Give U.S. smaller Mod-Cons!

Mike T., Swampeast MO

Please define "baseboard not keeping up".

From what you've told me you set the thermostat down considerably at night and again during the day. You say such works well in moderate weather but now I hear that you can't "keep up" in extremely cold weather.

If you size a mod-con--ANY mod-con--to near your actual loss and expect to maintain this sort of operation you will be sorely disappointed as NONE will "keep up".

ALH_4

Expectations

It seems like people expect more out of their indirect than a conventional water heater. For one, indirects are expensive compared to conventional water heaters. 40MBH with a 50 gallon will let two people who do not take long showers take showers back to back with a 2.5gpm shower head. Sounds fine to me.

-Andrew

Perry_2

Here is what I experience

I keep the thermostat set on constant during really cold weather (arround zero). The circulating pump never stops running - the boiler fires intermittently - and I cannot maintian temperature in some parts of the house (and much of the house on a really windy day - yes I still have some air leakage to seal up).

As was previously discussed - my boiler high temp limit is 150 F - and I should have been setting it higher so the baseboard would radiate more heat.

On the other hand - there is more than enough water temperature if I am circulating enough water. That is why I'm leaning towards the concept that my circulation flow may actually be quite low. My memory is also on days like this that the last radiator on the loop is noticably cooler as well (I only put thermometers on the pipes in Feb and we did not have much really cold weather).

With a Vicoden 200 and a Low Loss Header: If the boiler outlet is fixed at 167 F and I am running 10 GPM in the secondary loop: I am probably not going to see more than 150 F loop temperature anyway. On the other hand - with a new circulating pump, and perhaps a flowmeter, so that I know what the flow really is: It may be that 150 F will do just fine with adequte flow.

Perry

Josh_10

I'm with you Hot Rod. It is killing me inside but we are currently installing 200 gallons of hot water storage to provide a client with a 20 minute shower at 20GPM. We have to give them what they want but it is hard to watch them be so wasteful.

On a side note... How on earth do you lather up when the shower is hitting you from 10 different angles and you have a waterfall pouring on your head?

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Tony_23

well

150 is pretty low for supply temp. If you have 20 degree DeltaT the last bbd is seeing 135, maybe.

Flow is certainly important, but if you supplied another 10 deg on the coldest days it may keep up. I'd try and run constant circ on the system side and full reset on the boiler, with a mod/con.

Of course, it's all money out the window until you seal the drafts

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Mike T., Swampeast MO

I'm guilty of having one of those "car wash" showers myself with flow ability in that range.

How on earth do you lather up when the shower is hitting you from 10 different angles and you have a waterfall pouring on your head?

I don't and I don't believe anyone else who has used it does either. Lather up under one shower head--or just get wet and turn everything off and lather if you're doing the Navy thing.

Then I sometimes turn on a number of body sprays and the overhead, rotate a couple times and I'm perfectly rinsed. Works great when you're really dirty. Of course it's very possible to luxuriate when you're sore... Three massaging sprays from different directions and a number of high-velocity body sprays feel pretty darned good.

Perry_2

Do they wax and buff as well...

Gota ask: Do you come out all nice and shiny with a new coat of "armor polish"... to help you keep clean the rest of the day.

If so. Cool...

Perry

Mike T., Swampeast MO

If the boiler is cycling in such a period and you cannot maintain thermostat setpoint then you're not removing heat from the emitters rapidly enough.

Either your high limit of 150°F is too low or you have insufficient circulation. From the way you describe your system, the only ways circulation is insufficient is if the circulator is not functioning properly or if there is some sort of obstruction in the system.

With 150°F high limit you should be getting at least 34,500 btu/hr from your radiators (depending on flow and delta-t of course). Believe this is very close to your heat loss estimate. Something doesn't seem to be adding up. Perhaps the heat loss estimate is based on improvements that aren't yet complete? Perhaps the weather was WAY below design?

Mike T., Swampeast MO

No, but I can do a "steam clean" via Mr. Steam...

Ken_40

I'm not so sure...

indirects are all that much more. The sealed combustion mandate of water heaters has prices going from $150 for a plane-jane 40-gallon to almost $300 for the same thing with arrestor setup.

That same plane-jane unit had an unstated AFUE of around 60%, meaning of the stated ~34,000 BTU input, only provided ~20,000 BTU's of actual water heating.

Meanwhile, the condensing boiler with indirect cost a few bucks more, but delivers twice the gallonage of the plane-jane heater by virtue of the typically much higher input, coupled with the over 90% AFUE fuel efficiency!

A double home run IMHO!

ALH_4

Ok

I am certainly not disagreeing with the benefits of an indirect water heater. I just see potential for dissatisfied customers who thought they would have an endless shower or who have high flow rates. 120 gallon indirects are not inexpesive especially with respect to houses with 40,000 btu/h heat loads. $300 is a lot less than any 40gal or 50gal indirect I have priced, though I do not have much experience with anything but stainless steel tanks.

