Please! Guidance/thoughts/observations for dealing w/ a lemon combi unit that never worked well

dhw_probs

I have a Lochinvar Cadet (natural gas) about 6 years old that has never worked correctly: 1-2 times a year, despite annual maintenance it breaks and I wake with no heat or no hot water or both. Happenedfive times this year for about 50% of the cost of the unit itself (before installation costs) and even my very reputable Lochinvar-recommended tech now saying I should consider a new system. (details on the current issue below, if you want them)**

I'm burned out these temperamental high efficiency units that need more maintenance and parts that wear out more frequently and limited availability. Efficiency doesn't matter to me anymore. The Lochinvar was running w/o temp curves for half the winter due to issue anyway so efficiency gains were lost then anyway.

I want a system that will be reliable and low maintenance. I know issues happen, I understand occasionally I'll have an outage, but I don't want to have multiple per year. I expect that regularly scheduled maintenance-- which I pay for diligently-- should keep most issue at bay. I want a system that will allow 2 showers to go at a time and still heat the house. My Lochinvar is about 100,000 BTU for a 2,400 sqft house, and when it works, it works fine for this. Plenty of heat, plenty of hot water. At the beginning we could even run 2 showers, but somewhere along the line things degraded to where we can only run one now. Not sure why the heck that happened.

So that's where I'm at. My tech is recommending another high-efficiency unit as a drop-in replacement. (Laars). I hate the idea of dealing with another high efficiency unit & the issues that come with them. They're also about to quote me for a standard efficiency unit & 60 gallon tank, which they say will cost more, and I'll have to re-open the chimney that my former oil-based furnace used to use. But it's going to get cold so I'm out of time. I also out of patience, and most importantly I'm out of money. $$$ to fix the current issue is less than getting a new one but after 5 outages last year, where does that end? When does it make sense to bite the bullet and dip into emergency savings + finance the difference w/ debt to get a new system?

I'm just looking for some guidance here. You guys are the experts. What would you do, as a consumer? What things should I know, that I might not know, where making a decision here?

**Current issue:
Right now I have no hot water or heat (luckily too warm to need heat) because the main board is bad for the second time in 6 years and I'm looking at another large bill to replace it. In particular it's sending 13v instead of 24v to a valve, so it will only ignite to combustion about 1 in 20 attempts. Lochinvar support advised the tech to replace the board. There's also two corroded sensors that still work but might stop working at any moment & will add a few hundred $ to the fix if I do it now, money I'm sorely in need of, or even more if I wait to have them fixed on a separate call-out when they breakdown

Jamie Hall

First off -- kindly edit your post to remove the prices. No prices is one of our very few rules...

I think, though, before I went ahead with a replacement -- whether high efficiency or conventional -- I would make very sure that you aren't shooting the messenger. Multiple main board failures, while not unheard of, may suggest that there is something amiss with the power going to the main board. So I would check that very carefully indeed. Good grounds, good neutral, no loose connections, good and reliable breaker, etc. Is there something in the house or on the same transformer from the grid which could be causing occasional voltage spikes, even momentary, or voltage dropouts?

Now... I personally am not keen on combis. However, I have nothing against mod/con boilers -- in general, though they do require some more maintenance, they are pretty reliable. But what I would do is a separate heating boiler and water heater -- though if you have the gas flow available, I might look at one of the bigger instantaneous direct vented water heaters. Some are big enough to handle two showers at once, and most of them are, or can be, wall hung and direct vented.

JUGHNE

What kind of radiation do you have? Baseboard or cast iron or otherwise?

dhw_probs

@Jamie Hall Sorry, I removed specific costs & kept things general to still help understand the balance of financial consideration in this. Let me know if the edited post is still a problem. Also thanks for your insight.

"bigger instantaneous direct vented water heaters" Can you tell me more about these? Without citing prices, where do they land on the spectrum from low to high?

Otherwise:

Right now the issue is the main board, but I've had multiple issues that were mechanical. I've also had issues with passive sensors breaking when it wouldn't be possible for it to get burned out by a voltage spike since no current is sent down the wire, it's only resistance that's read by the main board. That comes both from my own circuitry knowledge & what a tech told me about this particular system. Could still be wrong, but sending voltage down a passive sensor w/ a diode in front of it should be close to impossible. If enough current manage to hit the diode going in the wrong direction, the diode should blow & prevent the sensor from getting fried. This is however just my recollection from a decade+ old electrical engineering & digital circuits course & hobbyist stuff since.

