pressurized storage how many days between fires?

[2.beans]

i have two 500 gallon tanks and was wondering how i stack up to everyone else. i brought the tanks up to 170* sunday AM and needed a fire tuesday PM. tank temp was down to 115*. this is just for my dhw, {three of us in the house} . am i way off? im thinking i didnt insulate well enough. i used 2" foil back sheets tops and sides then filled the inside with pink insulation almost to the top. i do need to tighten up the seems a bit but wanted some input before i sealed it up. thanks

 

[jebatty]

Without commenting on the insulation, it all depends on how much hot water you use. If you use enough, you could be firing daily. Do you have low-flow on everything? Shower rather than bath? "Navy shower" rather than the flood for a half hour? Shut off the tap or let it run? Use dish wash/rinse pans rather than let the faucet run to wash/rinse dishes? Wash dishes by hand rather than a dishwasher? Have low water use washing machine? Wash clothes with cold water? Are your hot water pipes insulated? etc.

 

[Nofossil]

i have two 500 gallon tanks and was wondering how i stack up to everyone else. i brought the tanks up to 170* sunday AM and needed a fire tuesday PM. tank temp was down to 115*. this is just for my dhw, {three of us in the house} . am i way off? im thinking i didnt insulate well enough. i used 2" foil back sheets tops and sides then filled the inside with pink insulation almost to the top. i do need to tighten up the seems a bit but wanted some input before i sealed it up. thanks

Quick back-of-the-envelope calculation:

Typical family of four, not doing any extraordinary energy saving measures will use about 60,000 BTU worth of hot water per day. Being generous, you got three days of hot water out of a 450,000 BTU tank charge. I would say that your standby losses likely exceed your hot water usage.

I insulated my storage tank with 12" minimum on the sides and 24" on the top, Multiple layers, carefully sealed against infiltration. With the temperature differential that you have between a 170 degree tank and the outside air, your storage needs to be MUCH better insulated than your house.

 

[2.beans]

Without commenting on the insulation, it all depends on how much hot water you use. If you use enough, you could be firing daily. Do you have low-flow on everything? Shower rather than bath? "Navy shower" rather than the flood for a half hour? Shut off the tap or let it run? Use dish wash/rinse pans rather than let the faucet run to wash/rinse dishes? Wash dishes by hand rather than a dishwasher? Have low water use washing machine? Wash clothes with cold water? Are your hot water pipes insulated? etc.

we didnt run the dishwasher (my wife does most of the dishes in the sink) or use hot water in the washing machine, took normal showers and drew baths for my four year old. im thinking i need to do more insulating, im sure nofossil hit it right on the head ,but im still wondering what results anyone else has had so far.

 

[Vtgent49]

I can get two days from an 80 gals tank, with 2 people, so I'd say you should gets lots more than that. I agree that the large delta T causes quite rapid losses. However, I'd also look carefully at your setup to see if there is any chance of a reverse thermosiphon action that might cool your tank. You need both good check valves, and pipe insulation, to stop the heat source from sucking the heat out, when the fire is off. Or the heat can rise inside your DHW pipes, and possibly find a way to circle back down.

Also, a tempering valve can cut the HW usage especially when you have 170, and only want 108 or whatever.

 

[2.beans]

my dhw has its own zone off from my primary loop that runs into a superstore tank, but the thermosiphion may be my issue. my primary circulator doesnt have a internal flow check and there isnt a flow check on the return side to the tank. ill try a ifc pump tonight.thanks for the idea.

 

[chuck172]

Off the subject but You mentioned IFC pumps. I'm curious if all Taco 00 pumps, even the older ones, are IFC.

 

[Nofossil]

my dhw has its own zone off from my primary loop that runs into a superstore tank, but the thermosiphion may be my issue. my primary circulator doesnt have a internal flow check and there isnt a flow check on the return side to the tank. ill try a ifc pump tonight.thanks for the idea.

The thermosiphon possibility is a good thing to check. Easy to tell - the pipes will be hot.

Taco does not have check valves in all their circs - the part number will contain 'ifc' if it has one.

 

[russlaw]

Being new to this forum, I’m not sure where I should ask this question but I’ll put it out here and hope I can get some discussion. I just purchased an EKO-40 and have limited space for thermal storage. I am looking at the possibility of installing a used 500 gallon propane tank for a pressurized system. I found an old study (1979-80) for NASA where sand was used for heat retention. In this case they used 1 ½ inch metal pipe surrounded by 6 inches of sand. The study is extremely detailed and way beyond my grasp but after reading some of this my thought was to pressurize the tank and check for leaks etc. and when everything checked out satisfactorily, build a frame around the tank and insulate the frame (maybe 6-8 inches of the hard foam insulation) and leave at least a 12 inch space between the tank and insulation for sand. The sand will absorb and retain the heat better than the insulation and some of that heat should transfer back to the tank when the cooler water is circulated back in the tank. Someone told me that this method was used in Alaska but I haven’t been able to find any information. Has anyone seen anything like this? Any thoughts?

