Heating problem - I don't understand HVAC

[Bricks]

Do you have any type of priority controls set up? If not you may just be pulling to many BTU`s at one time for the boiler to keep up. When my infloor slab kicks on it`l suck my boiler temps right down. So I prioritized my zones with a controller.

 

[KsWoodsMan]

Is the W2W HX plugged or possibly air-locked ?

Does the OWB sit at the same level as the house, Higher ? lower ?

Could the pump be having trouble drawing water uphill to the boiler if the OWB sits below the level of the house/basement ?

Does the supply for the HX go into the bottom or the top of the exchanger ? IMHO the hot supply should be going into the bottom to drive any trapped air out of it. Also to have the higest differential of heat transfer between systems. The hottest of the supply water will transfer more quickly to the coldest of the oil burners water.

Just some questions I'm throwing out there trying to help. I really dont think the HX is undersized. It might be airlocked. But since it is doing it's job so well I doubt that it's size is the problem. It really seems like it is being restricted in the supply from the OWB or the return to it. Either through the HX or the return line going back to the OWB. I think this because the house is able to draw the heat faster than the OWB can supply it. Even though the OWB is set to 200 not enough of that 200° water is going through the HX to keep up with the demand.

Hope you find it. I'm running out of ideas and caffine.

 

[Bcat22]

i'll go ahead and throw in my two cents....

My dad's place has a natural gas boiler, and a few years ago we wanted to try to make it More efficient. we noticed that the when the gas kicked off, the flue kept right on drawing air. since the HX from the burner to the water is about the same as any other heat exchanger, the water that sat in the heat exchanger became room temperature really fast. since his boiler sat in an old unsealed basement, this was usually pretty cold. to fix it, we added an automatic damper to close the flue when the burners weren't on.

i wonder, where do you have the water to water HX in your boiler setup. is it possible that the burner HX in your boiler is bleeding off a lot of heat , letting it go up the flue? i suppose that would depend on the boiler setup and where it is in your house.

Just tryin' to stir the pot a little with some other ideas.....

 

[urhstry]

what size is your pressure side HX pump for your boiler loop?Which way is the water flowing? I used the blow off and drains,put in Tee's on both and run a 3 speed grundfos on low,(60watts),and it works great.My entire loop including HX is only 16 ft,with the hx 3 ft over the top of the boiler.I used 3/4" copper for the entire loop.

My pump for the boiler loop is a 007. I used the incoming water and blow off valve. My loop is about 8 feet. 3/4 copper for me too.

 

[urhstry]

i'll go ahead and throw in my two cents....

My dad's place has a natural gas boiler, and a few years ago we wanted to try to make it More efficient. we noticed that the when the gas kicked off, the flue kept right on drawing air. since the HX from the burner to the water is about the same as any other heat exchanger, the water that sat in the heat exchanger became room temperature really fast. since his boiler sat in an old unsealed basement, this was usually pretty cold. to fix it, we added an automatic damper to close the flue when the burners weren't on.

i wonder, where do you have the water to water HX in your boiler setup. is it possible that the burner HX in your boiler is bleeding off a lot of heat , letting it go up the flue? i suppose that would depend on the boiler setup and where it is in your house.

Just tryin' to stir the pot a little with some other ideas.....

Thats a good point, however I actually shut off the chimney with some 1' insualtion board to shut off the cold air downflow.

I did notice that even when the water in the HX is at the 190 level, the water in the boiler is about 20 degrees lower. Do i need a bigger pump on that loop? I wouldn't think so but .....?

 

[KsWoodsMan]

I did notice that even when the water in the HX is at the 190 level, the water in the boiler is about 20 degrees lower. Do i need a bigger pump on that loop? I wouldn't think so but .....?

Yes . Otherwise your heat in the OWB just sits there outside instead of more of it being moved to the house. If you are still gettinmg that much of a drop in temperature you should increase the flow more still.

Did you ever figure out if the OWB sits higher or lower than the pumps ? I'm in Kansas so flat ground is pretty much a given. If the OWB is below the house it might be having trouble drawing enough water uphill to the pump.

Are you heating the return line going INTO the oil burner or the water coming OUT OF it going to your baseboard heaters ? I'd be heating the water going to the baseboards not the water coming from them. And you might be already.

When does the pump from the OWB run ? full time or only when there is a call for heat ?

 

[John D]

Depending on where in your boiler the fill valve is...you might consider puttign a T in the drain,and using the drain,and blow off,this way the heat is pushed thru the boiler from one endo the other keeping temps even.On my Weil Mcclain if i use the fill and blow off,i would have poor circulation,and temp issues as well,dut to them both being on top of the boiler,and close to each other..

 

[urhstry]

Yes . Otherwise your heat in the OWB just sits there outside instead of more of it being moved to the house. If you are still gettinmg that much of a drop in temperature you should increase the flow more still.