As for general electrical issues: The techs have tested every connection in & out of the machine & monitored it for more than a quick voltage reading. They've been great to work with, very diligent, and while not cheap, when the original estimate underestimated things and they needed to send out a team w/ two Lochinvar-certified techs and their overall expert on complex systems, they didn't charge me extra, so I hope I'm not coming across as angry at them. I also had some electrical work done on my house recently and the electricians ran general tests to see how/where they could add to the circuit break and there were no issues. An electrical issue isn't impossible, but if there is one then it is very far under the radar and not effecting anything else. I work in another tech field though, so I do know that such bugs can occur, but a reasonable effort at tracking down those issues hasn't shown anything.

dhw_probs

@JUGHNE I have baseboard in about 60% of my house, cast iron in the central older portion.

mattmia2

Something else is going on here. Mod cons and combis are less reliable than conventional boilers but not this unreliable. A bad neutral in your service or especially in a neighbor's service could cause current to flow through metallic components of your house that it normally wouldn't like the hydronic piping. A leak in the pressure side of the hx or vent could cause moisture or heat inside the unit that would damage things. Some mod cons pull the combustion air through the cabinet. if this is one of them then improper separation of the intake and exhaust will cause similar issues with damage inside the cabinet.

I am curious about these corroded sensors. Why is that happening? That isn't normal.

Unless power from the controller cooks it or lightning induces a current on the wiring, thermistor failures are really mechanical, either from them leaking and getting wet inside and corroding or from mechanical stresses breaking the connection to the resistive element or the element itself.

mattmia2

Or a condensate leak. Condensate is corrosive and will do a lot of damage if not fixed.

EBEBRATT-Ed

@dhw_probs

I feel your frustration. Lochinvar is usually pretty good stuff. Post where your are located maybe someone can help you out.


I would suggest one last call to Lochinvar. Before you call gather all the information and make your case calmly.

Impress on them that you have had it serviced every year by certified Lochinvar technicians

You have paid a lot of money to have a working system.

Weather it's installation errors, some funky job site condition who knows at this point.

6 years is not old for a boiler but neither is it new any longer.

I don't think I would sink any money into it at this point it is probably about half way through it's useful life considering what it's been through.

And stay away from combi's

gennady

Did tech measured voltage between common and hot terminals on gas valve?
Was full maintenance done recently? Including full disassembly of the boiler, cleaning heat exchanger and burner tube? Ignition electrode inspection? I found that good maintenance resolves 99% of high efficiency boilers issues. Assuming they are properly installed.

dhw_probs

@gennady Yep, we just had our full annual maintenance, they always give a run down of what they did and the things you mentioned sound about right. It took about two hours, so I think they were pretty thorough. It had only been 11 months since our previous such maintenance (we wanted it done early this year) and they've been out to the house 4 or 5 time in between checking over everything on the other issues we were having. I saw them checking & cleaning the electrodes myself.

They called Lochinvar itself to talk to one of their techs-- they do a ton of Knights & other units for industrial customers so they've got a pretty direct line-- who basically verified their finding that low voltage from the main board was the issue & a board replacement was required.

Proper installation might be an issue. The group I use now isn't who installed it.

dhw_probs

@EBEBRATT-Ed

Thanks-- The problem is I've only been using the current group to service it in the last two years. Before that it was the person who installed it. That person suggested Lochinvar, but when it had continuing problems they later admitted they really weren't familiar with high efficiency systems. So I called Lochinvar and asked them who in my area was certified, and have used that group since.

Hearing that from the original installation guy was... infuriating. When we got the new unit we hadn't insisted on any particular brand, model, efficiency level, anything. We'd trusted him with our system that was 30+ years old for years, so we trusted him to make a good recommendation for a new unit.

dhw_probs

@mattmia2

Unfortunately I don't really have answers to these. All I can say is that the group servicing the unit now is a massive customer of Lochinvar for both home & commercial settings and through this & the other problems, they've been over the whole setup with a fine tooth comb.

On the flame sensor though, as near as I can tell from poking around the internet, they have a lifespan of a 3-5 years, which matched what the tech told me. Mine hasn't been replaced in 6, so it seem reasonable that it could need replacing. I think the other sensor was for flue gas, which also seems within its normal lifespan. I wouldn't mind these smaller issues coming up & paying for them during normal maintenance upkeep if there weren't so many other problems during the year.

EBEBRATT-Ed

@dhw_probs

Only you can judge the ability of your service company and the problems you have had. If you think they can make it work then that may be the way to go.

gennady

dhw_probs said:

@gennady Yep, we just had our full annual maintenance, they always give a run down of what they did and the things you mentioned sound about right. It took about two hours, so I think they were pretty thorough. It had only been 11 months since our previous such maintenance (we wanted it done early this year) and they've been out to the house 4 or 5 time in between checking over everything on the other issues we were having. I saw them checking & cleaning the electrodes myself.

