Domestic hot water sidearm?

Thecornguy · Nov 9, 2014

Hello all,
I just got an eko40 with a1,000 propane tank. My house has three zones. I plan on installing this system outside and putting in underground pex. I was told by the dealer to use the heating zone circulator pumps to pull from the storage as needed. My question is: how would I hook up a heat exchanger to heat my domestic hot water if the house isn't calling for heat? Thank you and sorry if this question has already been answered.

ewdudley · Nov 9, 2014

Welcome to the forum.

You could just plumb the sidearm as a separate zone with its own zone valve.

But your main circulator would be pumping a lot more flow than a sidearm can take advantage of, which would cause mixing in storage that is usually undesirable. I would suggest using separate tiny pump that draws in parallel with the main pump, with check valves to prevent back flow from one pump through the other. B&G has some nice tiny pumps out these days that would move a gpm or two:

http://documentlibrary.xylemappliedwater.com/wp-content/blogs.dir/22/files/2012/07/A-133B.pdf

On the water heater side you could improve the performance of the sidearm if you were able to put the DHW tank up on a stand closer to the ceiling with the sidearm closer to the floor.

Another approach would be to skip the sidearm and have the storage tank modified to accept a DHW coil in the top of it. Then run a separate 1/2" PEX DHW circuit along side of the main PEX all the way out to storage with a tiny circulator like the ones above, which would keep your DHW tank in the house topped up.

Thecornguy · Nov 9, 2014

ewdudley said:
Welcome to the forum.

You could just plumb the sidearm as a separate zone with its own zone valve.

But your main circulator would be pumping a lot more flow than a sidearm can take advantage of, which would cause mixing in storage that is usually undesirable. I would suggest using separate tiny pump that draws in parallel with the main pump, with check valves to prevent back flow from one pump through the other. B&G has some nice tiny pumps out these days that would move a gpm or two:

http://documentlibrary.xylemappliedwater.com/wp-content/blogs.dir/22/files/2012/07/A-133B.pdf

On the water heater side you could improve the performance of the sidearm if you were able to put the DHW tank up on a stand closer to the ceiling with the sidearm closer to the floor.

Another approach would be to skip the sidearm and have the storage tank modified to accept a DHW coil in the top of it. Then run a separate 1/2" PEX DHW circuit all the way out to storage with a tiny circulator like the ones above that would keep your DHW tank in the house topped up.

Thanks dudly. I have three existing zone pumps. So I would need to put in another little pump that would continuously run to make heat available to the water heater at all times?

Thecornguy · Nov 9, 2014

The whole system is closed and pressurized. And it will be tied to my existing oil boiler.

maple1 · Nov 9, 2014

What do you have for a DHW tank, and are you expecting to heat DHW year round from storage? Or just when heating the house?

I have an 80 gallon electric DHW tank, and started out with an unpumped sidearm. That worked fine when burning for house heat. But was inadequate when trying to heat DHW from storage in the non-heating season. As ewdudley also said, it ruins stratification and will not put enough heat in your DHW tank once the storage gets much below 150 or so.

I added on a flat plate HX to the sidearm (just left the sidearm in place & hooked them up in series) and pump both sides - the boiler side gets pumped with my Alpha load pump that pumps the rest of the zones and gets controlled the same way (used a zone valve with end switch on that loop), and the DHW side gets pumped with the exact pump that he linked above (I used the third one down in the chart), that gets switched off & on thru a RIB relay also wired to the zone valve wiring. The zone valve is controlled by a Johnson A419, with probe mounted on the bottom inlet of my DHW tank as far in as I could get it, which is also where the HXs draw from. I can now run storage down to around 95/115 in the summer before the water out the taps gets too much on the cool side. Another feature the Johnson has that I didn't know about when I got it, is a second set of setpoints that can be switched off & on, that I use in the off-season. 'For now', I have that going through an ordinary wall switch - so when I start a burn, I will switch that off & the DHW setpoint will go 20° higher (can be programmed to what you want). When done burning, I switch it on. That puts a lot more heat in my 80 gallons of DHW & gets me further between burns & gives me more storage. I will replace the wall switch with a thermal switch that will get placed on my boiler return pipe, just outside the boiler, so it will do the setpoint sitch automatically when it senses a burn via hot return water. I have some thermal switches kicking around here, just haven't verified I have the right one & gotten around to it yet. Too many projects...

Thecornguy · Nov 9, 2014

maple1 said:
What do you have for a DHW tank, and are you expecting to heat DHW year round from storage? Or just when heating the house?

I have an 80 gallon electric DHW tank, and started out with an unpumped sidearm. That worked fine when burning for house heat. But was inadequate when trying to heat DHW from storage in the non-heating season. As ewdudley also said, it ruins stratification and will not put enough heat in your DHW tank once the storage gets much below 150 or so.

