Home>Discussions>INSULATION & HVAC>what makes Buderus boiler's water gauge temp "go" up
9 posts / 0 new
Last post
what makes Buderus boiler's water gauge temp "go" up

Please excuse my ignorance, but could anyone please explain "what"
makes the Buderus boiler's water gauge temp go up? I'm trying to understand why we come home every evening to a cold family room (on slab - with own thermostat), turn temp up, and it could be hours before the 20 x 16 room heats 3 or 4 degrees. That gauge on boiler is usually reading around 120 degrees.

Yet in the a.m. that gauge is around 150 degrees. Have been told that the water needs to heat up as quickly as possible in order for the room to heat up. Makes sense. But at night, nothin' seems to make that gauge go as high as during the daytime. One suggestion is to install higher output radiators in family room.
Have had 3 different HVAC guys say the system is fine.

Also have a Buderus indirect water heater.

If anyone can explain in simple layman terms, "why" this gauge
seems to be so low in the evenings, as compared to daytime, I'd be most appreciative. Am just trying to understand how the boiler "works". System has the Logomatic, & its set to "winter mode" right now).

Re: what makes Buderus boiler's water gauge temp "go" up

If you feel uncomfortably cold during any part of the day or nite, then regardless what the HVAC guys say, the system is NOT fine.

These newer systems have more complicated controls than the old days when you could just turn up the room t-stat and get more heat.

What they have now is Logamatic ODR (outdoor reset), and sometimes indoor reset as well---what happens is there is a temperature sensor on the outside of your house connected to the boiler that registers the outside temp & tells the boiler to make hot water at a certain pre-set temp and distrubute it to the radiators/baseboard/convectors---the general idea is that the COLDER the outside temp is, the HOTTER the Logamatic tells the boiler to heat the water, and vice versa, the WARMER the outside temp, the MILDER the boiler will be told to heat the water.

In your case, the Logamatic is clearly set at the wrong level & someone familiar with the system will have to come in to re-adjust it.

The outdoor reset saves a lot of money on fuel usage, but if it is set wrong, the house feels cold during certain times of the day.

You'll have to get someone in there that is familiar with the Logamatic to correct this problem---you can try calling Buderus at their factory in NH at 603-552-1100 (sorry, I don't have an 800 number), and ask for their Technical Support dept., and explain the problems you're having.

They should have a list of techs trained on Logamitic controls in your area that can be sent over.

You can also try posting your request for help at http://www.heatinghelp.com, where there is a number of experienced boiler techs who are familiar with these controls; after getting to the site, click onto "Ask Questions", then onto "Controls"

You can also Google "buderus logamitic controls problems" to get numerous sites on the internet that have dealt with this very common problem.

Let us know how you make out in finding a solution to this problem.

Re: what makes Buderus boiler's water gauge temp "go" up

Thanx so much for the clear, concise explanation. I pulled out the service manual and operating instructions, and came across the "heating curve selection" section. Makes more sense to me now "how" the system should work.

Went through the operating instructions to make sure the day and time were set properly (PM, not AM), and anything else that I could change if "off". Will call the HVAC contractor who installed (and serviced it in May) Monday with the information you've provided.
System is under warranty.

I had shut the system down (was in summer mode) until about
a month ago (now its in winter mode).

Re: what makes Buderus boiler's water gauge temp "go" up

Here's follow-up ....

Called HVAC folks who installed the system last evening when
I raised two t-stats to 68, but couldn't get either zone to reach 68 after 3 hrs. The BLR temp rose to 133, and then dropped to 106. This cycle went on for hours - took 5 minutes to reach temp, and then boiler would shut off and temp dropped to 106.

