Is a condensing boiler in a vacation home a bad idea?

AtTheBeach

Hi all, first post. Bought a small, well-insulated, 2-heating zone vacation house in Vermont. The 20 year old boiler died the minute it saw us. About to put in a propane condensing boiler (EK Accel CS) but the plumber is saying we will need to drain the domestic water tank (the one it comes with and heats) anytime we are gone for more than two weeks. I don't see this in the manual? Would we be better off getting a stand-alone water heater which we can just turn off when out of town?

Zman

I am not familiar with the EK line but, I seriously doubt your plumber is correct. You are leaving the home heated all winter, yes?

AtTheBeach

Yes, we'll be leaving the heat at 55 when not there. Supposedly because of Legionella?

EBEBRATT-Ed

Plumber has a point, but it has nothing to do with a condensing boiler. Any water tank could have Legionella if it has water in it and it's not heated

Jamie Hall

Well... no, you don't have to drain it. Keep it up to temperature, though.

That is, assuming that you either have someone to check the house every day (I mean it) to make sure that all is well, or you are prepared to replace everything that froze when the power went out. Which it does...

Zman

If legionella is a concern, run the water tank at 140 and mix it down to prevent scalding. Another option would be to turn the tank up to >140 when you return. I would certainly not drain the tank to prevent legionella.

SuperTech

Do not drain the tank or turn down the thermostat on it. Keep the tank at 140 degrees and use a quality thermostatic mixing valve like the one Caleffi makes. The boiler will only fire up a few times a day to maintain the temperature. 

motoguy128

I know Navien have an antifreeze function.  the trap is inside the cabinet.  I don’t see an issue. You could turn it down to 45f and not have an issue.  

Use a combi that has a little plate and frame instead of a larger internal storage tank.  

AtTheBeach

Thanks. It sounds like keeping it at 140 is the answer. So even if there is no "call" for hot water it'll be kept to that temp?

SuperTech

Yes. The tank has a thermostat that controls temperature. 

Solid_Fuel_Man

The higher the temp you keep the house (55 is a good number) the more time you get when something goes wrong. If the place is 45 then it doesn't take long to freeze.....

A condensing boiler is a fine choice. 

The Steam Whisperer

A condensing boiler in a building using very little heat ( setback temps and low heat loss) does sound like much sense. What good is the improved efficiency if the boiler is running very little. A simple, cast iron boiler with basic controls has a lot less to go wrong and will only use a small amount more fuel in this application. IMO, reliability and easy to repair is a much higher priority, especially in a home nor regularly occupied.

SuperTech

The Steam Whisperer said:

A condensing boiler in a building using very little heat ( setback temps and low heat loss) does sound like much sense. What good is the improved efficiency if the boiler is running very little. A simple, cast iron boiler with basic controls has a lot less to go wrong and will only use a small amount more fuel in this application. IMO, reliability and easy to repair is a much higher priority, especially in a home nor regularly occupied.

I couldn't agree with this more. Another thing to consider is the fact that a cast iron boiler will last much longer than anything else.

AtTheBeach

One of our top priorities was quiet as the boiler is located below the master bedroom and the kick on/kick off of the old one sounded like a 747. We have a few projects to do, including further insulation of that space.

Roger

It’s good to read everyone’s comments and to hear what is important to you in selecting your new boiler, @AtTheBeach . 

The Accel CS is just about as close to silent a boiler can get.  If you went away for a month, the high performance tank and heat exchanger can maintain the tank at 140F for less than one gallon of propane - there’s very little idle loss.  140F is appropriate to take care of legionella. 

For any unoccupied home, it is always advisable to monitor the temperate (and home) while away; either a friendly neighbor or some WiFi thermostats also have low temperature notifications.

As another option, our non-condensing boilers are also extremely quiet and use virtually all industry standard components (the ones that aren’t are easily bypassed for emergency heat and ease of service). The Accel CS is similarly designed, but like all condensing boilers, the primary burner and boiler control is not a typical service vehicle item. 

Please feel free to talk further with your heating pro, call Energy Kinetics at 800 323-2066, or of course post here for more information. 

Best,
Roger

Jamie Hall

I-d have to agree with most of what @Roger says, there -- even if he is a most convincing salesperson!

However.