 

[Nofossil]

Being new to this forum, I’m not sure where I should ask this question but I’ll put it out here and hope I can get some discussion. I just purchased an EKO-40 and have limited space for thermal storage. I am looking at the possibility of installing a used 500 gallon propane tank for a pressurized system. I found an old study (1979-80) for NASA where sand was used for heat retention. In this case they used 1 ½ inch metal pipe surrounded by 6 inches of sand. The study is extremely detailed and way beyond my grasp but after reading some of this my thought was to pressurize the tank and check for leaks etc. and when everything checked out satisfactorily, build a frame around the tank and insulate the frame (maybe 6-8 inches of the hard foam insulation) and leave at least a 12 inch space between the tank and insulation for sand. The sand will absorb and retain the heat better than the insulation and some of that heat should transfer back to the tank when the cooler water is circulated back in the tank. Someone told me that this method was used in Alaska but I haven’t been able to find any information. Has anyone seen anything like this? Any thoughts?

Welcome to the forum.

Good question for a first post, but this should really be a new topic. A search of older threads will turn up some discussion of the relative merits of rocks and water as heat storage mediums. Bottom line: If you can use water, it stores far more heat per pound and per cubic foot than rock. It's much easier and faster to transfer heat into and out of water as well. Rock or sand will store heat, but my sense is that you'd be better served by using the space for additional insulation to reduce standby losses.

 

[leaddog]

i have two 500 gallon tanks and was wondering how i stack up to everyone else. i brought the tanks up to 170* sunday AM and needed a fire tuesday PM. tank temp was down to 115*. this is just for my dhw, {three of us in the house} . am i way off? im thinking i didnt insulate well enough. i used 2" foil back sheets tops and sides then filled the inside with pink insulation almost to the top. i do need to tighten up the seems a bit but wanted some input before i sealed it up. thanks

One thought. when you say that you brought the temp up to 170* you may only have brought up the top of the tank that high do to stratification. therefore you wouldn't have as much stored btu's as thought. the bottem might have been only 120*.
leaddog

 

[bbb123]

i have two 500 gallon tanks and was wondering how i stack up to everyone else. i brought the tanks up to 170* sunday AM and needed a fire tuesday PM. tank temp was down to 115*. this is just for my dhw, {three of us in the house} . am i way off? im thinking i didnt insulate well enough. i used 2" foil back sheets tops and sides then filled the inside with pink insulation almost to the top. i do need to tighten up the seems a bit but wanted some input before i sealed it up. thanks

800 gallon storage I usually get 6-7 days I ran last Fri. morning up to 170 I'm at 110 now Thurs aft. Two girls wife and myself I do the quick shower but they used the 2 person Jacuzzi tub a couple times this week. Your losing heat somewhere.

 

[2.beans]

im am losing heat somewhere for sure, i have gages everywhere and the bottom of my tanks was at 160* return to my boiler. i didnt have time to change my circulator tonight but i should tommorow.

 

[EForest]

It's been 12 days since my last fire and the wife finally put the hammer down (luke warm shower this morning).
The boiler and both tanks were down to 100* today so I had to fire. I'm almost three hours into the burn and the average temp is 170*. Each tank has a DHW coil so i can draw them all down equal. This recent heat wave has got me thinking about solar in the near future. Would be great to go all summer without warming up the basement for DHW

 

[loggie]

Hey Ed,how are you doing with your switzer I'm sure you are happy with it how long does it take you to get up to temp with that much storage?Gary is building me a three pass 1250 still waiting I guess he is swamped now sorry to hijack the thread

 

[2.beans]

i don't know if anyones interested but i finally changed my primary circulator to an internal flow check one. that stopped the primary loop from thermo siphoning through the tanks. as i was tucking some left over insulation in the cracks i noticed that the supply and return pipes to the wood boiler felt real warm for not having a fire for a few days. so i installed a swing check on the supply line from the wood boiler to the tank. that stopped the wood boiler loop from thermo siphoning i had a fire on monday and got my tanks to 170 and tonight (friday) they were at around 130.

 

[Willman]

Good deal. The "Boiler Room" comes thru again.
Will

 

[Hansson]

I got 530 and I can mange 7-8 days in the summer.
From 105 Celsius to 35 Celsius.