I explained all to tech when he arrived. He said I'm not suppose to raise the temperature more than 4 degrees? What? First time I had heard that one, and frankly w/a $10K unit it seems crazy that I can't raise the temp to anything I want, and expect the temp to reach it. He suggested I switch for MANUAL operation, and showed me how to change it over (and to turn down HWT). He said he himself didn't have one of these units and was more comfortable "fixing" something mechanical, than a computer. But once it went to MANUAL, the heat was on, and finally the house reached 68 (after another hour). I realize yesterday was mild, and today is mild, but again, can't believe that such an expensive unit won't heat to what the homeowner "wants", when they want it (my father is elderly and always cold, so if he wants heat, he should be able to get heat -especially in a 16 x 20' familyroom).

Tech said outside sensor was reading 65, but it was 55 outside. He went outside to change something. Then once back in, he realized he was looking at night time setting, not OA setting.

Tech was ready to leave when he asked me to check hot water. It was boiling hot. So he went outside to check some documentation. He came back in to use my phone and went downstairs w/it. When he came back up, he said to forget about using MANUAL, and to go back to Automatic. Seems after talking to someone else, he changed his mind completely about MANUAL operation. He reminded again that its mild outside and not to raise the tstats more than 4 degrees because it confuses the computer.

So basically I paid $136 for service call (have a 5 yr warranty of unit) and ended up right where I started - on Automatic, 'cept told not to raise temp more than 4 degrees because I'm confusing the computer by raising and lowering the temp. Tech said to set it, and leave it.

Again, something seems very wrong with such an expensive system if the homeowner can't raise or lower their tstats for fear
of confusing the computer. Seems like the computer is running the show here, not the homeowner.

Re: what makes Buderus boiler's water gauge temp "go" up


Try contacting Buderus directly; I'm sure they can suggest a way to do a manual override so you have better control of the heat; in the process they'll give you an 800 # and assign you to a technician in Technical Support who will provide help free of charge.

Re: what makes Buderus boiler's water gauge temp "go" up

plan to call Buderus 1st thing Monday a.m. to inquire about the MANUAL option since I saw "it" work (but understand from friend in HVAC the prolonged MANUAL usage could negatively impact indirect water).

am sure there are probably some reading this who wonder "why" did
I purchase such a system, but at no time during researching or
sales presentation did anyone say anything about not being able to
rise a temperature more than 4 degrees at one time. or that it could take 3 hours for room to reach desired temperature

as I explain to others, sitting in a room for 3 hours, waiting for it to reach 68 degrees, is like sitting in a lukewarm tub, & adding just enough hot water to slowly raise the temperature 1 degree per hour. compare that to the sensation of getting into a super duper hot tub and immediately being able to "enjoy" the heat. no comparison. while it might use more energy to have the instant hot tub, benefits outweigh.

Re: what makes Buderus boiler's water gauge temp "go" up

Buderus has been contacted, and the HVAC folks who installed, have agreed to refund the "service call" charge. Head tech is coming out to take a look. Thanx for boiler info.:)

Re: what makes Buderus boiler's water gauge temp "go" up

..... meant to pass along Buderus' 1-800 number, in case others may also need it, 1-800-BUDERUS

Heat Loss

Forget the seetings and anything on the boiler for a second.

While Nashua explained the operation very well he forget the most important part. What is the heat loss of the home? It then needs to be broken into the heat loss of the zones. You then need to compare the amount of radiation output to the heat loss and find the curve your searching for. As an example.

Room is on its own zone and its heat loss is 10,000 btus (which means a 1 gallon per minute flow rate) Residential baseboard puts out on average 550 btu's per foot with 180 degree water. I would need about 19 feet of board.

Room 2 has the same heat loss but it's on a zone that has a total heat loss of 25,000 btus (2.5gpm flow rate) That same baseboard now can put out 580 btu's a foot with 180 degree water. You would now need 17 foot of baseboard.

Btu output of heat emitters change as water temps change. You also have to look at the layout of the room. Is there a couch of other piece of furniture blocking the now smaller amount of convection the board is producing with the smaller btu output.

Buderus is going to ask the same question. What was the heat loss. Now someone may just come in and turn it up and you will have heat but that also does not necessarily mean its fixed correctly. No matter whome or what you do without a heat loss the fix is a bandaid.

Sponsored Stories

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.