OWB Installation - installing plate HX

[xtonycrx]

Hey guys,

I just picked up a ML30 Portage and Main OWB and I am in the process of installing it. CUrrently I have my insulated pex buried, pad pored with the OWB sitting on it. Now for the fun part .

I am hooking it up using a plate heat exchanger to a pressurized oil boiler. The boiler has 1 outlet that splits to go to 2 separate pumps which heat my house and hot water. Each loop has its own inlet into the oil boiler. I don't intend to use a separate pump to hook up the exchanger.

I plan on joining the two inlets, running them into the heat exchanger and then going back into the oil boiler. I would block off the other inlet. Does anyone know if this set up is acceptable? Any input? I have attached a schematic drawing representing my installation.

 

[oneoldbanjo]

The diagram is not real clear - but it appears one loop provides heat for the house and the other one provides heat to the water heater.

I think we need to know a little more information about pipe sizes and the size of your plate exchanger to make informed suggestions - however my gut reaction is that your single plate exchanger may not be able to properly handle the flow from two pumps in the existing system.

Other options available to you may be to just install the plate exchanger into the heating loop inlet to the oil boiler and let the hot water mix inside the oil boiler with the return water coming back from the water heater. If that proves to be inadequate you could add another plate exchanger for the water heater loop. This might work out well to have two plate exchangers - if you installed valves that would allow you to bypass the plate exchanger in the heat/boiler loop and bypass valves from the hot water loop - you could isolate the water heater from the boiler and just send your hot OWB water through the loop for the water heater plate. This would allow you to make hot water when you don't need the whole house heated and you would not be heating up the boiler system.

 

[xtonycrx]

Thanks for the help. I also though about the heat exchanger being able to handle the flow from both pumps. But it appears that the all inlets and outlets are 1". The inlets are 1" copper while the outlet is 1 steel until it reaches both pumps then it goes into a manifold.

My heat exchanger is a 40 plate with 1" connections. My home is approximalty 2100sqft.

 

[oneoldbanjo]

One of the problems that I see with running both pumps through the single heat exchanger is that with double the flow the water will spend very little time inside the heat exchanger and the resulting temperature increase may not be large enough to make hot water to heat your house - plus the friction loss from doubling the fluid flow results in 4 times the resistance (fluid flow friction loss is proportionate to the square of the velocity).

Now for my disclaimer......I am a civil engineer and deal with flow through water lines, sewer lines, culverts, etc. and I am very well versed with fluid flow and hydraulics - I do not install or design heating systems. My comments are based on the application of fluid mechanics and my experience. You really should get the opinion of someone who installs and services these kind of systems. I offered my opinion based on my intuition that you may be trying to run twice the volume through a heat exchanger designed to handle the flow through a single 1" pipe - and you would be combining two 1" pipes into a single 1" heat exchanger.

 

[sstan]

I tried to digest the drawing and maybe don't understand ... I thought you had a set up similar to mine (my post of my install with pics) .. I have four pumps (one for hot water and then three heat zones) .. but mine has a manifold from hot side of boiler .. splits to the four zone's ... each zone comes back through the individual pumps then back into a return manifold and back to bottom of furnace. I just broke into the return line after the pumps and manifold went into the HX then back to the bottom of the oil burner. I had concerns of constricting the flows but the zones are 3/4" runs and the line from the pumps / manifold was only 1 1/4 originally so I do not think it will be a problem.

 

[LTREES]

Just a thought. Is there a problem running through the heat plate only and not circulating through the oil boiler. Some have a separate pump circulating the house water out of the heat plate and into the oil boiler. that keep the boiler hot so it does not fire up if the house does not call for heat and the boiler's temp drops. Or then again you can just run it into the boiler straight and run an unpressurized system. I talked to a CB dealer and he claims that the anticorrossion chemical CB has will actually help keep the house line and boiler clean. I have a 40 plate set up as you do. I am starting to have concerns about the restrictions it will have on the pumps and that I don't have it circulating through the boiler to keep it hot. My system is not running yet, just want to get it right before I add the water.


LT...

