Running out of hot water in shower in 5 min

tommydee

Oil. Boiler. Domestic hot water tankless. Everything is newer 4 years 
Should my aquastat have lower level settings? 
I have high level but no control over low level

I am running 
Carrier/Bryant bw5bah-140 boiler 
With honewell L7224/L7248 Aquastat 

I feel like hot water takes long and doesn't last long. Did my installer not install a correct aquastat? 

Larry Weingarten

Hi, A couple of thoughts outside of the boiler... Have you tested to make sure there is no crossover between hot and cold lines? Is there a mixing valve that's allowing cold into the hot side when it shouldn't? A simple test might be to feel pipes supplying hot water to the house/shower and see just where things cool down. If all of that is good, then it's time to play with the boiler and possibly controls.

Yours, Larry

tommydee

I will look into crossover .. where would a mixing valve be?
And pipe access is limited.. it's a 2nd floor shower 

tommydee

109A_5

Hello @tommydee,
Is this a new, seasonal, or 4 year old problem ?
Which Honeywell do you have L7224 or L7248 ? There is a difference.
A picture of the Right side of the boiler may help.

tommydee

109A_5 said:

Hello @tommydee, Is this a new, seasonal, or 4 year old problem ? Which Honeywell do you have L7224 or L7248 ? There is a difference. A picture of the Right side of the boiler may help.

I notice it in the winter months. I live in the north east..
Looks like a  L7248
Is that the right aquastat for my set up? I would think I should have setting for LL

GW

Just one shower, or all the faucets are acting up in 5 minutes? 

HVACNUT

Yes, that is a high limit only aquastat. If you have a tankless coil, you need the L7224 or any equivalent triple acting aquastat. 

When the tankless was added, the supplier and installer should've known better. It should be changed at no cost to you... unless it was you who installed it.

P.S. I love the pipe clearance for the swing out door. Awesome. 

P.P.S. There's 3 firing rates for that boiler. Does the heat load demand 120K BTU's on a design day? That's a lot. You (a qualified tech) might be able to knock it down to the BW5BAH-105 firing rate and save a few bucks.

lobuc

Is there no hot water holding/storage tank? A setup like that in my area would typically have a minimum of a small circ pump plumbed between coil and electric water heater. Lots of consistent temp hot water.

tommydee

HVACNUT said:

Yes, that is a high limit only aquastat. If you have a tankless coil, you need the L7224 or any equivalent triple acting aquastat. 

When the tankless was added, the supplier and installer should've known better. It should be changed at no cost to you... unless it was you who installed it.

P.S. I love the pipe clearance for the swing out door. Awesome. 

P.P.S. There's 3 firing rates for that boiler. Does the heat load demand 120K BTU's on a design day? That's a lot. You (a qualified tech) might be able to knock it down to the BW5BAH-105 firing rate and save a few bucks.

Yes it's a tankless coil. I will reach out to the company that installed it and see if they can replace it.. hope they do, but it was 4 years ago.

And yeah, I noticed that too.. I did get it knocked down after fighting with the company that I ordered an energy star rated boiler the -140 wasn't so they ordered a kit with a nozzle and a baffle or some other stuff to knock down to -105 and made it 85% efficient.
That's for noticing that 

STEVEusaPA

HVACNUT said:

…There's 3 firing rates for that boiler. Does the heat load demand 120K BTU's on a design day? That's a lot. You (a qualified tech) might be able to knock it down to the BW5BAH-105 firing rate and save a few bucks.

Keep in mind different firing rates require different set ups-nozzle, pump pressure, Probably a different head and a low fire baffle…and of course a complete combustion test.

109A_5

Hello @tommydee,
Do you have an ELL — External Low Limit (L7248L only) ? Where does that ZR wire go to on your unit ?

tommydee said:

I will look into crossover .. where would a mixing valve be?

A picture of the Right side of the boiler may help. The pipes and stuff on the right side near the rear of the boiler.

HVACNUT

109A_5 said:

Hello @tommydee, Do you have an ELL — External Low Limit (L7248L only) ? Where does that ZR wire go to on your unit ?

I will look into crossover .. where would a mixing valve be?

A picture of the Right side of the boiler may help. The pipes and stuff on the right side near the rear of the boiler.

I think I see the knob for a mixing valve on the right side, and a B/X wire leading from the L7248 to the coil location. Cant tell for sure but there might be a low limit aquastat there. Good call. 

tommydee

The ZR wire goes to this little guy... ohhhh is this an external low limit control??? 

109A_5

Hello @tommydee,

I was wondering how you had any DHW in the Summer time. I wonder if there is no DHW priority during the heating season.

DJD775

It's hard to see but is the low limit set at 140? When I had a domestic coil I had to have mine set to 160 for a sufficient amount of water in the winter. I had a triple aquastat that was set at 180h and 160l.