Thoughts on my plan for DHW

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taxidermist

Minister of Fire
Mar 11, 2008
1,057
Fowlerville MI
With summer near(I hope) I have a few changes in store for re plumbing my system. I was thinking of switching from a sidearm HX to a flat plate HX.

I was thinking of making it a demand type setup. I would put a flow switch on my DHW so when I open the faucet it triggers a pump to turn on and pump from my storage to HX and back to storage. What do ya think?

Rob
 
What is the downfall to your sidearm ? What are you hoping to gain ?
 
woodsmaster said:
What is the downfall to your sidearm ? What are you hoping to gain ?


Too slow to recover is the problem with the sidearm. I am looking for on demand hot water and less mixing in the tank from a pump always running.

Rob
 
I was planing on installing a sidearm this summer. how long does it take it to recover ? what size tank are you using ? Do you have a circulater on the sidearm and tank or just gravity feed on tank side?
How many people using hot water? Do you have a high efficiency washing machine ?

Sorry for all the Questions. I don't want to install one if it won't work well for me. I was considering running my boiler water threw the sidearm then to the panel rads then back to boiler or storage. Maybe have my circulater on a timer on 1/2 hour off 1/2 hour to avoid so much mixing in storage.
 
I was considering installing a circulater on the domestic water side also.
 
woodsmaster said:
I was planing on installing a sidearm this summer. how long does it take it to recover ? what size tank are you using ? Do you have a circulater on the sidearm and tank or just gravity feed on tank side?
How many people using hot water? Do you have a high efficiency washing machine ?

Sorry for all the Questions. I don't want to install one if it won't work well for me. I was considering running my boiler water threw the sidearm then to the panel rads then back to boiler or storage. Maybe have my circulater on a timer on 1/2 hour off 1/2 hour to avoid so much mixing in storage.

I have used it for 3 years with no real problems. Just sometimes when both of my kids need baths we run out of hot water with each bath at only half full. I have a 40 gal water heater. I have a pump running al the time from storage to side arm and air HX I do have a HE washing machine and I have 2 kids and a wife. When I have real hot tanks say 150* it dosent take real long to recover maybe 2 hrs at max. My reason is to maximize my use of water in my storage. If I dont have to circulate water all the time to keep things hot while I am not using them I feel I am wasting heat. This is the reason I am making my circ pumps a "on demand" system rather than a system that circulates water 24 - 7 causing mixing in my storage tanks.

Rob
 
Sounds like it would work better for you than the side arm. I have a 80 gallon water heater but a family of 5. Two girls and a wife that sometimes take long showers or fill the tub about to the top. I allready have the sidearm so i'll give it a try. I can get a 120 gallon resin tank water heater from my elec. co-op for $800 but dont want to spend the money on it. how big
of exchanger do you think it will take and how low do you think you will be able to let storage temps get and still have hot water at the tap?
 
woodsmaster said:
Sounds like it would work better for you than the side arm. I have a 80 gallon water heater but a family of 5. Two girls and a wife that sometimes take long showers or fill the tub about to the top. I allready have the sidearm so i'll give it a try. I can get a 120 gallon resin tank water heater from my elec. co-op for $800 but dont want to spend the money on it. how big
of exchanger do you think it will take and how low do you think you will be able to let storage temps get and still have hot water at the tap?


You will be fine with the 80 gal.

I have no idea as to size and temps. The bigger the better I bet!

Rob
 
Taxidermist, I have the same problem on my sidearm. It pretty much runs all the time. I am going to install a Termovar diverting valve so that if return from sidearm is still 160 degrees it will send it back through. I have my sidearm gated down to 2 gpm. The advantage to this system is is only draws 25 watts of power according to the Alpha readout. Even though limited flow it still seems to mix my tanks.
 
What about putting a recirculating water pump on the domestic side of your sidearm, it would drastically increase your recovery of the side arm. You could connect the domestic circulator and boiler side circulator to a aquastat in your hot water tank, that will stop the un-needed circulating of your storage, and standby electrical loss of pumps running all the time.
I think that would be pretty close price range to a flat plate exchanger, and flow switch. I think it might perform a little better too, becuase without a volume of water, you dont have a buffer for the range in tempurature swings of your storage.
 
afblue said:
What about putting a recirculating water pump on the domestic side of your sidearm, it would drastically increase your recovery of the side arm. You could connect the domestic circulator and boiler side circulator to a aquastat in your hot water tank, that will stop the un-needed circulating of your storage, and standby electrical loss of pumps running all the time.
I think that would be pretty close price range to a flat plate exchanger, and flow switch. I think it might perform a little better too, becuase without a volume of water, you dont have a buffer for the range in tempurature swings of your storage.


Still only have 40 gal of hot water.
 
I have a 20 plate on the load side, (yes, load side) of my water heater. Heater is off for 2 years now but still have it plumbed in with the flip of a breaker and twist of a mixing valve it is operational. Also the mixing valve is used two ways. The hot an cold inlets can flip. Seems to work fine.

But with the plate heater, I never run out of hot water. I could take an hour(s) long shower. only when my storage is lower than 125 my showers are warm not hot. Cold is all the way off.

I'd get rid of that sidarm and plumb in a plate.
 
Garnification --- " Also the mixing valve is used two ways. The hot an cold inlets can flip. Seems to work fine."

Could you explain this better ??
 
I believe I have a 16 plate (maybe a 20, it's been a while since I got the HX) setup as a demand system for DHW. I can get a reasonable shower down to 130 or so storage temperatures. This small of a plate HX is only good for 1 load, If I'm in the shower and the clothes washer or dishwasher is drawing hot water I notice a significant change in water temperature. This is not a big deal for me as we sequence our use of hot water. I would have bought a bigger plate HX, this on came with my OWB so I kept it when I changed over to the Tarm.

