Heating Two Houses

when I get my efm 520 hooked up and running I want to run under ground to my sons house next door. it is fifty feet from one to the other, each house is about 2000 sq foot .the stoker will be in my cellar . I believe the stoker should have no problem heating both? any suggestions on under ground pipe? also will the hot water coil supply enough hot water for both?

Here's the product that I'm using. Make sure what ever underground pex pipe you use is long enough from point A to B... I'm going to say no on coil for both houses, but the experts will chime in on that.

http://www.thermopex.com/?src=googletp&gclid=CK_r ... 4AodLB8AMQ

What do you have for a chimney? It needs to have good draft and a 7 or 8" thimble. Your 520 should be able to handle the load, but it will probably need to set at least at 6 teeth of feed.

The Thermopex that Wiz posted the link to is a good product. I know several people using it that are very happy with it. Be sure to bury some wire along with the pex...thermostat wire and some 14/2 in conduit...that way you can mount the circulator in your son's house and let him pay for the electric...you will use the underground wire to signal the EFM that there is a heat call.

Rather that trying to pipe water back and forth to the tankless coil, I would mount a heat exchanger in-line with the pex in your son's basement.

Thanks Rob, forgot to mention running conduit for tt wires. Actually I buried 2 conduit pipes, so shop had directv

The guys on here really know their stuff and they will be able to correct me if I go wrong, but would it be worth it to make a primary/secondary loop in this situation? Run a primary loop from your house over to your son's and then secondary loops to control each house accordingly? Just a thought. Didn't know if it would be more efficient.

24/7 circulation to the second building will provide faster response to a heating call from the remote load - but it will increase your line loss (re cost of operation) if you do not invest in very good installation on the transmission lines of that long loop

I wouldn't

Rob R. wrote:What do you have for a chimney? It needs to have good draft and a 7 or 8" thimble. Your 520 should be able to handle the load, but it will probably need to set at 5 or 6 teeth of feed.

The Thermopex that Wiz posted the link to is a good product. I know several people using it that are very happy with it. Be sure to bury some wire along with the pex...thermostat wire and some 14/2 in conduit...that way you can mount the circulator in your son's house and let him pay for the electric...you will use the underground wire to signal the EFM that there is a heat call.

Rather that trying to pipe water back and forth to the tankless coil, I would mount a heat exchanger in-line with the pex in your son's basement.

I have an outside chimney with a 8' flue also have stainless steel 8' triple wall and 8' stainless for pipe.

I would install an indirect heater, such as an Ergomax, which I use, to act as a buffer and hot water storage. Your son could then have his hot water available, through the ergomax coil, at all times and you wouldn't have to possibly overtax your coil. Someone should do the numbers for you.

I don't think you'll have any problem heating both houses with a stoker, but 6 teeth may not do it.

I'm not gonna say you can't heat 2 homes with a 520 because you certainly can.

But I will throw some caution to the wind here. That is a significant load if these homes are not insulated well etc. That is my only caution.

As Stokerman said... I think 6 teeth would be a minimum for 2 homes. and on those cold January days like where I live... i'm thinking 6 teeth isn't going to cut it really.

If your homes are not insulated well.... You'll have a tough time keeping up with demand.

IMO... FWIW...

Ideally when planning a project like this, you would carefully calculate the heating load, and base the boiler size on that. In this case, the homes are existing, insulation values are probably unknown, and it was my impression that they already own the boiler....so there is no sense going nuts with heat loss calculations, the 520 will either handle it or it won't. A conservative approach would be to install the boiler in house "A" and see how it handles it before hooking up the second home. Perhaps it makes the most sense to have a separate boiler in each home?

Another thought - if an EFM 520 is taxed by a 2000 sq. ft home, some work needs to be done to keep the heat in the structure. There is no sense heating the outdoors, even with coal.

How much fuel do these homes burn currently?

Rob is dead on with the heatling loss calculations.

And obviously we don't know how well your homes are insulated but I can tell you I went from burning oil to coal about 8 years ago. Oil was 1.92 per gallon, even with an old farmhouse I saved almost $1500 that first year in heating. Since then I have insulated the entire house. 15 new windows etc. which has helped even further.

Good luck! We are here to offer any assistance we can!

Hummmmm

I ASSummed the load loss calculations had already been done in consideration of the combined load

ME BAD !!!!! but then I am chastised in the past = calling for these preliminary annoying things

Rob R. wrote: In this case, the homes are existing, insulation values are probably unknown, and it was my impression that they already own the boiler....so there is no sense going nuts with heat loss calculations, the 520 will either handle it or it won't.

I agree with Rob on the calculations. If this project proceeds, the best way to make sure the 520 can handle the load is to be extra vigilant regarding factors that may prevent it from producing its max output. Things like monitoring your ash ring to ensure you have a good fuel/air mix, frequent cleaning of heat exchange surfaces and avoidance of junky and/or undersized coal can all help to make sure you don't come up short in the dead of winter.

That does sound like a substantial load for a 520. AFAIK two 2000 sf houses would normally have considerably more exterior surface area than would a single 4000 sf house, and any heat loss from the conduit would add further to the load. (Hmmm, I seem to be agreeing with Sting more than I thought here, though I still wouldn't want anyone to be foolish enough to rely on such heat loss calculations to limit the sizing of a coal boiler for an old house.) One option you might want to consider is swapping out the 520 for a bigger boiler up front. Another possibility would be keeping the 520 head and base but swapping out the S-20 stoker for one with a bigger feed tube that would reliably burn buck at 20-25 lb/hr.

Random thoughts on things I don't really know anything about :

- good to make sure the pipes moving boiler water to/from the second house are sized to account for extreme demand conditions as well as heat loss into the ground - otherwise the second house may not always keep up; and,

- x2 on the idea an indirect water heater might be needed in the second house. I'm not generally a proponent of them when a DHW coil is available, but I think getting satisfactory DHW performance in the second house off the coil might require a recirc line, and entail extra expense and heat loss. The one possibility to consider would be "bundling" the DHW line with the trunk line for boiler water going to the second house. If the trunk line is kept hot, the DHW wouldn't cool as it sits in the pipe. If anything, it might need a tempering valve in the second house.

Mike

- x2 on the idea an indirect water heater might be needed in the second house. I'm not generally a proponent of them when a DHW coil is available, but I think getting satisfactory DHW performance in the second house off the coil might require a recirc line, and entail extra expense and heat loss.

Exactly. With my Ergomax, I can get usable hot water for a shower or two, even after the boiler has been down for most of a day. The Ergomax is just part of the circulation loop. It's the only way I would try to provide domestic hot water to your son's house.

Rob R. wrote:Ideally when planning a project like this, you would carefully calculate the heating load, and base the boiler size on that. In this case, the homes are existing, insulation values are probably unknown, and it was my impression that they already own the boiler....so there is no sense going nuts with heat loss calculations, the 520 will either handle it or it won't. A conservative approach would be to install the boiler in house "A" and see how it handles it before hooking up the second home. Perhaps it makes the most sense to have a separate boiler in each home?

Another thought - if an EFM 520 is taxed by a 2000 sq. ft home, some work needs to be done to keep the heat in the structure. There is no sense heating the outdoors, even with coal.

How much fuel do these homes burn currently?

both houses have blown in insulation and new windows, new doors , not like a newly built home but upgraded from when they were built.