Since you're only firing every 4 or 5 days, the boiler is repeatedly going from room temp to full operating temp, doesn't this process stress a boiler? I would like to get rid of our propane bill by some day adding storage and heating our DHW with the boiler, but these fluctuations seem troublesome. Wondering if I'm better off with an efficient electric water heater for summer.
summer firing for DHW
- Thread starter tjvt
- Start date
-
Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.
We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.
We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.
- Status
Kind of had that in the back of my mind too - but I don't think it's that much more stress than it sees in heating season. I think in heating season, my boiler cools off to around 100f or so between firings. And with mine, in the warm weather, it seems to take a bit longer to get up to full temp I think due to decreased chimney draft. The fire sure seems lazier anyway. Then again I'm likely overdue for an ash cleanout too.
Last year I didn't burn in July & August. This year I'm still doing it, and getting 6-7 days between burns since I tidied up my insulation job a bit (still have a bit to do though) and added a FPHX. It was 4 days max last year. I'm now thinking that I'm not worrying about being hard on the boiler - and that maybe the weekly fires are keeping possible moisture out of it from sitting in humid summer air.
But as far as saving money goes, I don't think I'm that far ahead in that department - near as I can tell, it only cost us around $25/mo for those two summer months last year to do our DHW with the 80 gallon electric tank. So $25/mo for electricity, vs. wood at around 3/4 cu.ft./day, from what I'm doing anyway.
Last year I didn't burn in July & August. This year I'm still doing it, and getting 6-7 days between burns since I tidied up my insulation job a bit (still have a bit to do though) and added a FPHX. It was 4 days max last year. I'm now thinking that I'm not worrying about being hard on the boiler - and that maybe the weekly fires are keeping possible moisture out of it from sitting in humid summer air.
But as far as saving money goes, I don't think I'm that far ahead in that department - near as I can tell, it only cost us around $25/mo for those two summer months last year to do our DHW with the 80 gallon electric tank. So $25/mo for electricity, vs. wood at around 3/4 cu.ft./day, from what I'm doing anyway.
This is interesting to me, as the summer firing scenario is similar to running with storage, just more extreme. I'd really like to see some long term data on boiler life when kept consistently hot (no storage) versus starting and stopping (with storage).
Do you guys have a boiler protection setup? I thought that was supposed to prevent this sort of thing.
Yes, protection is there. But you still need to heat the boiler up from whatever it has cooled off to (70°), up to operating temperature. I think that wider overall boiler temp swing is what the OP was asking about. The return water is still coming back at 140°.
EDIT: Will also add, that it doesn't come back at 140, until the boiler gets warm enough to kick the pump on. Which is also a bit longer at the cooler start temp. Until it gets warm enough, mine does circulate some by convection during which time much cooler water is coming in the bottom (maybe 90-100°?). But that doesn't last long before things get warm enough to kick the loading pump on.
EDIT: Will also add, that it doesn't come back at 140, until the boiler gets warm enough to kick the pump on. Which is also a bit longer at the cooler start temp. Until it gets warm enough, mine does circulate some by convection during which time much cooler water is coming in the bottom (maybe 90-100°?). But that doesn't last long before things get warm enough to kick the loading pump on.
There's not that much water to heat up in a boiler, is there? It should get up to temp pretty fast. Aren't you heating up storage for dhw in the summer?
In any event, though I don't have a wood boiler, I think for the operating cost of an efficient electric water heater, taking a break from futzing around with wood for the summer would seem nice. Plus, you're outside more and you smell more of the wood smoke.
In any event, though I don't have a wood boiler, I think for the operating cost of an efficient electric water heater, taking a break from futzing around with wood for the summer would seem nice. Plus, you're outside more and you smell more of the wood smoke.
You're pretty well right about all of that. I think it's around 20 minutes from the time I light until the pump starts. Heating storage, yes.
