Boilers - Steam and Hot Water Systems - Over-firing?

A buddy who knows a lot more about boilers than I do was helping me replace a zone valve and when we got everything back up and running, I timed the firing duration to be about 13 minutes. He told me that was way too long, 3-4 minutes is typical, 5 at the very most. I timed the off portion of the cycle and not only was it only 6 minutes, but the temp gauge had only dropped 10 degrees to 170 even though the aquastat lo was set at 120.

Is 13 minutes too long to fire up to 180? I programmed my thermostat to run at 55 while sleeping, 60 for getting up in the am, and 65 in the evenings. We fire our wood stove, to about 70, many evenings when we are home, so the boiler doesn't have to fire at all. Still we burn 100 gals. in about 2 weeks. Do I have a real problem, or is this just par for the course?

No, your bud is a bit off base...

A cold system firing up could easily take 13 minutes or even longer, depending on the water volume in the system, to reach high limit of 180°. You are heating the cast iron in the boiler, all the water, all the piping, all the radiators...

In fact, 3-4 minutes is probably TOO SHORT.

The HIGH LIMIT has a built in 10-15° differential that is completely independent of the LOW limit... so the burner firing again at 170° is also perfectly normal.

The LOW limit and the DIFF dial work together to keep the boiler warm at a minimum temperature.

How do you heat your domestic hot water?

What model boiler is it?

Are you burning gas or oil?

And what kind of heat emitters in the house? Radiators? Baseboard? How many, how many feet, etc.

What's the heat loss of the house at design outdoor temperature? (This is a good thing to know and if you search around here you'll find some threads with tools to do it yourself.) The outdoor design cold temp for Kodiak is 13F.

The ideal boiler will run nearly continuously when it is at the design temperature outside. Less when it's warmer.

Short-cycling (<5 minutes on-time) is very inefficient, especially for oil-fired boilers. It takes a while for the flame to stabilize, the whole works to warm up as Trooper said, etc.

My unit is an oil-fired Weil-McClain Gold P-WTGO-4, heating 1100' sq. through 55' of baseboard. Design heat loss came out at 23,305, but this could be off because I just guessed at the R value of my walls and floor (15). We heat and store DHW in an Amtrol, I'm not sure of the size. We've also been having trouble with the Amtrol. We are either going to install a Quietside (already have a new one just sitting around) and configure it for DHW only, or look into setting up the Weil-McClain to heat it directly. I realize that's a whole different issue, but if anyone has any suggestions in that area, I'd like to hear them.

Is the Quietside a combo unit?...Even if not why would you run a high efficiency boiler for domestic water only when it could heat your house so much more efficiently than the Weil/Mclean...I am assuming the Quietside is gas fired???

The Quietside is oil fired and dual purpose. That's what I wanted to do originally. Then I was told that it would burn itself out trying to keep up unless I almost doubled my baseboard which is something I would rather not do.

Ridiculous.

55 ft of fin-tube has a nominal output with standard 180F supply water of 30,000 BTU/hr. If the house heat loss is 23,000 BTU/hr at design, then there's no need to add more baseboard unless your house gets cold when it's super-cold outside for extended periods (assuming the boiler is working properly).

For just heating the house, any boiler with a DOE output larger than about 30-40,000 BTU/hr is oversized.

I can only find info on the gas-fired Quietside DPW. But it comes in a 99,000 BTU/hr and a 120,000 BTU/hr model. The smaller one has basically three times more output capability than your house needs.

And either would do fine to make hot water.

The WTGO-4 has a DOE output of 145,000 BTU/hr. More than 4x what the house needs. Plenty of capacity for making hot water using an indirect water heater. A good 40-gallon indirect would work fine with that.

My Quietside says the input is 120,000 BTU with a max. temp. of 176 degrees on both Hydronic and DHW. The 176 max. temp. was given as the reason that I needed more baseboard. I'm also not sure on my heat loss calculation. How do I find the floor and wall R values? I think I figured them at 10-15. My house was built in the 50's on a subfloor with joists and pylons and skirted perimeter.

Xiphias: So it sounds like my Quietside is plenty to do the job as is. So, even if my heat loss estimate is off, I augment my heating with a wood stove anyway. So do you think I should be able to get through this winter fine with that set up and if the Quietside seems unable to keep up, add a little more baseboard before next winter? This would be good news.

Also, while I was out in the boiler room I timed a firing from 120 to 130 (I am assuming this was the differential NJ Trooper was talking about, except on the lo side. Is that right, is there a lo side diff. also?). It was just a little over 3 minutes. Maybe this is the type of firing my friend was thinking about.

