount of hot water without the space requirement and added heat lost associated with Storage types.

The need for redundancy is because these units will be serving a college dormitory.

 

[PEDARRIN2]

You have a problem of recovery vs storage. Recovery is basically how much hot water the water heater generates in a given hour. Storage is just what it says, storage of hot water.

An instantaneous water has great recovery, but that is not what you need.

If it is for a dormitory, then you will be needing a lot of hot water for a short part of the day ( i.e. morning showers).

An instantaneous water heater is probably not what you want. It would work, but would be wasted energy. It would supply your shower requirements for the 3 hours required but then it would be heating water at the same rate when there is insignificant needs.

An instantaneous water heater is useful if you have demands for an extended period of time where the hot water flows are fairly constant.

What you need is a heater sized to operate for expected hot water flows through the day and a storage tank for the dump load (large short term requirements, ie showers) That way you have the hot water for the showers put you are not wasting the energy to produce the larger amount of hot water.

Will the hot water heater feed water to a cafeteria or laundry? That might make the justification for instantaneous more easy to swallow.

You might need to find space someplace for a storage tank. Otherwise if you use an instantaneous heater, you will be throwing away money in energy.

 

[BravoCompany]

Thanks Pedarrin2 for the reply. I understand the need for storage, but that is a good point. Our original plan was to install 2 new 199 MBH, 100 Gallon, water heaters, however, after a site visit last week I now know that we can fit one unit, however the adjacent spot for the other is obstructed by an existing structural condition.

I’m thinking of installing an instantaneous unit simply to provide the redundancy that we are seeking in case one unit were to fail. Think of it as a water heater with one tank and a redundant set of burners.

I have never used one of these units and I’m curious if anyone else out there has, and if so were they satisfied or unsatisfied with their performance. Any such feedback would be helpful.

Thanks All

 

[PEDARRIN2]

I would also like to hear about use of instantaneous without storage.

I am somewhat familiar with steam instantaneous heaters but usually there is storage with them.

As a question, why only 199 MBH? Is it because of a boiler code. I know where I am at, we try to keep them under 199 MBH so that the owner does not have to get a boiler inspection annually.

If that is not a problem, you could go larger with a 100 gallon storage tank and maybe make up for the lack of the other 100 gallons storage. I know AO Smith makes a good 250 MBH heater with 100 gallon storage.