Even if the pump is pushing water out to the boiler that is less than 3 feet away?

Did you ever figure out if the OWB sits higher or lower than the pumps ? I'm in Kansas so flat ground is pretty much a given. If the OWB is below the house it might be having trouble drawing enough water uphill to the pump.

OWB is much higher than the oil burner.... a whole level up.

Are you heating the return line going INTO the oil burner or the water coming OUT OF it going to your baseboard heaters ? I'd be heating the water going to the baseboards not the water coming from them. And you might be already.

I am circulating the cold feed water going into the oil burner and out before the pressure valve.

When does the pump from the OWB run ? full time or only when there is a call for heat ?

Full time. There are no controllers on the circulators for the oil burner heat..they run once demand calls...whether it is up to temp or not. A controller would help I guess. Any suggestions on what to get? That is probably why I use so much oil if I run that.

 

[KsWoodsMan]

Even if the pump is pushing water out to the boiler that is less than 3 feet away?

OWB is much higher than the oil burner.... a whole level up.

I am circulating the cold feed water going into the oil burner and out before the pressure valve.

(the OWB pump runs) Full time. There are no controllers on the circulators for the oil burner heat..they run once demand calls...whether it is up to temp or not. A controller would help I guess. Any suggestions on what to get? That is probably why I use so much oil if I run that.

Something keeps telling me you have a SERIOUS restriction in either the supply line or return line to the OWB. I don't remember you saying what kind of insulation or protection the PEX lines had in the trench. I'm betting that if you ran a flow check on the lines from the OWB one of them is plugged, kinked or smashed somewhere.

Have you back flushed the HX to make sure nothing got past your WYE strainer before it was installed?

I'd even go so far as to check that the nipples on the OWB were drilled all the way out when they were welded to the it.

What keeps you from plumbing the OWB directly into the baseboard heat ? And using the controller from the Oil Burner to turn on the pump when there is a call for heat.

 

[Bcat22]

i just want to make sure i have this all strait...

when you describe where the HX is in your boiler loop, it sounds to me like it is meant to keep the water in the boiler hot all the time. is this right?

let me ask like this, is there a direct path that the water MUST take through the HX, or is it set up so that the HX has its own loop to/from the boiler.

i would really love to see a picture of the HX and boiler so i can see how it is hooked up.
it almost sounds to me like the HX is set up kinda like a side arm for DHW, but maybe that is just my wrong take.
it should be hooked up in line, basically spliced into the line, preferably after the boiler.

sorry to ask for so much detail, but more info will help

 

[urhstry]

Something keeps telling me you have a SERIOUS restriction in either the supply line or return line to the OWB. I don't remember you saying what kind of insulation or protection the PEX lines had in the trench. I'm betting that if you ran a flow check on the lines from the OWB one of them is plugged, kinked or smashed somewhere.

I have TSP for my connections. I can tell you that I am sure I do not have a restriction on the OWB lines. Before the season started I took out a wide bend and cut the lines to put in two 90's. Before the hook-up, I flushed the lines to make sure of that. Keeping in mind I have no temp loss from the OWB to the HX. I am almost positive that the poblem isn't in the OWB loop, but my plumbing loop.

Have you back flushed the HX to make sure nothing got past your WYE strainer before it was installed?

Not flushed since the above.

I'd even go so far as to check that the nipples on the OWB were drilled all the way out when they were welded to the it.

What keeps you from plumbing the OWB directly into the baseboard heat ? And using the controller from the Oil Burner to turn on the pump when there is a call for heat.

I am not sure how to do that and wanted to make sure I didn't pressurize anything. Like the title says....I don't understand HVAC real well.

 

[urhstry]

i just want to make sure i have this all straight...

when you describe where the HX is in your boiler loop, it sounds to me like it is meant to keep the water in the boiler hot all the time. is this right?

That is correct!

Let me ask like this, is there a direct path that the water MUST take through the HX, or is it set up so that the HX has its own loop to/from the boiler.

Has its own loop.

i would really love to see a picture of the HX and boiler so i can see how it is hooked up.

I will take one however it is going to be hard to show what is going on since space around the boiler area is tight.

It almost sounds to me like the HX is set up kinda like a side arm for DHW, but maybe that is just my wrong take.

Now that you said it that way, that is also correct. My theory was that the circulated water in the boiler would grab the heat from the HX and keep things up to temp. Especially if there was a time when there was no demand from the boiler, it would recover quickly.

It should be hooked up in line, basically spliced into the line, preferably after the boiler.

That is probably leading into my problem. I have the water from the fill going into the HX and back out through the blow off line.

sorry to ask for so much detail, but more info will help

I will get a picture of this and see if it shows what I did.

 

[KsWoodsMan]

Originally Posted by Bcat22
i just want to make sure i have this all straight...

when you describe where the HX is in your boiler loop, it sounds to me like it is meant to keep the water in the boiler hot all the time. is this right?

