Hot water loop off steam boiler?

Kjmass1

I'm looking to finish off my basement and was wondering if it's advised to run a hot water loop off an older boiler. I have a 200K Penco 1 pipe system that's way oversized for the EDR and house load. MassSave put it at 1973. Basement is 600sf 50% below grade, but has a small room under an addition that is mostly above grade, has 6 windows and a door. Total heatloss for the area is maybe 10k. Any good solutions here for heat? The steam system works great for the main house so don't want to jeopardize that. Thanks.

Jamie Hall

While I wouldn't say this is done all the time, adding a hot water loop is common enough. It's a little more complicated if the proposed radiation is above the boiler water line, but whether or not that is the case it's not at all difficult. It does need to be done right, of course.

If the proposed radiation is below the water line, it's a matter of finding a handy tapping on the boiler also below the water line, running a piper to a strainer, then a pump, then through the radiation and back to the wet return on the boiler. Add a thermostat to control the pump, and that's it.

There's plenty of capacity in the boiler for a small load like that.

SteamingatMohawk

@Jamie Hall I've seen a couple of discussions that talk about using a filter or strainer in water systems. When I owned houses with baseboard hot water, I never had any of those.

While circulating boiler water is different because of corrosion products, etc. I am curious as to the location of the device. As an assumption for consistency, I believe a filter is for small material, like corrosion products and particulates and a strainer is for much larger material.

The reason I mention it is I believe a suction strainer is good practice as is a filter on the discharge.

Anything that reduces the pump suction pressure too much could cause flashing/cavitation (depending on fluid temperature and pressure) and internal damage to the pump.

Kjmass1

Jamie Hall said:

While I wouldn't say this is done all the time, adding a hot water loop is common enough. It's a little more complicated if the proposed radiation is above the boiler water line, but whether or not that is the case it's not at all difficult. It does need to be done right, of course.

If the proposed radiation is below the water line, it's a matter of finding a handy tapping on the boiler also below the water line, running a piper to a strainer, then a pump, then through the radiation and back to the wet return on the boiler. Add a thermostat to control the pump, and that's it.

There's plenty of capacity in the boiler for a small load like that.

Thanks. Yes, all of the baseboards would be below the waterline since the basement is all the same level.

I'm assuming there is some sort of cut off so it boils the water hot enough for the radiation but not to make steam for the rest of the house if it isn't calling for heat?

I also feel like it probably won't have much demand for heat as the basement stays in the 50s now on cold days, get all of that insulated with closed cell foam, plus a warm boiler room throughout the winter it might sit at 60-65 without heat.

EBEBRATT-Ed

@Kjmass1

It certainly can be done. It becomes a little pricey to do it right. Without a heat exchanger you need a bronze pump which is a little pricey then pipe, valves fittings and baseboard and some knowhow on how to pipe it.

With a heat exchanger you need that plus 2 pumps (1 bronze) an expansion tank, water feeder, relief valve, air removal devise etc.

If you were going to heat the entire basement I would go this route.

For a small room that stays in the 50s without any heat I would reconsider and probably use electric baseboard.

To get 10,000 btus you only need 3000 watts of baseboard. (2) 6 footers at 240 volt will get you that. 12.5 amp load @240 volt. And they make electric cabinet heaters with a fan and panel radiators for the wall if you prefer

Around $200 + a thermostat at Supply House.com

Kjmass1

@EBEBRATT-Ed I like your thinking. Spend the money on the insulation and tightening everything up, and could even do 2 zones of electric so the coldest area runs independent of the general living. In theory might only need to heat from 60-70 on the coldest days of the year, vs the complexity of pumps all that copper etc. It would be just a big rec room/kids room mostly utilized on the weekends.

ethicalpaul

You can definitely run a hot water loop above the water line even if just circulating the boiler water (without a heat exchanger). You can't have leaks, or they will pull air into the loop which is not much of an issue when it's circulating but can become a problem if the water is not circulating for long periods. My highest loop is about 15 feet above water line. The highest theoretical height is your local barometric pressure measured in inches of water or roughly the low 30s of feet.

Put the filter screen before the bypass loop, that way if it gets clogged the symptom will be "no heat" rather than "pump destroyed". If the screen gets clogged, the pump will circulate the water around the bypass loop with little or no input of hot water from the boiler.

It's all explained in this fine article: https://heatinghelp.com/systems-help-center/how-to-run-a-hot-water-zone-off-a-steam-boiler/

Hap_Hazzard

Considering how much heat my pipes dump into my basement—even though I've insulated most of them—are you sure you can't heat that space just by removing insulation from any steam pipes that run through the space, or maybe just diverting some wet returns around it? You can use copper pipes for condensate, and maybe even add a fin-tube radiator or two.

Kjmass1

@Hap_Hazzard Probably could, but planning on burying them behind the framing. Need the head clearance to meet code.

da13ear

The previous owners of my place added a hot water loop when they extended the house. Its a closed 2 zone loop that runs into a plate heat exchanger. The other side of the heat exchanger connects to a pipe toward the bottom of the boiler and has a circulation pump cycling the water through the exchanger and back into the return.

The electronics are cool (complicated?). When either of the forced water zones need heat, the pumps circulate water on both sides of the exchanger while the boiler turns on. Once the boiler hits 175, an aquastat cuts it out but the pumps stay on until the tstat is satisfied.

one problem is that my plate heat exchanger clogs over time (like 10yrs). Some sort of filter or trap would have been nice to keep out the gnk. I just had someone install isolation valves on both sides so I can power flush the heat exchanger with my water heater water.

Happy to chat further.

Chris

Kjmass1

@da13ear Very interesting, thanks for the info.

Bodycount

I have a hot water loop on a second floor addition the previous owners installed. 

When it works, it works well. I’ve had numerous issues over the years. 

1- use a pump with bronze or stainless impeller. 

2- flush the system off season. 

3- I don’t have a strainer. Yet. 

4- my system uses a zone valve & aquastat. 

5- if it’s set up properly, I would prefer this over any electric heat. 

da13ear

@Bodycount What pump do you use? I am using a grundfos ups15-58fc and find that they work well, but are fickle and die easily in the heat.

Bodycount

Taco. 007 I think. Confirm the impeller material. I use the quick disconnect, shutoff flanges, because eventually you’ll have to change it. 

dopey27177

See the enclosure.

No heat exchanger needed.
Works up two floors with no special devices.

Jake