It is basically impossible for the boiler not to "keep up." It puts out nearly four times more heat than you can distribute with your existing baseboard.

Think of it this way. Your house is a Tolman skiff and your boiler is a Cat 3208.

There are two ways to describe "not keeping up".

1) boiler smaller than heat loss. This happens incredibly rarely. Most boilers have output at least twice the heat loss. The American phenomenon of oversizing.

2) distribution system output smaller than the heat loss. You could have a nuke plant in your basement, but if the heat loss is greater than the max baseboard output ability, the house will cool off.

The short version is, with a 120k boiler and heat loss less than 120k, if your house is cold, add more baseboard. It's not the boiler's fault. Or just fire up the woodstove.

Is that right, is there a lo side diff. also?

Yes, and there is probably a DIFF adjustment in the aquastat.

Thanks, I'm really learning alot from you guys. So if my baseboard is sufficient while running my Weil Mclain, it will be sufficient with most any 180 degree source. Does lowering the water temp. to 176 have a drastic effect on the baseboard BTU output? What I found online was that an accurate baseboard BTU calculation is pretty in-depth--number of fins per foot and fin surface area, pipe material, etc. I saw that you used 600 BTU per foot to estimate mine. Did you pick that because it is in the middle of the range? Am I pretty safe using this figure in most applications? Is there a simple calculation?

NJ Trooper - So it seems that my hi and lo differentials are both set at about 10 degrees. I am assuming that if they are adjustable, then there is no hard and fast rule that they are more efficient either closer to or further away from the hi/lo setting. Is that right?

My main DHW issue is that my Amtrol has a leak. I think the inner tank must have had a leak when we bought the house, and now the outer tank sprays water all over the place, so I keep it shut off until we need it (what a pain).

My choices:
1) Should I replace the Amtrol and possibly sell my Quietside?

2) Should I install the Quietside and sell or give away the Weil Mclain?

3) I've also thought about electrioc DHW, but would have to get a contractor to convert my home from 100 amp to 200 amp service and wire 220 into my boiler room. (I bought the house as a fixer-upper and this might improve the resale.)

Any thoughts?

I used 550 BTU/ft for baseboard output. That's a commonly-used 'average' number.

Lowering from 180 to 176 will have essentially no impact. Imperceptible relative to other factors like how hard the wind is blowing, how many people are in the house (a human body is generally good for 250-500 BTU/hr...), whether the stove is on, etc.

I'm totally unfamiliar with the Quietside so have no basis for an opinion on whether it's a good option.

If the W-M is well-maintained, then my inclination would be to replace the Amtrol/tankless-coil with a ~40 gallon indirect water heater, a dedicated circulator for the indirect, and a control that allows priority for the indirect so that the full output of the boiler can be directed to making hot water for a few minutes, then go back to space heating.

One way to do that would be to use something like a Taco -EXP zone valve control, and plug in a PC700 outdoor reset module, too. That will allow the boiler to function more efficiently using lower water temperatures when the outdoor temperature is above the max cold design temperature. Bunch of threads around here on that. IMHO, it would be a nice upgrade for efficiency and comfort.

What aquastat is installed on the boiler?

I hope the leaks in the Amtrol aren't allowing the boiler water to mix with the domestic!

The aquastat is a Honeywell, Triple aquastat; L8124A,C; L8151. Those numbers are on the label inside the front cover. I know what you mean, I'm not sure if there is hydronic mixing with the domestic. Since this trouble came up, we have limited that water source to showers only. Otherwise we heat it on the stove.

The amtrol currently has its own circulator, so that's all set. If I go that route, I'll have to find out if it is set up to take priority or not. I'll price indirect tanks today.

Thanks.

NJ Trooper - So it seems that my hi and lo differentials are both set at about 10 degrees. I am assuming that if they are adjustable, then there is no hard and fast rule that they are more efficient either closer to or further away from the hi/lo setting. Is that right?

Since you are running an indirect, the LOW should be set as low as it can go. I would set the DIFF dial to 20, simply because 10 might give a really short cycle (like 3 minutes!) It's more efficient to let the firing cycle be a bit longer, let the water get a bit warmer, and then have that much longer of an OFF cycle... net result is about the same amount of fuel, but better for the equipment, and possibly a bit more efficient.

The DIFF setting on the HIGH side is FIXED, non-adjustable, so you get what you get.