That is correct!

Let me ask like this, is there a direct path that the water MUST take through the HX, or is it set up so that the HX has its own loop to/from the boiler.

Has its own loop.

i would really love to see a picture of the HX and boiler so i can see how it is hooked up.

I will take one however it is going to be hard to show what is going on since space around the boiler area is tight.

It almost sounds to me like the HX is set up kinda like a side arm for DHW, but maybe that is just my wrong take.

Now that you said it that way, that is also correct. My theory was that the circulated water in the boiler would grab the heat from the HX and keep things up to temp. Especially if there was a time when there was no demand from the boiler, it would recover quickly.

It should be hooked up in line, basically spliced into the line, preferably after the boiler.

That is probably leading into my problem. I have the water from the fill going into the HX and back out through the blow off line.

sorry to ask for so much detail, but more info will help

I will get a picture of this and see if it shows what I did..

Heating the water with , essentially, a side arm loop sounds like where the bottle neck is. Thermosiphon WON"T move as much heat into the boiler as a forced circulation path will.

After flushing and back flushing the HX, plumb it directly into the path of the water GOING to the baseboards. To hell with trying to keep the water in the oil boiler hot. For now let the OWB pump run continiously. Let the pump in the boiler push the water through the HX to the baseboards. The water in the lines to the base boards will be hot waiting to be circulated when there is a call for heat. This draws the heat needed, from the OWB/HX, on it's way to heat the house.

I'm certain the guy you had come check it wasn't familiar with your system or he probably didn't want to mess with it.

Pictures !

 

[John D]

After flushing and back flushing the HX, plumb it directly into the path of the water GOING to the baseboards. To hell with trying to keep the water in the oil boiler hot. Just let the pump in the boiler push the water through the HX to the baseboards. This draws the heat needed from the HX on it's way to heat the house.


Pictures !

I wanted to do this in my home,the problem is in many setups the boiler inlet,and outlet lines are 1 1/4" or larger,I have 3 circulators,one for the superstore,and 2 heating zones...and I felt putting the HX there with its 1" lines and fittings would place a restriction on the system when more than one circ was running,which happens quite often...sometimes there are 3-7gpm circs running...I think mine are 1 1/2" coming out,there quite a bit larger than 1"...although im not 100% sure..doing it this way would also "save" a pump,and 60 watts of electric consumption...as your using existing pumps

 

[KsWoodsMan]

John D , I didn't intend to edit my last post for clarity after it was quoted. as quoted I don't think it was as clearly stated as intended.

I see your point about the 1" lines and HX restricting the flow to 1.25" lines or larger.

As it is now he is barely getting any heat from his system and the OWB sits out there barely doing much of anything. He has one pump feeding his base boards with 2 zones. From what he described, the "side arm" loop isn't directly in the path of the circulated water. Any improvement will probably be readily noticeable and fine tuning can be done when there are fewer demands on his heating system.

 

[mtfallsmikey]

All of the above are good suggestions, but still no piping diagram/pics, it's kinda hard to diagnose without them.
Here's an idea of what may be happening IMO...

If your indoor heating system is traveling thru the oil boiler, your temperature loss/swing may be happening there...why?
The boiler, when heated by the water transferred thru the HX by the OWB, can cause an updraft thru the oil boiler, sending some (not all) of the heat right up thru the chimney. Check the line temp. of the supply/return pipes on the boiler where it comes into and out of the boiler...this has happened before.

 

[itn]

just a thought. buddy of mine was having trouble with his boiler keeping up once it got very cold. he was using a programmable thermostat that dropped the temp to 60 at night and during the day when he was gone or asleep. when it got really cold it wouldn't keep up. he ended up just leavin his thermostat at 70 and only dropping it to 68 at off peak times. fixed his problem.

 

[mtfallsmikey]

To do this really right....put the HX in the main supply line out from the boiler, but before the air scoop/flow control valve, and use 3-way zone valves to isolate the BB loops from the boiiler.

 

[Bcat22]

All of the above are good suggestions, but still no piping diagram/pics, it's kinda hard to diagnose without them.
Here's an idea of what may be happening IMO...

If your indoor heating system is traveling thru the oil boiler, your temperature loss/swing may be happening there...why?
The boiler, when heated by the water transferred thru the HX by the OWB, can cause an updraft thru the oil boiler, sending some (not all) of the heat right up thru the chimney. Check the line temp. of the supply/return pipes on the boiler where it comes into and out of the boiler...this has happened before.

we already covered that, he has the flue blocked

 

[urhstry]

John D, that is EXACTLY what I thought and why I did not do it that way. My pipes are 1.5 inches so piping in 1" pex to it wouldn't do much ...from what I was told. Piping in the HX to the baseboard lines could be do-able but I have 4 zones.....4 different lines run to them. That brings me back to piping it into 1.5" lines. Hope I am explaining this clearly. Pics on the way....