Lochinvar Solutions gas boiler

jimt

I had old oil boiler replaced with Lochinvar Solutions gas boiler couple months ago. Contractor only replaced boiler. Re-used same indirect h/w tank and outdoor reset control from old boiler. Now that it has gotten cold I noticed that it runs differently than oil boiler. For example:
Today the outside air temp is 37*. When I came home from being away all day the in-side temp on thermostat was set at 64*, and I moved thermostat to 68* and went downstairs to actually monitor the boiler. Boiler ran 9 min until water temp reached 140*. Shut off for 3 min until water temp dropped to 120*. I then monitored for the next 20 min and found that boiler would kick on when water temp dropped to 120* run for about 50 seconds until temp reached 140* then shut off for about 1:30 until temp dropped back to 120*. This cycle continued until inside temp reached 68* and heat was no longer being called for. The entire time the circulator was moving water through the base board.

It just seems to me that the constant on/off of the boiler is not efficient. Is this the way the boiler is designed to run? (It runs about the same way when making hot water for indirect too.)

Zman

It sounds like the boiler is over sized. Especially at those operating conditions. How does it perform with very cold outdoor temps. How was the sizing determined? Heat loss calc or replace existing?

Eastman

The Loch Solutions comes with an ODR control, perhaps it was the outside air sensor that was reused?

Is this system configured for low temperature operation? The manual states that temperatures below 140 are not recommended unless some form of low temp boiler protection was installed.

Your old boiler probably used higher temperature ODR settings which reduces cycling during heat calls, and in particular, during recovery from setback.

jimt

Boiler is 75,000 btu
Current settings: Max setpoint 170*, Min setpoint 115*, High fire offset 15*

My house has alot of baseboard. All exterior walls have baseboard and even some of the interior walls too!

delta T

What pump/s are installed? how is the near boiler piping arranged? Pics would help. Also, Hatterasguy is right, what rating is 75k, input or DOE rating? if it is a 75k input and you have "a lot" of baseboard, then the only thing I can imagine is that the pump is for some reason not moving enough water. Especially since it short cycles the same way on the DHW call. I was with Zman at first that the boiler is over sized, but the same symptoms can show on an under pumped system. it may be the pump or it may a restriction somewhere. Pics please!

jimt

Baseboard with fins is 89 feet. There is also 17 feet or so of baseboard with no fins.

jimt

Tag on boiler says 75,000 is Input Rating.
Green pump on top says Taco 007-F5
White one near base says Taco 007-BEF7J

jimt

These 3 circulators were re-used from oil boiler. 2 heat zones and 1 indirect hw tank.

hot_rod

Typically around 550 but/ ft of baseboard X 89' = 48,950. Rough number as the end of the bb run may not be transferring the same btu with lower supply temp. Is the system zoned?

75K input X 82% efficiency is around 61K output minus any elevation derate.

So not grossly oversized, not knowing the actual building load?

Only on a design day would you expect to see the boiler run n on-stop. Any condition less than design will cause the boiler to cycle.

Most agree the boiler should run a min. of 10 minutes on every call.

jimt

How do I tell if boiler is running on high or low setting?

I have no issues with actually function of the boiler. Keeps house warm and water hot. Just wondered if short run times will cause premature failure and/or major loss of efficiency?

The new boiler is saving me money over oil boiler.

jimt

I just wonder if the re-used outdoor reset control is the issue. See picture. This used to be attached to old oil boiler.

I just monitored the demand from the 40 gal indirect h/w tank after a shower. During the time I monitored. The boiler would fire 1:10 and then rest for between 3:10 and 5:40. But the temp gauge never went above 140* or below 120*.

I monitored it for 18 minutes until demand was satisfied and the circulator stopped. It was probably calling for hot water before I started timing it.

Doesn't that seem too long to satisfy h/w need?
(But again we have never run out of hot water for showers.)

Eastman

That is just a zone control panel I believe, nothing to do with ODR. Do you have more than one thermostat in the house?

jimt

There are 2 zones. Main floor - 1 thermostat. Finished basement - 1 thermostat. Basement thermostat is usual turned off.

Eastman

How many feet of baseboard are on the main floor? Where is the 17 feet of finless baseboard?

jimt

89 ft is on main floor. The 17 ft finless is also on main floor. The finless is mostly along some of the interior walls.

The basement is rarely heated. It has its own thermostat and about 20 ft baseboard to heat 430 sq ft.

wrxz24

jimt said:

I just wonder if the re-used outdoor reset control is the issue. See picture. This used to be attached to old oil boiler.

I just monitored the demand from the 40 gal indirect h/w tank after a shower. During the time I monitored. The boiler would fire 1:10 and then rest for between 3:10 and 5:40. But the temp gauge never went above 140* or below 120*.