I was pretty well decided I would stop burning somewhere around a month ago. But a few little things have kept me burning. Tightening up my insulation has improved things greatly from last year w.r.t. too much warmth in the house from burning, and I only have to do it once a week. I am usually away for 3-4 weeks in August - that won't be happening now. I have some trash wood around & old pallets to get rid of - running a wheelbarrow full at a time into the basement every couple of weeks is picking away at that, while displacing $25/mo of electricity (almost a non-factor, but $25 is $25). And, we haven't had much real summer weather here yet.
And I don't smell any wood smoke - ever.
maple has got his stuff together.
i too am getting 7 days of DHW this summer. i would not be burning however if i had an electic hot water heater. i would love to install HWHP and likely will next summer. my indirect tank was brand new along with the oil boiler when i bought the house so i left them in place. i use about a cord through the summer. the varms are lightweight and i think only 20-something gallons of water. they heat up quick and start pumping hot water to storage in short order.
i will echo that there is never a smoke smell. slight roasty if the wind is right, kinda like chestnuts after you take them off the heat. but not smoke so long as there is gasification.
so who has the oldest running boiler that has been heating DHW through the summer?
i too am getting 7 days of DHW this summer. i would not be burning however if i had an electic hot water heater. i would love to install HWHP and likely will next summer. my indirect tank was brand new along with the oil boiler when i bought the house so i left them in place. i use about a cord through the summer. the varms are lightweight and i think only 20-something gallons of water. they heat up quick and start pumping hot water to storage in short order.
i will echo that there is never a smoke smell. slight roasty if the wind is right, kinda like chestnuts after you take them off the heat. but not smoke so long as there is gasification.
so who has the oldest running boiler that has been heating DHW through the summer?
Tell me why you folks believe you are stressing the boiler by heating it up from room temperature to operating temperature every three or four days. Depending on your high limit setting your boiler doesn't get any hotter than 180 -200 degrees F and that's far below any temperature used to stress or stress relieve steel. Yes, the refractory sees much higher temperatures but heating and cooling it is not what causes it to fail. The refractory is very porous which causes it to be a poor conductor of heat thus only a small area is at the 2000 degrees or so and the heat only penetrates to a shallow depth. That's why it works. If it were 90% alumina the heat would penetrate completely through and then you'd see some stress in the form of shards of ceramic popping all over the place.
As for heating DHW with wood in the summer, I've tried it. Charging 500 gallons of storage every three or four days. It not only leaked heat into my basement which stratified up to the living space I was cooling it also was costly. On average, people heating DHW with wood use about a cord per season. If you buy your wood cut split and delivered your average cost is $180.00/cord. I have seriously checked operating costs for my Geyser HPWH with a Kill a Watt meter and it's costing me 77 cents a day or $24.00/month @ .15/KWH. That means I can run my Geyser for 7 months for the cost of a cord of wood.
As for heating DHW with wood in the summer, I've tried it. Charging 500 gallons of storage every three or four days. It not only leaked heat into my basement which stratified up to the living space I was cooling it also was costly. On average, people heating DHW with wood use about a cord per season. If you buy your wood cut split and delivered your average cost is $180.00/cord. I have seriously checked operating costs for my Geyser HPWH with a Kill a Watt meter and it's costing me 77 cents a day or $24.00/month @ .15/KWH. That means I can run my Geyser for 7 months for the cost of a cord of wood.
As for stressing the steel I believe that's a non issue. For the Jetstream, with its large refractory base, after 30 plus years of operation have consistently shown long periods of no fire. After 7 days or more I have to go through a 30 minute warm up, burning about 8 lbs of wood with no forced combustion air, only draft inducer this allows the refractory a more gradual rise in temperature to full operating temperature . Even sitting for 7 days or more, the unit can be into full gasification mode in 5 minutes but when starting the next fire, small pieces of refractory will be found in the bottom of the burn chamber. Just think about pouring water on the remains of a campfire and listen to the rocks pop , taking refractory from 60 degrees to 1,350 degrees in 5 minutes or less causes very rapid expansion. When allowed a slow 30 minute warm up there are no small refractory pieces to be found in the bottom of the burn chamber before the next fire .
Doing a refractory repair the oval shape is the burn chamber .
