Print

[Ole Smokey]

Great forum! First post.

The house we bought had an OWB of unknown manufacture. 2 story with a crawlspace. Built in 2006, well insulated and 2146 sq ft. Two heat pump system with an air handler in the crawlspace and one in the attic for the second story. Water to Air heat exchanger installed in each air handler. No provision for domestic hot water and I will need to figure out how to get it properly. Also 700 sq ft attached garage under a bonus room that is heated and cooled. Dual thermostats already installed in the house - one for the heat pumps and one for the OWB.

I purchased a new P & M ML30 and would like assistance choosing the correct components for installation on what was left of the previous plumbing. I'm working with 2 loops of 3/4" pex (I know, wish it was 1" but working with what I have) one for each hx. 20A 120V service existing at the stove but need to hook it up.

The stove is placed on the existing pad with no connections at this point. I would like to do this the right way or at least the best way I can working with what I have. I know you need to know the run distance for the pex and number of fittings also. I will get that info this evening. I like the idea of temp gauges on the returns. I'm in Virginia. So I guess I need to know:

1. What pumps to use? Best way to install them exactly?

2. How to best setup for domestic hot water? Bypass loop for hot water in the summer option? Use a plate exchanger on the 1st floor loop for domestic hot water?

3. What other info do I need to provide?

Thanks in advance for the help! I'm looking forward to getting up and running.

[slimjim]

First am I understanding properly that you have a total of less than 3000 square feet of well insulated space on that boiler, if so you have nowhere near enough heat load on it and I would like to know who sold it, would you please PM me with that info.

[Ole Smokey]

SlimJim PM sent

[Ole Smokey]

Thanks to Slimjim for helping me thus far! I actually have more sq footage to heat than I thought and have a plan to make certain that I have adequate load on the ML30 and will monitor its performance in my application.

I have a sketch of my current setup and would like advice on plumbing, pumps to use, etc. I prefer to mount the pumps in my crawlspace.

Thanks in advance for the help.

[slimjim]

Ole Smokey you will need a plate exchanger on the heat side as well in order to go up to the attic, could you possibly run some ductwork up there instead and put the coil in the basement in order to avoid another plate exchanger?

[Ole Smokey]

I currently have a 2 zone heat pump system in the house. The first floor air handler is located in the crawl space with vents in the floor. The second floor air handler is located in the attic with vents in the ceiling. I am working with a system that was installed by the previous owner. The boiler was not part of the sale of the house but the water to air heat exchangers are there with 3/4" pex loops/water lines for each floor. There is no provision for domestic hot water (I believe the previous boiler was setup with an internal coil in the water jacket of the boiler for DHW.)

So at this time I have 4 pex lines undergound run to the boiler I purchased and not connected. One supply and one return for each of the heat exchangers for each floor. I would love to be able to run this system on one pump/one loop but not sure that I can due to the 3/4" line size.

I assume I will have to tap into one of the heat loops to incorporate the DHW. I also assume this would be better in the first floor loop since heat rises and the demand would be less for the first floor?

Twin thermostats are there on each floor - one for heat pump operation and one for the boiler heat system.

To add to the confusion, I may install an auxillary heater in the attached garage to increase the heat demand of the boiler (less idle time/corrosion possibility).

I'm trying to adapt to what I have already. Thanks!

[Scott7m]

Ole Smokey you will need a plate exchanger on the heat side as well in order to go up to the attic, could you possibly run some ductwork up there instead and put the coil in the basement in order to avoid another plate exchanger?

??

Why does he need a plate exchanger for anything besides domestic hot water?

Simply come in with thr main loop and hit a 20 plate for domestic use, have 2 close t setups to control each fan.  Let the fan turn on small circs ar the t's and allow the water to bypass them when its not calling for heat

[slimjim]

The hight of the attic heat exchanger is in the attic, I would imagine by the description that it is 14 -18 feet above the boiler, what happens with a power loss and a non pressurized boiler is that the water above drains out the top of the boiler and leaves an air trap at the top of the system, can it work? yes. Is it problematic? yes.

[Ole Smokey]

I'm going to run one pump for this system on one loop. A Taco 009 from boiler to 20 plate exchanger into water heater tank, (mixing valve on outlet), then run to first floor water to air exchanger in crawl space air handler, then to second floor water to air heat exchanger in attic, then back to stove.

Will also plumb a water supply into this loop below the height of the water level in the boiler when full. Hoping this will make it easier to top off the system when necessary and purge air in the loop when I fill it initially.

Unless I hear compelling evidence that I am screwing up, this is what I'm going with.

I plan on monitoring the supply and return temps.

[yoderheating]

 You are not going to get very good hot water off a 3/4 line running through a 20 plate, 3/4 just doesn't push enough volume to work well. You may need to leave your hot water heater on to assist, just play it by ear. I would hook the dhw to the upstairs line because you will use more heat downstairs.
 Slim is correct that an attic unit can easily airlock. Another reason to use a flat plate for an attic is the chance of freezing unless you use glycol. I know of one case where power went off, the coil in the attic froze and broke, power came back on and they lost a lot of water into the attic. For this reason, even though I have insurance, I refuse to install into an unheated attic without a plate between it and the furnace.

[slimjim]

Well said Yoder, Thank you.

[Scott7m]

Well said Yoder, Thank you.

Yep, I've Done some and explained the risk of freezing, but never had an air issue yet.  I'll keep that in mind tho in the future

[slimjim]

I have come in after the fact to install plate exchangers on several installations for exactly this reason.