Here's the thing though... because you are running an indirect, there is no reason (well, _possibly_ no reason) to be keeping that boiler warm 24/7. Switching to a cold start aquastat would make sense... if ... here's the reason... if your boiler doesn't leak when you let it cool off. Sometimes a boiler that has lived all it's life as a warm start will start to leak from the sections if allowed to cool off. Going to cold start will save a lot of fuel though.

I'm also not sure on my heat loss calculation. How do I find the floor and wall R values? I think I figured them at 10-15. My house was built in the 50's on a subfloor with joists and pylons and skirted perimeter.

When in doubt, it's probably best to err on the side of caution and enter a lower R value than you guess at. If the studwalls are standard 2x4 construction, then the most you can possibly have is R13. You said built in the 50's ... and I would be inclined to think that the insulation may not be up to par with modern stuff... and has probably settled, maybe gotten damp over the years from condensation, etc... so a conservative guess might be R8 for the walls?

The part about a subfloor on pylons though... is the underside of the subfloor insulated? Is it a dirt floor underneath? is the skirting somehow insulated? There might be huge room for improvement in insulation under the home... there could well be a lot of moisture infiltration... is there a vapor barrier? You might find that the best money you spend is on insulating the underside.

So this is off the boiler topic... but anyway...

If you are running an indirect, you would probably need at least 80K BTU to get decent recovery time on the hot water. And that's going to be more than the heat loss in the home.

I think I've been sold on pulling out the W-M and using both sides of the Quietside. I priced an indirect tank (I don't remember the make) at over $1300. We really don't have a need to store hot water with only the three of us. I spoke with a neighbor who has a WTGO-3 tankless and it has been working for him (although he also plans on installing a Quietside for better efficiency).

Since I really don't need a tank, I'd rather not try to keep cast iron at 120 degrees year round. The Quietside has a small (2 gal?) tank and aluminum heat exchangers, and it's already sitting there next to my brokren down Amtrol. I re-calculated my heat loss using R8 for the walls and R5 for the floor. I do not believe the underside is insulated. Only part of the floor has a vapor barrier (laminate floor installed), and the skirting is not insulated. I also entered .75/hr for air changes. I would have gone with 1, but my wood stove has a very strong draw, so I'm thinking the house isn't way leaky. With this calculation I have more like 31,500. I found out my baseboard is 580/ft.x55ft.=31,900.

Since I have a wood stove to use in the evenings, I figure if my estimates are still off, the stove should be plenty of buffer and I can add baseboard, if needed, next spring. Of course, this will be after I get some insulation under the house, which I might be able to get a start on before spring.

Does it sound like I have any major flaws in this plan, or is it a reasonable aproach?

Some thoughts.

An indirect water heater does not require the boiler to be hot 24/7. It can be what's known as 'cold start', which is quite common. The tank gets charged up when its aquastat calls for heat, then it goes back to heating the house. It's about the most efficient way to heat domestic water, and the good tanks will last a very very long time (hence the moderately high up front cost).

Not trying to sound anti-Quietside. I just know nothing about them in terms of performance and durability. If you go with this option, install it absolutely to the letter regarding piping, pumping, venting, etc. (And if you go for it, ask questions and share info here!)

A genuine 'Manual J' heat loss inherently overestimates the heat loss by anywhere from 10-30% when you apply reasonable assumptions.

There is no better investment, in terms of reduced heating costs and short payback time, than improving the building envelope by insulating and air sealing. There's a good DIY guide to this at the energystar.gov site. Here:

http://www.energystar.gov/ia/partners/publications/pubdocs/DIY_Guide_May_2008.pdf

And most insulation, windows, etc. are eligible for a 30% federal tax credit.

Just when I thought it was all settled in my mind, I ran into a guy who is not a plumbing contractor but works for one. He said he has installed several of the Quietsides and does not think it will get me much above 65 degrees through the winter here. That's about where I keep the heat set, but I don't like that being the max it will do.

We talked about different configurations. He suggested it might be an option to leave the W-M and add the Quietside into the existing system. Run the Quietside in the light months and summer for DHW with the W-M shut down, and bring it in during the heavier months. It seemed like a great solution to me. Or is this unreasonable?

IMHO, it's just ridiculous to have two combustion appliances when you only need one.

Clean and tune up the W-M.

If it's not already cold start, convert it so it is.

Get a good indirect with a dedicated circ. Check out HTP Superstor, Heat-Flo, Triangle Tube Smart, etc.