I will say again what I said before: unless you have someone reliable to check on the structure -- on a daily basis in colder weather, perhaps less often in less bad conditions -- sooner or later the power is going to fail and you just won't know about it.

A dismaying number of folks are planning to rely on their wi-fi house monitor for this. This may work, if the failure is in the heating system (it does happen). It won't tell you about a power failure, because in a power failure the wi-fi won't be working -- either in the house or the internet connection (including cellular service) in the area. Or both.

At which point, the structure will freeze, and you will be none the wiser until you come to look at it later.

A friendly neighbour is a good idea, indeed -- although it could be any competent, reliable person in the area. However, may I point out that perhaps he or she might be discreetly compensated for their diligence, unless it is all in the family? When the power goes out at oh dark hundred Christmas Eve, he or she is going to have to get the truck out of the barn, plow their drive, like as not plow the Town road, plow your drive, check on the problem, and then do something about it. Or in some cases, go out on horseback -- or skis or snowshoes. Think about it.

WMno57

The modem, router, and thermostat require very little power. They could run for days in a power outage if you plug them into a small UPS (Uninterruptible Power Supply).

pecmsg

ASHRAE Recommends 140*F water for 1 Hour to kill the Legionella bacteria. If your going to be away then lower water temps are allowed as long as 140* is maintained for at least 1 hour before use. 

You can still use vacation mode 

Jamie Hall

WMno57 said:

The modem, router, and thermostat require very little power. They could run for days in a power outage if you plug them into a small UPS (Uninterruptible Power Supply).

Quite true. Which completely ignores the fact that the internet switchgear and amplifiers (for fibre optic or copper) and the cellular telephone system, for cell' 'phone coverage, will run for, in most cases, 8 hours maximum. If you're lucky.

Do not translate your urban/suburban thinking and experience to rural areas. It doesn't work that way. Sorry.

hot_rod

If it has a tank, I'd bet it will take a bit of fuel to keep a tank at 140F in a 55 space. Whenever the tanks is at 140 and ambient is 55 you have an 85° delta.
I'd guess 3° per hour loss, so if the tank operates off a 15° delta, every 5 hours it will need some heat input. So lets say every 5 hours the boiler will fire to raise the temperature from 125- 140F, the delta of the tank control. Depending on the boiler output, it would be a short run, maybe 15 minutes. A 92K boiler would use 23,000 BTU, 1/4 a gallon of LP.

Knowing the R value around the tank, you could calculate the amount of LP used over a period of time. I'd guess 1/2 gallon per day or more to maintain the tank at 140F??

Does this math sound correct?

Most indirect tanks claim less than 3° per hour loss, I think that test was done in a warm room, I've heard an 80° room

Maybe the boiler control has a way to record hours that the boiler is on a DHW call, that would give you a basis to calculate fuel usage, and cost to keep the tank warm.

So what is the lesser of two evils? pay the price to maintain a 140° tank, or shut it down and risk a potential bacteria growth. tough call.

Jamie Hall

Your math looks good to me, @hot_rod !

And perhaps to amplify a little on some of the discussion -- from practical experience in looking after several properties which are vacation or summer homes. We try -- very hard indeed -- to persuade people who keep their houses open in the winter (that is, not drained and winterized) to keep them at 55. Yes, it does mean more oil or LP. However, in the event of a "problem" -- which, as I say, always seems to hit at about 3 AM in a blizzard -- that gives us a little more time to scramble around and protect the place. The problem may be a power failure. It may be a boiler failing to light. It may be even a window broken by a tree falling. All of those have happened to us. If your structure is held at 45, it may well be dropping to if not below freezing before we can get there and do something about it. The extra 10 degrees makes it a little less frantic.

Roger

Thank you for your comments about estimating heat loss in our tank, @hot_rod . Even at 55° in the house, idle losses are minimal due to the heavy insulation and the heat trap built into the tank. It takes more than a day to cool off enough to fire a reheat cycle. 

Actual field and lab idle test results show that the fuel use will be less than a gallon of propane per month to maintain temperature at 68F ambient (no actual hot water use). In the Department of Energy Study https://www.bnl.gov/isd/documents/41399.pdf , an active household only uses about 1/2 gallon of propane a day equivalent (64 gallons/day of hot water with a 77F rise). 55F ambient will increases idle loss by maybe 20% vs 68F. So less than a gallon per month of propane is still a solid estimate for the idle state. 