 

[Scootermsp]

How mine is done---works well

http://i525.photobucket.com/albums/cc336/scootermsp/IMG_0467-1.jpg
http://i525.photobucket.com/albums/cc336/scootermsp/IMG_0468.jpg
http://i525.photobucket.com/albums/cc336/scootermsp/IMG_0469.jpg

The circ pump stays on 24/7 as does the OWB circ pump. This set up allows for a pressurized system to remain pressurized and the OWB loop to remain at atmosheric pressure. I've run all 3 zones of heat and Hot water simultaneously and it keeps up easily. My HX is a 30 plate.opcorn:

 

[xtonycrx]

One of the problems that I see with running both pumps through the single heat exchanger is that with double the flow the water will spend very little time inside the heat exchanger and the resulting temperature increase may not be large enough to make hot water to heat your house - plus the friction loss from doubling the fluid flow results in 4 times the resistance (fluid flow friction loss is proportionate to the square of the velocity).

Now for my disclaimer......I am a civil engineer and deal with flow through water lines, sewer lines, culverts, etc. and I am very well versed with fluid flow and hydraulics - I do not install or design heating systems. My comments are based on the application of fluid mechanics and my experience. You really should get the opinion of someone who installs and services these kind of systems. I offered my opinion based on my intuition that you may be trying to run twice the volume through a heat exchanger designed to handle the flow through a single 1" pipe - and you would be combining two 1" pipes into a single 1" heat exchanger.

I agree with you completely and understand all the theory you have brought up (Mech Engineer ). However I am thinking that it will be pretty rare when both pumps will be running at the same time. My hot water load is very little, just the wife an I.

I tried to digest the drawing and maybe don't understand ... I thought you had a set up similar to mine (my post of my install with pics) .. I have four pumps (one for hot water and then three heat zones) .. but mine has a manifold from hot side of boiler .. splits to the four zone's ... each zone comes back through the individual pumps then back into a return manifold and back to bottom of furnace. I just broke into the return line after the pumps and manifold went into the HX then back to the bottom of the oil burner. I had concerns of constricting the flows but the zones are 3/4" runs and the line from the pumps / manifold was only 1 1/4 originally so I do not think it will be a problem.[\quote]

That is essentially the same setup is mine, just in a different configuration. Have you had up running yet? How did it work?

Thanks for the help.

 

[sstan]

Can't be much help as it's a new install and only been running a week and the weather has been great. Biggest problem so far is the fire has been going out because there is no not enough call for heat to have the OWB fire up too often! Only the domestic HW loop has been calling for heat. I did start up all four zones as a test the day I started it and it seems ok but it was 65 degrees out and not a great test! In my case only two zones are real active (HW zone and family area).. the other two are for parts of the house we do not turn the heat on much (son's bedroom and at 13 he needs some motivation to get out of bed!). Suppose to be cold this weekend .. maybe I will get a better idea!

 

[xtonycrx]

I think I am going to give my planed setup a whirl. If I run into problems I will install a separate circulating pump. My current setup makes is difficult to do this so I will try the easy way first.

 

[oneoldbanjo]

I would think that the easiest thing to try would be to tie it into only one of the loops first. I would probably just plumb the plate exchanger into the "heat" loop of your house and let the water heater pull the water from the oil boiler just like it currently does. If you put the plate exchanger in the line just before the boiler it will put the hot water in the boiler and the water will mix in the boiler and give both sides the tempered water (Which is what I would try first). If you put it on the outlet side the heaters will get the really hot water and the boiler (and water heater) will then receive the left over heat for the water heater.

 

[xtonycrx]

I would think that the easiest thing to try would be to tie it into only one of the loops first. I would probably just plumb the plate exchanger into the "heat" loop of your house and let the water heater pull the water from the oil boiler just like it currently does. If you put the plate exchanger in the line just before the boiler it will put the hot water in the boiler and the water will mix in the boiler and give both sides the tempered water (Which is what I would try first). If you put it on the outlet side the heaters will get the really hot water and the boiler (and water heater) will then receive the left over heat for the water heater.

Hmm interesting thought! I guess the only problem would then be if my house hasn't called for any heat in a while (spring/fall) I may not have much hot water....... Is this a valid line of thought?

 

[oneoldbanjo]

I guess I assumed that the pump in your "heat" loop ran 24/7 - and that there was a blower, zone valve or some other device connected to the thermostat. What controls the pumps on the heat/water heater loops in your current system?