Get a Taco ZVC-EXP (which can do zone valves plus a circ for the indirect), and optionally plug a PC-700 outdoor reset control.

You will have a fine, reliable, efficient and comfortable heating system.

Okay, I just checked the local builder supply (the only one on the island). Their plumbing guy doesn't come in on Fri. and Sat. The person I asked is didn't know what I was talking about, asked someone else, and the only one they have in the store, they think is sold, but there are two replacements on order--due to come in some time in November. They said it is a Power Store Boilermate SW 240L, which gives me nothing on Google. I called the only hardware store on the island and they don't stock indirect tanks, but someone in purchasing is checking to see if they can order one. I am assuming it will have to come in on the weekly barge and wouldn't make it in for 3-4 weeks. I'll have to see what they come up with.

Next problem. Besides changing out the aquastat, what needs to happen to make my W-M a cold start if the cast iron leaks?

Quietsides and does not think it will get me much above 65 degrees through the winter here.

I'm not suggesting/condoning anything here, I know nothing about the Quietside boilers... but:

How/why on earth would a 120K BTU boiler not be able to heat a home that has a heat loss of your stated/estimated 32K BTU? or even 60, or 90, or for that matter 120?

If you can produce 120K BTU, and you HAVE THE HEAT EMITTERS to put the heat into the home, then why on earth? or even why in Alaska?

I don't get it.

It sounds more to me like the examples he worked on were UNDER RADIATED. Because if your heat loss exceeds the capacity of your radiation, there isn't a boiler big enough to heat your home. Even Xiphias 'nuke plant'... if you can't move the heat into the home, it just doesn't matter how big a boiler you install.

Boilermate SW 240L

Sounds like Amtrol to me! I wonder if it's a 'branded' item, made by Amtrol, sold by someone else.

If you use the L7224U aquastat, you can turn the warm start on or off... so turn it off and run it as a cold start. If you have a problem with 'weeping' (odds are you won't), then turn the warm start back on.

I don't get it either. It's like I'm in the Twilight Zone up here every time I try to get heating info. I get a far different story from everyone I talk to and it has me scrambled. I really am grateful you guys are on here giving advice. I've only been on here twice, but both times the feedback I receive is pretty well centered and all in the same ballpark. I really don't know what the deal is up here.

That's good news about the aquastat. Again, up here I was told I would need a new one. I am having a local plumbing store order a Crown MS40 for me on Monday (it won't be here until 11/11). This was after I passed on their suggestion that I have them install a Toyo 180for $3500-3800. They also showed me a Honeywell AQ200 they would set up with two zones for $1200-1500. I like what it does, but if I go with that, it won't be for a while.

One of the plumbers at this shop told me it was definitely worth a try to set up the W-M as a cold start. He mentioned that condensation might be an issue. He also said that he thinks that if it has spent most of its time with a lo of 120, then the chances of the cast iron not leaking are really good. I was very surprised to hear him say that.

Jeeze... I know you are out in the boonies... gotta git yer supplies from a barge or a ski plane, but some of those prices seem way way outta line!

He mentioned that condensation might be an issue

Probably not... what did you say you have, like 60 feet of fin-tube baseboard? That stuff heats up pretty fast... the problem is more prevalent with systems that have a large volume of water/cast iron, where when the boiler fires, it takes a half hour for the system to come up to temp.

ALL systems condense... but as long as you can keep the condensing time to a minimum, and then it gets hot enough during the cycle to dry out again, there's really no big deal.

Acid is only corrosive when mixed with water... so if it dries out during the cycle, yer good ta go.

When the system is cleaned after the heating season, you may notice a bit more 'crud' inside... that should be about it.

AQ251... a few price snippets...

Patriot Supply - (http://www.patriot-supply.com/search_new.cfm?q=aq251*&search=Go)

The MS-40 is a good tank.

Nate, can you snap a couple pics of this install so we can see what the larger context is (e.g., piping, venting stuff)?

This might also be a good time to add the Taco zvc-exp with room for the pc-700. that will give you similar functionality to the AQ stuff for a lot less.

I will take pics of the install. I am also thinking about a side wall venting kit so I can tighten up my boiler room. Should I use this thread or make a new one for the install?

Keep this thread.

If you can both bring in combustion air from outside and vent to outside, that's great. The major gain for building tightness is using outside air for combustion so the boiler isn't sucking in air from wherever it can get it from the house. For the Weil-McLain, however, this would mean some kind of fan in a can set up, and they can be noisy, require a fair amount of maintenance, etc.