I don't see moving just the tempering valve having much effect on the shower temperature stability unless the tempering valve is just on the tub/shower supply line. Why not get a tempering faucet set for the tub?
Moving the WH to the branching point, though, would reduce the wait time for hot water at the faucets.

Thanks randy. We were leaning toward a new Weil-McClain GV90+ boiler and in indirect. Now we are tilting towards a Rinnai and no tank.

I suppose that putting the new temp valve near use points would make it marginally easier for installing an indirect tank there later if someone needs it later. That is likely. Right now it is only dad in the house, but the next occupants might be a family of several and adding a tank will probably be desirable at that point.

An advantage of tempering close to po would be easier adjustment at shower head. Think of it like this. With temp valve mounted near source,when hot water is initialy called for at shower,120F water leaves the temp valve. Warming pipes from valve to shower reduce's temp to 105 and dad adjust's to suit then step's under shower. The temp valve continues delivering 120F water and shortly 120F is what begain's reaching shower raiseing dad's adjustment upwards 15F. No scald will occur but water is suddenly 15F warmer than what dad wanted. Dad readjusts shower and all is well except for agervation dad suffered. Dad calls son to inform son the valve was/is a waste of money because he has to adjust shower twice. Emagine if you will what occur's if 30 feet of cold line is moved from after valve and placed before it simply by moving the valve closer to shower. I don't think flow reliability when other facuets are opened/closed will be improved. If that is a problem,increasing line size to where branchs start and/or installing a pressure regulator just before branches will help. A less expensive means (DIY INSTALL) of protecting dad from accidential scald is installing ASSE-1962 TAFR device on shower arm.

Thanks, klem1. Now there is a constantly-fired boiler with a DHW coil in it. It has never worked very well for supplying constant-temperature water with temperature varying with the flow. I trust that just about anything will work better than what is there now so at this point, I am trying to figure out what kind of inexpensive tweaking will make the new boiler work as best that it can. Dad will not want to invest a lot of dough. My assumption is that a tempering valve will be required at this date so I ask where it might best be placed.

I agree it's likly required and would be a wise move even if it isn't required. I know as applied to op this is kinda like preaching to the choir but for the benifit of lurkers , scald protection is simply insurance you hope never to use. Even when there is no toddlers, handicap or elderly in the house scald guard should be in place. My story involve's our 12 yo at the time granddaughter. We rented a cabin where she went into the shower and the hot stem blew out when she turned it on. The water was very hot from a boiler with circulitation pump. Thankfuly she was not directly in front of the rushing water and not badly burned. Even a healthy adult would have been blistered if hit in the belly,,,,, or elsewhere.

Ouch!

The old boiler had a "tankless coil" and definitely requires a tempering valve. Those old coils slug hot water especially as they age and scale up. They are also the least efficient method of making hot water.

Your choices are a boiler with indirect tank, boiler and Rinnai & possibly a Combi boiler which combines a plate HX in the boiler to handle the DHW load.

The first question is, what is the heat loss of the building? What kind and how much radiation is all ready in the building. How many feet of actual element is there in the enclosures? does it heat the building? Don't oversize your boiler. There is no benefit to having to much boiler. Once you figure that out, what is the GPM load of hot water. That answer determines if a combi can work.

My preferred method and that which I use in my house is the Rinnai tankless on the opposite side of the house from the boiler, which puts it right under the hot water load giving the best operation. If the system is split, in late April you turn the boiler off for the summer and let your tankless do its thing.

The boiler is 55 years old (original to the house) so I don't think that a tempering valve was required when it was installed. When the village went to wells in place of spring water the coil was cleaned annually. A spare was purchased to avoid down time. A water softener largely fixed that so I don't think that the cleaning was kept up as it should have been.

Long-term investment in efficiency will not pay off in this case. Pulling out the oil burner and substituting a gas burner in the existing boiler was a consideration, but dad decided that the Crane was too old to risk it.

Cost considerations means that $1500 for a separate water heater is not being considered. Venting anything out the side of the house for two appliances might be problematic due to the layout of the house. (The new boiler might have to go up the existing chimney with plastic pulled through it and I assume that a separate water heater would require a second exhaust. )

Dad does not have large hot water needs. My position right now is that if someone in the future needs more hot water, they can install an indirect tank run off what ever he puts in now.

