Woodmaster 4400 supply and return switched?

[MiSolar]

Hello, hoping you guys can help me figure something out. I just moved into a house with a woodmaster 4400 and I believe that the hot water supply line was hooked up to the cold water return instead by mistake. Currently the hot water comes into the house and goes to a flat plate exchanger for DHW and then goes to the lower, blower side of the water to air exchanger. It leaves on the upper side closest to the registers.

From what I have read, this is not the best way to route the water through the water to air exchanger and I would prefer if the hottest water got to the furnace before going to the DHW. Does it sound like this is hooked up backwards? Based on the connections, it looks like the easiest to switch would be the lines behind the boiler. The pex lines go loose into a pvc pipe to the house. I know this isn't an ideal set up either and I might fix it this summer. The lines to the back of the boiler are about 1 foot different in length. I was hoping I could pull one line in a foot and pull out the other line a foot and reconnect to the correct locations. I haven't done any plumbing with pex before. Is there anything I should know? It looks like there is some kind of sealant used in the threads of the connection to the valve. Will I need something similar when I reconnect? Thanks!

 

[Karl_northwind]

You have a pretty typical setup. the DHW pulls off heat for very short periods of time usually, and the resulting lower temp heating water is probably still fine to provide some, if not quite as much as before, heat to the water to air HX. if the furnace is blowing thru the coil, and the DHW HX is later, whenever the furnace is blowing, the boiler water will not be hot enough to deliver much heat to the DHW.

at least that's the logic I've seen from the OWB installer guys in my area. I don't think you have too much to worry about on that front. but you should definitely think about the underground lines. if you're burning wood at 35% efficiency, make sure you are losing as little as possible to the ground between the house and boiler. what sort of distance is that in the PVC line?

karl

 

[MiSolar]

The distance from the boiler to the house is about 75 feet. I would like to dig it up this summer and foam the line in place while I add lines to some solar hot water collectors.

I was reading in another thread that people achieved 10% higher register air by reversing the flow in the water to air exchanger. I'd be happy just getting that switched. Can you desolder the copper pipes from the hx while the pex is still attached?

 

[maple1]

Is it keeping your house warm?

I think I would leave it as is - realistically, DHW is not a very high heat demand & it shouldn't be pulling much heat out before the water hits your WAHX.

Have you measured any pipe temps? That should tell you what's what - measure everywhere it goes in & out of something. I would be really interested to see the difference between where it leaves the boiler, and enters the house - sounds like you would be losing a ton of heat underground. Good idea redoing that.

 

[MiSolar]

The house is staying warm. It is sluggish to recover in the morning though. I have been working on sealing ducts and will insulated the vented crawlspace they are in also.

What's the best way to insulate the plenum that contains the hx?

Water coming into the house is reading about 156 F when the boiler reads 175 F on the display. I'm measuring the 156 with a temperature sensor taped and insulated on the line coming into the house. I record those temperatures with an Arduino microprocessor.

 

[maple1]

Ya, that's pretty huge heat loss there - 20°? Guys who do the underground the right way report only a degree or two. That's a lot of wood to send into the ground.

 

[MiSolar]

The cold water return is likely sapping some of the heat because it touches the hot water pipe in the pvc. I'd like to see the temperature difference a lot closer to 0°. Any ideas on how I could seal up the ends on the pvc tubing better? Is there any reason not to add some kind of insulation to the back on the boiler? It gets pretty warm back there.

 

[Karl_northwind]

NO, you will have to take the lex off to de-solder stuff. if you want to change it and depending on your skill set, you could just cut and switch the Pex lines with Pex fittings. and 20 deg is a lot of loss. foam in place is a good way to go, as you already have the pex.
to insulate the plenum, the usual is to seal the joints, and then wrap it in a blanket of ~2" insulation with an outer aluminum layer. it's something you get at a heating supply house.

karl

 

[maple1]

The cold water return is likely sapping some of the heat because it touches the hot water pipe in the pvc. I'd like to see the temperature difference a lot closer to 0°. Any ideas on how I could seal up the ends on the pvc tubing better? Is there any reason not to add some kind of insulation to the back on the boiler? It gets pretty warm back there.

I don't think sealing the PVC will help with much.

You're also likely losing a lot of heat in the return line too - did you measure the temps on the return pipe where it leaves the house, and where it enters the boiler?

Then that brings about the issue of return temp protection at the boiler return. Does you boiler have return temp protection? If not, it is getting a steady diet of return water that is much too cold, which is making excess creosote condensation in the firebox & may be quietly eating away at your boiler.