Combi-Core efficiencies????

leo g_13

we have just got a 14 townhouse project (told we have it, but the contract has not been signed yet). The project managers want me to check into using the BW Combi-core for each unit. I was just wondering if anyone knew this units' efficiency rating. On their site, they state X amount of BTU's available for heating, but that just won't cut it with my local inspectors. I have to show them the math to prove that these units can deliver the copiuos amounts of DHW as well as the neccesary BTU's for heating.

Thanx!

Leo G

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Alan(CaliforniaRadiant)Forbes

Efficiency

Sorry, I can't answer your efficiency question, but am wondering why these units are being considered given their many problems.

From a previous thread:

DATE: Sep 29, 2001
SUBJECT: Combicor vs. Two Tanks?
NAME: C. Arnold

Looking for an opinion from an installer or two or three- pros and cons or
getting the BW Combicor to do it all, or getting two midpriced waterheaters,
one for heating (closed loop), and one for the house. Not many hydronic
installers in my area to ask...



DATE: Sep 29, 2001
SUBJECT: Combi-Cor disaster
NAME: Bill@Bay Hydronic

Out of about 20 installed, 10 failures in first 4 years. Most in first 18 months.
HX coil corroded through. Probably more failed but nobody ever told me.

Everyone I know who has tried Combi-Cor reports same or worse
statistics.

Bill

DATE: Sep 29, 2001
SUBJECT: Same experience
NAME: Mark Hunt

not as many though. And it wasn't because of glycol as there was none in the
system. It's a good thing that high pressure goes to low pressure. Consider a
tank and a plate HX with a bronze pump between the tank and the HX.
Hope this helps. Mark Hunt


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Waylon Lowery

Wow......

you are scaring me. We installed two CombiCorrs two years ago and haven't had any problems. However, I think I'd better do a follow up call. I also have another installation pending.

Does anyone else have any other bad experiences with the CombiCorr?

hr

About the same as Bill

probably installed a couple dozen. As far as I know they have all failed, in under 10 years.

I cut two failed ones open. For some reason the coating on the hx coil peels off leaving the thin walled aluminum hx tube exposed. I think it becomes an anode rod then

Also the connection where the hx coil goes through the galv nipple on top will leak.

They need a LOT of pump to perform near the rated output of the coil, I've found.

Efficiency wise they are jut a HW tank with an internal coil. I'd guess mid 70% like any water heater. Maybe less as you need to run them 160° F to get much output from the HX.

This is some of the coil coating I pulled from the bottom of one I cut open. Also the nipple that the aluminun coil exists the heater through.

They have a thin monofiliment line under that coating, somehow. If the HX leaks, water vents to the outside. Clever idea! This is how it pass as a double walled HX, in areas that require it.

Bill feels the coils bounce and flex during shipping and temperature swings, I'll bet he is correct in that also stresses the coil.

I added the brass nut to repressurize the coil on one I cut the top off to repressurize and see all the pin holes spray.

In every case I went back and installed two WHs, one for the radiant (a 65K burner model) and a second for the DHW.

They do stand behind the warranty, but it takes a day to replumb when you go with two tanks. IF you have flue capacity! I eat the labor.

Too bad, a great concept, bad coil selection, IMO. PAP or copper may have been better.

hot rod

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hr

About the same as Bill

As far as I know about 20 of mine failed within 10 years.

I cut the top off a couple to see what the heck was happening.

For some reason the plastic coating falls off the aluminum HX coil. then the coil becomes an anode rod I suppose!

The connection where the aluminum coil comes out of the tank corrodes the aluminum coil also.

They used a thin monofiliment looking line under the plastic coating, If the coil leaks the water sprays from the top of the nipple where the line comes out.

Clever idea to get around the double walled requirement, required in some areas.

These pictures show the plastic coating I removed from one I cut open. also the nipple that the HX exists the tank from. The brass nut is where I repressurized the coil to find the pin hole leaks, after I cut one open.

Too bad it is a great concept for small radiant/ dhw use. bad coil selection, IMO!

Takes a lot of pump to get that HX to perform to spec, and 160 or higher tank temperatures!

Efficiency wise about the same as any tank type WH. Maybe less when you run 160° or higher.

hot rod

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Dave Stroman

I believe they changed the plastic coating to PEX. Perhaps that will hold up better. I have one gas fired unit in and several indirects installed with no problems.

Dave in Denver

DaveGateway

Triangle Tube

Has the Delta series combo with the SS inner tank for DHW, steel out tank for heating. Pricey. Proabably as much as a small gas boiler with indirect. Depending on the size of the townhouse and how many baths, wouldn't a wall hung combo unit work also? I don't know how you are going to prove manufacturer's specs? Does anyone ever test a boiler or indirect's posted numbers?

Paul Pollets

Combi Failures

I've replaced 3 out of 12 installed in the past 7 years. All of these projects were "budget" jobs under 1000SF, and the customers were advised of their short term life expectancy. I would not recommend them for condo use. The longest lasting appliance delivering the lowest fuel costs would be a boiler, an indirect DHWTank, and outdoor reset control. Water heaters will never cut it as a heat source, in my opinion. We've all been through this discussion many times. Caveat Emptor.

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leo g_13

well thanx

for all of your replies! Once again the diversity of this place comes through. People from all parts have seemed to have the same experience, no matter the water conditions, and as I am just up the highway from Paul, then i would expect the same results. I informed the general today, that from what you guys have told me, we would not be offering the combi-core. So now we are back to the original quote, a nice small locally built boiler with the tekmar 356 and a stand alone gas fired tank. i could not get them to go for an indirect, as these are spec units.

Once again, A HUGE THANX TO ALL YOU WALLIES FOR POSSIBLY SAVING ME FROM GRIEF!!!!!

Leo G

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Weezbo

Good thinking:)

however, the triangle tube might prove a tidy idea with the Taco pump block. and come in closer to budget than you would have thought.