I added on a flat plate HX to the sidearm (just left the sidearm in place & hooked them up in series) and pump both sides - the boiler side gets pumped with my Alpha load pump that pumps the rest of the zones and gets controlled the same way (used a zone valve with end switch on that loop), and the DHW side gets pumped with the exact pump that he linked above (I used the third one down in the chart), that gets switched off & on thru a RIB relay also wired to the zone valve wiring. The zone valve is controlled by a Johnson A419, with probe mounted on the bottom inlet of my DHW tank as far in as I could get it, which is also where the HXs draw from. I can now run storage down to around 95/115 in the summer before the water out the taps gets too much on the cool side. Another feature the Johnson has that I didn't know about when I got it, is a second set of setpoints that can be switched off & on, that I use in the off-season. 'For now', I have that going through an ordinary wall switch - so when I start a burn, I will switch that off & the DHW setpoint will go 20° higher (can be programmed to what you want). When done burning, I switch it off. That puts a lot more heat in my 80 gallons of DHW & gets me further between burns & gives me more storage. I will replace the wall switch with a thermal switch that will get placed on my boiler return pipe, just outside the boiler, so it will do the setpoint sitch automatically when it senses a burn via hot return water. I have some thermal switches kicking around here, just haven't verified I have the right one & gotten around to it yet. Too many projects...

Thanks maple. Wow that's alot of "Greek to me" please excuse me I am way at the bottom of the learning curve. When it comes to all of this. I have a 50 gallon electric water heater that would be nice to use free of charge in the summer. The way it was explained to me the eko would be looped into the bottom of the propane storage tank (laying long ways) with its own pump. Then the house would be looped into the top of the tank. Stratification is basically heat rising from the bottom of the tank to the top?

ewdudley · Nov 9, 2014

Thecornguy said:
Thanks dudly. I have three existing zone pumps. So I would need to put in another little pump that would continuously run to make heat available to the water heater at all times?

I'm guessing the sidearm would deliver on the order of 10,000 btu per hour or more and DHW heat consumption for a typical household is on the order of 30,000 btu per day, so it would be best to have an aquastat to turn off the DHW circuit once the bottom of your DHW tank is up to temperature, as @maple1 describes above.

maple1 · Nov 9, 2014

Thecornguy said:
Thanks maple. Wow that's alot of "Greek to me" please excuse me I am way at the bottom of the learning curve. When it comes to all of this. I have a 50 gallon electric water heater that would be nice to use free of charge in the summer. The way it was explained to me the eko would be looped into the bottom of the propane storage tank (laying long ways) with its own pump. Then the house would be looped into the top of the tank. Stratification is basically heat rising from the bottom of the tank to the top?

When the tanks are fully charged (say 180 top to bottom), and as the water from them is used, hot will get drawn out of the top & cold will get put in the bottom. With good stratification, it will stay that way and what you will have is a dividing line between hotter & colder that will rise as the heat gets used. That way, you will have useable hot water until the line gets all the way to the top. If the water gets mixed up too much & stratification gets lost, the water will maintain constant temperature top to bottom (more or less), and the water will not stay as useable for as long. Not sure I explained that the best. I really encountered that face to face when trying to use the sidearm when not heating for heat.

There would be quite a jump for you in complexity in going from a sidearm setup that only heats DHW in house heating season, to a setup that would heat good from storage year round. You very well might be better off just heating DHW with electricity in the summer and only counting on the sidearm when you are heating the house. Lots on here with storage do that anyway, as heating DHW with an electric tank is not really all that costly. I could do ours for around $30/month - and likely would have this past summer, if I didn't have a bunch of crap wood to get rid of. I might do it next summer again too and let my storage go cold (which is what I did my first summer), depending how much junk wood I find myself with again. In using the sidearm when heating the house, it sends some heat to the DHW tank whenever the house loads are being used - by simple convection, no other pumps or controls needed. So you'd have to decide how much complexity you want to add and whether it's worth it. Also, I find DHW demand quite a bit lower in the summer. How many in the house? Do you use a lot of DHW? A big DHW tank can be key sometimes too - for more reserve when using a lot. The sidearm won't make it as fast as it's used, so reserve might be an issue depending on use - which is why I went with an 80.

avc8130 · Nov 9, 2014

You said you are putting the boiler and storage outside? And plumbing into the house with pex?

How the heck are the load circulators ever supposed to handle that? I think you got some questionable advice there.

More likely, you will need to plumb in a "loop" for the boiler/storage to the house with a dedicated and properly sized pump. Then your load circulators will pull from that.

You could either run the sidearm on part of that loop, like all of the outdoor guys do (but this will hurt stratification in the storage) or run it off a zone like some others have suggested.

