Rinnai QP85 ??

[yeldogt]

Wondering if anybody has even used one of the Rinnai condensing boilers with the included 24g water tank for DHW. Thought only Viessmann made this type.

They sit on the floor and use less space vs a typical wall boiler and 40g indirect.

 

[Jackfre]

I know that product well. It is a nice package and will give you a lot of hot water. The tank is SS as is the HX. It has a very robust ODR. You can pretty much make it sing any song you want it to. The ODR set-up is the older sequential push button type without the digital display. When purchasing you have to buy the piping package. You have the three options for L, R or Top exit for you piping lay-out. Questions?

 

[yeldogt]

Jackfre: Saw it while looking through some Rinnai information --- I'm not sure I understand "push button style"

My new project (house and studio). Heating load for house in the 50k range -- Studio is lower. I was able to pick up a 76K BTU Viessmann 200 & LLH for about 2k. Could not pass it up. Thinking I could use it someplace -- it's the smallest unit .. modulates down to around 13k.

The problem is space -- the mechanical room for the house is very tight and I'm not sure I have the space for boiler and indirect. The house will have three types of radiant (slab/warmboard/plates) --- my plan is to use ODR based on what the Warmboard requires and zone off the slab w/o thermostats. The house will also have a furnace -- since it has ductwork for AC

Can the QP85 control another temp?

I'm not sure what the Viessmann 222 costs -- looks like the QP85 is in the 5k range for the unit. My other possibility is a horizontal indirect hidden away from mechanical room. The house will have two bathrooms -- it's just the two of use now. Place has a second bedroom and a loft -- not a huge how water user.

 

[Jackfre]

Push button Style, it is the old style reset interface. It is all push button, but you do not have the visual screen to lead you along. So you step thru parameters. It is simple, but most mod cons today have the better display. Rinnai’s new boiler and your Veissmann have the better digital display.
As far as controlling multiple temps off the boiler, you may have every zone calling with all three settings required. Your primary loop will, on the QP, be set by Parameter 2 in your initial set-up and will modulate temp off the outdoor sensor. Multiple temps will be provided off your secondary loop either thru tempering or injection. The boiler cannot, on its own do that. You will have DHW priority.

 

[yeldogt]

Jackfre -- just clicked in you are the Rinnai expert!

Are they coming out with new model ?

This is actually my first project using a mod con boiler -- since most of my homes have been rehabs/conversions of very old buildings I always used high mass boilers. Always used Buderus w/ Eccomatic type controller -- no readout with those -- simple dials to set the curves. They do have a main ODR and the ability to have a secondary .... that's worked out well as all my previous projects had some type of radiators (typical USA type or panel) along with various floor radiant. I would set them up with the main ODR for the radiation and the secondary would take care of the radiant floor.

About 1/2 of this project is also a very old stone building (1870) -- with the Warmboard I should be able to get enough BTU's into the space to eliminate the need for any high temp radiation. I am running some PEX to potential spots just in case (towel warmers and I may heat a large staircase) ... I'm not thinking the need for two temps will occur .. but, it's nice to have just in case.

 

[yeldogt]

Jackfre -- just clicked in you are the Rinnai expert!

Are they coming out with new model ?

This is actually my first project using a mod con boiler -- since most of my homes have been rehabs/conversions of very old buildings I always used high mass boilers. Always used Buderus w/ Eccomatic type controller -- no readout with those -- simple dials to set the curves. They do have a main ODR and the ability to have a secondary .... that's worked out well as all my previous projects had some type of radiators (typical USA type or panel) along with various floor radiant. I would set them up with the main ODR for the radiation and the secondary would take care of the radiant floor.

About 1/2 of this project is also a very old stone building (1870) -- with the Warmboard I should be able to get enough BTU's into the space to eliminate the need for any high temp radiation. I am running some PEX to potential spots just in case (towel warmers and I may heat a large staircase) ... I'm not thinking the need for two temps will occur .. but, it's nice to have just in case.

 

[Jackfre]

Rinnai introduced a new boiler last spring. I have installed only one, but was most impressed with its installation, set-up and operation and it does have the digital screen common in most mod cons today. The new model is not available in the QP product. When I saw your heat emitter choices I was thinking that you could likely get away with a single temp. Some of the panel rad sizing may have to be increased but calf’s, calcs, calcs.
I think we are describing the same thing from the P/S piping and temps. You run a primary loop at X temp. Your additional controls handle and lower temps needed. Right?

 

[yeldogt]

Jack -- With the high mass Buderus CI boilers -- I always followed the "pumping away" layout. The ODR #1 controlled the main loop out to whatever high temp radiators I was using -- it is in effect one big primary loop. With the Buderus control if you needed a second ODR temp for say radiant floor -- it was as simple as getting another module and plugging it into the controller. This would get you the lower temp for the floor heat by way of a second pump and a mixing valve tied to that second module -- ORD #2. I have even used a simple bypass valve and pump to get a lower temp when it was not as critical.

