Seeking to reduce heat loss to ground on OWB system

mille755

Hello,

I have a hydronic heating system. In my basement i have a Weil Mclain Natural Gas Boiler with 3 Seperately pumped zones for the house. Baseboard heating units comprise the loops/zones.

In my shop i have a Aqua Therm Wood Boiler, there is a floor loop in the part of the shop the boiler is located in and a hydronic heater with a fan in the other part of the shop.

I use the wood boiler as long as i have wood Previous owner said he did about 10 cords a year, i cant ever get more than about 5-6 cords put away, and it probably doesnt end up the driest. I probably burn about 20-30 or so pallets every year from work as well.

The pump for the wood boiler runs continuously as is common in these setups. Its about 100 or 150' 1 way to the house and its run with 1" Pex-Al-Pex. i get about 3-5° temp drop out and back, when there is no demand in the house. I dont know how many GPM i am pumping its a taco 007, guestimating 3-4 gpm i calculated that i am probably losing a cord of wood every 1-2 months just heating the ground.

Easy fix is to turn the pump on only when there is demand, but i understand that can cause hot spots in the wood boiler. Other idea is to add a bypass with zone valve, open zone valve when there is no call for heat, it will pump thru the least resistance. I already have a tube between the house and shop i can send a signal wire thru.

Please tell me the downsides of my plan, i know it will take an extra minute to get heat.

I have a bunch of photos, but idk if i will be able to post as a new member.

Erin Holohan Haskell

Welcome @mille755. Just click on the image icon above the text box to post photos. Here are more tips for using the forum: https://heatinghelp.com/forum-user-manual

mille755

Over-temp aquastat turns on pump to front garage loop to dump heat if for some reason the boiler runs away.

mille755

More Shop system photos

mille755

Photos of house system and how it is configured, any comments welcome.
I will explain that i think this system was put together by trial and error.
From the explanation from the previous owner and my experience with the system i will say:

Originally there was ghost flow (undesired heating) due to the WB pump causing flow and i have verified it was thru the loop marked with a 3. Which makes sense if you see how many tees elbows and reduced diameter piping the WB loop made while trying to get thru the NG boiler., it ends up pumping partially thru one of the loops. Also the closely spaced tees way of tying in was not followed, and it pumps thru the boiler which makes the ghost flow a lot more likely.

Is it ok to use the safety relief port to tie into? As shown here?

So to combat the ghost flow he put in a taco zone valve with bypass, but i think perhaps the bypass did not allow enough flow or got plugged (he mentioned there being a small orifice for the bypass) and the WB unit may have over temped a couple times(i know it did when i shutoff the manual bypass).

So then he put a manual bypass in and said he keeps it at a 45 and when i have closed the manual bypass i have occasionally over-temped the WB mostly when burning pallets(they tend to overshoot).

Any comments welcome on this system.

I also used to get a lot of ghost flow thru the porch loop until i installed a pump with an IFC, now that is solved.

mille755

hot_rod

Would freezing be an issue if the lines to the house were not flowing?
if not a 3 way zone valve would work. It eliminates the stratification in the tank, but may still be a better trade off
Are the underground pipes not insulated? Standing water in the trench?

mille755

Yes they are insulated and they are far enough down that they wouldn't freeze. I am only losing 3-5 degrees round trip, but continuously it adds up.

So I was thinking that I wouldn't really need a three-way valve because the bypass is going to be so short compared to the normal loop that I shouldn't get much flow if any flow in the normal loop? Am I wrong in thinking that?

GroundUp

The only way to fix this properly is to dig up the lines and replace them with something better insulated. Thermopex, Insulpex, Rhinoflex, and Logstor are the only 4 that would completely eliminate the possibility of this heat loss and groundwater intrusion. Something Like Insul-Seal is an option but will cost 2-3x that of one of the prior 4 options. The Aquatherm needs constant circulation and lots of it, probably more than this 007 is providing. Bypassing it with a 3 way is an option, but the repeated thermal shock from the 50 degree groundwater returning to a 200 degree water jacket when the bypass closes WILL crack a weld. It happens all the time with Aquatherms specifically, I've seen it twice this year already.

3-5 degrees with the piping and circ you have is not bad, but is it accurate? The cool return line and hot supply line will always be exchanging BTUs given their close proximity, so it's nearly impossible to figure out what's actually lost to the ground.

mille755

All right, sounds like that's a bad idea. I guess I'll just deal with it. I was also thinking maybe a Delta t-based pump would lower the flow when there's no call for heat? I don't really know much about this, are there other pumps you could trigger to run at two different flow rates? Just another idea.

hot_rod

mille755 said:

All right, sounds like that's a bad idea. I guess I'll just deal with it. I was also thinking maybe a Delta t-based pump would lower the flow when there's no call for heat? I don't really know much about this, are there other pumps you could trigger to run at two different flow rates? Just another idea.

The Aquatherm wants a certain flow all the time I piped them with a primary loop, a dedicated pump just for the boiler

A variable speed pump may not keep the boiler protected 

I don’t see an easy work around that would be worth the time and $$