I hear what you are saying about the heat loss. We had an evaluation of the house last fall under a New York state program (NYSERDA) so we have some numbers. Main contenders for the boiler included more than one brand of modulating boiler and Weill-Mcclain GV+ (non modulating with a cast iron primary and SS secondary exchanger.) We were leaning toward the latter due to lower expense of one bid.

Recently we hit the reset button because I found that dad is most probably eligible for a 50% rebate on the cost in the NYSERDA program. There is only one contractor that is eligible under the program (BPI certified) within an hour drive. I don't have any problem with that contractor, but they were high. I am talking with them again, but I have to hold their feet to the fire (I'll use the Crane) on proper sizing. I'd like to use them because they are less than a mile away. That is a big deal if the boiler breaks in a blizzard. They quoted a Rinnai, but the DHW/heating output for that line appears low compared to other brands so I am not sure it is the best fit. I may go back to them and ask what other brands they are comfortable with.

I'd like to think that a condensing or modulating-condensing boiler will work well enough to make the investment in the house. It has seen a lot of improvements in insulation and windows since it was originally built so it is very likely over-radiatored for 180 F water. There are three radiator runs, ground level [16 kBTU], conditioned basement [11 kBTU] and sun room [12kBTU]. The last does not get used in the coldest weather and has radiation that is probably closely matched the demand since it is a late addition. I guess what we'd need is a measure of the radiator output at condensing temp compared to those figures to know for sure. Lastly, I don't know what temperature was used for the heat loss calculations. I have been told that -10 or -20 is most appropriate for the area. Yes, it does get that cold and sometimes even colder there.

The rebate program pays out up to $5000 so we are very willing to make a $10k investment but I want to put the money were it will do the most good in a relatively short time. At the same time, we can try to avoid ham-stringing future owners of the property in case we get a savvy buyer that is not simply blinded by the bright lights on the read-out from a fancy-pants modulating boiler that might not work well due to poor system interaction.

This post was edited by ionized on Fri, Nov 28, 14 at 14:25

The output of the Rinnai's is about identical to any other tankless brand based upon EF and burner input. The reason it looks lower is that they give you a straight number. I represented Rinnai for 20 years and know that category very well. I've talked with contractors all over America and the consistent comment is! "I've installed them all. I have fewer problems with the Rinnai's than any others." My 20 yrs with them in a six state area bears that out.

Depending upon what the heat loss is, your Dad might like a product like the Rinnai 110e Combi boiler. It is 110kbtu input at 95% and at a 75* temp rise will make 3.2 GPM of domestic. There are many other brands of combis. It is the fastest growing segment in the boiler industry.

Thanks Jackfre. I appreciate your input. The proposal or the Rinnai calls for a RINE110CN which the intaller says is a 95% boiler. I must have been smoking crack when I though Rinnais had lower DHW output. I just looked at the information that I collected again and see that it is on par. I could not find this particular model (CN).

They have not done a heat loss calculation yet. I hope that they roll over and do one without much more prodding. The rep told me that he measured the Al fin rads and matched that :-(

I have the heat loss from the energy evaluator who quoted a Navien and a Triangle tube, but he is an hour away. I've also got quotes for a Baxi which modulates to 1/7. None of this matters much since the Rinnai installer is the only one close by that is BPI-certified. (Ironic since they seem comfortable going ahead without a heat-loss calc.) I have proposals (2) for Weill-Mcclain GV90+ 4 with an indirect tank as well.

I recall seeing two smaller capacity Rinnai boilers, one pretty close to the heat loss total from the energy evaluation (47,451) at 50K and another in between, maybe 75k. If the heat loss is really 47,451 BTU, it seems like the 110 is way too big. The current boiler, the evaluator wrote, has an output of 73,800. If we go to a smaller Rinnai, I guess the DHW output will be lower as well, but I don't know if that will be a problem. Do you have an opinion there?

It seems like with the heat loss from the structure, the radiator length and the boiler output, one should be able to predict how much time the boiler would be in an efficient mode.