-Andrew

Perry_2

But how big do the inderects have to be?

I grabbed a bucket, a gallon jug, a marker, and a watch that counts by seconds.

2 gal of water into into the Bucket. Marked it.

Tested my showers - to see how long it took to fill the bucket. Or that was the intent. In reality I ended the test at 60 seconds.

Downstairs shower at about 1 GPM. Upstairs shower at about 2 GPM. I note that the upstairs shower has one of those oldie but goody - banned - 5 GPM heads on it (the one I like). Yet, all I get is 2 GPM from it. The downstairs shower has a modern "2.5 GPM" head.

Stuck a thermometer into the bucket for the upstairs shower - it seems I like my showers at about 110 F.

So if 2 people were taking showers at the same time it would be 3 GPM of hot water. I'm normally in the shower 10 minutes; 15 minutes if I want to soak.

So lets assume 45 gal of 110 F water. A 40+ gallon hot water tank would seem to be adequate even if there were two people in the house taking showers at the same time. That's about 27,000 Btu of heat input to recover - and who cared if it took a while to recover after the showers are done (and you would get 10,000 of that recovery in that 15 minute period with a 40,000 boiler). There is no other major hot water use for a while.

This makes more sense than buying a boiler that could fire at 107,100 Btu/Hr when the heating load is 40,000 Btu/Hr.

It seems to me that a 100 gal tank would easily allow 4 people to shower in succession (at 15 minutes per shower) and and might even allow 6 people.

It may pay to check assumptions about actual shower water flow. Measuring at actual flows and temperatues really allow you to zero in. You could also point out to someone who is concerned about cost the advantage of changing an actual high flow shower head to a low flow shower head.

Keep in mind that DHW tanks are normally held hotter than 110 F. Methinks I'll try and target mine lower than now - but with a larger tank (well insulated).

Perry

Gary Jansen_4

LLH header temperature

Remember, the low loss header is a mixing chamber. max mixed temp out of the header is 158 F. Also, as a former contractor, I hooked a lot of Vitodens 6-24's up to watermakers from 40 gallon to 120. All worked like a charm. Micro loads on any boiler can be handled with a buffer tank. I preferred to have the buffer on the return side of the LLH to lengthen the run time. Also, if you have ever watched a Vitodens operate with microloading, (had 1 that needed 1850 btu's for a towel warmer in the summer) it's a thing of beauty. Small pulses of heat to handle even the smallest load. I call it microbursting. It really is not short cycling. Regards, Gary

ALH_4

Exactly

That was my original point. Why do people have a smaller energy efficient house and then dump 10gpm or more of 100F to 110F water down the drain? Also why does it seem the 30 minute shower is common?

Yes, a small boiler can provide satisfactory performance for people who use water reasonably, which is most people I think. However some of the people springing for Viessmann boilers and DHW tanks also spring for fancy showers and large tubs. If it takes 30,000 btu to heat a 120-gallon water heater from 100 to 130, how will dhw priority work with a 40,000 btu/h boiler? Is a 45 minute recovery acceptable? If the boiler cannot be on priority for 45 minutes at a time, how long will it take to recover if it's not on priority? Can it be run without priority? Not on radiant floors without a mixing valve.

These situations are asking for complaints. As I see it, at some point the domestic is completely separate from the heating. Though, someone with low water usage as well as a small heat loss will be just fine.

-Andrew

ALH_4

Pulses

But a 6/24 is 80,000 btu. I am still not convinced of the benefit of a buffer tank with a condensing boiler. Plus you have the heat loss off the tank and you have to buy the tank. And if the burner shuts off and the lights again is that not a cycle? I think the Vitodens can handle this cycling as well as anything, but it still has to take its toll eventually. I still say let it cycle. I feel that many houses with hydronic heat are over-zoned. Towel warmers are crazy in the summer. Why fire up an 80MBH-200MBH appliance for a 2000 btu load? Almost certainly it takes more fuel to heat up all the distribution piping than it does to warm the towel. It's a good application for electricity on a timer in my opinion after having wrestled with this idea on a 15-60.

-Andrew

D107

running without DHW priority might work in some cases--

with average size homes and reasonable water use. (HO here.) Just met with a contractor today who echoed my concerns of a below-design day and a 45 dhw priority period. Says he's seen boilers get locked on DHW priority when people go away during the winter.

A 50 gallon indirect can take care of two consecutive 10 min showers and a hot wash load; with dhw priority it might take a few hours to recover on a cold day but if you can plan your hot water use ahead should be OK. Question then becomes how much of an effect will there be on space heating with the indirect adding to your heat loss during that time. Seems like a slight decrease in boiler output spread out over a longer time might be better than a complete dhw priority lockout for 45 min+ on a design day.

David

ALH_4

Sorry

Constantin,

I'm sorry I was jumping all over. I was talking about a project where I had a 15/60 and a towel warmer. We ended up going electric.

-Andrew