Locknivar Noble Firetube combi not heating water fast enough

dseltz

We have the Locknivar Noble Firetube combi boiler and it is taking a long time to heat the water (going to the taps). We have well water which is cold. There is also a mixer on the system that adds water from the well to the hot water coming out of the boiler. I would also say the exhaust is pretty loud. If you are standing outside anywhere near the vent it is very noticeable.

Has anyone else noticed the slow water heatup?

Thanks,

Dave

DZoro

Make sure the domestic hot water pre heat option is on. What were the combustion numbers when the system was installed?

Zman

On the hot water issue, someone should verify the boiler settings and be sure the mixing valve is functioning correctly. Beyond that, what model boiler is it and what is your water usage like? High flow shower and tub fill valves could be maxing you out.

The noise is likely related to poor combustion. The boiler should have been commissioned using a combustion analyzer and checked again during scheduled service. Many contractors do not do this but it is mandatory.

DZoro

What size Noble do you have?

bob eck

Like Dzoro said make sure the pre Heat is on and is the mixing valve working correctly. Did you have you water tested? Do you have hard water? If you have hard water and if you do not have a water softener lime hardness scale can build up in the heat exchanger and cause poor heat exchange.
If the boiler is working correctly seconds after turning on a hot water faucet the hot water should be coming out of the boiler going to the faucets. Turn on a hot water faucet feel the pipe after the mixing valve going to the faucets see how long that takes to get hot. Should not take long. How far of a run is it from the boiler to your shower. That could take 1 to 3 minutes. If it takes that long most likely it is not the fault of the boiler.
Where do you live.

dseltz

Hi Everyone, Thanks for the replies. To try to answer the questions:

- I have the NKC199N.
- I don't know if the domestic hot water pre heat option is on. i assume I would go into the menu system to check this but it needs a password.
- The mixing value is working. If I adjust it i certainly can see the results.
- I have not had my water tested since the unit was installed.
- We do have hard water but we do have a water softener. It is fairly new (installed last fall) so I don't think it would be a lime hardness scale issue yet.
- I would say our water usage is low. It's usually just my wife and I. This is not a matter of running out of water. That does not happen. It's just that it takes a while to heat up. a good 30 seconds (when system is cold).
- I don't know the combustion numbers when the system was installed.

Zman

I would suggest having someone service the boiler who can do a combustion analysis.
The password should be in the installation manual. If I remember correctly, the techs at Lochinvar must be fans of 80's music. The password is some portion of Tommy Tutone's "Jenny I got your number"

Jamie Hall

30 seconds? From a cold start? That's jolly good. Consider. There is -- assuming 30 feet of half inch pipe -- three tenths of a gallon of cold water sitting in the pipe when you turn on the tap. Assume a 1.5 gpm fixture. That will take a minimum of 12 seconds to flush out right there. Then the combi has to have fired up and brought the tubing -- and the water in it -- up to temperature. Even with a big burner, that's not going to be instantaneous.

I'd say a 30 seconds to hot water response is pretty darn good.

But I do wish the advertising blokes hadn't hit on the idea of using the term "instantaneous" for these things. "On demand", yes, no problem. "Instantaneous"? No. The only way you could get close to truly instantaneous hot water is to have a storage tank type water heater at the fixture. Like -- right at the fixture.

DZoro

Agree with Jamie, with the pre heat option on. That unit will have hot water INSIDE it at all times. But that hot water is IN the unit and not waiting at your faucet.
That unit will give you 4.8 gpm of hot water, with cold well water.
Set up properly, analysis done it will be quiet. There will be some air venting volume noise at 100% fire. But that is only the rush of air through the pipe sounds. No howling, or other noise.
A good installer would leave the combustion report inside or in the instructions of your unit.
D

dseltz

Pre-heat option is enabled. And I timed how long it takes to heat the water in the morning and it's 70 seconds. I'll have to find a good person to service it.

Thanks for the help.

bob eck

Where is it taking 70 seconds to get hot water? How long does it take hot water to be going out of the mixing valve?
If the preheat is on it should take 15 seconds or so to have hot water leaving the mixing valve. If it takes 15 - 20 seconds for hot water leaving the mixing valve and it still takes another 30 - 40 plus seconds to get to the faucet that is not the combi boiler fault.

Jamie Hall

70 seconds still isn't bad, unless the runs are very short. Perhaps we are dealing with unduly high expectations here?

One option -- for truly nearly instantaneous hot water (10 to 15 seconds) is to use electric or propane local heaters, at the point of use. That is, actually in place in the bathroom or kitchen or wherever hot water is needed. Quite common in the UK. Of course they take a lot of gas or a lot of electricity (11 KW/220V (50 amp circuit) for a 3 gpm unit, for instance), which has to be brought to the point of use, too... there's no free lunch.

dseltz

The 70 seconds was in the kitchen on the main floor. Combi is in the basement. Not sure how long it takes for hot water to be going out of the mixing valve.

70 seconds is worse then my old boiler but that was not a combi unit so I think you're right that my expectations may be unduly high. 70 seconds seemed like a long time to wait (and a lot of water to waste).

Gary Jansen_4

You could add a small recirc pump. The Noble install manual shows how to pipe it properly. Lochinvar also recommends keeping the domestic side in preheat mode if you pursue this option.

DZoro

At the bottom of the boiler the domestic hot water comes out and goes to the mixing valve "hot side". When you turn on the hot water at any faucet does that pipe get hot or warm up quickly?
At the same time does the boiler also fire up? Should be around 60-100% fire in a short amount of time.
Did you find the combustion numbers for the unit?
What is your flame signal number?

If the unit has not been set up with the proper numbers you possibly could have delayed ignition if any of the above items don't happen very quickly.

dseltz

When we turn on the hot water (cold system) the boiler comes on right away and the hot inlet to the mixing valve starts to get hotter right away. I don't have the combustion numbers for the unit.

DZoro

Sounds like the boiler is doing its job. The hot is coming out right away.
It's just that the Hot has to push all the cold out of the water piping to which ever faucet you turn on.

In some situations a stand alone water tank can slowly migrate warm water up during down times.

This will not happen with the on demand. Your savings of no wasted hot water, greatly out weigh a stand alone tank system.

For longevity and good performance of your system. Make sure you get the combustion analysis performed, and are set to the levels in the owner/installer manual. It's a great system if installed correctly, and performing to proper specifications.
D

Larry Weingarten

Hi, I might now look at the plumbing. I'd test for a cross connection first. To do this, shut off cold water into the boiler and open a hot tap. Water flow should stop in seconds. (not sure if your mixing valve will interfere with this, but if you can shut off the cold to the mixer... good) Next I'd calculate the volume of water in the line between boiler and tap. Measure flow rate at the tap. Understand that it should take roughly double the volume of water in the pipe being run out before hot water arrives. Do let us know what you find!

Yours, Larry