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[RSI]

Oversizing the plate doesn't hurt anything. A 10 plate will more than keep up. The only reason to go bigger is lower the restriction on the boiler line. A 10 plate will slow the water flow down quite a bit. I have a manifold setup on mine so it is in parallel with the other heat exchangers so the 10 plate restriction doesn't matter.

If the sidearm is the type with just a 3/4" pipe through the center I wouldn't bother using it. The shell in tube type are much better. (they run seven 3/8" copper pipes through the center instead of one 3/4" pipe)

[Ridgekid]

First - Thanks to all that replied.

Lets assume I could use a Plate HX for DHW. To be be honest, I have not seen scale coming out of my HWH drain for years. I have only lost one heating element in 18 years. I do have iron in my water but it's so minute a house filter removes 99% of it. I change the house filter once a month.

I agree with RSI. If I hook up a plate HX, it needs to be before the HWH. Otherwise, why have a HWH? If I preheat the water GOING to the HWH my electric use in winter time will be very little. If after the HWH I still have to heat the water in the tank unless I leave the breaker off. I need to price and size a Plate HX.

Might be able to skip the Thermostatic valve if I install it as described above. No way I would go through 50 gallons of HW at 140F before the 160F water kicked in.

CB recommends drawing heat to the HWH first, then the furnace HX. WHY? My return water temp is 160F at worst. (I know... I've only operated it 5 days, but that much I know) That should be more than efficent to heat water.

Yeah I'm leaning towards a plate HX now. Sure would be alot easier to hook up than a sidearm. I was at Home Depot today and they carry Pex fittings. Not sure about the piping. It doesn't look like it's for OWB use. They definetely did not carry 1" central pex (Green pipe). I might have to peal back the last 15' of Thermopex I had left and dig out the pipe out of the neoprene.

Comments?

[RSI]

They recommend the water heater first because side arms work better with hotter water.
Using a plate exchanger as a pre-heater doesn't really have any temperature control. It works out fairly well for some people though. The more water you use the hotter it will get coming out of the faucet. If you go a long time between using it then it will cool down and the water heater will kick in if you leave it turned on. It seems to help a lot to turn the water heater way down if you leave it on because the water isn't quite as hot at the bottom so it keeps kicking on. The temperature varies quite a bit but since the whole tank is that temperature it will stay the same and you don't keep having to adjust the faucets. Sudden changes are bad which makes putting it after the tank much worse. (no buffer effect)

All pex is rated at the same temp and pressure so it should work. It probably doesn't have oxygen barrier but you have an open system so it doesn't really do you any good anyway.

[yoderheating]

 As a dealer I can tell you that on 90% of homes flat plates work much better then side arms. The only time I would ever recommend using a side arm is if you plan on going several days between using hot water. Almost everyone uses a little hot water every day. The problem most people have is with running out of hot water, a common problem with side arms unless you put an additional pump on them. Put a 1inch 20 plate on the fill side of your hwh and it will work great. I've done hundreds of them and have never had a customer use so little hot water that is caused a problem.
 The reason you want to go to the hwh first is because you want a steady temperature there.  It doesn't matter if the heat from your duct system varies a little so hit it second. Also,  make sure the water from the outdoor furnace is on the "downstream" side of your heat exchangers for both hot water and heat. It will work more efficiently that way. Good luck!

[RSI]

Do you put a mixing valve on them?

[dirtryder]

First - Thanks to all that replied.
I agree with RSI. If I hook up a plate HX, it needs to be before the HWH. Otherwise, why have a HWH? If I preheat the water GOING to the HWH my electric use in winter time will be very little. If after the HWH I still have to heat the water in the tank unless I leave the breaker off. I need to price and size a Plate HX.
Comments?

Yes,  I have a comment.
When you have a fire in the OWB, you turn OFF the HWH. That is the whole idea. People want to heat water, let it sit in a tank to "cool" then heat water to mix into 30, 40, or 50 gals of "cooled" water.  Why folks do this is beyond me. You "loose" heat from the water coming out of the HX to the tank water. Leaving the HWH ON and "pre-heating" the water going in with a HX is missing the whole point also. If you put in a HX before the tank AND a side arm to keep it hot is just a waste of money.