Jackfre, if you have any other comments that will help me get a good performance/price ratio within the budget constraints, I am all ears. I am curious if additional controls, beyond the included standard outdoor sensor and on-board logic are desirable. Dad has three snap-action thermostats right now. (Two are 70s Honeywell mechanical set-back models and one is a straight manual thermostat.) Unfortunately, he is not likely to adapt well to pushing a lot of buttons to program an electronic control system,

My comment on the hot water capacity was on the tankless water heaters. On the boilers it is a bit different story. there are three Rinnai combi boilers that might work for you. there is an E50C, E75C, and the E100C. Hot water capacities are at 2.1gpm, 2.1 gpm and 3.2 gpm respectively at a 75* temp rise. It being only your Dad in the house look carefully at his demands prior to saying 2.1 is not enough. By the time you mix it to use temp it is more like 2.5 gpm. your Dad's call on this. It being a NG unit the minimum fire on the 75 & 100 is, I think, 17,500 btu. The 50 goes down to 13,500. All of them come with a very robust outdoor reset program.

You have pretty good handle on the heat loss etc. and seem to have a good contractor, right? I'd suggest discussion with him and see where it goes. One thing to be aware of. The E75 & 110 have a low loss header included in the box. It is an option on the E50.

Your Dad will have to have a 3 zone relay panel like the Taco or Tekmar to which the three stats will be wired. That relay panel, which is simple for your contractor, will make the call to the boiler regardless if 1, 2 or 3 zones are calling. As far as the electronic set-up, that is done by the contractor and once set up should require no participation from your Dad. The boiler will actually store how much gas it uses for heat and again for hot water.

Thanks again. There will be no tub filling at the house. (The tub was professionally cut away when my mom was terminally ill so she could shuffle into a shower on the ground floor.) The other bathroom has always been shower-only. That leaves only the typical laundry and kitchen stuff. He does not do simultaneous hot water (shower + anything else) now so I am sure that dad's attitude will be that he won't miss anything that he does not have now. I guess that the 2.1 gpm would make it if the 75 degree rise gets above 130. I don't know what the ground temp is off hand, but it is pretty low. I guess that if it is low enough, we'll have to consider higher capacity and a mis match on the boiler for heating.

The DHW will be another thing to talk to the installer about. The guy I've been talking to is called "Energy Services Consultant, HVAC/Insulation Estimator". When I brought up sizing, he said that he might talk with "the engineer". I don't know if it is one that is on staff or is a consultant. I should probably let him know that I'd like to be in on the conversation if that is possible.

If there is even a small chance that an indirect tank will be added later, should a zone controller with capacity for 4 zones be installed? I guess I am wondering it the added cost at this point will be trivial or substantial.

The Rinnai RS100 "room control" caught my eye, but there is not much information about its characteristics on the Rinnai site. Can you comment on its utility?

We went through the same thing with my folks and in-laws. It is a difficult enough situation without having the long distance between you. Take care of Dad!

Given your Dad's hot water use, I do not think you need to "go big" on the heat side. That 2.1 gal is at a 75* rise. Max temp in a shower is 110. Generally water gets cold in Jan, Feb & March when the frost gets into the ground, but base ground water temps according to the USGS are in the 55* range most of the year. Every system has a personality, but I would be surprised if it varied much from this.

If your father is ok with the help the contractor should be as well. I would not worry about the indirect. You can discuss a larger zone control if you wish, but do not think it is worthwhile. The RS100 has found very little application here in the States, In Europe where they do a lot of constant circa systems it is a nice control, but that is not a system we use very frequently in the States, so forget it, is my suggestion.

Your other option if you choose to go with an indirect is to go with the Q85S and an indirect of your and the contractors choice. That is a straight heating boiler (17-85kbtu). Rinnai offers an optional 3-way valve kit for the indirect that allows you to use the boiler circ for the indirect as well as the heat. It eliminates the need for the dhw circ and aqua stat for the indirect. It is nice kit.

Thank, yet again. You've been a big help, Jackfre. We should hear from the program this week. I expect to find positive and start talking with the BPI contractor intensively.

Reply on the rebate program is taking forever. Size looks like I should be going quite small based on degree days and on fuel usage. I am thinking that the smallest boiler that I can get will do it with an indirect tank and yield the highest efficiency since we won't be doing much in the way of system revisions.