With the new project. The warm-board is primary in much of the house so that's the main temp concern -- that water may be too hot for the slab ... and a bit too cold for the plates. There will be separate manifolds for each type of floor heat. Think I can manage the slab with lower flow. I have used panel radiators in another project sized for lower temp water doing the floors -- if you can get away with it -- makes for a simple and less costly set up. My theory is the Warmboard temp will be enough for bathroom towel racks if I go that route.

The modcons toss the old way out ... I'm going to use a LLH and my hope was only one temp out to all the radiant. The QP is a great idea .... I have a few months before the decision.

If I can make space for an indirect -- the Viessman will work and it has two ODR curves built in just in case.

Thanks for the info. These tank/modcons give you the best of both worlds. They are a perfect fit for many situations.

 

[Jackfre]

Ok, we are on the same page. LLH to mixing/tempering valve with secondary side circs. The only thing about these units, both V and the QP is that these things are packaged TIGHT. The QP's I am aware of in the field have done well by the owners. You can't really go wrong with either. I sold some of the QP's here in CA as V was unable to hit the low NOX numbers. I do not know if they rectified that. Good luck with it.

 

[yeldogt]

Ok, we are on the same page. LLH to mixing/tempering valve with secondary side circs. The only thing about these units, both V and the QP is that these things are packaged TIGHT. The QP's I am aware of in the field have done well by the owners. You can't really go wrong with either. I sold some of the QP's here in CA as V was unable to hit the low NOX numbers. I do not know if they rectified that. Good luck with it.

Thanks for the information.

Yes, they do have a lot going on in a tight space ... I was just watching an hour video on the Viessmann 222. The nice thing is it's all done for you .... w/ two pumps and all the controls. Just unpack it and The DHW is in and out. The smaller unit has impressive output. The V has a strange way to heat the DHW tank.

This is my first project using all propane .. have had individual situations with propane ... but never a whole project.

 

[Jackfre]

I am not sure how the viessmann does it but the QP has what they call a "charged tank" rather than an indirect. There is an internal plate HX off the primary loop which uses the modulating pump in the boiler. A secondary circ runs the water to the tank. Given the efficiency of the plate HX and the way it is piped it out produces the indirect. Why, because each gallon of hot water exiting the plate is fed to the top of the tank so it can go directly to the faucet. You are not waiting for the entire tank to warm. It is pretty neat in operation.

 

[yeldogt]

I am not sure how the viessmann does it but the QP has what they call a "charged tank" rather than an indirect. There is an internal plate HX off the primary loop which uses the modulating pump in the boiler. A secondary circ runs the water to the tank. Given the efficiency of the plate HX and the way it is piped it out produces the indirect. Why, because each gallon of hot water exiting the plate is fed to the top of the tank so it can go directly to the faucet. You are not waiting for the entire tank to warm. It is pretty neat in operation.

That sounds just how the V works -- I did not have time to hunt down a drawing.

It uses a heat exchanger at the top of the tank and comes with both the main pump for boiler and DHW charge pump. The wall mod cons from V do not come with any pump. Not sure how the combi ants work -- they may come piped w/ pump.

 

[Jackfre]

Don’t know why I didn’t come up with this sooner, but you say it is only you and your wife, with two baths. You can get 4+gpm of hot water from the Rinnai M090C combi. It is the newer boiler with the better reset interface and will take up less room than the QP. Worth a look?

 

[Jackfre]

Much less dough as well

 

[yeldogt]

Don’t know why I didn’t come up with this sooner, but you say it is only you and your wife, with two baths. You can get 4+gpm of hot water from the Rinnai M090C combi. It is the newer boiler with the better reset interface and will take up less room than the QP. Worth a look?

This house is on a well (cold water in winter) ... I also have a small septic system. I'm not a fan of "on demand" type hot water systems anyway ... although they have a place in the mix of systems. I am going to do a home run water set up .. but I don't want to deal with the hot water delay.

 

[Jackfre]

I think that with the recirc you want I would go with a tank as well. I am going to install a new Rinnai RUR at my daughter old, new house. The meatheads have the tank kitty corner from the kitchen sink. I am going to run delivery times from cold start as the current tank sits. Then install the tankless without recirc, the tankless with the cross over valve under the kitchen and then with a dedicated recirc line I will run. When I do the recirc on the Rinnai I will use their wireless control and wireless push button (kitchen) and motion sensors in the baths. How are you planning to control your recirc?

 

[yeldogt]

Jackfre -- I'm sure in a new house with proper home run PEX piping the "on demand" work well. A local house is going up now with three propane fired units -- they are using mostly 3/8 PEX. It's a big house and the firm doing it is first rate -- but, there is no way it's cost effective. They are more concerned about fuel use and the inability to increase the on lot propane storage -- they are not using combi units. The heat is separate. With natural gas available --- no way they would have gone that route.

My preferred route for recirculation control has always used the KISS system. In many cases it's possible to piggyback off a light that would always be used ... if all on dimmers a separate switch with indicator light. Leviton has a nice Decora with small indicator -- there is no way you can leave it on and since the circuit has a thermostat it's really not running all that much.

I'm looking forward to seeing this new house finished --- the 3/8 PEX flow fits the majority of faucet flows -- so the need for recirculation in many homes is eliminated.