![[Hearth.com] summer firing for DHW](https://www.hearth.com/talk/data/attachments/135/135505-f1773ed37d382fc6ba914bfa1fbe5a48.jpg?hash=tjpslNit5b "[Hearth.com] summer firing for DHW")
The rectangular shape contains the tunnel or nozzel ,which sits below the heat exchanger fire tubes, and the pipe is for the forced preheated combustion air .
![[Hearth.com] summer firing for DHW](https://www.hearth.com/talk/data/attachments/135/135507-28afea9509d47ed9c27984b518b4a6ed.jpg?hash=ZSNRfpL9rf "[Hearth.com] summer firing for DHW")
Doing a refractory repair the oval shape is the burn chamber .
The rectangular shape contains the tunnel or nozzel ,which sits below the heat exchanger fire tubes, and the pipe is for the forced preheated combustion air .
I burn 100 pounds of wood every Sunday and take my unpressurized storage from 45 to 85c top temp. I can feel the heat in that corner of the basement for most of the day, but it doesn't seem to affect the upstairs much with all the windows and all that are open in the summer.
I have 820 gallons of storage and one area where I think using storage for DHW excels is the unlimited hot water I have in between burns. I usually take 2 showers a day, my wife one, and my son takes a full bath each night. I remember the days of taking showers with my tankless coil oil furnace and feeling the water temps shift up and down (plus hearing the furnace kick on and off during the shower). I'll never go back. I don't know how an electric hot water heater compares to that - most of my showers are in the 10-15 minutes range.
I have an anti scald valve on my dhw output that is set at 120f. When I take a shower on Sunday nights, I may have to move the handle about 5/8 towards full hot as the tank is at max temp. By Saturday night a week later, I may need to put the handle almost to full hot to get it the way I like it. I've never been able to take a long enough shower to see it affect the storage tank temp. I think I lose more heat in standby loss than I do by moving water through the dhw coil. If I have hot water when I start a shower, I'm either to going to have hot water at the end of the shower or I am going to drown.
I thought it might be fun to play with a heat pump to heat my storage, but we have a TV room in the basement and if it is below 70 down there (which is always) my wife watches TV wrapped up in her favorite blanket. I'm afraid a heat pump would make it too cool down there for her to be comfortable off heating season - or I would need to turn the heat on in the TV room during the summer which would be nuts.
I just did a clean up of the boiler this week and my refractory isn't showing any sign of wear yet.
I have 820 gallons of storage and one area where I think using storage for DHW excels is the unlimited hot water I have in between burns. I usually take 2 showers a day, my wife one, and my son takes a full bath each night. I remember the days of taking showers with my tankless coil oil furnace and feeling the water temps shift up and down (plus hearing the furnace kick on and off during the shower). I'll never go back. I don't know how an electric hot water heater compares to that - most of my showers are in the 10-15 minutes range.
I have an anti scald valve on my dhw output that is set at 120f. When I take a shower on Sunday nights, I may have to move the handle about 5/8 towards full hot as the tank is at max temp. By Saturday night a week later, I may need to put the handle almost to full hot to get it the way I like it. I've never been able to take a long enough shower to see it affect the storage tank temp. I think I lose more heat in standby loss than I do by moving water through the dhw coil. If I have hot water when I start a shower, I'm either to going to have hot water at the end of the shower or I am going to drown.
I thought it might be fun to play with a heat pump to heat my storage, but we have a TV room in the basement and if it is below 70 down there (which is always) my wife watches TV wrapped up in her favorite blanket. I'm afraid a heat pump would make it too cool down there for her to be comfortable off heating season - or I would need to turn the heat on in the TV room during the summer which would be nuts.
I just did a clean up of the boiler this week and my refractory isn't showing any sign of wear yet.
Duct the HPWH into the living space! I finally did this and could not be more pleased with the results! It cools our bedroom and produces about a gallon of condensate/day. We have frighteningly simmilar hot water demands, right down to the son's bath......