I monitored it for 18 minutes until demand was satisfied and the circulator stopped. It was probably calling for hot water before I started timing it.

Doesn't that seem too long to satisfy h/w need?
(But again we have never run out of hot water for showers.)

I just went through a similar situation with my indirect and recovery times. For me, my issues were two things.
1) piping was 3/4 inch when it should of been 1 inch
2). The coil in the tank had years of baked on lime that slowed the heat transfer and caused the boiler to short cycle.

After fixing the issue, my indirect recovers in about 8 minutes.
Before fixing, in a 3 day span, my boiler would run about 9 hrs for dhw.
Now in a 3 day span, it ran only 2 hrs. This is with 4 people with daily showers, wash, dishwasher etc.

My boiler only does 1 cycle to recover dhw. If yours takes more than 1 cycle to recover I would start with piping and dirty coil.

For what it is worth, the indirect recovery time improved when I went from 3/4 to 1 inch before I cleaned the coil.

icesailor

@wrxz24:

"" After fixing the issue, my indirect recovers in about 8 minutes.
Before fixing, in a 3 day span, my boiler would run about 9 hrs for dhw.
Now in a 3 day span, it ran only 2 hrs. This is with 4 people with daily showers, wash, dishwasher etc. ""

Did the boiler run for 9 hours or just the circulator. Just because a circulator is running, doesn't mean that the boiler/burner is running. Unless it is a Mod-Con and the thing is running on modulation and the hot water transfer is insufficient to heat the indirect tank. In which case, raising the boiler temperature outside the ODR is the solution. The clean coil is a better solution.

Kind of like adding insulation to your house.

Eastman

Can you take a picture of the control boards on the boiler?

Is the finless baseboard supposed to be finless? Can you take a pic of that?

A few more of the piping that goes to and from the zone circulators would be nice too.

wrxz24

icesailor said:

@wrxz24:

"" After fixing the issue, my indirect recovers in about 8 minutes.
Before fixing, in a 3 day span, my boiler would run about 9 hrs for dhw.
Now in a 3 day span, it ran only 2 hrs. This is with 4 people with daily showers, wash, dishwasher etc. ""

Did the boiler run for 9 hours or just the circulator. Just because a circulator is running, doesn't mean that the boiler/burner is running. Unless it is a Mod-Con and the thing is running on modulation and the hot water transfer is insufficient to heat the indirect tank. In which case, raising the boiler temperature outside the ODR is the solution. The clean coil is a better solution.

Kind of like adding insulation to your house.

The boiler ran 9 hrs. The dhw does not use odr, tank temp is for 140, boiler is set for 190. Many cycles to get the thing recovered. The boiler would hit setpoint fairly quick and modulate down but since the transfer was so slow due to smaller piping and a limed up coil, the boiler would exceed the setpoint and shut down and start back up after a 4 minute post pump. This happened until it recovered.

Now, the boiler hits set point and modulates down until the tank is recovered. Just one cycle.

jimt

See pics of:
Control settings
Circulators
Baseboard that shows where fins stop

icesailor

That would be the sign of an insulated coil. That coil sounds like it needs an annual cleaning. Just like the boiler. If the scale/insulation is on the inside. Some coils with boiler water running through the inside of the coil, with the coil in the potable water, will Lime Up on the outside and the only wat to clean them is of you can pull the whole coil and soak it in an acid bath. Vaughan "Top Performers" are one that comes to mind.

A nice reason why Tankless Coil Heaters on oil boilers are nice. Because they never get scuzzed up on the outside. Just on the inside where you can pump acid through them and clean them to like new.

Eastman

Major Problem #1: There is nothing connected to the CN10 TANK AQUA--STAT terminal.

A sensor at this terminal, as described in the install manual and interpreted by me, is required to initiate a DHW priority call. "When there is a water heating demand the temperature control will increase boiler set point to 180°F" You don't have a sensor hooked up to the CN10 terminal, hence the boiler doesn't see the DHW demands as a special case. Hence the boiler isn't producing the 180 degree water that allows for maximum indirect water heater performance. The boiler is firing for a water heating demand just as it would for any other space heating demand. It's treating it just like a call from your main floor thermostat or basement thermostat. This is why the boiler is short cycling as it tries to heat the indirect tank. You can't heat 130ish degree water in the tank effectively with an ODR setpoint of 130ish degree water.

Major Problem #2: There doesn't appear to be any kind of low temperature protection system for the boiler. Does it seem like the boiler usually fires to 140 and then cuts out? Why is 140 such a popular set point for your boiler?