If you plan on heating your DHW year round from wood, I would do neither. I'd swap out that electric tank for a proper indirect. The recovery and efficiency of making DHW will be much better, and the system will actually be much simpler.

ac

Thecornguy · Nov 9, 2014

avc8130 said:
You said you are putting the boiler and storage outside? And plumbing into the house with pex?

How the heck are the load circulators ever supposed to handle that? I think you got some questionable advice there.

More likely, you will need to plumb in a "loop" for the boiler/storage to the house with a dedicated and properly sized pump. Then your load circulators will pull from that.

You could either run the sidearm on part of that loop, like all of the outdoor guys do (but this will hurt stratification in the storage) or run it off a zone like some others have suggested.

If you plan on heating your DHW year round from wood, I would do neither. I'd swap out that electric tank for a proper indirect. The recovery and efficiency of making DHW will be much better, and the system will actually be much simpler.

ac

You don't think the zone circulatory will handle that? Why wouldn't they? They are designed to push water from the basement to the second floor. That is much more head than pumping water basically level through a 1" pipe. Am I missing something?

maple1 · Nov 9, 2014

How far between the boiler/storage, and house?

Thecornguy · Nov 9, 2014

maple1 said:
How far between the boiler/storage, and house?

About 80 feet

maple1 · Nov 9, 2014

I'm on my crappy tablet right now - but that 160' round trip is a huge extra load for your load circ. But we know not much about the rest of the system and circs and are going beyond the sidearm topic and getting into other cans of worms.

avc8130 · Nov 9, 2014

Thecornguy said:
You don't think the zone circulatory will handle that? Why wouldn't they? They are designed to push water from the basement to the second floor. That is much more head than pumping water basically level through a 1" pipe. Am I missing something?

You've got a lot to learn!

Your zone circulators don't "push" ANYTHING right now. They are working within a CLOSED system. What goes up must come down. They are merely circulating. They only "fight" the friction of the piping system.

160 feet for the amount of BTUs that would be typically needed will NOT work with a 007 also trying to pump a zone in the house. You'll need a properly sized pump whose specific job it is to bring the BTUs needed to the house for use by the zone circulators.

maple1 · Nov 10, 2014

If you plan on heating your DHW year round from wood, I would do neither. I'd swap out that electric tank for a proper indirect. The recovery and efficiency of making DHW will be much better, and the system will actually be much simpler.

Not sure about that part. Simpler yes, but I don't think an indirect gets as much out of the supply water as a flat plate does - therefore ending up with too much mixing in storage & loss of stratification, and less time between firings. Plus you would use the ability to let the fire go out & heat DHW quite economically with electricity, should you so chose. Also quite sure you could add on a FPHX, small circ, and controls for it for less than the cost of a new indirect tank - although I've never gone looking for an indirect so don't know exactly what they cost.

avc8130 · Nov 10, 2014

maple1 said:
If you plan on heating your DHW year round from wood, I would do neither. I'd swap out that electric tank for a proper indirect. The recovery and efficiency of making DHW will be much better, and the system will actually be much simpler.

Not sure about that part. Simpler yes, but I don't think an indirect gets as much out of the supply water as a flat plate does - therefore ending up with too much mixing in storage & loss of stratification, and less time between firings. Plus you would use the ability to let the fire go out & heat DHW quite economically with electricity, should you so chose. Also quite sure you could add on a FPHX, small circ, and controls for it for less than the cost of a new indirect tank - although I've never gone looking for an indirect so don't know exactly what they cost.

How well do the FPHX setups recover? On the same argument about mixing up storage, pumping the DHW will mix it up and reduce the temperature immediately available for use during times it is charging.

One of my coworkers runs an indirect off storage all summer long. He doesn't seem to have any issues. He does run a Bumble Bee for his storage to load pump, so the water heading back is targeted at 140F.

Add a HPHW to that indirect and he has the ability to heat with electric...cheaply.

Many ways to skin the cat, at the end they all have hot water.

ac

maple1 · Nov 10, 2014

Mine recovers very well. In actuality, when it responds to a call for heat, with DHW being used at the same time, it functions as an on-demand heater and can make it almost as fast as it is being used. Well, to a point - not likely anything can keep up with one of those extended teenager showers. It also puts the hot water it makes right into the top of the tank, right where it is being drawn from - which would increase the temperature immediately available for use and help with stratification of the DHW water.

Adding a HPWH into anything heating DHW is likely a good idea - in this case, I would likely do the sidearm for when you are burning for heat, and the HPWH for the rest of the year, depending how much using the conventional electric heater is costing. At $30/mo (what ours costs us), and assuming you might cut it in half by adding a HPWH (saving $90/year at 6 months a year), it might be a longer ROI than what one might want - that would likely come down to DIY skills in avoiding install costs.

