Water to air HX question

[anthony.d]

I'm a new guy here, and hoping to maybe get a question or two answered. I installed a new CB 5036 about five weeks ago. Heating 1700 sq ft home, not the greatest windows, but insulated good.

The boiler is only hooked up to a 18 x 20 HX in the plenum and the plenum is 18 x 26. I plan on installing the exchanger for domestic hot water and other kick space heaters next summer/fall.

I have the Taco 009 mounted outside on the boiler connected to 1" pex about a 65 foot run from boiler to hx. I have a temperature gauge on supply and return line in the basement. I don't seem to be loosing any heat coming to the house, or very very little. But here is my question.

Lets say the boiler is up to temp (180*), the supply line is at 180* and when the furnace kicks on there is a temp. drop of about 22*. (Return line is at 158*). Is this a normal drop?

Another question is I have a digital thermostat hooked into the furnace. And I can set the span of when the furnace kicks on and off around a certain temp. I have it set to where it kicks on when its almost 2* below the set temperature of lets say (72*).

My furnace would be on I believe about 40 minutes to get the house back to 72*, and then be off for an hour or so. My boiler water temperature has now dropped to about 166*, and doing a burn to get it back to 180* takes about 25 min. Does this temperature drop calculate to about 24000 btu of water heat was used since the boiler holds about 200 gallons? And does my HX that is rated at 120,000 btu, actually would transfer 120,000 btu of heat in an hour if I were able to supply 180* thru it for the hole hour?

Any answers or comments would be great thanks.

Anthony

 

[ohioburner]

I have a Heatmor and I loose 8* over the HX. Don't know if that is good or bad but it is working great. My HX is the same size as yours but I got a B&G pump. 22* seems like alot. There are alot of people on here that will answer your question better then I can. Welcome to the site.

 

[Windwalker7]

I lose about 20* when the furnace fan kicks on.

 

[trialanderror]

i have 1" logstor pex, 220k btu HX,

easily 20* temp drop, noticable where i can touch the incoming and outgoing and esaily notice a difference...


and no, heat exchangers rate their BTU/hr with the temp in/out and GPM....

look at this and carefully do some math/calculations

http://northlanddistrib.com/heat-exchangers/water-to-air.php

you can have a massive HX, but if the water moves slow, you can't pull hardcore BTU's to match it's rating....

hope this helps some questions you have.


edit
another big help is to have a digital thermostat for the house. I bought one, and it's tottally bad ass. it's got a temp swing setting. I got it setup enough where the blower will come on 4 sometimes up to 6 times in an hour, but only run for 2 or 3 minutes. By doing that it doesn't zap my water temp down so much, there fore OWB doesn't have to run so long to meet recovery temp....

my hx is so big if it runs for 25 minutes it'll chill my water from 185 to 155 no problem....and i have a kenworth radiator in my garage that's big enough to hold 4 20" box fans, and that pulls my water temp down FAST.....

 

[mtfallsmikey]

Temp. differential between supply/return is otherwise known as Delta T. 22 deg. is spot on. Older thermostats had a variable wirewound resistor to set "differential", which is the same as the swing/or cycles-per-hour in today's digitals. Most HX's SHOULD have charts or graphs showing the BTU output at various temps./GPM flow. The difference between 150-180 deg. water on avg. would derate the coil by approx. 50%. Depending on how your system is piped, etc., that 009 may be oversized for your app., and moving the water too fast.

 

[anthony.d]

My HX

Reading posts and doing a little research, I think I don't have enough water flow from boiler to HX to maximize the btu output.

The Taco 009 that I have only flows 8 gpm, with elbows, swing check valve, and other fittings, I'm sure I'm lower than that.

I measured the incoming and outgoing air, befor and after the HX and its about 69* and 122*.

I plan at least buying the Taco 007 which flows 20gpm this weekend, maybe the 011, but I'll have to see what kind of funds I have.

I want to get this figured out, befor the heavy cold sets in. I just seems to take too long to increase the house temp 2* compared to the LP furnace.

Thanks for the info guys.

 

[mtfallsmikey]

Reading posts and doing a little research, I think I don't have enough water flow from boiler to HX to maximize the btu output.

The Taco 009 that I have only flows 8 gpm, with elbows, swing check valve, and other fittings, I'm sure I'm lower than that.

I measured the incoming and outgoing air, befor and after the HX and its about 69* and 122*.

I plan at least buying the Taco 007 which flows 20gpm this weekend, maybe the 011, but I'll have to see what kind of funds I have.

I want to get this figured out, befor the heavy cold sets in. I just seems to take too long to increase the house temp 2* compared to the LP furnace.

Thanks for the info guys.

Being honest...and seeing what others get out of their HX's...120-130 deg. discharge air to the ductwork, with 170-180 deg. hot water going in is about right. What fan speed are you using?