Back-up/supplemental heat

Jack

https://forum.heatinghelp.com/discussion/comment/1881434#Comment_1881434

Taht was the requirement in ‘91 when I started with Rinnai. I was on the 31 committee for about 15 yrs and it was always interesting listening to the guys on the committee when they would ask. When and where something or other became part of the code. As to the 9” in 54 I will say I didn’t have problems with the windows of doors and that over a couple hundred thousand installs in my territory. it has been one of the best parts of listening to Dan because he frequently tells us assorted stories on these types of things

Steamhead

ISTR the reasoning was to keep exhaust gases, which could contain CO, from being sucked into the building.

tim smith

Maybe consider a high quality gas fireplace for additional heat/backup heat. They will run during a power outage except for fan unless you want to provide a battery backup system to provide fan power. Just a thought. They are not super efficient but the high quality ones, maybe Valor or Mendota or the like are not awful. You can get close to 75% thermal efficiency I think. Also nice for ambience when you are home.

CTB

We built a new house last year in Massachusetts - Climate Zone 5A, - same as the author. We worked through a number of the same considerations and trade-offs. Mass. Energy code is very rigorous, so insulation is very good (not sure if upgrading is an option for you). House has ducted Mitsubishi heat pump (single outdoor unit with a branch box service 3 indoor units). It is not hyperheat - main use is for cooling, and heating during the shoulder months of Oct., Nov, March and April . On about December 1st, we start the underfloor heating - 1/2" pex with a combination of extruded Uponor/Wirsbo Joist Trak Heat Transfer Panel and a cheaper, simpler stamped aluminum plates. The "big room" with ~18' ceiling and a lot of big windows, is served by a dedicated hydronic manifold with a temperature reducing mixing valve. Another manifold and TRV handle another portion of the house. We also have pex buried in the oversized garage floor…anti-freeze with its own pump a flat plate heat exchanger in between.

The secret weapon is the ability to change the outdoor air temp. reset on out Viessmann boiler. The "slope" is minimal (100 degree F water) in December & March and about 135 deg. or so in Jan/Feb. They define slope as increase in loop temp for every reduced degree in OAT. If you set the slope at 2, you will get 2 degree hotter loop temp for every 1 degree drop in OAT.

The boiler loop temps are subsequently reduced by the TRVs - about 100 degrees with 10 degree delta T. We also have multi-speed Grundfos circulators, and go to the highest speed on the coldest days if I feel like tweaking it). Wood flooring gets to about 80 degrees on the coldest days to maintain the room at 70 degrees.

We also have a large Mendota fireplace - agree with another's comment that the efficiency is about 75% on this (corroborated by one of their engineers).

Not sure if your current boiler allows you to adjust OAT Reset, but that might be your most cost-effective option for comfort. From what I understand about ModCon boilers, expected life is 15 years, so perhaps an early retirement makes sense.

Energy costs are extremely high here ($0.36 per kWh) - that's the reason why did not pay extra for the Mitsubishi hyperheat… although it has extended low temp range, the operating cost is crazy, and is not deceasing anytime soon. Natural gas is also very expensive here - $2.60 per therm.

There were many good suggestion about backup heat, with a few pieces of electric baseboard the most obvious. Good luck!

Jack

Just read through this thread again and want to add a couple things to the Rinnai feature set. They have modulating gas valves and fans. The EX22 will modulate from 8200-21000 btuh. The EX38 will modulate from 13300-36500 on LP. Built in programmable stat. As well for times when you are away the stat can be set in 2* increments below the normal 55* low setting. It will re-start after a power outage. The supplied vent requires a 3” hole through the wall and sits behind the unit. Vent extensions are available for more verticals rise. They are ideal for basement heating as a result of the venting options. Should you install a Rinnai you will find that it is a good companion in the space due to the cool cabinet and quiet operation. Oh, and once you have a gas line at your installation point it is a two hour install, soup to nuts. Your Fujitsu’s aren’t the most attractive but you love them because they are a good value and do what you need. Same with the Rinnai.

Gas fireplaces are popular. You do get some heat and you do get the flame but there are compromises in that the primary goal is to see the fire And you do not get equal air circulation to the Rinnai. The Rinnai direct vent is a heating device, period.

You mention a vent free heater. The very best of them is the Rinnai 824. 8000-24,000 btu modulating fan and burner. It is a beast. Silent and cool to the touch, programmable stat. It is a space heater, not wall furnace. It is intended for occasional use. It will not re-start. You get into trouble with vent free product when you think it can do what a vented product can. They cannot and should not be pushed to do so. Happy Heating!

ColdHouse

The amount of input here has been tremendous and much appreciated as the OP.

To recap, we leave sometime in February for warmer places, for 2 months. I now own six 1,500 Watt Lasko ceramic electric heaters. I have the six separate 20 amp circuits identified and will have them in place throughout the house prior to leaving, but not turned on. I am looking into cell based temperature alarm systems now. I plan on having the house checked on regularly by humanoids, lol. In the event of a main heating failure, I will instruct my SIL to turn on mini-splits if temps above +10 and if colder to use the electrics, until a repair can be made.

Since starting this post, the weather has shifted to a warmer stretch, so take this for what it is worth. I had the circulator in my Great room/hard to heat room fail right before Christmas. I had a spare circulator but it was a larger HP. Old one was a 1/40th HP and the new 1/25th. We haven’t had the coolest weather since to full test, but the room seems to be heating way better and the room Tsat getting satisfied and the floor temps are higher when checking with a IR gun. Yers ago I was told if the temp differential was 10 degrees between supply and return that the pump wasn’t an issue? I am now seeing a 5 degree dif with new pump. This coming Friday, temps are dipping into teens to singles overnight so a test is coming.

Robert_25

If the radiant floor is not able to easily put enough heat into that room, having a tighter differential on the radiant circuit means the average temperature of the floor will be higher….which is a good thing. Good timing with the upcoming cold snap, but sure to report back with the results.

kaliber50

https://forum.heatinghelp.com/discussion/203243/back-up-supplemental-heat

I am just here to sympathize with you hehe and nothing really to add I don't think, but nonetheless here we go.

I have had a similar situation as you since 2017 and have been tweaking my system over the years ever since (with some gradual success).

I have a weekend home in North East PA which I also like to keep warm to mitigate freezing when we are away for the rest of the week; 26" cathedral ceiling; glass wall; (3) radiant loops with one that is not used due to a blockage in the run. I have done the following over the years (with some help from the folks on here. Thx guys).

-Re-configured some of the plumbing that made no sense (i.e. mixing valve installed after the radiant loop circulator vs before)

-Installed flow meters for each loop which made me realize I had low flow (around .14-.25 gpm)

-Bought a thermal camera with K-type clamp which showed me I had input radiant temp of around 110 F

-Added 24K worth of BTUs via Mitsubishi Hyperheat Mini splits (has helped a lot but with that, I also get a hotter rooms on the higher floors due to rising heated air

Still working on it and every little improvement I do gets me closer to where I want my radiant to be operationally. The goal for me is to prevent me having to rip out my system since I and my wife do like the comfort of radiant