Need some words

Mac_R

I have a customer who is looking at a new system.  He lives in a med rancher well insulated.  The main reason he is looking at a new system is because he is cold in the winter.  I have done a heat loss and the home only requires 44,000 BTU to heat the home properly.  The unit that is in there is 158,000 BTU.  I know a system that is that over sized can cause problems.  I am having a problem in putting this into words that the customer can understand.  Any help will be appreciated. 

Greg Maxwell

?????

Something isnt adding up. You did a heat loss on the house, and came up with 44,000. How many ft of baseboard is there? He has a boiler 3 times bigger than he needs, that is too bad, but wont have anything to do with the operation of the system. What is that boiler firing at? Is it maintaining temp?

chapchap70

What does he mean by too cold?

A couple of basic questions:



Are we to assume that the customer has called his service company because he has had a "not enough heat" condition?  When he raised the thermostat, does the temperature in the rooms rise to the point where he is comfortable? 



Does he have a boiler or furnace?  If he has a furnace, is there enough humidity in the air to make the people not "feel" cold?



If the heating system is that much oversized, he is wasting fuel but the not enough heat situation is more important to this customer and has to be addressed first.  It could be that he does not have enough radiation in the rooms.

Mac_R

Specks

It is cast iron radiators in every room.  More than enough.  The person who put the unit in did the old that was there sizing.  The customer has put in new windows, doors, re-insulated the walls and attic.  The load calc came out to 44,000 BTUs.  I think we have a couple of things going on here. 

1.  There is air in the radiators.  The customer tells me there is a waterfall noise.

2.  The system is so over sized that it is just sitting there short cycling and not running long enough to heat the home properly. 

The customer has timed the system run cycles.  on the coldest days it will run for 15Min then be off for 10Min.  so it is getting up to temp then shutting down.

Classic short cycle.

Greg Maxwell

2 Seperate issues

First - the air in the rads. What is the boiler pressure? Does the air return after being bled? How is it piped?

Second - Boiler size. What is the boiler. Whats the firing rate, and what is the hi/lo limit setting?

billtwocase

if it was

that grossly oversized, it wouldn't be short cycling that often. Need for info on his old boiler as Greg mentioned. Could be a few different problems, and one is not the oversized boiler. I would be looking into the air/possible pressure problem, valves at the radiators that are partially open, or even closed, thermostat issue, cycle or anticipator, zone valve, circs, or flow checks? How many zones? Domestic hot water tied in? Need more info.

Mac_R

more specks

He had air in the radiators.  It was from the boiler being piped the old school way.  Fill valve piped right into the low side of the circulator on the return line along with a maid of the mist air vent just above the low side of the circulator.  it was sucking air in through the vent.  How ever I know that a unit that over sized can cause some problems with heating the home evenly.  Two zones.  one is the main house with cast iron radiation and the second zone is for an addition with baseboard convectors.  He has a DHW coil in the boiler.

Greg Maxwell

Air Problem

Thats good that you identified the problem. Putting a hy-vent on the suction side of a pump is never a good thing. If you want to remove the air problems for good, install a Spiro-Vent air eliminator.