I have a propane HWH that is turned OFF during my burning season. If for some reason my OWB stops producing hot water, I just light my HWH. Yes, it may take 15 mins to heat the tank but I have never in my life needed hot water faster than that. TRUST me, in the summer when OWB is off and circulater pump is off, my HWH water going through my HX is NOT affected by it.

One last question, if you put 175 degree water from your HX "into" your tank..........you are using "lots" of hot water.....so all the water is replaced with nice fresh HOT water........what is your tank safety valve temp setting?  I'll bet it's not more than 175

In any case, enjoy your OWB........

[yoderheating]

 RSI, I never have used a mixing valve. Most people want the extra hot water and if they don't I explain to them they can control it by lowering the outdoor furnace temperature. I set the furnace rather low and if they want to adjust it they can.

[RSI]

I know it isn't real likely to happen but what if they have leave a faucet running and forget to latch the boiler door? They could have 200 degree water coming out faucet / shower. You have a kid step into a shower and get cooked and who do you think they will come after?
I know I sure wouldn't want to be liable for doing anything that could do that.

[Ridgekid]

Keep the great info coming!!!

CB offers a 5 x 12-30, 1" ports. I assume this is a 30 plate? OR one with mounting studs 5 x 12 - 10 1" ports.  If you Heating dealers have something better to offer please PM me. (It would be shipped to 15748)

My relief valve on the HWH is set at 150# at 210F.

To Yoder: Are you suggesting that my supply from from OWB should be connected to the top of my HX? (I have an upflow furnace). In other words, cold air moves up, hot water moves down? It's actually the way it's hooked up and I thought it was wrong because I thought air would get trapped in the HX.

Comment about a plate exchanger install: Heating my house is more important than heating water. Even if it's just to assit my HWH I would prefer to go the the furnace HX first, then the HWH. If the furnace is not operating I would be sending to the HWH anyway. This would also keep the water temp down in the HWH. (I don't need 185F water*). Based on this, would you still recommend going to the the plate HX first?

*= I know it won't get that hot, but I don't know what the transfer or temp rise is.

[RSI]

It looks like the first one is probably a 30 plate and the second is a 10 plate.
The plates are in parallel so the more you have the less restriction you have.
Are you having a problem with the heat output from your water to air heat exchanger in the furnace? If not, I would put the plate first unless it will be harder to install that way.

What kind of prices are those plate heat exchangers from CB?

[Ridgekid]

I have a CB5036 to heat 2700 sq ft. Thats all I have hooked up to it, so no problems. I get 125F air when the furnace is on.

Adding the DHW kit is only 15' downstream of the furnace.

No clue what prices CB offers. I would have to call the dealer. The 30 plate is P/n 5734 the 10 plate is P/N 5738.

[RSI]

I would check with the dealer to see what they get. There is no reason to go bigger than a 20 plate. The 10 plate would work but probably restrict the flow a little (depends on pump, piping, etc)
You should be looking at somewhere around $150 for a 10 plate and $50 for each step up in size (10, 20, 30, plate etc.)

[Ridgekid]

In General: The OWB is 100' away from the furnace. (85' of it is underground piping). The HWH would be an additional 15'. The Furnace HX is approximately 2' lower than the boiler bottom in elevation. I have a Taco 009 F5 pump.

[yoderheating]

 Yes, on a updraft furnace you would want the hottest water coming in the top of the heat exchanger. It may sound strange but this will make the air warmer then running it the other way.  If you are getting 120+ heat out of your vents I doubt you have any air in the system, and once you purge the system of air you generally don't have a problem with it.
 

[Ridgekid]

Yoder-Based on your info I moved the temp probe (Redichek) to the inlet side of the HX.

The weatherman said cold again tonight with highs in the 50's next two days so I started the unit back up. I was really surpised the water temp was still 138F after 48 hours off.

When the dealer installed my piping some of the fittings were "Crimped" style. Although we agreed none would be used. One of them are leaking this morning. I hope when the unit gets hot the expansion will stop the leak. (only dripping). I put a 5 gallon bucket underneath to watch.

Need to call the dealer........