The install manual stipulates over and over again that this boiler can not operate below a 140 degree inlet temperature at the heat exchanger. If the boiler inlet sensor detects water below 140, the burner will operate at high fire until the inlet temperature sensor hits 140. So, even if the ODR configuration would normally call for, say, 130 degrees on a mild 35 degree day, the burner must operate to produce 140 in an attempt to protect the boiler from damaging condensation.

Here it is word for word from the manual:
"If the inlet sensor is used to determine set point, the minimum set point is fixed at 140°F (60°C). If a system sensor is used the range of this parameter is 110°F (43°C) to 140°F (60°C) and can be adjusted using the middle knob on the temperature controller. The two-stage thermostat will apply the outdoor air reset set point to the system sensor, while also applying a fixed 140°F (60°C) set point to the inlet sensor. If inlet water temperature drops below 140°F (60°C) the temperature controller will force the boiler to high fire. Requiring a minimum 140°F (60°C) inlet water temperature will help prevent problems with condensation. For systems requiring return temperatures less than 140°F (60°C), a bypass must be installed. Reference Low Temperature Bypass Requirements for additional information."

In a nutshell, the low minimum ODR setting and lack of low temperature condensation protection is potentially damaging the boiler while simultaneously preventing the burner form taking advantage of the half fire output of the two stage gas valve.

To be continued...

Eastman

Continuing...

Let's step back and see if this analysis is consistent with your experience.

When a call for heat is initiated there is a period of warm up before the baseboard delivers full output to the rooms. You described this stabilized phase in your first post: "I then monitored for the next 20 min and found that boiler would kick on when water temp dropped to 120* run for about 50 seconds until temp reached 140* then shut off for about 1:30 until temp dropped back to 120*.

Summarizing: the boiler outputs about 130 degree water on average. The burner is on for 50 seconds and off for 90 seconds.

Changing focus here, baseboard has a known heat output per foot at a given water temperature. If you check out Slant Fins website, for example, you'll find that 265 btus per foot shouldn't be too bad of an estimate for some of the common types of convectors found in the residential market. You have 89-17=72 feet of finned baseboard on the calling zone. So the stabilized output of the baseboard at roughly 130 degrees is 265*72=19,080 btus per hour.

Back to the boiler. Energy is conserved. So what is coming out of the baseboard, on average, must be put in by the boiler, on average. Let's assume the boiler is only operating on high fire. What is the average out put then over the 50 second on and 90 second off cycle? As Hatterasguy noted, high fire produces about 62,000 btus per hour if we assume 82% efficiency. That equates to an average output of about 22,140 btus. 22k input is pretty close to the 19k estimated output of the baseboard. So yes, the boiler seems to be stuck in high fire mode.

For the time being, I would suggest raising the setpoint minimum to 140 and increasing the high fire offset to it's maximum of 20. At some point the manufacture's recommended low temperature protection valve should be installed. Without this device, the boiler's ability to utilize the advantages of it's two stage gas valve is crippled. Have the system reviewed and brought into full compliance with the diagrams in the install manual. Make sure that pex tubing is of the variety that has an O2 barrier to prevent unnecessary corrosion. (Plastic without an O2 barrier allows oxygen to enter the system.)

jimt

Eastman's advice worked!
Changed setting to Max Setpoint 160*, Min Setpoint 140*, High Fire Offset 20*

From cold start boiler ran 8:45 on high & 3:00 on low until 145*. Off for 3:00 until temp dropped to 135*. (This was 1st time I observed boiler on low setting) Circulator running constant to baseboard.

Then ran 1:00 high & 2:40 on low until temp back to 145*. Off for 3:00 until dropped back to 135*

This cycle continued until thermostat setting was reached. Took 36 minutes for inside temp to go from 63* to 67* This seems fine to me! And appears to be similar to old oil boiler.

Does it sound as if system if operating as designed now?
Just wondering why boiler temp drops to 135* when Min setpoint is 140*?

Also wonder if Major Problem #1 needs addressed? If I never ran out h/w when boiler temp was 120-140, there should be no issue with 135-145. Or will the 180* priority be more efficient?

icesailor

Eastman's comment and explanation should be copied and copyrighted, placed in plastic, and passed out at every eat and greet held at any supply house or boiler manufacturers instructional classes. It should be posted conspicuously on The Wall someplace for easy reference.

There should be certification of any and all installers. And any that can't quote that chapter and verse, shouldn't get their certifications.

Call that "Boiler Control Settings. 101".

SWEI

The VAL3000 is a thermostatic boiler protection valve, though somewhat overpriced IMO.

We stock the LK 823 valves at competitive prices. PM me if you need one.

Brydug

My Lochinvar Solutions boiler is acting up. When the flame starts up it burns for a minute or two then slowly goes out then starts up again. Any ideas?

JUGHNE

Low gas pressure has been a problem in some areas of the country lately. Neighbors have any problems?