By far the most frustrating and annoying part of the system has been the flow sensor. I originally bought one of the Penn low flow 3/4 NPT paddle type switches. It was ok for a little while, but the corrosion starts to build up between the paddle and the body causing the sensor to get sticky. It's not a problem for showers or hand washing, but it would not sense flow for the dishwasher. In my attempts to clean and adjust it I cracked the bellows and the unit developed a small leak.

Next I stumbled upon a thermal dispersion flow switch, this seemed to be exactly what I needed as it could be set for very low flow rates. I bought on from Omega Engineering (who has been a good company to deal with in the past). In my opinion, this was a HUGE MISTAKE. The switch lasted a couple of months in service. I returned it to Omega for warranty and 4 months later received a new sensor. This one made it a couple of weeks before failure. Being curious, I dissected the unit to see what was wrong. The switch is cheaply made and it looks like the sensing element can be easily damaged. Perhaps my second switch was damaged in transit and broke during operation. I had already decided not to go though another lengthy ordeal with Omega to get a new one and abandoned this implementation. I also discovered this part is made by some off shore company and sold by a few different places (Dwyer being another). I don't believe my installation is to blame, I double checked all of the requirements both times to be sure I was not damaging the sensor. So, for what it's worth I would not recommend this type of sensor. There are other thermal dispersion flow switches on the market that appear to be more robust, but they are also pricey.

I went back to the paddle style flow switch (bought another a PEX supply). AS with the first, it made it a few month before becoming stick any not wanting to activate at low flow. I have modified it a bit and it works better. There should be something better out there, the on demand DHW manufacturers must be using something fairly accurate and inexpensive. I have plans to make my own dispersion switch, but theres always more projects than time.

If you find an inexpensive flow switch that looks good, let me know as I'm still interested. If I ever get to making a solar collector I'm going to use the 16 plate HX for that and get a larger HX for my DHW. That would also be a good time to get rid of the flow switch i have now for something more reliable.
 
I was wondering if a guy could use a water meter to activate a pump. They seem to last a long time without cleaning. You would have to use a relay and transformer probably though. I'll have to check usa bluebook.
 
I want to use a larger indirect water heater for a small buffer on a pellet boiler and also use the IWH for DHW. My plan is to get a tank large enough to handle the output of the pellet boiler and then use a plate HX to supply the heating loop. There are only 4 of us and so I plan to tap off the outlet of the IWH for our DHW and that way kill two birds with one stone. Any thoughts on this outrageous scheme? Will it work and is there a less expensive way? I don't have a lot of space for large tanks in my boiler room.
 
Oh no! Another thing to think about. My brain hurts.
I was sort of not paying too much attention to this topic but the slantfin pic. got my eye.
Will this be a better answer to dhw with storage for the summer months?
 
My thinking here is that is what I want to heat is located on, an often, windy and frigid hilltop and that to be ready for some of the winter days (weeks) here could be cause to oversize a boiler. Instead, I wanted to be able to buffer a little heat for cold emergencies and, to save space, use the same tank for DHW in both summer and winter.
 
SmokeEater said:
My thinking here is that is what I want to heat is located on, an often, windy and frigid hilltop and that to be ready for some of the winter days (weeks) here could be cause to oversize a boiler. Instead, I wanted to be able to buffer a little heat for cold emergencies and, to save space, use the same tank for DHW in both summer and winter.

Callefi and others make buffer tanks both with and without 'tankless coils' for DHW. Instead of an indirect coil for heating DHW, the buffer tank holds hot water and the DHW is heated by a tankless coil in the top of the buffer thank.

I made a home-brew buffer tank out of a 30 gal propane tank that is working quite well, a 100 gallon short fat tank might have been even better.

There's a transfer pump that pumps to the buffer tank if top-of-storage temperature is greater than top-of-buffer temperature and bottom-of-buffer temperature is below minimum (I'm using 115 degF, seems to work well.)

https://www.hearth.com/econtent/index.php/forums/viewthread/66601/



--ewd
 
Thanks for the Caleffi link, lots of good stuff at their site. My water is very soft and therefore corrosive. I will need a tank with replaceable anodes or a stainless tank. Think your homebrew tank has some great ideas to explore. The 100 gal vertical propane tank is along the lines I was had in mind, but didn't think of that tank. I suspect propane tanks have specs similar to commercial hot water tanks, maybe better. The 'prototype' tank on the link sent also gives me some good ideas. I would like to heat this smaller buffer/DHW tank with a delta T of 40 or 50 degrees. That way I could theoretically store about 29,000 Btus for instant circulation and that would help to compensate for the rapid winter temp changes we often get. My thoughts are that since the tank would contain potable water, I could just mix it and use it as DHW.
 
Taxidermist,

Did you implement your plate heat exhanger? I have a 20 plate 4" x 12" HX (Brazetek) installed on the cold side of my DHW heater. I have it set up to feed hot water into the tank. I have the intention of leaving the propane on should the temp ever drop, but that should be unlikely.

The circ pump for the boiler water on this line is governed by a flow switch, however the flow switch is not sensitive enough to turn on when I am running "warm water," or even when my kitchen faucet is running full bore on hot. It was a waste of $95. I was thinking about installing a surface mount aquastat on the heat exchanger. I could also use an immersion type aquastat, but I could avoid the extra plumbing with the surface mount type. I was curious if you found a solution that worked, and if you thought the aquastat would work.

I was also concerned about water being too hot with this method, so I installed a thermostatic mixing valve on the outgoing hot water pipe. I haven't had any scalding hot water yet...

Boomerj
 
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