Terrible hotwater output from tankless combi unit

sanjayp

I recently purchased a home with a Triangle Tube 125K BTU heating/hot water combi unit. This is for a 2000 sq foot house. Given the winter season, the heating has been running. The amount of hot water supply coming out of the hot water faucet side is terrible if I am running more than one faucet. For example, if the tub is running (btw, pressure doesn't seem to particular high for the water coming out), the sink in the same bathroom has a low supply of hot water until the tub sink is off. It's ridiculous. I can't see how this will sustain a family of 2 adults and 2 kids. Can this be repaired? Or is this how these combi units work? Even at 125K BTU, I would still think I can run heating, a shower and 1 sink at the same time. I miss the old fashioned tank water heaters!

Sanjay

Zman

You could verify that the unit is performing up to spec with a 5 gallon bucket and a watch. If it is you may want to consider low flow fixtures. If not, troubleshooting is in order.
Haterusguy also makes a good point.

Jamie Hall

Troubleshooting might be in order -- but consider: Q = 500 X gpm X delta T. Equals 500 times 3 times 70 for your tub. Equals 105,000 BTUh right there. You can't get more than that out of your combi. They are meant for one bathroom and some heat; that's all.

kcopp

As the others have mentioned combi boilers have their limitations. There are always options. A storage tanks would be in order, if you have the room. BTW...how many baths in the place?

hot_rod

agree with mad hatter, you don't have enough "horsepower" to get more than MAYBE 3 gpm. If your incoming water is lower than 50°F, as many places are in the winter, expect even less performance.

Solar pre-heat helps, but somewhat un-predictable.

That being said, most of Europe, large and small families, get along with small tankless and comb boilers, a different lifestyle and water consumption.

wogpa67

you need to get your water tested. those small heat hx get fouled up easily

Jamie Hall

hot rod said:

agree with mad hatter, you don't have enough "horsepower" to get more than MAYBE 3 gpm. If your incoming water is lower than 50°F, as many places are in the winter, expect even less performance.

Solar pre-heat helps, but somewhat un-predictable.

That being said, most of Europe, large and small families, get along with small tankless and comb boilers, a different lifestyle and water consumption.

I would add to the most of Europe... at least in Scotland, what you will find is a tankless for each bathroom, if there is more than one.

SWEI

Jamie Hall said:

most of Europe... at least in Scotland, what you will find is a tankless for each bathroom, if there is more than one.

Often hanging on the wall in the bathroom (sometimes in the shower) where you can turn the knob to get whatever temperature you need. Piping becomes very simple -- one cold water line to the space.

hot_rod

right down the the simplest "electric shower head" device

icesailor

Stinky Europeans.

Do they have GFCI's on those? In the USA, they would at least have that lamp cord in Liquid Tight tubing and fittings.

hot_rod

Do't know about GFCI, most are 230V if that makes you feel better

SWEI

They call them RCD's -- and yes, they are mandated for many applications.

nicholas bonham-carter

230 V-now I feel better!--NBC

icesailor

SWEI said:

They call them RCD's -- and yes, they are mandated for many applications.

"RCD" ??

What's that.

SWEI

Residual Current Detector (Brit-speak for GFCI.)

icesailor

Damn Brits. Why can't they just learn English like we speak over here. That thing they speak across the pond is all gibberish.