They called Lochinvar itself to talk to one of their techs-- they do a ton of Knights & other units for industrial customers so they've got a pretty direct line-- who basically verified their finding that low voltage from the main board was the issue & a board replacement was required.

Proper installation might be an issue. The group I use now isn't who installed it.

Can they provide photos of what was done during maintenance? Something like that (photos are not from that boiler)

JUGHNE

I have installed ModCons, cast iron and serviced both....mostly older.

I have never seen a Combi in the wild. However from reading the Wall for 10 years I can see several disadvantages to them.

First they are vastly over sized for heating the house.
Your house may need only perhaps one half of the 100,000 for heating.

Second, with no HW storage they must fire every time HW is called for, even just to wash your hands etc.
That amounts to a large unit with multiple starts and stops per day....let alone per year.
The same thing would apply to a wall hung water heater without storage.

I have done boiler replacements using ModCons mainly only because the old chimney is not usable.

I have changed only one cast iron boiler, 50+ years old but not leaking.
But in a closet sitting directly on carpet and burned a hole in the floor.
Changed the NG tank WH, (same age) also.

I service some that are 40+ years old and were neglected most of their life. They work until they leak. Also, most of these are steamers and had a hard life but still with us.

IIWM, and I wanted a happy customer, I would recommend a CI boiler with indirect WH tank, especially if you have a usable/repairable chimney.

The indirect tank has priority call over heating. It could heat your tank in short time.
House heat and HW heat do not happen simultaneously, this has worked for many in the past. The house "coasts" thru the WH cycle.
Or if you want to keep things simple install a stand alone NG WH tank, sharing the chimney with CI boiler.

Typically the CI would give you about 85% AFUE.
NG tank WH don't have good efficiency numbers, but good record of reliability and low cost repairs.....plus you would not be without both heat and HW.

ModCons achieve that high 95ish% AFUE only when the return water temp is low.
That coolish return water is what causes the CONdensing of the flue gases, milking more BTU's out of the fire by the means of phase change...vapor gases condense to liquid; this can add 10% to the efficiency of the ModCon.
Probably won't happen with BB heaters. Or with an indirect WH tank. Could happen with the CI rads.

I have a ModCon Lochinvar KBN in my house, I have mostly infloor tubing and can heat the house with 120 degree supply water temp.

But I had to replace the board and fan recently. Had I not been in the business to get wholesale prices and use my "free" labor, that efficiency increase of 10% over a cast iron boiler would have been completely dissolved.

Just thoughts from an old guy....FWIW.
Others here will disagree with me for not being "green" enough.

dhw_probs

@JUGHNE Thanks, yeah the group I'm working with gave me two quotes-- one for a drop-in replacement new combi unit and, since I'm soured on them & their high maintenance requirements, they also gave me a quote for a standard efficiency Lennox CI, which is what we'll go with.

JUGHNE

What size of CI?
It is easy to oversize any boiler and still have problems with short cycling.

Has a heat loss calculation been done on your house?
It is very doubtful you need 100,000 buth.
Where are you located?

The design day outdoor temp may be only a few times a year, then the boiler is too large for the rest of the season. CI boiler will not modulate down...most are full fire when on.

dhw_probs

@JUGHNE

I'm in the northeast, 80 year old home, 2,400 sqft. A typical winter day is about 25 to 35 degrees, but for 2-3 weeks/year we're in the single digits. My insulation is mediocre. Downstairs are all single-pane windows. In the winter inside the house, walls that border the outside are slightly cool to the touch. Upstairs is newer construction with better windows & insulation. The old central part of the house has large 2.5'x3.5' (approximately) panels with hot-water radiators inside. The rest of house is baseboard hot water.

A while back, using info I read from this board, I did a rough estimate of BTU needs measuring sqft off all outside walls, windows ratings, sqft of total windows, a guess at insulation quality in the older part of the house, etc. I came up with about 120,000 BTU, trying to be conservative in my estimates and not estimating too low.

The engineer that spec'ed out the system that's about to be installed was here for a while taking measurements, measuring windows, wall temperature vs. outside temperature, etc. He mentioned we were in a zone-4 climate for this sort of calculation. He came up with about 105,000 to 110,000 BTU. and recommended a 125,000 BTU system. I asked if we should go up a level in system to have a larger buffer, and he explained that, no, 125,000BTU w/ some of that capacity periodically going to an indirect water heater was the appropriate size to have a little bit of a buffer.

JUGHNE

He is to be commended for not taking the opportunity to up sale you on a larger boiler.
I think this seldom happens.