 

[xtonycrx]

I guess I assumed that the pump in your "heat" loop ran 24/7 - and that there was a blower, zone valve or some other device connected to the thermostat. What controls the pumps on the heat/water heater loops in your current system?

My home heating has two thermostats which control two zone valves and the pump. My hotwater is controled by a thermostat inside my hotwater tank which turns on the hotwater pump. My hotwater loop does not have a zone valve.

EDIT: essentially neither of my oil boiler pumps are circulating unless there is a demand for heat either my the hot water tank or baseboards.

 

[xtonycrx]

I tried to digest the drawing and maybe don't understand ... I thought you had a set up similar to mine (my post of my install with pics) .. I have four pumps (one for hot water and then three heat zones) .. but mine has a manifold from hot side of boiler .. splits to the four zone's ... each zone comes back through the individual pumps then back into a return manifold and back to bottom of furnace. I just broke into the return line after the pumps and manifold went into the HX then back to the bottom of the oil burner. I had concerns of constricting the flows but the zones are 3/4" runs and the line from the pumps / manifold was only 1 1/4 originally so I do not think it will be a problem.

So when there is zero heat load from your house and hot water do you still have a pump that is circulating or do your pumps only turn on when there is demand?

 

[oneoldbanjo]

You have an interesting dilemna.....

So what would happen if you hotwired your the pump in your heat loop to run 24/7 - would the zone valves bypass the water and allow it to just pass through the system without making so much heat it cooked you out?

Alternatively - what would happen if you had the plate exchanger in your water heater loop running 24/7. The water in the water heater would probably get hotter than normal - but would never be hotter than the water coming in from your OWB. When the heat season is over or you had a warm day you could just let the water heater pump run it's normal cycle - however when it called for heat on the water heater it would not only be heating up the water in the water heater - it would also be heating the water in the boiler again as the pump came on and circulated water back and forth from the oil boiler and the water heater.

The hookup of my system was also a bit weird. I have a forced air system and the normal method is to install the heat exchanger in the plenum and just put in a second thermostat and fan center - so that when the thermostat calls for heat it just turns the blower on and runs air through the exchanger. Hot water from the OWB is constantly flowing through the new heat exchanger installed in the furnace plenum. I got a really fancy heat pump however and it has a computer controlled blower that is variable speed and it could not be controlled with any exterior stimulas (thermostat or fan center). What we had to do was connect the new thermostat to a zone valve that contolled water flow to the new heat exchanger - and then just set the blower control in the furnace to run all the time. This actually works very well as during mild weather we run the blower on a very low setting and you really can't hear the blower running - and as the temperature gets colder we can turn the blower speed up. This results in a very even heat throughout the house and we don't have temperature fluctuation as the blower comes on and goes off.

 

[xtonycrx]

That is a very interesting thought. I am actually going to look into it. Everything about the setup would be easier. The only thing I need to worry about is the maximum temperature limit of my hot water tank. Later if I was worried about being burned by the hot water I could install a mixing valve.

I have a question: What tells the oil furnace to fire? Is it the temperature of the water in the boiler or the thermostats and the temperature in the boiler? I'm just thinking about insureing my furnace doesn't fire in the winter.

 

[oneoldbanjo]

My guess would be that the thermostat in your house controls the zone valves. Your Oil Boiler is probably controlled by a temperature sensor that is set to keep the water between two set points. Whe the boiler water gets cold the burner come on and when it gets hot it turns the burner off.

 

[sstan]

In my case the water temp in the oil burner .. a thermostat setining in burner control on furnace. On my system there is two switches running to the control box .. one controls the burner and one controls the zone pumps.. I turned the burner off .. I also set the oil burner temp setting down to as low as it will go .. this way if I ever go away in the winter I will flip the switch back on and if the OWB goes out it will not freeze up.. the oil burner will keep the owb warm.

 

[xtonycrx]

In my case the water temp in the oil burner .. a thermostat setining in burner control on furnace. On my system there is two switches running to the control box .. one controls the burner and one controls the zone pumps.. I turned the burner off .. I also set the oil burner temp setting down to as low as it will go .. this way if I ever go away in the winter I will flip the switch back on and if the OWB goes out it will not freeze up.. the oil burner will keep the owb warm.

So you have a boiler water control and a theromstat control? Is it as simple as flipping a switch to turn off the thermostat control?