heaters for water source heat pumps

zepfan

does anyone know of a way, aside from a freestanding boiler to add heat to a closed loop system that has several small water source heat pumps on it? The application is a tenant in a building that they have water supplied from the building, but there is no heat source currently in the loop. The issue then is that when the units go into heat pump mode in the winter, the water temperature gets so cold that the units then lock out on freeze protection. From what I can tell with this space being on the first floor, are the only units that ever attempt to go into the heating mode. I did not know if anyone made inline heaters that could be installed in the individual lines to the unit, as the tenant has no access to the penthouse of the building where a boiler could be installed to re heat the water, and there is very little ceiling space to install a boiler in the ceiling. thanks to all

Jamie Hall

Ok this sounds a little weird. What are the heat pumps heating? What is the water source? Is it the heat pumps that are going into lockout?

And how many BTUh are we talking about here?

At first look, I'd have to say that almost any heat source you add is kind of going to defeat the purpose of the heat pumps, and if it is any really significant number of BTUh, you are probably looking at a wall hung boiler of some kind.

pecmsg

@Jamie Hall
I believe the OP is talking about a building water loop getting too cold during heating mode.
Yes, a boiler is needed to maintain a minimum loop temperature.

zepfan

The water is from the cooling tower, with each individual unit being around 24,000 to 30,000 btus. A heat source is needed to reheat the water, that the heat pumps are absorbing in the heating mode

Jamie Hall

Well, physics is a b___h. If those heat pumps are extracting 24 to 30 K BTUh, and the water is getting too cold, you are going to need to add 24K to 30K back for each heat pump. That is beginning to look like a pretty decent sized boiler, or possibly an individual wall mounted boiler (could be electric) for each heat pump.

jumper

Jamie Hall said:

Well, physics is a b___h. If those heat pumps are extracting 24 to 30 K BTUh, and the water is getting too cold, you are going to need to add 24K to 30K back for each heat pump. That is beginning to look like a pretty decent sized boiler, or possibly an individual wall mounted boiler (could be electric) for each heat pump.

Sometimes. On milder days a big "aircooler" ( radiator+fan ) can extract enough heat to satisfy heat pumps. For frigid weather boiler is required as stated. Where things get interesting are when days are warm but nights are cold. Possibility of storage? Make senses to switch over from heat pumps to individual electric room heaters when it is cold outside.

ratio

If the loop was truly engineered without heat, I gotta ask why not. I can imagine a place that doesn't really need heat, but then I gotta ask where's that heat going to?

Maybe there's supposed to be aux heat like perimeter electric baseboards in operation?

neilc

is it too silly to ask,
you're shutting off the cooling tower, isolating it, come heat season, correct?
still need to make heat there somewhere

wesPA

Condensing boilers are ideal for this, due to the low return temps. Most of the systems I work with that are set up like this use a boiler(s) to maintain the heat pump loop around 65-70 during the winter months. During the summer, the cooling tower keeps the loop at 85 or below

EBEBRATT-Ed

Thats a "boiler tower" system. Very common in the 1980s.

Used in office buildings and schools the permitter units heat in the winter and some interior units cool in the winter depending on the winter heat load, people, lights, computers etc. The boiler wouldn't have to supply much heat.

But it should have been designed with a boiler and a water tower (actually a closed-circuit cooler was used).

I have senn some of the "energy efficient" systems get out of wack when the building usage changes or lights are converted from 1980s lighting to more efficient LEDs etc

They do make electric boilers cost $$$ to run

pedmec

we have a lot of buildings we work on that are water source heat pumps. most of the buildings use copper fin tube boilers due to the high output btu plus the small footprint. these are pretty good systems when installed correctly. problems that we have found is that the engineers didn't think of the cold water return temperatures to the boiler and plugged the heat exchangers.

zepfan

Thanks to all that responded. It looks like an electric boiler may be the only option. The building does not have natural gas, so that would take a condensing model off the board. Thanks again and take care

jumper

zepfan said:

Thanks to all that responded. It looks like an electric boiler may be the only option. The building does not have natural gas, so that would take a condensing model off the board. Thanks again and take care

Another option is heat pump. Technically a cascade system. Might even save electricity during A/C season.

pecmsg

zepfan said:

Thanks to all that responded. It looks like an electric boiler may be the only option. The building does not have natural gas, so that would take a condensing model off the board. Thanks again and take care

Somewhere it’s listed minimum water temp for heating mode. Generally around 50*. Check with the manufacture. 

No NG what about oil?

EBEBRATT-Ed

@pecmsg

I always found those systems set to run 70-80 deg water

pecmsg

Run at yes but there is a minimum temperature. Cheaper to heat at a lower water temperature and let the heat pump do the rest.