TS
I haven't used my electric water heater in three years 
the heating elements are burnt out and I haven't bothered to replace them. The boiler don't get much cooler between fires than it does in the winter. I use about half a cord for summer dhw. I burn about once a week.
the heating elements are burnt out and I haven't bothered to replace them. The boiler don't get much cooler between fires than it does in the winter. I use about half a cord for summer dhw. I burn about once a week.Talking about the Geyser. Would it be more efficient to put it in the attached garage adjacent to the basement?
Very hot and humid in garage in summer months. I would think the geyser would produce better there than in a cool basement.
gg
Very hot and humid in garage in summer months. I would think the geyser would produce better there than in a cool basement.
gg
Hold on a second,
You're saying you can get 3-4 days of hot water without storage?
And Coal reaper is getting 7?
Does any body shower or wash clothes
Do you guys have indirect tanks, or a coil in the boiler?
I am firing up at a minimum, once a day but more likely twice a day and sometimes 3.
I am charging a SuperStor 40 indirect which is set to 125*
I have the boiler shut off at 205* and it usually swings to 210*, then I go out and shut the power off.
But after 4 showers or a couple loads of laundry the boiler will be down to 140-150* so I turn on the power and relight it.
If I don't refire and it drops down to 120-130* it seems that the circ pump keeps running and it takes a long time to satisfy (if it even does) the stat on the indirect.
My boiler is in the attached garage, with 75' of insulated pex running along the basement ceiling over to the primary loop on the wall of the basement next to the oil burner and where the indirect tank is too.
You're saying you can get 3-4 days of hot water without storage?
And Coal reaper is getting 7?
Does any body shower or wash clothes
Do you guys have indirect tanks, or a coil in the boiler?
I am firing up at a minimum, once a day but more likely twice a day and sometimes 3.
I am charging a SuperStor 40 indirect which is set to 125*
I have the boiler shut off at 205* and it usually swings to 210*, then I go out and shut the power off.
But after 4 showers or a couple loads of laundry the boiler will be down to 140-150* so I turn on the power and relight it.
If I don't refire and it drops down to 120-130* it seems that the circ pump keeps running and it takes a long time to satisfy (if it even does) the stat on the indirect.
My boiler is in the attached garage, with 75' of insulated pex running along the basement ceiling over to the primary loop on the wall of the basement next to the oil burner and where the indirect tank is too.
I can get 6-7 days between firings. I still have a couple spots to improve my insulation on, not sure when I'll get round to that.
When firing I charge my 80 gal. electric HW tank to around 145-150. (Between burns the stat is 20° lower). I also have more insulation added to it. It goes a long time before it needs heated again. It heats with a flat plate HX & sidearm in series (didn't plan it that way 100%, it just turned out that way). I also have about 2 rolls of pex inside my storage enclosure, most on top of the top tank, that all my DHW runs through before it hits my electric. I get a lot of DHW heat out of just doing that. My storage is down to about 90/115 before I burn again.
When firing I charge my 80 gal. electric HW tank to around 145-150. (Between burns the stat is 20° lower). I also have more insulation added to it. It goes a long time before it needs heated again. It heats with a flat plate HX & sidearm in series (didn't plan it that way 100%, it just turned out that way). I also have about 2 rolls of pex inside my storage enclosure, most on top of the top tank, that all my DHW runs through before it hits my electric. I get a lot of DHW heat out of just doing that. My storage is down to about 90/115 before I burn again.
i charge trying to just about kiss 200*F. day 7 there is ZERO hot water to recharge my indirect. water coming from storage is down to 120 or so. clothes wash is with cold water. dishwasher goes every night. wife and i get a shower a day and each of two kids bath every other day.
what helps? 5" spray insulation on tanks and spray foamed trench to house. and diffusers maybe? and the BUMBLE BEE! seriosly, that HEC-2 (or similar run at set-point) works very nice to bring heat from storage to house. when there is a call for heat that thing cranks at 6GPM and then backs off down to 3GPM in order to maintain 130* going back to the storage tanks. this clears the lines fast to get hot water to the house and then settles everything down for good stratification. i had it at 120* last summer but in the winter it wasnt enough to satisfy. see pump curve attached.