Yes lots of choices - the world would be a pretty boring place if we all did everything the same way.

avc8130 · Nov 10, 2014

maple1 said:
Mine recovers very well. In actuality, when it responds to a call for heat, with DHW being used at the same time, it functions as an on-demand heater and can make it almost as fast as it is being used. Well, to a point - not likely anything can keep up with one of those extended teenager showers. It also puts the hot water it makes right into the top of the tank, right where it is being drawn from - which would increase the temperature immediately available for use and help with stratification of the DHW water.

Adding a HPWH into anything heating DHW is likely a good idea - in this case, I would likely do the sidearm for when you are burning for heat, and the HPWH for the rest of the year, depending how much using the conventional electric heater is costing. At $30/mo (what ours costs us), and assuming you might cut it in half by adding a HPWH (saving $90/year at 6 months a year), it might be a longer ROI than what one might want - that would likely come down to DIY skills in avoiding install costs.

Yes lots of choices - the world would be a pretty boring place if we all did everything the same way.

Good call on the ROI of the HPWH. I use the same argument for electric vs burning to heat DHW in the summer. $30/month. Would you burn wood to heat your home if you could heat the home for $30/month? No? Then why burn it to heat hot water for $30/month?

Most of the guys I know claim to use a little over a cord to heat DHW during non-heating season. By me that is ~$200 worth of wood (whether you get it "free" or not it is still WORTH $200). Once the math is done, you realize the "savings" heating DHW with wood during summer isn't much in the long run.

Realistically, the same applies during the heating season. That same cord is going "missing" into the DHW. The same water could be heated for $30/month. Maybe the real solution is to just use electric for DHW and save all of the money on pumps/exchangers/etc.

ac

maple1 · Nov 10, 2014

Getting a bit futher away from the OP - but I would agree with the summer burning & wood cost. The stuff I used this summer was junk & I don't think I could have given it away for free to anyone who might have been going by - so it was either leave it to rot completely away, or use it to displace a couple hundred dollars worth of electricity. I chose the latter. Next year might be different, and my first year I didn't burn all summer since I was short of wood. I don't think it would apply equally to the winter, as in the winter the heating system is hot all the time. Or more of it. A good part of the heat you get out of the wood when heating with wood in the summer is spent just on getting the boiler up to temp. Math can get pretty fuzzy trying to figure some of that stuff out though. Then there is stuff you can't put numbers to - like, what one likes to do & doesn't like to do. If you enjoy making a fire once a week all year while cleaning the yard up of junk wood & tree debris, that's different than it being a chore to do so after doing it every day all winter & it feeling like a break not doing it all summer even though it might mean a bti more out of pocket. I've been in both places - so much so with the break thing that I've burned oil all summer for DHW before rather than making fires.

JP11 · Nov 10, 2014

I did the wood over summer thing this year.

Won't again.

The storage isn't insulated as well as you think, and it's a lot of waste heat (mine is inside the house)

Made my living space above the boiler room warmer, and made the AC work harder.

This year.. HPHW. Got a Nyletherm from Tom. 300 bucks. Tied it to the indirect.

JP

barnartist · Nov 12, 2014

I went simple, it's not the best, but I put a 15 minute timer in my shower room that kicks on my pump. I use 1 1/4 pex lines in my run from my boiler outside to my house. On my hot side manifold, my DHW gets first demand. It's a 007 pump, it seems to do well. I put a flat plate heat exchanger on top of my DHW tank, so I heat the water before it goes into the DHW tank. I do not have a temp gauge to see what king of exchange I am getting, but it works. I know this because I turned off power to my DHW heater for an extended period, and I had enough hot water.

I would like to find a water flow sensor to kick on that pump. I suppose it may cycle too often that way when kids wash hands or small dishes get washed. Anyway, my 2 cents.

avc8130 · Nov 12, 2014

barnartist said:
I went simple, it's not the best, but I put a 15 minute timer in my shower room that kicks on my pump. I use 1 1/4 pex lines in my run from my boiler outside to my house. On my hot side manifold, my DHW gets first demand. It's a 007 pump, it seems to do well. I put a flat plate heat exchanger on top of my DHW tank, so I heat the water before it goes into the DHW tank. I do not have a temp gauge to see what king of exchange I am getting, but it works. I know this because I turned off power to my DHW heater for an extended period, and I had enough hot water.

I would like to find a water flow sensor to kick on that pump. I suppose it may cycle too often that way when kids wash hands or small dishes get washed. Anyway, my 2 cents.

That seems easiest enough to me. I have a 15-min timer for the fan in the bathroom when showering, turning a 2nd timer doesn't seem like a huge deal to me.

My indirect has a 007 pump. It is bang-on 20F delta T.

ac

Domestic hot water sidearm?

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