@Jamie Hall , your 55F house winter storm scenario is solid advice to buy more time for the power to be restored. 

Roger

Solid_Fuel_Man

Wi-fi thermostats will give you a notification if the power fails. If the t-stat fails to communicate (power outage, internet failure, etc.) You get a notification. Then you you then call your go-to guy and have him check the place out. You can also have the notifications sent to you and your go-to guy simultaneously. Some even have enough smarts to see when they call for heat and the temp doesnt begin to rise as normal it will send a warning. Gives more time for the guy to check stuff out. 

They are pretty stone cold reliable for the $150 or so bucks they cost. 

There is always the red light in the window on the low temp thermostat we all know about too! That's as long as you have a neighbor who watches out for you. 

STEVEusaPA

To go in another direction, if it’s a vacation home, how much is it used in the winter? Public water or well?
I love hydronics, but maybe forced air is a better choice for this situation. A lot less to worry about, and easier to winterize, especially if 'the big one' is coming and extended winter power outages are likely.

AtTheBeach

Thanks for all these thoughtful (and thought-provoking) responses. We do have sensors plus a paid person who watches over nearby houses. Also considering a generator which the neighbors recommend. Re: hydronics vs forced air, the house exists with hydronic already, no ducting. We did briefly consider minisplits but the layout is choppy. In a perfect world that's what we would have built. It's very rural with well water and one of us would like to be up there in the winter more than the other. We're going to look into tankless before pulling the trigger on a condensing boiler.

nicholas bonham-carter

When selecting a generator, be sure the one you choose will produce the pure waveform needed for modern condensing boilers.
A tankless water heater is not a good substitute for a heating boiler, as they are designed for two different purposes.—NBC

scott w.

If you want to monitor the temperature and the electricity of a vacation home look at a sensaphone 400. All you need is a landline, program the sensaphone and plug it into the telephone jack. It will call you and tell you if the temp goes under what you set as a low limit or electricity is off. I would go away in the winter and worry the person checking the house would go in weekly and the heat would go off shortly after they left. Weekly checks are not enough in really cold weather . I found the Sensaphone Corporation which makes a great monitoring device. It is a bit confusing to read the programming instructions and the average person may have to read the instructions several times to get the jist of how to program it properly. It works really well and you can call your landline any time and the sensaphone will give the temperature and state the electricity is on or off.

Jamie Hall

The Sensaphone is a good unit -- and as you note it works even when the power is off. In most rural areas, if you have a wire landline at all, it just keeps working even when everything else is down.

And I agree -- once a week for your caretaker is not often enough in the winter. We try to hit the places we watch at least twice a week -- spaced out -- and immediately after any major storm (true 4 wheel drive trucks are very useful!)

WMno57

@scott w. Great idea! The telephone network has very high uptime.

"Many telephone service providers attempt to achieve dial-tone availability more than 99.999% of the time the telephone is taken off-hook. This is an often cited benchmark in marketing and systems-engineering comparisons, called the "five nines" reliability standard. It is equivalent to having a dial-tone available for all but about five minutes each year."

https://en.wikipedia.org/wiki/Plain_old_telephone_service#Reliability

Jamie Hall said:

WMno57 said:

The modem, router, and thermostat require very little power. They could run for days in a power outage if you plug them into a small UPS (Uninterruptible Power Supply).

Quite true. Which completely ignores the fact that the internet switchgear and amplifiers (for fibre optic or copper) and the cellular telephone system, for cell' 'phone coverage, will run for, in most cases, 8 hours maximum. If you're lucky.

Do not translate your urban/suburban thinking and experience to rural areas. It doesn't work that way. Sorry.

Jamie, Much of the cellular and internet infrastructure in the USA has both UPS and genset protection. Not 100% uptime, but probably higher than the electric grid.

Jamie Hall

"Much of the cellular and internet infrastructure in the USA has both UPS and genset protection. Not 100% uptime, but probably higher than the electric grid"

Quite true. In the last power outage around this area -- a couple of weeks ago -- the power went out right away. The internet lasted almost 20 minutes. The cell' 'phones lasted 8 hours. The copper land line? Never did go out. You use the land line to call the power company and the internet providers and the cell phone people...