OWB ? House too warm

[Coldfront]

The manual says the pump needs to run continuously when the boiler is fired. I guess otherwise it will overheat. The only other thing it heats is the domestic hot water heater. The furnace fan is not coming on the heat is just rising with convection she has a garage but it is not piped for heat, now the ground is frozen. And it is not like it was warm out last night 15 degrees f. Btw the Wood Master 3300 is the smallest one they make. I think what it needs is a valve like suggested to devert the water from the heat exchanger and loop it someplace else. It would be nice to run it into the garage.

 

[Del_]

The manual says the pump needs to run continuously when the boiler is fired. I guess otherwise it will overheat. The only other thing it heats is the hot water heater. The furnace fan is not coming on the heat is just rising with convection she has a garage but it is not piped for heat, now the ground is frozen. And it is not like it was warm out last night 15 degrees f.

There is a lot of thermal stress created in the system when the hot water loop pump kicks on and off. Also domestic hot water would be affected. Also if there in not anti freeze in the wood boiler freezing at cold spots in the system may be a problem.

 

[NSMaple1]

Sounds like the hx is oversized for the application. Some decent fixes have been suggested. Is there a speed selector on the circ pump by chance?

 

[Coldfront]

I'm not sure but I think the only thing the inside house wood thermostat does is control the furnace fan to kick on. I did tell her to try closing all the heat vents in the house. I will try calling the manufacture of the wood boiler tomorrow and see what they say.

 

[NSMaple1]

I will offer another suggestion though. You could do a little bit of replumbing and set up primary/secondary flows. You would need to add another circ that would run when the furnace blower does (which might require the use of a relay, or not), and 2 T's. No valves needed.

 

[NSMaple1]

If the boiler people didn't do the design & install, they might not help. This isn't the boilers fault, its in the system design.

 

[Coldfront]

I have heard of others with owb who have this over heating house temp problem before. I occasionally had it myself with a in basement side by side wood / gas furnace. No control other than open windows. Problem with that is if you leave the house and forget to close the windows and fire goes out, there goes your gas bill or come home to a very cold house.

 

[NSMaple1]

They have a system design issue also, then.

 

[Coldfront]

Is there such a thing as thermostatically controlled vents to outside air that could be installed on outside walls? The other concern with leaving windows open is security.

 

[Oxford]

I have seen many, many manufacturers show constant flow through the water to air hx as part of their standard installation. Also through an exchanger on the DHW circuit usually in series with the furnace coil. Usually, this means overheated houses and scalding hot water, but those points are usually minimized in the sales literature. By far the best way is to use primary/secondary pumping,as others have suggested. In my opinion, of course. This will require one pump running continuously to establish and maintain flow in a boiler loop, then thermostatically controlled pumps to establish flow to the exchangers when desired. This means more wiring, more plumbing, and some actual design taking place, but I've never seen it not work.

 

[zogger]

I thought about loading less wood, but that would kind of defeat the purpose of a owb and 12 hour burn time.

I thought a water boiler heated up a huge amount of water so you didn't necessarily have to have long burn times? Once the whole tank is hot, the fire can about go out and you still suck heat from the thermal mass of all that hot water.

Anyway, new heater during shakedown, feed it a lesser amount of wood, or shoulder season wood. A lot of people would love to have that problem to solve, plenty of heat! Better than the opposite, never get enough heat!

 

[lindnova]

I wouldn't want to open windows and waste all the heat.

Looks like either a 3 way valve, damper or a separate pump circuit would be the solution. I would vote for the 3 way valve.

I would not turn off the pump. That could cause frozen water lines and is not good for the boiler not to have circulation (hot spots). Also you want the outdoor boiler to stay hot - I have mine at 180 with 160 fan on.

Mine has a bypass so I can still have domestic hot water during warm days in the spring and not overheat the house. If your daughters is overheating at 15° it is not an intermittent problem.

 

[Marshy]

I will bet the donut against the hole that this is piped so that there is constant flow from the boiler through the heat exchanger in the furnace plenum. If so, and in relatively mild weather with a tight house, then that constant heat source is going to warm the air stream and cause air movement by convection, causing the house to overheat without the thermostat ever calling. There's nothing mechanically or operationally wrong with any of it, except that it's too big for the home and has about the same relative engineering sophistication as a pointed stick.

Can I like this comment twice?

if you install that valve and actuator, you will deadhead the pump. The correct way is to pipe in and install a 3-way valve.

Bingo, 3 way valve. One side is supply, one is to the heat exchanger and the third should be piped as a bypass to the heat exchanger and be sent back to the boiler. When the thermostat calls for deman water sent to the heat exchanger. The bypass can be tied into the pipe downstream if the heat exchanger, just remember to use a check valve in-between the tie-in and the HTX.

 

[Coldfront]

Here is another idea what about a 3 way valve set up that you could adjust manually to trickle the hot water though the heat exchanger inlet and have the bulk of the hot water bypass to the outlet line of heat exchanger through a one way check valve. But still able to open it and not bypass when it is extremely cold out. Or is that what that thermostatically controlled valve mentioned before is supposed to do?

 

[Coldfront]

Ok Marshy that is exactly what I was talking about.

 

[lindnova]

Here is another idea what about a 3 way valve set up that you could adjust manually to trickle the hot water though the heat exchanger inlet and have the bulk of the hot water bypass to the outlet line of heat exchanger through a one way check valve. But still able to open it and not bypass when it is extremely cold out. Or is that what that thermostatically controlled valve mentioned before is supposed to do?

I have 2 ball valves for my bypass and have tried turning down the valve to the exchanger and it did not work because the small flow still warms up the plenum which will put heat into the house slowly yet not provide enough heat to actually heat the house. If you had the valves it would be worth a try, but I would not go through the work to try it.

 

[hupte]

The manual says the pump needs to run continuously when the boiler is fired. I guess otherwise it will overheat. The only other thing it heats is the domestic hot water heater. The furnace fan is not coming on the heat is just rising with convection she has a garage but it is not piped for heat, now the ground is frozen. And it is not like it was warm out last night 15 degrees f. Btw the Wood Master 3300 is the smallest one they make. I think what it needs is a valve like suggested to devert the water from the heat exchanger and loop it someplace else. It would be nice to run it into the garage.

the boiler wont overheat. the only way to overheat an owb is an aquastat malfunction, or leaving the door open. many ppl heat their domestic water year round. that requires very little heat. and they don't have an issue with overheating the boiler. you have a couple of different options. what I always do when installing a boiler to a hot air HX inside a forced air furnace is to install a bypass so when its warm out you can bypass the furnace. I'll try to get a pic posted. is your domestic water plumbed in series with the furnace or do you have some type of manifold set up? cause that could make the difference whether you need to plumb in a bypass. all you need for a bypass is 3 valves.

 

[hupte]

here is a pic of a bypass set up its all one inch pex. I should have turned the flash on, and held my hands steadier. good thing I make money installing owbs cause I would starve as a photographer. lol.

 

[Coldfront]

I have 2 ball valves for my bypass and have tried turning down the valve to the exchanger and it did not work because the small flow still warms up the plenum which will put heat into the house slowly yet not provide enough heat to actually heat the house. If you had the valves it would be worth a try, but I would not go through the work to try it.

But couldn't you manually just keep opening / closing the heat ex. bypass manual valve until you reached your desired temp. Yes I know it would be a pain in the ass, but should be possible without any extra wiring thermostats, and only involve installing 3 valves 2 adjustable valves and a one way check valve.

 

[Coldfront]

It seems apparent that the thermostat controlled furnace blower fan is not going to be nessessary to keep this house warm unless it gets well below zero f.