Heat and hot water

happydave

We have large up scale condos we service that use a power vented water heater that supplies 140-150 ° water to a manifold that mixes for domestic and hot water to two hydro- coils. The closets in the Center of the buildings are tight, you need to remove the firedoor and jams to get the new ,wider tanks in. On a good day it can take up to 4 or more hour's with the up down elevator, lifting over the pan,etc..


My question is has anyone used a on demand water heater to do this. Splitting the manifolds is not a option for combi. Straight pvc up thru roof. Any thoughts?

njtommy

Yes you can use a tankless for this. Rheem even sells a package for this set up.

http://www.rheem.com/products/integrated_systems/

kcopp

You are going to have to revise your set up any ways. The largest standard gas water heater is 50 gallons now and the outside dimensions are prob to big too fit in that space w/ the new water heater standards that came down last year.

GW

I can't picture exactly what you're describing but you may wish to take some time and make extra sure you won't have anyone complaining about the different nuances with the tankless. Whenever I deal with stuff that involves "groups" of people (as opposed to one man, one lady, one couple), I'm extra fearful a rotten apple will find their way to the party.

Paul48

How are the domestic and heating isolated from each other?

happydave

Each condo has a mechanical closet , everything is either copper or cpvc. Domestic goes thru a honeywell AM100 tempering valve.

kcopp

But no Heat exchanger to separate the domestic from the heating water....

GW

That was my inability to picture this, it's not normal to send domestic through the ahu. I believe there are domestic rated coils out there yet I don't have any experience with them.

happydave

No , water heater is used as a boiler

GW

Ok try and ensure these systems are legit if you haven’t already.

happydave

Passed state and local inspections when built 10 years ago. We didn't do the building but we have serviced since day one.

GW

Ok great but in our society last man holds the bag. If a PE designed this stuff when plans were drawn I'd sleep better. Are the coils rated for domestic water, and everything is copper brass stainless? Is there a way for the water to get moved a bit during the off season? Just wondering out loud, I definitely don't want to be a stick in the mud.

happydave

I've always thought about that, legionares disease etc....

Paul48

Does the system appear on engineering documents? There is the potential for someone to get sick as the result of doing that, and if you change something, you'll own it. Just sayin'

GW

Combine that notion with the fact that it's a multi community, too many moving parts

Jack

This was a big deal in MA several years ago and the Board was up in arms about it. I believe it was Woburn's inspector who fought the "open loop" heating/AH idea. Net/net the large apartment developers won that battle and the water heater/AH heating systems are in millions of apartments across the country and have been for many years. The systems have the pump timer to circulate regularly and keep the water moving. I was involved in the conversion of at least a few thousand apartments when representing Rinnai in NE. Energy savings were consistently in the 50+% range and the systems have been reliable and show much better life than the tanks serving the same systems. There is good business to be had doing these change-outs.

A few issues may come up. One is the circulator sizing/flow rate issue of the circ in the AH. My experience was that this was a very rare occurrence and a very high percentage worked fine. Gas line sizing is always a consideration with tankless, as you know, but I found that all of the apts the were converted operated fine as piped. Luck? Keep your eyes open. The fact is that in a single to two bedroom apts. you are running at such low inputs that the line sizing wasn't an issue. It is worth a discussion with the utility and building owner. The other fly in the ointment is condensate removal. I prefer to use a small condensing tankless in these applications as, due to the very low flows in cold climates, you can still get a bit of condensate in the vent system with non-condensing units.

Many apt owners would loose 4-5 tanks/per month out of a couple hundred units and try the tankless. Upon monitoring the performance they would generally make it a hard spec. Like these systems or not there are a lot of them out there.

4Johnpipe

Take a look at the specifications on this. See if it meets your needs. It takes care of legionella using a timed pump excercising built in. Just installed one a month or so ago...
http://htproducts.com/crossover.html

4Johnpipe

This is the install. We will be going back after the house is raised.