Power requirements for Peerless Boiler

[Randy Boyd]

I just bought a house in Massachusetts. It has a near brand-new Peerless Boiler MI-05-SPRK-WPC-N unit for 3-zone heating of the house. We've been hit relentlessly this year with extreme winds that finally killed power to my region for days. Since this boiler requires power to function, we were very cold.

Now that I'm aware that it needs power to work, I intend to install a battery backup system just for the boiler. To do that, I need to know the expected power draw for the unit. None of the manuals that are available even tell me what the maximum load is for install, let alone expected average draw. I sent an email requesting these statistics directly to Peerless Boiler, but in case they take excessively long to get back to me - or worse, send a rubber stamp response having nothing to do with my request - I'm asking here as well. The sooner the better, as I really don't want to deal with another storm without heat.

 

[Dana]

The boiler doesn't take very much power at all- usually far less than the circulation pump(s), which you'll need to actually get heat. What pumps are on the system?

At 115,000 BTU/hr out that thing is more than 2x oversized for most homes in Haverhill (as if it's ever going to drop below the -50s F), more than 3x the heat loads of smaller houses. AFUE is tested at a presumptive 1.7x oversize factor. ASHRAE recommends no more than a 1.4x oversizing for best comfort & efficiency.

With three zones it's ridiculously oversized for the radiation of any single zone (the zone radiation can't deliver the 115K into the rooms), and may even be oversized for the whole house's radiation. Unfortunately this is typical. If it's less than 20 years old it's not worth replacing with a right-sized boiler, but if it's over 25 years old there are MassSave subsidies for replacing it with a higher efficiency boiler, at which point it can be right-sized.

 

[Sponsor]

 

[Randy Boyd]

Thanks for the quick reply! After you talking about the size of the boiler, I went to an online calculator and with the approximate square footage to heat (there's some rooms that aren't in the 3 zones) being 1500, that means the recommended BTUs would be 66,000. Definitely around half the output of the one we have installed. Trust me, this is just a taste of the headache the previous owners left us with, but I digress...

It's running 3 Taco 007-F5 circulators, each rated at 115V/0.71A. I don't know how often they're running, but if they were constantly going (unlikely) that means a power draw of under 245W.

To your best guess, what would you rate the max power draw of the boiler itself? I can plan for worst-case and be pleasantly surprised at any excess I end up with.

 

[NY_Rob]

With three 007 circulators and the boiler, a battery backup isn't going to hold the load for long... maybe 20min?

IMO- you'd be better off looking at one of the mini 2000 watt portable inverter generators that will run for 6hrs on a gallon of gas.
You could then use it for other things too since it's an inverter unit.
https://www.amazon.com/WEN-56200i-2...520701659&sr=8-3&keywords=2000+watt+generator

 

[Randy Boyd]

Thanks for the idea, Rob. I was already thinking about getting a small generator as well. This covers both bases.

 

[Jadnashua]

The boiler probably has a plug, so moving it to an extension cord on the generator would be easy, but the rest of the controls may be hard wired, so you'd need a disconnect switch and a way to plug them into the generator as well.

Several families in the area have either died or were seriously impacted by CO from improper use of a generator in the last few days in the Boston area...don't become one of them! CO is a serious issue when using any combustion device. I'd want to have some battery operated CO detectors working if I were going to use a generator. FWIW, with the recent storms, you might have trouble finding a generator!

One alternative might be something like Tesla's power wall unit...a big battery with an inverter. It could be sized to power more things in the house, and be an automatic switch, but all of this convenience comes with a cost. By far, a small generator would be the least expensive for your minimum objective, but not all that convenient.

 

[Randy Boyd]

The boiler probably has a plug, so moving it to an extension cord on the generator would be easy, but the rest of the controls may be hard wired, so you'd need a disconnect switch and a way to plug them into the generator as well.

Several families in the area have either died or were seriously impacted by CO from improper use of a generator in the last few days in the Boston area...don't become one of them! CO is a serious issue when using any combustion device. I'd want to have some battery operated CO detectors working if I were going to use a generator. FWIW, with the recent storms, you might have trouble finding a generator!

One alternative might be something like Tesla's power wall unit...a big battery with an inverter. It could be sized to power more things in the house, and be an automatic switch, but all of this convenience comes with a cost. By far, a small generator would be the least expensive for your minimum objective, but not all that convenient.

The whole unit is hard wired, but since there's one main line going to an already in place emergency disconnect I can convert it to a plug-in system for this convenience, which is what I anticipated doing anyway.