what hurts? my oil boiler is in the loop. i have the flue blocked off to minimize heat loss but the whole boiler still cycles temp every time i recharge DHW.
infinity mike is likely seeing a good deal heat loss of the stack. the WG is essentially your only storage tank, correct? i know those things aint insulated much if at all either...
what helps? 5" spray insulation on tanks and spray foamed trench to house. and diffusers maybe? and the BUMBLE BEE! seriosly, that HEC-2 (or similar run at set-point) works very nice to bring heat from storage to house. when there is a call for heat that thing cranks at 6GPM and then backs off down to 3GPM in order to maintain 130* going back to the storage tanks. this clears the lines fast to get hot water to the house and then settles everything down for good stratification. i had it at 120* last summer but in the winter it wasnt enough to satisfy. see pump curve attached.
what hurts? my oil boiler is in the loop. i have the flue blocked off to minimize heat loss but the whole boiler still cycles temp every time i recharge DHW.
infinity mike is likely seeing a good deal heat loss of the stack. the WG is essentially your only storage tank, correct? i know those things aint insulated much if at all either...
Attachments
![[Hearth.com] summer firing for DHW](/talk/data/attachments/136/136471-ff71cb83fcf8a3fc3295e5f4001043b4.jpg?hash=ES1qlakNFq)
im, does that thing cyle a lot when you are burning or do you run small loads? im am trying to get rid of some 16" black birch now and it takes me 3 loads to fully charge as the bottom of tanks ends up quite cool like maples. the only time i do 3 full loads in a day is when its below 10* outside.
Ok I don't feel so bad,
I was reading this off my cell and it doesn't show signatures.
Now being on the pc, I can see that Coal Reaper has storage and so does Maple, BUT does the OP have storage?
I DO NOT have storage. Just the 60 gallons in the Wood Gun and the 40 gallons in the indirect.
To answer your question Coal Reaper, NO it doesn't cycle or idle alot.
I burn very small batches of pallet blocks, 4"x4"x4", I put about a 10 - 14 blocks at a time.
When the Wood Gun reaches 205* It shuts down automatically but then I go and kill the power to it so it doesn't try and turn back on when the 30* differential trips.
I was reading this off my cell and it doesn't show signatures.
Now being on the pc, I can see that Coal Reaper has storage and so does Maple, BUT does the OP have storage?
I DO NOT have storage. Just the 60 gallons in the Wood Gun and the 40 gallons in the indirect.
To answer your question Coal Reaper, NO it doesn't cycle or idle alot.
I burn very small batches of pallet blocks, 4"x4"x4", I put about a 10 - 14 blocks at a time.
When the Wood Gun reaches 205* It shuts down automatically but then I go and kill the power to it so it doesn't try and turn back on when the 30* differential trips.
This a video I shot last summer.
I do say in there that I can get 12-14 hours between burns, That is true if there is minimal water usage, like if I bring everything to temp at 5:30 am and then my wife does a load of laundry or runs the dishwasher. it may be down to 150* ish when I get home form work, So I will charge it.
BUT when the evening comes and we all take showers, it will need to fire it up again. and that will last the overnight and be at about 170* just from its own heat loss.
I do say in there that I can get 12-14 hours between burns, That is true if there is minimal water usage, like if I bring everything to temp at 5:30 am and then my wife does a load of laundry or runs the dishwasher. it may be down to 150* ish when I get home form work, So I will charge it.
BUT when the evening comes and we all take showers, it will need to fire it up again. and that will last the overnight and be at about 170* just from its own heat loss.
I'm only charging my storage up to 180 or so. If I push 185 I can usually get 7 days no problem, but if I only do 175 or so I will be streatching it to get 7. Likely only a warm shower on day 7 - which is OK this time of the year. Storage seems to drop just under 10° a day when not burning - like 8 or 9°. Looking back I know I could improve things if I can get more insulation stuffed under my tanks - I kind of rushed & glossed over that at the time, just stuffed some pieces of foamboard under where they would fit. I plan to get a couple bags of cellulose & try to jam some in from one side. Nothing like hindsight....
- Status
Similar threads
