New furnace takes longer to heat up house than old furnace

waitingandwaiting603

Greetings good people - Why did our old furnace heat up our space quicker than our new furnace? Its baseboard, hot water.

Last winter, we replaced our Weil McLean HE-4 with a Lochinvar WHB155. Stats are below.

I've asked the installer (well respected plumbing and heating business) why, and they say - make sure your baseboard heating fins are all cleaned out, which they are.

Are there any settings I (homeowner and pretty saavy in anything mechanical/electrical) can adjust on the WHB155 to help improve the response time?

OLD: Weil-Mclain - HE-4 series 3
efficiency: 82.3
Input: 100K
MBU/HR: 82K


NEW: Lochinvar WHB155N
efficiency: 95.0
Input: 155,000
MBU/HR: 147,250

Thank you.

ethicalpaul

Sorry to answer your question with a question, but:

Why if an old 82% efficient boiler with 82K MBU heated your house apparently successfully, did they replace it with a 95% efficient boiler that returns almost twice as much MBU?

waitingandwaiting603

I requested a larger boiler. In part because the price difference was negligible between it and the next smaller model, and the house has been added onto a number of times, and we wanted to fully heat areas we’ve been holding off on in the past. 

Rich_49

Was any type of heat loss calc or survey of the installed radiation done ?

waitingandwaiting603

I didn’t recall seeing a heat loss calc. It may have been done by them. House was recently re-insulated through but while we still had old boiler. 

JUGHNE

Pictures of the piping and boiler, a good shot showing all, would get everyone's attention.
And what direction is the arrow on the pumps pointing?

This is probably piped differently than the old boiler.

Jamie Hall

Most likely is that the new boiler is operating at a lower, possibly much lower, temperature in an effort to keep it in or close to the condensing range. This is the only way the new boiler can achieve the higher efficiency than your old one did. The heat emitted by your baseboards is very much affected by the temperature of the water provided.

You will undoubtedly be able to heat the house just as fast -- though no faster -- with the new boiler as you did with the old one, but you will have about the same efficiency as the old one; unless the old one was not functioning, you will have gained nothing by the exchange. You will need to adjust the controls on the new boiler to put out the hotter water you need.

If a heat loss was not done, and you have added insulation, unless you also added a good deal of space, I regret to say that the new boiler is probably grossly oversized, and you will find yourself with an unhappy tradeoff between slow heat and quick cycling of the new boiler.

sunlight33

Lochinvar WHB155N has a 10:1 turndown ratio so it shouldn't short cycle much.

GW

Yes what Jamie said
either there’s a piping-install problem or the 
new boiler is looking at outdoor temperature and making “milder” water temps
(making the ground assumption absolutely everything is the same with the distribution system, that’s a different conversation)

i always try to spell this out before the Homeowner perceives a problem. 

If it is the boiler temperature, I’m sure the installer can make an adjustment but it would basically negate the whole reason why you bought high efficiency.

It will be kind of cool if someday people would  leave the thermostats alone. But in the meantime, it’s like comparing a Prius to a big old pick up truck, they don’t operate the same way

EBEBRATT-Ed

As others have posted the new boiler may be running longer at lower water temperatures and hopefully saving fuel.

Unfortunately you probably have an oversized boiler now

Hot_water_fan

Are you using a setback? If it has a boost function, that'd be worth using. The boiler will recover from the setback at a higher temperature than use a lower temperature to maintain heat. Keeps using the efficient temperatures for most of the time. Next time get a smaller boiler . 82k btu output is still likely 2x too big.

waitingandwaiting603

There is no outdoor sensor, this the plumbing contractor said to me, and is indicated on the control panel. Said it was optional. 

I’ll get some pictures shortly. 

I use the old rotary Honeywell thermostat and yes, turn it back 6/8 degrees at night.  It stays at 60 until the next day around 3 when it gets turned up to 66/68. Then it take until 9 pm or so to get up to 66. 

Gilmorrie

I think you should call back the installer and get his opinion. Let us know what he says.

Hot_water_fan

So add in the outdoor reset and set up boost if possible. Also check if the output is throttled back any: modulating boilers can be artificially lowered down to about 40% of max. That handles the boiler part at least. 

Jamie Hall

The old round Honeywell -- probably some flavour of T87 -- is just fine. You may find, however, that for optimum performance from the new boiler that you want to use a smaller setback, so it will recover in a more timely way without going into boost mode.

MikeAmann

What brand aquastat is your new boiler using?

GW

how hot does the water get? the boiler should tell you this number. As you say- something is different. Flow or temp or both