As for the generator, I'm fortunate in that I have an air circulation system in my basement that I can plug into the generator to keep exhausting the exhaust outside while my family is safe in the 3 floors upstairs. And with the boiler being on the other side of my home, we could keep ourselves further safe by charging the phones there.

At least it will be safer than what we had to do this last storm which was use our gas stove for hours a day in the kitchen to keep warm.

I'm also very familiar with the power wall system. Very convenient but not cheap. If we had variable power rates like in other countries or Hawaii I would invest in one in a heartbeat, though. It would at least make my solar panels useful during outages though...

 

[NY_Rob]

When I suggested the small generator I never envisioned someone using it indoors!

Never... never... never... run it indoors!! Not even in an attached garage with the garage door opened.

CO rises and will find it's way up from the basement no matter how much ventilation you have in your basement.

Just run an extension cord from the generator (running outdoors) to whatever you want to power indoors. If you want to make it really nice- wire in a manual transfer switch.

 

[Dana]

Thanks for the quick reply! After you talking about the size of the boiler, I went to an online calculator and with the approximate square footage to heat (there's some rooms that aren't in the 3 zones) being 1500, that means the recommended BTUs would be 66,000. Definitely around half the output of the one we have installed. Trust me, this is just a taste of the headache the previous owners left us with, but I digress...

It's running 3 Taco 007-F5 circulators, each rated at 115V/0.71A. I don't know how often they're running, but if they were constantly going (unlikely) that means a power draw of under 245W.

To your best guess, what would you rate the max power draw of the boiler itself? I can plan for worst-case and be pleasantly surprised at any excess I end up with.

That has to be the world's crappiest online load calculator. A boiler output of 66K for 1500 square feet is 44 BTU per square foot of conditioned space, which is the approximate heat load ratio of 1500' tent at 0F. Heat load is not a function of the conditioned floor area- it's all about the exterior surfaces of the building, the thermal conductivity of the materials, and the air leakage/ventilation rates.

Most tight, insulated 1500' homes (even 2x4/R13 homes with only R19 in the attic) will have a heat load ratio of less than 30,000 BTU, many will be under 25,000 BTU/hr. A 1500' current code min (2x6/R20 w/R49 in the attic and U0.32 windows) will usually be under 20,000 BTU/hr, unless overventilated without benefit of heat recovery ventilation.

As a point of reference: My 2x4 framed sub-code 1920s bungalow with 2400' of above grade living space (plus 1600' of insulated basement that never drops below 65F in winter) comes in at just about 40,000 BTU/hr @ 0F. Your house would have to be the draftiest house in Haverhill to actually need 66,000BTU/hr of boiler output even at -10F.

If it doesn't already have a smart heat purging control (I haven't read the manual), at your 3-5x oversize factor it's probably worth investing in a retrofit heat purge controller, assuming you're going to keep the nearly-new boiler. If you're considering swapping it out for something more appropriate in the next few years, the retrofit controls money is better applied toward the boiler upgrade.

Regarding the power needed to run your heating system...

Y0u're looking at a continuous draw of more than 300 watts when all zones are calling for heat. Assuming a 10-15 % average duty cycle due to the ridiculous oversizing factor that's on the order of 10 kwh/day, which is a LOT of battery expense just for the once per decade storm event. The portable gas powered generator and an isolation switch to keep from backfeeding the grid is a lot cheaper to install, and can be sized to run all of the critical circuits in your house (boiler, refrigerator, etc.).

A friend of mine in Boylston MA is totally in the woods, and gets more frequent power outages than most. He invested in a propane powered 10Kw generator that automatically switches in when the power goes down. There are similar natural gas fired units out there that would cost substantially less than the amount of battery it would take to run just your heating system for a day. (They got to really popular items in NJ after Superstorm Sandy.)

 

[Jadnashua]

While I was waiting for a new gas valve for my boiler, I did run my stove for a few hours. I have a fairly decent, calibrated CO meter that's nearly new, so the calibration should still be quite accurate. After a couple of hours, it was bouncing between zero-ppm and one-ppm. IOW, a properly running gas stove shouldn't generate much of any CO. Now, I wouldn't do that without a good meter as a CO detector may not go off until you've been exposed to a much higher CO level. Not all stoves are running this clean.

I would not run a generator inside the house unless it had a dedicated exterior exhaust that you knew wouldn't overheat and exhausted far enough away from the house so you didn't get blowback. Plus, the noise would be a pain. Keep in mind that part of that exhaust is heated air you paid for, too, requiring outside air to replenish.